Noto, May 13-18 2018 IAU Symposium 342 · To Giacomo Cuttone, Director of INFN - Laboratori...

Perseus in Sicily: from black hole to cluster outskirts

Noto, May 13-18 2018IAU Symposium 342

© Pier Raffaele Platania, front cover.Corso Vittorio Emanuele, Noto 2016.

Project © Pier Raffaele Plataniafor IAUS342, Perseus in SicilyNOTO, May 13 - 18, 2018

Acknowledgements

A special thanks to:

To Nicola D’Amico, President of INAF.To Tiziana Venturi, Director of Istituto di Radioastronomia.To Grazia Umana, Director of Catania Astrophysical Observatory.To Giacomo Cuttone, Director of INFN - Laboratori Nazionali del Sud.To Corrado Bonfanti, Mayor of Noto.To Giusy Solerte, Head of Tourism.To Frankie Terranova, Head of Culture.To Urbano Pannuzzo, General Manager of the Theatre Tina di Lorenzo.To Concetto Veneziano, Dean of Students at Istituto di Istruzione Superiore “Matteo Raeli”.To Cristina Cataneo, Corrada Fatale, Francesco Montalto, Paolo Vendetti, Professors at Liceo Matteo Raeli, Noto.To Valentina Alfò e Piero Giarratana, ProNoto.To Salvatore Cavallo, Corrado Spataro and entire B.O.D. of the C.U.M.O. Noto.To Associazione Astrofili Netini “Nuccia Corradina Ferro”.

Thanks to:

A heartfelt thanks to the staff of Noto Radio Telescope:Buttaccio Salvatore, Cassaro Pietro, Contavalle Corrado, Giacalone Francesco, Lombardo Nicoletta, Nicotra Gaetano, Nicotra Leonardo, Nocita Carlo, Papaleo Luigi, Paternò Mario, Platania Pier Raffaele, Tuccari Gino.

This publication has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730562 [RadioNet]

P e r s e u s i n S i c i l y from black hole to cluster outskirts

IAU SYMPOSIUM 342NOTO, May 13 - 18, 2018

Symposium wi-fi connection:Network name: PerseusNetwork pword: #IAUS342

It is valid for entire session of conference; inside the theatre and at Grand Hotel Sofia.

Science rationale

The Perseus cluster has recently been the stage of some ground-break-ing discoveries: on ultra-fine linear scales, space-VLBI has revealed fundamental details of the jet launching mechanism; on large scales, at superb energy resolution, Hitomi has revealed surprising details about the gas dynamics shaking our current understanding of the cool core phenomenon; in gamma rays of high and very high energy, dra-matic activity with extremely short time scales has been reported both in NGC1275 and IC310. The importance and timeliness of discussing these and other topics, including feedback, is enhanced by the many developments recently achieved also in the fields of theory of accre-tion and particle acceleration, as well as to the great improvement in performance and accuracy of numerical simulations and imaging tech-niques.

We will gather multi-wavelength observers and theoreticians, experts from the event horizon out to the Megaparsec scales, encouraging interactions and discussion in the beautiful Sicilian city of Noto, a lo-cation rich in history, culture, nature, well-being, and science, near to the INAF 32m radio telescope and the CTA-ASTRI prototype.

Scientific Organization committee

Keiichi Asada (Academia Sinica Institute of Astronomy and Astrophysics, Taiwan)

Roger Blandford (Stanford University, USA)

Geoff Bower (Academia Sinica Institute of Astronomy and Astrophysics, Taiwan)

Elisabete de Gouveia Dal Pino (IAG – Universidade de Sao Paulo, Brazil), co-Chair

Shep Doeleman (Harvard University, USA)

Andy Fabian (University of Cambridge, UK)

Marcello Giroletti (Institute of Radioastronomy, Italy), co-Chair

Paola Grandi (Institute of Space Astrophysics and Cosmic Physics, Italy)

Christine Jones (USA, Smithsonian Astrophysical Observatory), co-Chair

Chung-Pei Ma (University of California, USA)

Hiroshi Nagai (National Astronomical Observatory of Japan, Japan), co-Chair

Rodrigo Nemmen (Astronomy Department – Universidade de Sao Paulo, Brazil)

Lawrence Rudnick (University of Minnesota, USA)

Aneta Siemiginowska (Smithsonian Astrophysical Observatory, USA)

Lukasz Stawarz (Jagiellonian University, Poland)

Feng Yuan (Shanghai Astronomical Observatory, China)

IAUS 342 - Perseus in Sicily

Local Organization committee

Marcello Giroletti (INAF Istituto di Radioastronomia, Bologna), co-Chair

Barbara Neri (INAF Istituto di Radioastronomia, Bologna), co-Chair

Carlo Nocita (INAF Istituto di Radioastronomia, Noto), co-Chair

Grazia Umana (INAF Osservatorio Astrofisico di Catania), co-Chair

Giancarlo Bellassai (INAF Osservatorio Astrofisico di Catania)

Milena Bufano (INAF Osservatorio Astrofisico di Catania)

Eugenio Martinetti (INAF Osservatorio Astrofisico di Catania)

Pier Raffaele Platania (INAF Istituto di Radioastronomia, Noto)

Gina Santagati (INAF Osservatorio Astrofisico di Catania)


T h e S y m p o s i u m

09:00 Welcome speeches

Session 1 – Black hole masses. Chair: Geoffrey Bower

09:20 Karl Gebhardt Measurements of masses in supermassive black holes09:50 Eleonora Sani NGC 1275: An Outlier of the Black Hole-Host Scaling Relations10:10 Luka Popovic Black hole mass measurements in AGN: Polarization in broad emission lines10:30 Coffee break

Session 2 – Black Hole vicinity: theory and simulations. Chair: Sasha Tchekovskoy

11:00 Monika Moscibrodzka Black Hole Accretion in Low Luminosity Active Galactic Nuclei11:30 Yosuke Mizuno Testing Theories of Gravity via BH Shadows and Modeling of Relativistic Jets11:50 Luca Ciotti Fully analytical solutions for Bondi accretion in galaxies with a central black hole12:10 Ziri Younsi Modelling the polarised emission from black holes on event horizon-scales12:30 Elisabete de Gouveia Dal Pino Particle acceleration and the origin of the very high energy emission around black holes and relativistic jets12:50 Lunch

Session 3 – Black Hole vicinity: observations. Chair: Denise Gabuzda

14:20 Kazunori Akiyama Imaging and Filming Black Holes with the Event Horizon Telescope14:50 Geoffrey Bower Probes of Accretion and Outflow in Low Luminosity AGN Using Millimeter Polarimetry15:10 Jongho Park Substantial winds from hot accretion flows confining the relativistic jet of M8715:30 Fabio Bacchini Numerical methods for particle and ray tracing in general relativity15:50 Freek Roelofs On the Prospects of Imaging Sagittarius A* from Space16:10 Coffee break

Session 4 – Past and future legacy. Chair: Christine Jones

16:40 Michiel Brentjens Ger de Bruyn legacy work on the Perseus cluster17:10 Melanie Johnston-Hollitt Observations of clusters and AGNs with the SKA17:40 Matteo Guainazzi The Hot Universe with XARM and Athena18:10 Elina Lindfors Observations of AGNs and the Cluster in Perseus with the Cherenkov Telescope Array18:40 Outreach event: Theatre play by “Il cuore di Argante” Lecture reading by Istituto di Istruzione Superiore M. Raeli Noto. “The myth of Perseus”

Monday, May 14 - Teatro Comunale

Session 1Black hole masses

Chair: Rodrigo NemmenMonday, May 14 - Teatro Comunale

Measurements of masses in supermassive black holes

Karl Gebhardt


We have now measured over 100 black hole masses with spatially-resolved kinematics and the important role that black holes play in galaxy evolution is becoming more clear. There still remain significant issues however with regards to understand the demographics, as we do not have as good of control of both systematics for the measurements and good representation for the range of galaxy type. I will overview the current state of the data and models, with particular attention to the important understanding that NGC1275 provides.

NGC 1275: An Outlier of the Black Hole-Host Scaling Relations

Eleonora Sani

Co-authors:

Alessandro Marconi, Angela Bongiorno, Christian Vignali, Fabio La Franca, Federica Ricci, Francesca Onori,

Francesco Shankar, Marcella Brusa, Stefano Bianchi

Lying at the center of Perseus cluster, NGC 1275 represent the archetypal BH-galaxy system that is supposed to fit well with the MBH-host scaling relations obtained for quiescent galaxies. Since it harbors an obscured AGN, only recently our group has been able to estimate its black hole mass. I will compare such measurements with those obtained by molecular gas kinematics showing how such measurements overestimate the BH mass. Based on this I’ll show how NGC 1275 falls well outside the intrinsic dispersion of the MBH-σ* plane being 1.2 dex (in black hole mass) displaced with respect to the scaling relations. We then perform a 2D morphological decomposition analysis on Spitzer/IRAC images at 3.6 μm and find that, beyond the bright compact nucleus that domi-nates the central emission, NGC 1275 follows a de Vaucouleurs profile with no sign of significant star formation nor clear merger remnants. Nonetheless, its displacement on the MBH-L3.6,bul plane with respect to the scaling relation is as high as observed in the MBH-σ *. We explore various scenarios to interpret such behaviors, of which the most realistic one is the evolutionary pattern followed by NGC 1275 to approach the scaling relation. We indeed speculate that NGC 1275 might be a specimen for those galaxies in which the black holes adjusted to its host.


Black hole mass measurements in AGN: Polarization in broad emission lines

Luka Popovic

Co-authors:Victor Afanasiev, Djordje Savic

We present a new method for supermassive black hole (SMBH) mass measurements in Type 1 active galactic nuclei (AGN) using polarization angle across broad lines (see Afanasiev and Popovic, ApJL, 800, 35). This method gives measured masses which are in a good agreement with reverberation estimates. Additionally, we explore the possibilities and limits of this method using the STOKES ra-diative transfer code (Savic et al. 2018, A&A accepted, https://arxiv.org/abs/1801.06097) taking a dominant Keplerian motion in the broad line region (BLR). We found that method can be used for the direct SMBH mass estimation in the cases when additional to Kepler motion) radial inflows or vertical outflows are present in the BLR. Some advantages of the method will be discussed.


Session 2 Black Hole vicinity: theory and simulations

Chair: Rodrigo NemmenMonday, May 14 - Teatro Comunale

Black Hole Accretion in Low Luminosity Active Galactic Nuclei

Monika Moscibrodzka

The Event Horizon Telescope (EHT) will soon produce full polarization images of the luminous plasma surrounding the event horizon of the low accretion rate systems: Sgr A and M87. I will present new three-dimentional general relativistic magnetohydrodynamics simulations of radially extended accretion flows with jets. Simulations are postprocessed with fully polarized general rel-ativistic multiwavelength radiative transfer simulations to predict observed polarization properties and rotation measures in accretion flows of EHT main targets Sgr A/M87. The same models can be now used to model spectra and rotation measures in similar low luminosity active galactic nulcei.


Testing Theories of Gravity via BH Shadows and Modeling of Relativistic Jets

Yosuke Mizuno

Co-authors:

Ziri Younsi, Christian Fromm, Oliver Porth,Mariafelicia De Laurentis,

Hector Olivares, Heino Falcke, Michael Kramer, Luciano Rezzolla

Upcoming sub-millimetre VLBI images of Sgr A* carried out by the EHT Collaboration are expect-ed to provide critical evidence for the existence of this supermassive black hole. In this work we assess our present ability to use EHTC images to determine if they correspond to a Kerr black hole as predicted by Einstein’s theory of general relativity or to a black hole in alternative theories of gravity. To this end, we perform GRMHD simulations and use GRRT calculations to generate syn-thetic shadow images of a magnetised accretion flow onto a Kerr black hole and a non-rotating dilaton BH, which we take as a representative solution of an alternative theory of gravity. Taking into account the VLBI configuration of the 2017 EHT observation, we find that it could be difficult to distinguish between black holes from different theories of gravity, unless additional information (e.g. from orbiting pulsars or stars) were available. We will also present our theoretical modeling procedure for applying persec-scale relativistic jet dynamics.


Fully analytical solutions for Bondi accretion in galaxies with a central black hole

Luca Ciotti

Co-authors:

Silvia Pellegrini

We generalize the classical Bondi accretion theory on black holes to take into account the ef-fects of the gravitational potential of the host galaxy, and of radiation pressure in the optically thin limit. The fully analytical solution is obtained in terms of the Lambert–Euler W-function. The flow structure is found to be sensitive to the shape of the mass profile of the host galaxy. These results and the formulae that are provided, allow for a direct evaluation of all flow properties. As an application, we examine the departure from the true mass accretion rate of estimates obtained using the gas properties at various distances from the black hole, under the hypothesis of classical Bondi accretion. These results can be useful in numerical simulations.


Modelling the polarised emission from black holes on event horizon-scales

Ziri Younsi

Co-authors:

Oliver Porth, Yosuke Mizuno,Christian Fromm, Luciano Rezzolla

In the coming years, VLBI observations will be able to resolve nearby SMBH candidates, most notably Sgr A* and M87, on event horizon-scales. Promisingly, recent observations of Sgr A* with the Event Horizon Telescope (EHT) have revealed structure at this scale. In particular, the detection and measurement of the back hole “shadow” is expected to enable the existence of astrophysical black holes to be verified directly. Whilst in theory the description of this shadow is straightfor-ward, in reality its observational appearance is in no small part determined by the properties of the surrounding accretion flow, which on event horizon-scales is highly turbulent.

In this talk I introduce the new polarised general-relativistic radiative transfer (GRRT) code BHOSS, which accurately solves the equations of polarised radiative transfer in arbitrary strong-gravity en-vironments. BHOSS simultaneously conserves energy and angular momentum, as well as preserves the mathematical and physical properties of geodesic evolution (i.e., covariance, phase-space vol-ume and time-symmetry) to near-machine precision using several advanced numerical techniques and schemes. I will discuss how fully-polarised GRRT calculations coupled with GRMHD simula-tions of accretion onto black holes can be applied to create accurate, physically-realistic images of astrophysical black holes on event horizon-scales, providing insight into both their fundamental properties and the nature of their surrounding accretion flow environment.


Particle acceleration and the origin of the very high energy emissionaround black holes and relativistic jets

Elisabete de Gouveia Dal Pino

Co-authors:

Grzegorz Kowal , Luis Kadowaki,Yosuke Mizuno, Tania Elizabeth Medina-Torrejon

Particle acceleration induced by fast magnetic reconnection in the surrounds of black holes and their relativistic jets may help to solve current puzzles specially related to the interpretation of the very high energy (VHE) emission produced in AGNs and compact sources in general. In this talk, we will discuss this process in the framework of these sources, showing our recent results of an-alytical and three-dimensional numerical MHD simulations including test particles. Our MHD and general relativistic-MHD numerical simulations of accretion disk-corona systems reveal the growth of turbulence driven by MHD instabilities that lead to the development both of large scale magnet-ic loops and magnetic reconnection in the corona with fast reconnection rates around 0.13-0.17 $V_A$ (where $V_A$ is the local Alfven speed), which resemble the solar corona. This is crucial for assessing recent theories of particle acceleration and VHE emission driven by turbulence-in-duced fast magnetic reconnection around compact objects (e.g., de Gouveia Dal Pino et al. 2016 and references therein). In addition, our numerical simulations of relativistic MHD jets subject to current-driven-kink instability reveal the formation of several localized sites of fast reconnection induced by kink turbulence (with reconnection rates around 0.15 $V_A$). The injection of thou-sands of test particles in these reconnection regions of the jet result in their acceleration up to energies of several PeVs, thus demonstrating the ability of this process to accelerate particles and produce the associated VHE in these sources. Finally, in view of the results above, we will discuss how this process can explain the observed VHE luminosity-black hole mass correlation, spanning 10 orders of magnitude, which involves hundreds of non-blazar sources and microquasars.


Session 3 Black Hole vicinity: observations

Chair: Denise GabuzdaMonday, May 14 - Teatro Comunale

Imaging and Filming Black Holes with the Event Horizon Telescope

Kazunori Akiyama

The immediate vicinity of a black hole is a critical region to understand high-energy astrophysical phenomena such as accretion and jet formation. This region also may provide images imprinting general relativistic effects, including the shadow of the event horizon. With the advent of the Event Horizon Telescope (EHT), a global short-mm VLBI array, such regions have been accessible for the Galactic Center Sgr A* and the nearby radio galaxy M87. Toward photographing horizon-scales structure, significant progress has recently been made, including state-of-the-art interferometric imaging techniques mitigating many challenges in VLBI imaging. This talk will give a current over-view of the EHT as well as new interferometric imaging techniques originally developed for the EHT that can improve images of existing AGN observations with VLBI and enhance their science capabilities.


Probes of Accretion and Outflow in Low Luminosity AGN Using Millimeter Polarimetry

Geoffrey Bower

Linear polarization that is generated close to the black hole in LLAGN must propagate through a dense, magnetized accretion flow. The observed Faraday rotation is a strong constraint on the integrated accretion flow properties as has been demonstrated for 3C 84, Sgr A*, M87, and other sources. Observations can constrain the mode of accretion and the accretion rate as a function of radius inside of the Bondi radius, a region that is difficult or impossible to explore with other tech-niques. These polarimetric probes set boundary conditions for high angular resolution observa-tions of these systems that will enable us to convincingly extract fundamental accretion, outflow, and general relativistic physics.


Substantial winds from hot accretion flows confining the relativistic jet of M87

Jongho Park

Co-authors:

Kazuhiro Hada, Motoki Kino, Masanori Nakamura, Sascha Trippe

Most galaxies in the Universe are thought to harbour slow accreting or quiescent supermassive black holes at their center. Hot, geometrically thick but optically thin accretion flows might be re-sponsible for their low luminosity. One of the important properties of hot accretion flows is the presence of convection or winds, leading to decrease of mass accretion rate with decreasing dis-tance from the black hole as shown in various numerical simulations. However, it has been chal-lenging to put constraints on the accretion physics by observations due to the difficulty of resolv-ing well inside the region under the influence of black hole’s gravity. Here we report an analysis of archival radio interferometric observations of M87, one of the closest radio galaxies that possess relativistic jets. The data reveal a systematic decrease of Faraday rotation of the jet with increasing distance between ~10 and ~400 mas from the black hole. We conclude that there are substantial winds from hot accretion flows thermally confining the jet, which results in jet collimation and acceleration. This implies that the amount of matter accreted onto the black hole is significantly smaller than what was previously expected based on large scale X-ray observations and extraction of rotational energy of a spinning black hole to power the jet is at work.


Numerical methods for particle and ray tracing in general relativity

Fabio Bacchini

Co-authors:

Bart Ripperda, Lorenzo Sironi

We present our recent developments on numerical algorithms for computing photon and parti-cle trajectories in the surrounding of compact objects. Strong gravity around neutron star or black holes causes relativistic effects on the motion of massive particles and distorts light rays sue to gravitational lensing. Fast, efficient numerical methods are required in order to solve the geodes-ic equation and compute i) the black hole shadow obtained by tracing light rays from the object to a distant observer, and ii) obtain information on the dynamics of the plasma at the microscop-ic scale. Here, we present generalized algorithms capable of simulating ensembles of photons or massive particles in any 3+1 split spacetime, with the option of including external forces such as the Lorentz force. The coupling of these tools with GRMHD simulations is the key point for obtain-ing a complete view on the complex dynamics of accretion disks and jets and for comparing sim-ulations with upcoming observational results from the Event Horizon Telescope.


On the Prospects of Imaging Sagittarius A* from Space

Freek Roelofs

Co-author:

Heino Falcke

Very Long Baseline Interferometry (VLBI) at sub-millimeter waves has the potential to image the shadow of the black hole in the Galactic Center, Sagittarius A (Sgr A), and thereby test basic predictions of the theory of general relativity. In our work, the imaging prospects of a new Space VLBI mission concept have been investigated. An initial design study of the concept has been per-formed for the purpose of the Event Horizon Imager (EHI) experiment. The concept may be suita-ble for imaging Sgr A at frequencies up to ~690 GHz, which has significant advantages over per-forming Earth-based VLBI at 230 GHz. The investigated setup consists of two satellites in polar or equatorial circular Medium-Earth Orbits with slightly different radii. This setup will result in a dense spiral-shaped uv-coverage with long baselines, allowing for extremely high-resolution and high-fidelity imaging of radio sources. We simulate observations of a general relativistic magneto-hydrodynamics (GRMHD) model of the accretion flow around Sgr A for the proposed configuration and noise calculated from model system parameters. After gridding the uv-plane and averaging visibilities accumulated over multiple months of integration, images of Sgr A* with a resolution of up to 4 uas (about 8% of the shadow diameter) could be reconstructed. The black hole shadow could be measured much more precisely than with ground-based VLBI, allowing for stronger tests of General Relativity and accretion models.


Session 4Past and future legacy

Chair: Christine JonesMonday, May 14 - Teatro Comunale

Ger de Bruyn legacy work on the Perseus cluster

Michiel Brentjens


On July 9th, 2017, mere days before his 69th birthday, Prof. Ger de Bruyn passed away after a brief, aggressive illness. Throughout his career he has been interested in a wide range of topics, but Perseus A and its environment have interested him almost continuously for the past 35 years.

In this talk, I try to provide insight into his way of working and present highlights of his research on the Perseus cluster field in general, be it published, unpublished, or “work-in-progress”.

Observations of clusters and AGNs with the SKA

Melanie Johnston-Hollitt


The Square Kilometre Array (SKA) and its precursor telescopes present a significant advance in our ability to detect, characterise and ultimately understand radio emission, both from individual Active Galactic Nuclei (AGN) and the diffuse, low surface brightness emission associated with gal-axy clusters. With a total frequency coverage spanning from 50 MHz to 15 GHz, combined with deep sensitivity and unprecedented spectral resolution, these instruments together will allow us to probe radio emission across a vast region of parameter space. Such data will allow us to poten-tially characterise the full life-cycle of active galaxies, and to resolve the outstanding questions on the origin of diffuse emission in galaxy clusters. In addition, the combination of radio data with the superb multi-wavelength information expected from other next generation facilities (optical, X-ray and SZ), will allow the first comprehensive correlation of radio sources as a function of both environment and cosmic time. In this talk I will highlight some of the exciting possibilities that lay ahead in the field and show some of the most interesting current results.

The Hot Universe with XARM and Athena

Matteo Guainazzi

X-ray spectroscopy is at the eve of a true revolution. Micro-calorimeter detectors with an energy resolution of a few eV over the whole energy range between a few tens and ~10 keV are planned to be flown on two approved missions: the JAXA-led XARM (“X-ray Astronomy Recovery Mission”; launch due by the end of the Japanese Fiscal Year 2020) and the ESA L-class mission Athena (launch due in the early 2030s). The study of large-scale baryonic structures and of their evolution is at the core of the Athena science objectives: mapping the physical parameters of bound baryonic structures, the chemical and physical evolution of the inter-group and -cluster medium, and the location and kinematics of missing baryons in the hot phase of the intergalactic medium. These objectives will be pursued through an unprecedented combination of energy (~2.5 eV) and spatial resolution (~5” HEW), coupled to an effective area more than one order of magnitude larger than any other existing or planned X-ray mission. XARM will constitute a juicy appetizer: building on the solid technological heritage of the “Hitomi” soft X-ray payload, XARM aims at pioneering un-precedented high resolution X-ray spectroscopy, with four main scientific objectives: 1) Structure formation of the Universe and evolution of clusters of galaxies; 2) Circulation history of baryonic matters in the Universe; 3) Transport and circulation of energy in the Universe; 4) New science with unprecedented high resolution X-ray spectroscopy.


Observations of AGNs and the Cluster in Perseus with the Cherenkov Telescope Array

Elina Lindfors

Co-authors:

Fabio Zandanel

The current generation of imaging air cherenkov telescopes (IACTs), MAGIC, H.E.S.S. and VERI-TAS, has revolutionized our knowledge of the very high energy (VHE, defined here as >100 GeV) gamma-ray universe. In 2003 only 6 VHE gamma-ray sources were known. Today, thanks to the IACTs, over a hundred such Galactic and extragalactic sources have been discovered: supernova remnants, pulsars and pulsar wind nebulae, active galactic nuclei (AGN), radio galaxies and star-burst galaxies. Often these discoveries challenged current theoretical models and changed our understanding how these objects operate. The IACT discoveries have paved way for a highly ambi-tious new plan: the huge Cherenkov Telescope Array (CTA), which will capitalize on the power of this technique to greatly expand the scientific reach of ground-based gamma-ray telescopes. Com-pared to the existing IACT arrays, CTA will have substantially better angular resolution and energy resolution, will cover a much wider energy range, and will have up to an order of magnitude better sensitivity. In this talk I will review the prospects for observation of the AGNs NGC1275 and IC310 with CTA. They will be monitored regularly as part of the AGN Key Science program of CTA with weekly cadence for 5 years. I will also discuss the planned observations of the cluster itself. This is one of the key science programs of CTA as based on theoretical studies and hydrodynamical simulations Perseus should be the brightest cluster of galaxies in gamma-rays.


Session 5 – Radio observations of Perseus and other clusters. Chair: Melanie Johnston-Hollitt

09:00 Ruta Kale Low frequency observations of radio relics and halos: windows to the non-thermal phenomena09:30 Marie-lou Gendron-Marsolais Probing the non-thermal emission in Abell 2146 and the Perseus cluster with the JVLA10:00 Chat Hull High-dynamic-range 21 cm JVLA observations of the Perseus Cluster10:20 Coffee break

Session 6 – VLBI observations of 3C 84. Chair: Hiroshi Nagai

10:50 Gabriele Giovannini Radioastron observations of the jet launch region in 3C8411:20 Tuomas Savolainen Mini-cocoon around the parsec-scale jet in 3C8411:40 Junghwan Oh Double nuclear structure discovered in 3C8412:00 Jeffrey Hodgson 3C 84 and a solution to the “Doppler crisis”?12:20 Lunch

Session 7 – 3C 84 and the radio-gamma connection. Chair: Rodrigo Nemmen

13:50 Monica Orienti On the radio and gamma-rays connection in extragalactic relativistic jets14:20 Alastair Edge The AGN activity of NGC1275 and the ubiquity of AGN in cool core BCGs14:40 Hiroshi Nagai Inflow and Outflow in NGC127515:00 Kazuhiro Hada Observations of nearby relativistic jets with EAVN and EATING VLBI15:20 Bong Won Sohn EATING VLBI observations of 3C84, Mrk501 and TXS 0506+05615:40 Coffee break

Session 8 – Outflows and feedback (1). Chair: Elisabete de Gouveia dal Pino

16:10 Francoise Combes Molecular gas filamentary structures in galaxy clusters16:40 Raffaella Morganti Young radio jets breaking free: tracing molecular and HI fast outflows in the central regions17:00 Francesco Massaro Deciphering the large-scale environment of radio galaxies in the local Universe: where do they born, grow and die17:30 Tour of the city

Tuesday, May 15 - Grand Hotel Sofia

Session 5Radio observations of Perseus and other clusters

Chair: Melanie Johnston-HollittTuesday, May 15 - Grand Hotel Sofia

Low frequency observations of radio relics and halos: windows to the non-thermal phenomena

Ruta Kale

Clusters of galaxies are the largest gravitationally-bound systems in the Universe composed of dark matter, galaxies and diffuse intra-cluster medium (ICM). Fundamental questions on the non-thermal energy content of the ICM and its role in the evolution of embedded radio sources are still not answered. Extended radio sources associated with the ICM itself, termed as radio rel-ics and halos, are the direct probes of the non-thermal components, namely, the magnetic field and cosmic rays. The feedback at the cluster core and the merging of sub-clusters stir the ICM and drive shocks and turbulence in it. Thus galaxy clusters are ideal laboratories to study the evolu-tion of radio galaxy lobes in dense environments, the acceleration of particles at shocks and tur-bulence, and the amplification of magnetic fields. These phenomena leave imprints on the radio spectra and can be probed by detailed spatial and spectral study in radio bands. I will review the recent progress achieved and then describe the results from our low frequency observations with the Giant Metrewave Radio Telescope (GMRT) and from the new broadband system that is the up-graded GMRT (uGMRT).


Probing the non-thermal emission in Abell 2146 and the Perseus cluster with the JVLA

Marie-lou Gendron-Marsolais

Co-authors:

Marie-lou Gendron-Marsolais, Julie Hlavacek-Larrondo

Jets created from accretion onto supermassive black holes release relativistic particles on large distances. These strongly affect the intracluster medium when located in the center of a brightest cluster galaxy. On the other hand, the hierarchical merging of subclusters and groups, from which cluster originate, also generates perturbations into the intracluster medium through shocks and turbulence, constituting a potential source of reacceleration for these particles. In this talk, I will present deep multi-configuration low radio frequency observations from the Karl G. Jansky Very Large Array of two unique clusters, probing the non-thermal emission from the old particle popu-lation of the AGN outflows. Recently awarded of 550 hours of Chandra observations, Abell 2146 is one of the rare clusters undergoing a spectacular merger in the plane of the sky. Our recent deep multi-configuration JVLA 1.4 GHz observations have revealed the presence of a structure extending to 850 kpc in size, with some of the lowest radio powers detected thus far in any cluster. The flux measurements of the halo, its morphology and measurements of the dynamical state of the cluster suggest that the halo was recently created (~ 0.3 Gyr after core passage). This makes A2146 ex-tremely interesting to study, allowing us to probe the complete evolutionary stages of halos. I will also present results on 230-470 MHz JVLA observations of the Perseus cluster. Our observations of this nearby relaxed cool core cluster have revealed a multitude of new structures associated with the mini-halo, extending to hundreds of kpc in size. Its irregular morphology seems to be have been influenced both by the AGN activity and by the sloshing motion of the cluster’ gas. In addi-tion, it has a filamentary structure similar to that seen in radio relics found in merging clusters. I will also present an analysis of the several interesting head-tail radio galaxies in the Perseus clus-ter. These results both illustrate the high-quality images that can be obtained with the new JVLA at low radio-frequencies.


High-dynamic-range 21 cm JVLA observations of the Perseus Cluster

Chat Hull

Co-authors:

Rick Perley, Michael McCourt, James McBride

We present 21 cm (L-band) JVLA observations of the Perseus Cluster, comprising data from all four array configurations. The resulting image is nearly an order of magnitude deeper than any im-age made of NGC 1275 and its environs at this frequency. After editing the data in AIPS and using cutting-edge CASA tools to produce a wideband, multi-term, w-projected image, we have achieved a dynamic range of 1,000,000:1 near the center of the image (about 2 arcmin, or ~40 kpc, from the central source), and 2,500,000:1 at the edges of the ~1-degree-wide map. The original goal of this multi-year project was to search for synchrotron counterparts to the H-alpha filaments in the outskirts of NGC 1275. While we do not detect any obvious counterparts to the H-alpha filaments, there are some hints of potential synchrotron filaments in the region of interest approximately 2 arcmin from the central source. Even if this is a truly null result, we will still be able to place im-portant constraints on the star-formation properties in these enigmatic H-alpha structures that surround many BCGs. Furthermore, the sensitivity and resolution of these observations allow us to elucidate several new structures, including flocculent emission associated with the head-tail gal-axy NGC 1272, and a faint, corkscrew-like structure to the south of NGC 1275.


Session 6VLBI observations of 3C 84

Chair: Hiroshi NagaiTuesday, May 15 - Grand Hotel Sofia

Radioastron observations of the jet launch region in 3C84

Gabriele Giovannini

I will present and discuss a study on the sub-pc scale of the radio galaxy 3C84, based on space VLBI observations obtained with RadioAstron. High resolution images will allow to investigate the jet origin and its properties starting from about 100 gravitational radii. I will compare these data with results obtained with VLBA at 15 and 43 GHz and with a long time monitor of the nuclear properties of 3C84.


Mini-cocoon around the parsec-scale jet in 3C84

Tuomas Savolainen

We have used the ultra high angular resolution provided by the space-VLBI mission RadioAstron to study the structure of the radio jet in 3C84 close to its formation site. Our space-VLBI images well resolve the sub-parsec jet in transverse direction, revealing structures that are not seen in the ground-based VLBI data. At 5 GHz we detect a previously unseen low-intensity emission from a cocoon-like structure around the recently restarted, one parsec long, jet. This is to our knowledge the first time such structure is seen on parsec scale. Here we may be witnessing a newly restarted jet which has begun to fill a cavity around it with hot plasma as it carves its way through the am-bient medium of the central region of the galaxy. The pressure of the hot mini-cocoon may also provide a natural explanation for the cylindrical jet profile seen in the even higher resolution ima-ges at 22 GHz.


Double nuclear structure discovered in 3C84

Junghwan Oh

Co-authors:

Jeffrey Hodgson, Sascha Trippe,Thomas Krichbaum, Jae-Young Kim, Bindu Rani

We present a sub-parsec scale observation study of 3C84 with Global mm-VLBI Array (GMVA). For the proximity of 3C84 (z=0.018), the source is one of the best test-beds to probe the jet launch-ing mechanism, whether the jet is disk-launched (Blandford-Payne) or Black Hole launched (Bland-ford-Znajek). At 3mm, GMVA can achieve the angular resolution of 50 micro-arc-sec, which cor-responds to 550 R_S for 3C84, adopting the SMBH mass of 3.2 x 10^8 solar mass (Park & Trippe 2017). From 8 epochs of observation from 2008 to 2015, we discovered a “double” nuclear struc-ture in the core region, that is consistently appeared through all epochs. The average separation is 70 micro-arc-sec, and there is significant correlation between position angle and brightness tem-perature of those double components. Based on their high brightness temperature (10e10 K) and larger separation than estimated disk size (Morgan 2010), we concluded that the double structure is not showing the jet base but is likely to be the helical motion of the jet. The possible Black Hole locations using the jet profile, both for conical and parabolic fit, are also calculated.


3C 84 and a solution to the “Doppler crisis”?

Jeffrey Hodgson

Co-authors:

Bindu Rani, Florent Mertens


The inner parsecs of the radio core of 3C 84 is a complex region with multiple bright regions that are moving at various speeds and in many directions. Nevertheless, the apparent motions of these components are typically subluminal and yet 3C 84 is one of the brightest Gamma-ray sour-ces, having also been detected at TeV energies, leading to the question of how such high energies can be created without significant Doppler boosting. We performed a wavelet kinematic analysis of 3C 84 using high resolution 7 mm VLBA data. We find behaviour that is reminiscent of a Gam-ma-ray burst, with faster traveling shocks catching up with slower moving shocks before hitting the external medium, correlated with high energy flaring. We propose this mechanism as a solu-tion to the “Doppler crisis”.

Session 73C 84 and the radio-gamma connection

Chair: Rodrigo NemmenTuesday, May 15 - Grand Hotel Sofia

On the radio and gamma-rays connection in extragalactic relativistic jets

Monica Orienti

Relativistic jets are one of the most powerful manifestations of the release of energy produced around supermassive black holes at the centre of active galactic nuclei (AGN). Their emission is observed across the entire electromagnetic spectrum, from the radio band to gamma rays. Despite decades of efforts, many aspects of the physics of relativistic jets remain elusive. In particular, the location and the mechanisms responsible for the high-energy emission and the connection of the variability at different wavelengths are among the greatest challenges in the study of AGN. Recent high resolution radio observations of flaring objects locate the high energy emitting region down-stream the jet at parsec scale distance from the central engine. Furthermore, monitoring campaigns of the most active blazars indicate that not all the high energy flares have the same characteristics in the various energy bands, even from the same source, making the interpretation of the mecha-nism responsible for the high-energy emission not trivial.

In this talk I will discuss gamma-ray properties of blazars obtained by Fermi Large Area Tele-scope observations and the connection between radio and high-energy emission in relativistic jets, and I will focus on the importance of high angular resolution observations.


The AGN activity of NGC1275 and the ubiquity of AGN in cool core BCGs

Alastair Edge

Brightest Cluster Galaxies in cool core clusters are host to most of the powerful radio galaxies in the local Universe and almost every one has some low level AGN activity in their cores. NGC1275, as the BCG of the X-ray brightest cluster of galaxies, plays an important role as prototype of this population. NGC1275 has been monitored in the radio to gamma-ray bands over the past 40-50 years and has exhibited a cycle of AGN activity over this time. In the past 5 years it has reached a level of activity comparable to that seen in the early 1980’s. I will review this activity, what it tells us about the AGN and how NGC1275 relates to other comparable BCGs in more distant clusters.


Inflow and Outflow in NGC1275

Hiroshi Nagai

3C 84 is bright radio source associated with NGC1275. Multiple radio lobes are found on differ-ent angular scales, suggesting intermittent radio jet activities. The most recent prominent activity started in ~2005 (Nagai et al. 2010). The restarted jet extends up to ~1 pc to the south from the core and a hotspot and lobe-like structure are formed at the southern end (e.g., Nagai et al. 2014), which suggests a strong interaction between jet and ambient medium.

The intermittent jet activity of 3C 84 indirectly predicts that the accretion flow is strongly inho-mogeneous. We recently found an abrupt change of the hotspot position with an enhancement of polarized emission at millimeter wavelength by VLBI observations. We concluded this is likely to be caused by the interaction with the jet and inhomogeneous ambient medium on 1-pc scale (Nagai et al. 2017).

All these findings seem to be consistent with recent numerical simulations of giant elliptical gal-axies, which predicts that the accretion flow is dominated by chaotic cold accretion and leads to a deflection of jets and strong variation in the AGN luminosity (e.g., Gaspari et al. 2013).

I will review a series of our VLBI observations and discuss ona) jet physics of 3C 84,b) the connection between jet activity and accretion flow properties,c) high energy emission mechanism.I will also introduce our recent ALMA observations targeting molecular gas at inner <100 pc scale

to unveil the properties of cold accretion.


Observations of nearby relativistic jets with EAVN and EATING VLBI

Kazuhiro Hada

Co-authors:

EAVN and EATING VLBI Collaboration

The international collaboration of VLBI in East Asia is rapidly growing. Besides the recent suc-cessful regular operation of the KVN and VERA Array (KaVA), the effort of joint VLBI operation in EA is being expanded into China. This promotes the formation of the East Asian VLBI Network (EAVN), which offers detailed imaging of the innermost regions of relativistic jets at cm wavelengths and thus complementary to the Event Horizon Telescope operated at mm wavelengths.

A feature of the KaVA/EAVN is that the array operates for a quasi-full year. Thanks to this, the KaVA/EAVN is suitable for monitoring the relativistic jets in blazars and radio galaxies at high ca-dences. In particular, over the past few years, KaVA has intensively been monitoring the innermost regions of two important nearby radio galaxies 3C84 and M87, revealing the detailed kinematics of the jets at pc-to-subpc scales. Our monitoring of these sources is now upgrading from KaVA to EAVN by adding Chinese stations. This allows us to probe their nuclear structures in more detail.

In this contribution I will introduce the EAVN and its application to AGN observations including our recent studies on 3C84 and M87. I will also present our expanded EAVN program that collab-orates with the Italian VLBI network (including Noto), so-called the EATING VLBI, which forms a nearly global VLBI array and 3C84 is an ideal target.


EATING VLBI observations of 3C84, Mrk501 and TXS 0506+056

Bong Won Sohn

Co-authors:

Gabriele Giovannini, Kazuhiro Hada

Thanks to the approved research project between KASI and IRA/INAF DIFA/Unibo: EATING VLBI, East Asia To Italy: Nearly Global VLBI, we have the opportunity to perform observations using the Italian VLBI telecopes together with the KVN and VERA arrays (KaVA). An important point of this project is the high resolution observation of AGN using KaVA and the Italian telescopes together, i.e. Nearly Global VLBI. The addition of the Italian telescopes is necessary to increase the angular resolution to obtain detailed images. In this proposal we request two epoch observations of three AGNs with a strong interest by the Korean, Italian and Japanese research groups: 3C 84, Mrk 501 and TXS 0506+056. These powerful sources are characterized by the presence of resolved jets with a limb-brightened structure. The origin of this structure it is not yet clear and present models suggest a possible connection with the Gamma-ray emission detected from AGN. We will present the recent EATING VLBI results of these sources.


Session 8Outflows and feedback (1)

Chair: Hiroshi NagaiTuesday, May 15 - Grand Hotel Sofia

Molecular gas filamentary structures in galaxy clusters

Francoise Combes

Recent molecular line observations with ALMA and NOEMA in several Brightest Cluster Galaxies (BCG) have revealed the large-scale filamentary structure at the center of cool core clusters.

These filaments extend over 20-100kpc, they are tightly correlated with ionised gas (Halpha, [NII]) emission, and have characteristic shapes: either radial and straight, or also showing a U-turn, like a horse-shoe structure. The kinematics is quite regular and laminar, and the derived infall time is much smaller than the free-fall time. The filaments extend up to the radius where the cooling time becomes larger than the infall time. Filaments can be perturbed by the sloshing of the BCG in its cluster, and spectacular cooling wakes have been observed. Filaments tend to occur at the border of cavities driven in the X-ray gas by the AGN radio jets.


Young radio jets breaking free: tracing molecular and HI fast outflows in the central regions

Raffaella Morganti

Co-authors:

Tom Oosterloo, Robert Schulz, Clive Tadhunter

Our view of the gas and its physical conditions in the central region of AGN has been enriched by the discover of fast and massive outflows of HI and molecular gas. These outflows can be driv-en by radiation but also by the interaction of the radio plasma with the ISM. Understanding the origin and quantifying their impact requires to trace their location and derive their physical condi-tions (density of the gas, mass, mass outflow rate and kinetic energy of the outflow etc.). Particu-larly interesting has been the finding that in the first phase of their life, jet in radio galaxies can be particularly effective in driving such outflows. This crucial phase is at the heart of the idea of feedback, therefore making these objects particularly relevant for studying feedback in action.

In this talk we present the results obtained from high spatial resolution observations (VLBI and ALMA) to trace the HI and molecular gas down to scales ranging from hundred to tens of pc in young radio galaxies. We will describe the kinematics of the gas and its conditions, including the comparison with other phases of the ISM. Comparison with numerical simulation will also be pre-sented. The observations trace not only the distribution of the cold gas but they also identify an evolutionary sequence in which the radio jets may play a key role as they evolve and grow.

Outflows of up to 100 Msun/yr have been found in molecular gas while the HI is showing that the outflowing gas is clumpy as also predicted from numerical simulations.


Deciphering the large-scale environment of radio galaxies in the local Universe:where do they born, grow and die

Francesco Massaro

Co-authors:

Nuria Álvarez Crespo, Alessandro Capetti, Ranieri D. Baldi,

Riccardo Campana, Ignazio Pillitteri, Alessandro Paggi

In radio galaxies the gravitational energy of gas accreting onto supermassive black holes is ef-ficiently converted into kinetic energy of relativistic jets. In these massive elliptical galaxies the jet emission reaches distances of hundreds of thousands of light years and can exceed the total stellar emission of their hosts by orders of magnitude. It is still unclear what causes the onset of their activity and, in particular, the role played by the large-scale environment. Since the early 70’s extended radio galaxies were divided in two main classes based on radio morphology, into edge-darkened (FRI type) and edge- brightened (FRII type) radio sources. Later in the 80’s they were classified on the basis of the optical emission lines as HERGs and LERGs. These dichotomies ap-pear to be linked to the environment on Mpc scale, with FRIs and FRIIs LERGs generally inhabiting galaxy-rich environments (being members of groups or galaxy clusters) while FRIIs- HERGs tend to be more isolated. Here we present a detailed statistical analysis of the large-scale environment of well-defined and statistically homogenous samples of FRIs and FRIIs in the local Universe. This study reveals that they live in similarly rich large-scale environments and that these environments do not appear to be directly connected with their radio morphologies and/or with their accretion modes.


Session 9 – Outflows and feedback (2)- Chair: Raffaella Morganti

09:00 Anna Lia Longinotti Ultra fast outflows, and their connection to accretion and ejection processes in AGNs09:30 Silvia Pellegrini AGN feedback and the origin and fate of the hot gas in early-type galaxies09:50 Kiran Lakhchaura Cold gas in giant elliptical galaxies10:10 Yuan Li The Effects of Ram Pressure on the Cold Clouds in the Centers of Galaxy Clusters10:30 Feng Yuan Numerical study of AGN feedback in an isolated elliptical galaxy10:50 Coffee break

Session 10 – Outflows and feedback (3). Chair: Feng Yuan

11:20 Debora Sijacki AGN feedback: from z ~ 6 protoclusters to massive galaxy clusters in the local Universe11:50 William Eduardo Clavijo Bohórquez AGN and Star Formation Feedback in Active Galaxies12:10 Jeremy Lim Prodigious and Continuous Formation of Super Star Clusters from Cooled Intracluster Gas12:30 Rukmani Vijayaraghavan The Physics of Galaxy Transformation during Cluster Assembly: Clues from the Perseus Cluster12:50 William Forman Characterizing the Outburst of the Supermassive Black Hole in M8713:10 Poster presentations. Chair: Monika Moscibrodzka13:40 Lunch

15:00 Excursion and social dinner

Wednesday, May 16 - Grand Hotel Sofia


Chair: Raffaella MorgantiWednesday, May 16 - Grand Hotel Sofia

Ultra fast outflows, and their connection to accretion and ejection processes in AGNs

Anna Lia Longinotti

Ultra fast outflows, and their connection to accretion and ejection processes in AGNs

The growing evidence for energy-conserving outflows in powerful and luminous AGN supports the idea that high-velocity winds launched from the accretion disc evolve systematically after un-dergoing a shock with the ambient medium and that they are capable to expel enough mass and energy so as to produce feedback.

This talk will give an overview of recent results on AGN ultra fast outflows, with focus ongrating X-ray spectra of bright sources.I will review how UFO work, their observational properties and their relation with AGN outflows

in other bands, what is their impact on the host galaxies and their role in feedback processes.


AGN feedback and the origin and fate of the hot gas in early-type galaxies

Silvia Pellegrini

Co-authors:

Luca Ciotti, Andrea Negri, J.P. Ostriker

We present recent results for the evolution of the hot gas in isolated early-type galaxies (ETGs), obtained from two-dimensional, grid-type hydrodynamical simulations, with parsec-scale central resolution, and including a physically self-consistent treatment of the mechanical (from winds) and radiative AGN feedback. The simulations have been run for a large set of galaxy models, in or-der to compare with recent determinations of important scalings between the hot gas and galaxy properties. We will discuss general and more specific, new aspects about the origin of the hot gas, and the role of AGN feedback in determining its properties, such as: 1) the flow phase (outflow or inflow) in low and high mass ETGs; 2) the alternance of high and low radiative efficiency accretion periods, and the duty-cycle of AGN activity; 3) the coexistence of cold, inflowing, and hot, outflow-ing gas phases during nuclear outburst, and the positive and negative effect of AGN activity for star formation; 4) the good match between the X-ray luminosity (Lx) and temperature of the gas, that is fed by stellar mass losses and SN ejecta, at the rate predicted by stellar evolution, with re-cent estimates of their observed values, showing that the mass input from the stellar population is able to account for a major part (all) of the observed Lx. Thus, after z~2, AGN feedback seems very important to maintain massive ETGs in a time-averaged quasi-steady state, keeping low star formation and the black hole mass, but does not dramatically alter the gas content originating in stellar recycled material, to the point that accretion from an external (circumgalactic) medium is required. In particular, the present-day Lx cannot be used as diagnostic of the impact of AGN ac-tivity, within a scenario where the hot gas mostly originates from the stellar population.


Cold gas in giant elliptical galaxies

Kiran Lakhchaura

Co-authors:

Norbert Werner, Ming Sun

Elliptical galaxies are known to host a complex multi-phase interstellar medium covering an im-pressive temperature range of ~50-10^7 K. Based on the results obtained from the X-ray analyses of a sample of 49 nearby X-ray and optically bright elliptical galaxies, we have tried to look for the connection between the properties of the hot X-ray phase and the relatively colder H-$\alpha$ filaments, and their roles in SMBH accretion and AGN feedback cycles. We have also investigated the conditions required for the formation of cooling instabilities viz., the t$_{cool}$/t$_{ff}$ ratio, the shape of the entropy profiles and the gas motions in the central regions of the galaxies. In my talk, I will discuss some interesting results from this work.


The Effects of Ram Pressure on the Cold Clouds in the Centers of Galaxy Clusters

Yuan Li

Co-authors:

Mateusz Ruszkowski, Grant Tremblay

I will discuss the effect of ram pressure on the cold clouds in the centers of cool-core galaxy clusters, and in particular, how it reduces cloud velocity and sometimes causes an offset between the cold gas and young stars. Our work is mainly analytical, but motivated and guided by obser-vations and our simulations of an idealized Perseus-like galaxy cluster. The velocities of the mo-lecular gas in both observations and our simulations fall in the range of 100–400 km s-1, which is much lower than expected if they fall from a few tens of kiloparsecs ballistically. Our proposed explanation here is that the clouds are actually “fluffier” because they are co-moving with a warm-hot layer, and they are moving agains AGN winds at small radii. Another effect of ram pressure is that because it only affects gas but not stars, it can cause a separation between a filament and young stars that formed in the filament as they move through the ICM together. This separation has been observed in Perseus and also exists in our simulations. We show that the star-filament offset, combined with line-of-sight velocity measurements, can help determine the true motion of the cold gas, and thus distinguish between inflows and outflows.


Numerical study of AGN feedback in an isolated elliptical galaxy

Feng Yuan

Co-authors:

Jerry Ostriker, Luis Ho

This talk will be based on our most recently submitted a series of (three) papers. We investigate the effects of AGN feedback on the cosmological evolution of an isolated elliptical galaxy by per-forming two-dimensional high-resolution hydrodynamical numerical simulations. The inner bound-ary of the simulation is chosen so that the Bondi radius is resolved.

Compared to previous works, the two accretion modes, namely hot and cold, which correspond to different accretion rates and have different radiation and wind outputs, are carefully discriminated and the feedback effects by radiation and wind in each mode are taken into account. The most up-dated AGN physics, including the descriptions of radiation and wind from the hot accretion flows and wind from cold accretion disks, are adopted. Physical processes like star formation, Type Ia and Type II supernovae are taken into account. We study the AGN light curve, typical AGN lifetime, growth of the black hole mass, AGN duty-cycle, star formation, and the X-ray surface brightness of the galaxy. The respective roles of radiation and wind feedbacks are examined and it is found that they are different for different problems of interest such as AGN luminosity and star formation.



Chair: Feng YuanWednesday, May 16 - Grand Hotel Sofia

AGN feedback: from z ~ 6 protoclusters to massive galaxy clusters in the local Universe

Debora Sijacki

I this talk I will present cosmological simulations of supermassive black hole formation and growth at extremely high resolution. Using a novel method that permits to resolve gas flows around black holes all the way from large cosmological scales to the Bondi radii of black holes themselves, I will demonstrate that it is possible to estimate much more accurately gas properties in the vicinity of black holes than has been feasible before in galaxy and cosmological simulations. I will hence outline which consequences this has for the growth of z = 6 quasars and for the morphologies of their host galaxies embedded within protoclusters. I will further show results from a new series of cosmological simulations of galaxy groups and clusters in the local Universe with the aim to pin down how their properties are shaped by AGN feedback and which physical processes are key in-gredients in overcoming the cooling flow catastrophe.


AGN and Star Formation Feedback in Active Galaxies

William Eduardo Clavijo Bohórquez

Co-authors:


Large scale, weakly collimated outflows are very common in some active galaxies. In complex systems, where (SF) coexists with an active galactic nucleus (AGN), like in Seyferts, and probably dwarf galaxies and ULIRGs, it is unclear yet the relative role that the AGN and the SF play in the driving of the outflows, which frequently exhibit persistent high-speed cold structures.

In this work we present high-resolution 3D hydrodynamical and magnetohydrodynamical (MHD) numerical simulations of the formation of these outflows considering both the feedback from the AGN outflow (with opening angles between 0 and 10 degrees), and the supernovae (SNe)-driven wind (including the contributions of type I and II).

The results indicate that the presence of an AGN wind with large opening angles and of mag-netic fields substantially affect the evolution of these systems. While magnetic foelds help to pre-serve dense structures of the ISM which are swept by the SN and AGN outflows, the large-opening angle AGN wind may temporarily exhaust the gas near the nuclear region (thus extinguishing star formation) and account for the highest speed features in the wind at kpc scales, although these are not as cold as required by the observations. The SN-driven wind is the main responsible for the mass-loading of the outflows, while the AGN wind accounts for the highest speed component which reaches velocities up to a few 10,000 km/s. Finally, the implications of these findings in the framework of dwarf galaxies evolution will be also discussed.


Prodigious and Continuous Formation of Super Star Clusters from Cooled Intracluster Gas

Jeremy Lim

Co-authors:

Emily Wong, Youichi Ohyama, Thomas Broadhurst

The core of the Perseus cluster hosts a rich variety of phenomena - residual cooling of the intra-cluster gas in the form of a spectacular multiphase (ionised, atomic, and molecular) nebula, young star clusters, and bulk reheating of the intracluster gas through powerful AGN activity in the clus-ter central giant elliptical galaxy (NGC 1275). Here, we separate star clusters belonging to NGC 1275 from those likely associated with other cluster members along the line of sight: we show that NGC 1275 have formed many thousands of star clusters at an approximately constant rate over, at least, the past ~1 Gyr. Furthermore, these star clusters share the same luminosity and mass function (as well as sizes) as the even more numerous globular clusters in NGC 1275. Compris-ing therefore progenitor globular clusters, similar objects have hitherto been discovered at large numbers only in interacting or merging gas-rich galaxies, where they are referred to as super star clusters. While the globular clusters in NGC 1275 exhibit an isotropic spatial distribution, the su-per star clusters in this galaxy exhibit a complex spatial distribution that is closely related to - but not necessarily coincident with - the multiphase nebula. Formed therefore from cooled intraclus-ter gas, the less massive super star clusters may be disrupted over time to contribute to the stel-lar envelope of NGC 1275, whereas the more massive super star clusters will increase the present population of globular clusters in this galaxy by ~10%. The formation of super star clusters from cooled intracluster gas represents a previously unrecognised mode of star formation, and prom-ises insights to the stellar growth of massive cluster elliptical galaxies as well as the formation of globular clusters in the early Universe.


The Physics of Galaxy Transformation during Cluster Assembly: Clues from the Perseus Cluster

Rukmani Vijayaraghavan

Co-authors:

John Gallagher, Ralf Kotulla

Galaxies in clusters are stripped of their gas, and in the long term, this results in the cessation of star formation. Galaxies can also undergo mergers and collision with other galaxies in group and cluster environments, modifying their morphology and evolution. This can happen well before galaxies fall into clusters, in prior group environments -- a process referred to as ‘pre-processing’. In addition, merging clusters can drive shocks which accelerate galaxy transformation process; mergers can also briefly increase galaxy interaction rates. The actively assembling Perseus cluster is an ideal environment to understand how, when, and where cluster galaxies are transformed: its large-scale X-ray morphology as well as the elongated distribution of giant spirals in the center in-dicate that it recently merged with a massive system. I will present results where we have used ob-servations of interacting galaxies, measurements of heated dust emission, jellyfish galaxies, and galaxy radial velocities along with theoretical models for galaxy evolution in merging and isolated clusters to understand the assembly history of the Perseus cluster.


Characterizing the Outburst of the Supermassive Black Hole in M87

William Forman

Supermassive black holes (SMBHs) play key roles in galaxy and cluster evolution. This is most clearly seen in the “fossil record” that is imprinted in the gas rich atmospheres of early type gal-axies, groups, and clusters by powerful SMBH outbursts. I will discuss the outburst history of M87 as chronicled in its radio and X-ray images and the implications of these outbursts for heating gas rich environments. Based on a simple shock model of M87’s 12 Myr old outburst, I will present the properties of the outburst including its age, total energy, and duration.

I conclude by describing a future X-ray mission, Lynx, whose sub-arcsecond angular resolution would allow us to study the evolution of SMBHs and hot, X-ray emitting atmospheres from high redshifts to the present.


Session 11 – X-ray observations of 3C84 & AGNs. Chair: Francesco Massaro

09:00 Christopher Reynolds An X-ray view of the active galactic nucleus in NGC127509:30 Yasushi Fukazawa X-ray probing of NGC 1275 nuclear region with Hitomi, Swift, and Suzaku09:50 Francesca Panessa Jets and outflows in AGN: a radio and X-ray view10:10 Vijay Mahatma Probing the dynamics and energetics of radio galaxies10:30 Coffee break

Session 12 – X-ray observations of Perseus and other clusters. Chair: Eugene Churazov

11:00 Jeremy Sanders The deep Chandra view of the core of the Perseus cluster11:30 Takayuki Tamura High energy resolution X-ray spectroscopy of the Perseus core with Hitomi12:00 Natalia Lyskova Close-up view of an ongoing merger between the NGC 4839 group and the Coma cluster12:20 Alessandro Ignesti Thermal – non-thermal connection in radio mini halos.12:40 Lunch

Session 13 – Galaxy cluster dynamics and energetics. Chair: Irina Zhuravleva

14:10 Eugene Churazov gas structure and dynamics in galaxy clusters;14:40 Kristian Ehlert Dynamics of AGN bubbles and cosmic rays in cool core clusters15:00 Michele Doro Constraints to dark matter lifetime with deep observations of Perseus with the MAGIC telescopes15:20 Elias Koulouridis The XXL survey: The role of cluster mass in AGN activity15:40 Coffee break

Session 14 – The AGN-cluster interaction in Perseus. Chair: Francoise Combes

16:10 Irina Zhuravleva AGN-driven Perturbations in the Hot Gas in the Perseus Cluster16:40 Martin Bourne Moving mesh simulation of jet feedback in galaxy clusters17:00 Yi-Hao Chen Feedback in the Perseus Cluster: Magnetized Jets, Bubbles, and Heat Pumps17:20 Congyao Zhang Generation of Internal Waves by Buoyant Bubbles in Galaxy Clusters and Heating of Intracluster Medium17:40 Paramita Barai Intermediate-Mass Black Hole Feedback in Dwarf Galaxies: a View from Cosmological Simulations18:30 Visit and dinner at the radio telescope

Thursday, May 17 - Grand Hotel Sofia

Session 11X-ray observations of 3C84 & AGNs

Chair: Francesco MassaroThursday, May 17 - Grand Hotel Sofia

An X-ray view of the active galactic nucleus in NGC1275

Christopher Reynolds

X-ray observations probe the physics of the active galactic nucleus (AGN) in NGC1275 and its immediate circumnuclear region. Focusing on high-resolution spectral data from the 2016 Hitomi observation and late-2017 deep Chandra grating observations, I shall discuss (1) X-ray probes of the cold flows feeding the AGN; (2) constraints on wide-angle ionized outflows from the accretion disk; (3) constraints on absorption/emission by axion-like dark matter in the surrounding cluster.


X-ray probing of NGC 1275 nuclear region with Hitomi, Swift, and Suzaku

Yasushi Fukazawa

NGC 1275 has been known as a ppint-like X-ray source with a continuum and a Fe-K line. Unlike radio and GeV/TeV gamma-ray emissions, origin of X-ray emission is not yet understood; is it a jet emission like blazars or an accretion corona emission like Seyfert galaxies. X-ray emission is important to determine the SED of jet emission to constrain jet parameters and also understand the relation between accretion and jet. Here we report a recent X-ray probing of NGC 1275 nucle-ar region with Hitomi/SXS, Swift/XRT, and Suzaku/XIS. Hitomi/SXS gave the first opportunity to measure a Fe-K line of AGNs with several eV resolution. The line center is consistent with the neu-tral iron emission, and the width is constrained to be 500-1600 km/s (FWHM). This ruled out the origin of broad line region and inner accretion disk. A low-covering-fraction molecular torus or a rotating molecular disk around pc scales, illuminated by accretion corona emission, is suggested as a possible origin. For the continuum emission, Suzaku/XIS monitor observations revealed that the X-ray flux has gradually increased as the GeV gamma-ray flux. Swift/XRT showed a several-days flux increase, associated with the GeV gamma-ray flare. These results on the continuum emission suggests a contribution of jet emission to the X-ray emission. Based on the combined results of Fe-K line and continuum, we discuss some scenarios for X-ray emitting region.


Jets and outflows in AGN: a radio and X-ray view

Francesca Panessa

From recent results, a sizable fraction of AGN shows outflowing material in the X-ray (and UV) spectra. These observational facts show that the existence of outflows is becoming a widespread feature of AGN over an ample range of frequencies. The connection between X-ray-detected winds and their radio counterparts is a crucial element in pinning down the accretion-ejection mecha-nism, as it has been recently proposed that in radio-quiet quasars, the radio emission could be a by-product of the outflow activity. However, the origin of the weak and confined radio emission in the majority of AGN is still under debate. I will present a characterization of the radio emission at high resolution of nearby AGN together with cases of co-existence of jets and winds in AGN and their radio/X-ray connection.


Probing the dynamics and energetics of radio galaxies

Vijay Mahatma

Co-authors:

Martin Hardcastle, Wendy Williams,Judith Croston, Judith Ineson

Radio jets are the large-scale and extragalactic footprints of accretion onto supermassive black holes, and are suggested to be the key ingredient controlling the galaxy mass function. Of particu-lar importance is their jet power - the time-averaged energetic feedback into their environment. To determine a jet power, an accurate estimate of the age of the radio source is required, which is known to give discrepant results based on the method of calculation. Here, we attempt to resolve the spectral age/dynamical age discrepancy using high resolution radio and X-ray observations of two powerful radio galaxies, and consequently determine their source energetics. I also present some recent observations of the rare classes of remnant and restarting radio galaxies, which are crucial to inferring the global duty cycle of radio galaxies.


Session 12X-ray observations of Perseus and other clusters

Chair: Eugene ChurazovThursday, May 17 - Grand Hotel Sofia

The deep Chandra view of the core of the Perseus cluster

Jeremy Sanders

Chandra has observed the core of the Perseus cluster for over 1 Ms, revealing a wealth of struc-ture around the central AGN in this X-ray brightest cluster. We see the central radio bubbles of the nucleus displacing the X-ray emitting material and surrounded by weak shocks, cavities from pre-vious outbursts, cool filamentary X-ray emitting material, ripple-like features and cold fronts. I will present the Chandra data and new images with edge-filtering techniques applied to it, enhancing the details that we see. I will discuss what we infer about the nature of AGN feedback and cooling in Perseus and other clusters. I will also discuss how comparisons with simulations tell us about the nature of the intracluster medium.


High energy resolution X-ray spectroscopy of the Perseus core with Hitomi

Takayuki Tamura

We have developed a new X-ray observatory, Hitomi, and launched in 2016 February. This was equipped with an X-ray calorimeter with a 5 eV (FWHM) energy resolution over an energy range of 2-12 keV and over a 3’ by 3’ field of view. We observed the core of the Perseus cluster. The cluster X-ray emission peaks sharply toward the galaxy and its central active galactic nucleus, 3C 84. The AGN also develops jets and radio lobes where high-energy particles and X-ray-emitting-hot gas in-teract. Based on the X-ray spectroscopy, we measured Doppler shifts and broadening of the Fe-K emission lines. Resolved line emissions also enabled us to constrain thermal structure around the core. Furthermore, elemental abundance ratios are determined accurately. Based on these new measurements dynamical plasma structure around the central AGN will be discussed.


Close-up view of an ongoing merger between the NGC 4839 group and the Coma cluster

Natalia Lyskova

Co-authors:

Eugene Churazov, William Forman,Christine Jones, Elke Roediger, Klaus Dolag

We present XMM and Chandra observations of the massive galaxy group NGC 4839 falling into the Coma cluster core, which reveal a very complex morphology. The obtained density and tem-perature distributions of hot gas in merging components do not reveal a strong shock front ar-guing against strongly supersonic merger in the sky plane. By comparing X-ray observations with hydrodynamic simulations we constrain the velocity and geometry of the merger of the NGC 4839 group with the main cluster and discuss its implications.


Thermal – non-thermal connection in radio mini halos

Alessandro Ignesti

Co-authors:

EGianfranco Brunetti, Simona Giacintucci, Myriam Gitti


Radio observations revealed that several cool-core clusters host a mini-halo, a diffuse, steep-spec-trum radio source located in their cores. Recent studies suggested that the complex mechanisms of particle re-acceleration, which are required to justify the size of the radio-emitting region, may be related to the turbulence injected by processes like the cooling flow or the sloshing of gas in the cool core. On the other hand, it is still unclear if the central AGN may play a role in the formation of mini-halos by providing the seed of relativistic electrons for the re-acceleration mechanisms.

We perform a point-to-point comparison of the radio and the X-ray brightness of a sample of mi-ni-halos, by sampling the diffuse radio emission with a Monte-Carlo approach.

We find that mini-halos have super-linear scalings between radio and X-rays, with radio bright-ness declining more steeply than the X-ray brightness. This trend is opposite to that generally ob-served in giant radio halos, thus marking a difference in the physics of the two radio sources.

Furthermore, we discuss the possibility to infer combined constraints on the particle diffusion and acceleration efficiency in mini-halos from the scalings between radio and X-ray brightness.

Session 13Galaxy cluster dynamics and energetics

Chair: Irina ZhuravlevaThursday, May 17 - Grand Hotel Sofia

Gas structure and dynamics in galaxy clusters

Eugene Bohórquez


Large scale, weakly collimated outflows are very common in some active galaxies. In complex systems, where (SF) coexists with an active galactic nucleus (AGN), like in Seyferts, and probably dwarf galaxies and ULIRGs, it is unclear yet the relative role that the AGN and the SF play in the driving of the outflows, which frequently exhibit persistent high-speed cold structures.

In this work we present high-resolution 3D hydrodynamical and magnetohydrodynamical (MHD) numerical simulations of the formation of these outflows considering both the feedback from the AGN outflow (with opening angles between 0 and 10 degrees), and the supernovae (SNe)-driven wind (including the contributions of type I and II).

The results indicate that the presence of an AGN wind with large opening angles and of mag-netic fields substantially affect the evolution of these systems. While magnetic fields help to pre-serve dense structures of the ISM which are swept by the SN and AGN outflows, the large-opening angle AGN wind may temporarily exhaust the gas near the nuclear region (thus extinguishing star formation) and account for the highest speed features in the wind at kpc scales, although these are not as cold as required by the observations. The SN-driven wind is the main responsible for the mass-loading of the outflows, while the AGN wind accounts for the highest speed component which reaches velocities up to a few 10,000 km/s. Finally, the implications of these findings in the framework of dwarf galaxies evolution will be also discussed.

Dynamics of AGN bubbles and cosmic rays in cool core clusters

Kristian Ehlert Christoph Pfrommer, Rainer Weinberge

Co-authors:

Volker Springel, Ruediger Pakmor

Feedback processes by active galactic nuclei (AGN) in the center of clusters appear responsible for preventing large-scale cooling flows and impeding star formation. However, the detailed heat-ing mechanism remains uncertain. A promising idea relies on the dissipation of Alfven waves that are generated by streaming cosmic rays (CRs). We use 3D magnetohydrodynamical simulations with the Arepo code to study the evolution of self-consistently inflated bubbles that are filled by CRs in a turbulent cluster atmosphere. We find that a single injection event recovers the necessary CR distribution and heating rate postulated for the CR model. In addition, we verify that magnetic fields drape around the bubble, which initially confines the CRs and suppresses the formation of interface instabilities. As the bubble rises buoyantly, we notice a significant amplification of radial magnetic filaments in the wake of the bubble, which allows CRs to be conducted from the bubble to the cooling intracluster medium. Varying jet parameters, we obtain a rich and diverse set of jet and bubble morphologies ranging from FRI to FRII jets and identify jet energy as the leading order parameter. In contrast, the jet luminosity is primarily responsible for setting the Mach numbers of the shocks that are driven into the intracluster medium and produce FRI jet morphologies that are consistent with observations.


Constraints to dark matter lifetime with deep observations of Perseus with the MAGIC telescopes

Michele Doro

Co-authors:

Joaquim Palacio, Monica Vasquez Acosta, Javier Rico

WIMPs are theoretical elementary particles that interact weakly and have mass in the TeV range. They would constitute at least a part of the whole dark matter content and they arise naturaly in different Beyond the Standard Model theories. The MAGIC telescopes are sensitive to gamma rays that would be produced in the annihilation or decay of WIMPs into Standard Model particles. Such emission is expected (and potentially observable) from nearby dark matter over-densities, such as the Galactic Center, dwarf spheroidal satellite galaxies or galaxy clusters. In the last years, MAGIC has conducted an extensive observational campaign in search of dark matter signals from these objects.

In this talk we present the results of 400 hours of MAGIC observations on the Perseus galaxy cluster, the deepest observational campaign on any galaxy cluster performed so far in the very high energy range of the electromagnetic spectrum. Galaxy clusters are the largest known gravi-tationally bound structures in the Universe, with masses of ~10^15 Solar masses. There is strong evidence that galaxy clusters are dark matter dominated objects, and therefore promising targets for dark matter searches, particularly for decay signals. We apply a likelihood analysis optimized for the spectral and morphological features expected in the dark matter decay signals. We search for signs of dark matter in the mass range between 200 GeV and 20 TeV and constrain decay life-times to be between 10^25 and 10^26 s, almost one order of magnitude stronger than previous MAGIC results and among the most constraining limits on decay lifetimes for masses above 10 TeV.


The XXL survey: The role of cluster mass in AGN activity

Elias Koulouridis

I will present the results of a study of the AGN frequency in a homogeneous and well studied sample of 167 bona-fide X-ray galaxy clusters 0.1< z<0.5 from the XXL survey, from the cluster core to the outskirts. The results can provide evidence of the physical mechanisms that drive AGN and galaxy evolution within clusters, testing the efficacy of ram pressure gas stripping and galaxy merging in dense environments. The XXL cluster sample mostly comprises poor and moderate-ly rich structures (M=1e13-4e14 Mo), a poorly studied population that bridges the gap between optically selected groups and massive X-ray selected clusters. Our aim is to statistically study the demographics of cluster AGNs as a function of cluster mass, and host galaxy position. We detect a statistically significant excess of X-ray AGN between r500 and 2r500 when compared to the field density and to the other annuli, implying possible black hole triggering in the outskirts be-fore entering the hot intra-cluster medium (ICM). The excess sharply decreases towards the clus-ter centre, where the AGN density drops towards the field value. The latter indicates that the AGN suppression mechanism in our sample of XXL clusters is less effective than the one observed in more massive clusters. Our results support the idea that the interactions between the hot ICM and in-falling cluster galaxies is an effective gas stripping mechanism. The ‘cluster mass - AGN densi-ty’ anti-correlation provides evidence of how deeper gravitational potential lead to more effective AGN suppression. On the other hand, AGN triggering is evident at the outskirts, supporting previ-ous studies which also reported enhanced galaxy merging. These galaxies should still retain their gas reservoir, before entering the central cluster region.


Session 14The AGN-cluster interaction in Perseus

Chair: Francoise CombesThursday, May 17 - Grand Hotel Sofia

AGN-driven Perturbations in the Hot Gas in the Perseus Cluster

Irina Zhuravleva

Co-authors:

Eugene Churazov, Patricia Arevalo,Alexander Schekochihin, Steven Allen, Willian Forman

Deep Chandra observations of the core of the Perseus cluster revealed a wealth of structures in the hot gas associated with AGN activity (e.g. shocks, bubbles of relativistic plasma, turbulence, sloshing motions). Although individual bright structures are well-studied, the nature and energetics of the less prominent perturbations that occupy the bulk of the core volume are not understood. Measuring statistical properties (e.g. power spectrum) of gas emissivity fluctuations imprinted in the soft- and hard-band X-ray images, we measured the equation of state of gas perturbations in the whole cluster core. In my talk, I will discuss these measurements and show that about 80 per cent of the total variance of perturbations have isobaric nature, i.e. consistent with subsonic dis-placements of the gas and gas cooling, and only about 5 per cent of the variance is associated with shocks and sound waves. Such energy partition supports the scenario of gentle AGN feedback. Using a statistical linear relation between the amplitude of density fluctuations and velocity, we measured the velocity power spectrum of gas motions and showed that turbulent heating rate is consistent with the radiative cooling rate at each radius within the Perseus core. Remarkably, di-rect Hitomi observations are consistent with this result. This suggests that turbulence may play an important role in the cooling-heating balance of the cluster.


Moving mesh simulation of jet feedback in galaxy clusters

Martin Bourne

Co-authors:

Debora Sijacki

AGN feedback plays an important role in galaxy evolution, particularly in galaxy clusters, such as Perseus. One channel of feedback occurs through powerful jets that inflate large cavities of relativistic plasma and is critical in regulating the heating of the intracluster medium (ICM). How-ever, how the mechanical energy of the jets is isotropically communicated to the ICM remains an open question. Given the large dynamic range in the mechanisms governing AGN feedback and its interaction with galaxy clusters, attempting to simulate all of the relevant scales is a formidable task. I will present a recently developed scheme for modelling jet feedback in the moving-mesh code AREPO. The method relies upon a super-Lagrangian refinement technique that provides vast-ly improved resolution close to the SMBH while still allowing courser resolution on larger scales. The technique allows us to launch a high resolution jet on relatively small scales and capture its propagation and evolution to large distances (~100 kpc), the lobes inflation process and its inter-action with the ICM, including turbulence generation (or lack thereof). Finally (and perhaps most importantly), I will discuss how the gas kinematics in our simulated clusters compare with those measure through Hitomi observations of the Perseus cluster and outline the conclusions we can draw from such comparisons.


Feedback in the Perseus Cluster: Magnetized Jets, Bubbles, and Heat Pump

Yi-Hao Chen

Co-authors:

Sebastian Heinz

Radio-mode feedback from relativistic jets is one of the prominent heating mechanisms in clus-ters of galaxies. We present high-resolution MHD simulations of jets with dynamically important magnetic fields, interacting with an environment modeled to represent the Perseus cluster. We show that the topology of the magnetic field affects the collimation as well as the stability of the jets, with important implications for the morphologies of the radio lobes and X-ray cavities. Us-ing an implicit treatment to solve the particle transport equation, we follow the cooling history of the synchrotron-emitting plasma to generate synthetic radio maps that show realistic spectral index distributions and polarimetry with distinct polarization features due to different magnetic field topologies of the jets. We investigate the thermodynamics of the ICM due to the gas motion triggered by the action of the jets and show that cool and low entropy gas is lifted efficiently in the wake of the inflating radio lobe. The redistribution of entropy suggests that heat conduction can play a more significant role in the thermal evolution of the cluster core in the presence of jets, which act effectively as a heat pump, thus heating the ICM more efficiently than jets would by themselves in an isentropic cluster. We discuss the effect of jet activity on metal-redistribution in clusters.


Generation of Internal Waves by Buoyant Bubbles in Galaxy Clustersand Heating of Intracluster Medium

Congyao Zhang

Co-authors:

Alexander Schekochihin, Eugene Churazov

Buoyant bubbles of relativistic plasma in cluster cores plausibly play a key role in conveying the energy from a supermassive black hole to the intracluster medium (ICM) - the process known as radio mode AGN feedback. Energy conservation guarantees that a bubble loses most of its energy to the ICM after crossing several pressure scale heights. However, actual processes responsible for

transferring the energy to the ICM are still being debated. One attractive possibility is the ex-citation of internal waves, which are trapped in the cluster’s core and eventually dissipate. Here we show that a sufficient condition for efficient excitation of these waves in stratified cluster at-mospheres is flattening of the bubbles in the radial direction. In our numerical simulations, we model the bubbles phenomenologically as rigid bodies buoyantly rising in the stratified cluster atmosphere. We find that the terminal velocities of the flattened bubbles are small enough so that the Froude number Fr<1. The effects of stratification make the dominant contribution to the total drag force balancing the buoyancy force. In particular, clear signs of internal waves are seen in the simulations. These waves propagate horizontally and downwards from the rising bubble, spread-ing their energy over large volumes of the ICM. If our findings are scaled to the conditions of the Perseus cluster, the expected terminal velocity is ~ 100-200 km/s near the cluster cores, which is in broad agreement with direct measurements by the Hitomi satellite.


Intermediate-Mass Black Hole Feedback in Dwarf Galaxies: a View from Cosmological Simulations

Paramita Barai

Co-authors:


Black holes are usually observed to be of stellar-mass or supermassive. By natural extension, there should be a population of Intermediate-Mass Black Holes (IMBHs: with mass between 100 to 10^6 Msun) in the Universe; which has started to been observed. An exciting claim has been made recently by Silk, J. (2017, ApJ, 839, L13): that there can be IMBHs at the centers of essentially all old Dwarf Galaxies. Early feedback by IMBHs in gas-rich dwarf galaxies at z=5-8, can potentially solve multiple dwarf galaxy problems (e.g. core-cusp, number) within the A-cold-dark-matter cos-mology.

We are performing Cosmological Hydrodynamical Simulations to test the case for IMBHs in Dwarf Galaxies. Our simulations employ the 3D TreePM SPH code GADGET-3, and include metal cooling, star formation, chemical enrichment, supernova feedback, AGN accretion and feedback (Barai, P.et al. 2016, MNRAS, 461, 1548). We are simulating small (2 Mpc)^3 cosmological volumes with peri-odic boundary conditions, starting from z=100. Black holes of mass 1000 Msun are seeded inside halos when they reach a mass of 10^7 Msun. The black holes grow by accretion of gas from their surroundings and by merger with other black holes, and consequently eject feedback energy. We analyze the simulation output in post-processing to study the growth of the first IMBHs, and their impact on star-formation.

Our conclusions, based on numerical simulation results, support the phenomenological ideas made by Silk(2017). IMBHs at the centers of dwarf galaxies can be a strong source of feedback to quench star-formation and generate outflows. At the same time, these IMBHs form the missing link between stellar-mass and supermassive BHs.


Session 15 – Gamma-ray observations of 3C 84 and other AGNs (1). Chair: Paola Grandi

09:00 Eleonora Torresi Gamma-ray emission in radio galaxies, from MeV to TeV09:30 Rodrigo Nemmen Searching for QPOs in the gamma-ray emission of NGC 127509:50 Narek Sahakyan Rapid Gamma-Ray Variability of NGC 127510:10 Giulia Migliori Young radio sources in gamma-rays: 3C 84 and PKS 1718-64910:30 Coffee break

Session 16 – Gamma-ray observations of 3C 84 and other AGNs (2). Chair: Monica Orienti

11:00 Rocco Lico Exploring the the radio and GeV-TeV gamma-ray connection in the different blazar sub-classes11:20 Dorit Glawion IC 310: Lightning from the Black Hole?11:40 Juan Carlos Rodriguez Ramirez Very High Energy and Neutrino Emission from NGC1275 and IC310: GRMHD Simulations of Magnetic Reconnection and Radiative Transfer/Particle Calculations.12:00 Lunch

Session 17 – Magnetic fields and relativistic jets. Chair: Keiichi Asada

13:30 Denise Gabuzda Magnetic fields in relativistic jets14:00 Elena Nokhrina The correlation between magnetic flux and jet power14:20 Andrzej Zdziarski Discrepancies in estimates of the blazar jet power; Extended-jet models of broad-band spectra of BL Lacs14:40 Xinwu Cao Why only a small fraction of quasars are radio loud?15:00 Coffee break

Session 18 – Simulations of jets and winds. Chair: Gabriele Giovannini

15:30 Alexander Tchekhovskoy Black hole accretion and relativistic jets16:00 Sergey Bogovalov Ratio of kinetic-to-bolometric luminosity at the “cold” disk accretion onto black holes16:20 Izak van der Westhuizen Monte-Carlo emission modelling of hydrodynamic AGN jet simulations16:40 Bhargav Vaidya Hybrid Framework for modelling non-thermal emission and particle acceleration from magnetised relativistic flows.17:00 Defu Bu Wind production from central black hole accretion flow and region beyond AGNs17:20 Concluding remarks

Friday, May 18 - Grand Hotel Sofia

Session 15Gamma-ray observations of 3C 84 and other AGNs (1)

Chair: Paola GrandiFriday, May 18 - Grand Hotel Sofia

Gamma-ray emission in radio galaxies, from MeV to TeV

Eleonora Torresi


Radio galaxies have recently arisen as a new class of high and very-high energy emitters mainly thanks to observations with the Large Area Telescope on board the Fermi Gamma-ray Space Tel-escope and the current Imaging Atmospheric Cherenkov Telescopes. The favourable orientation of their jets relative to us makes radio galaxies extremely relevant for addressing important open questions such as: (i) revealing the jet structure complexity, (ii) localising the emitting region(s) of high and very-high energy radiation and (iii) understanding the physical processes producing these photons. I will present an overview of the main results on gamma-ray emission studies of ra-dio galaxies from MeV to TeV energies, evaluating the impact of future CTA observations as well. These results will be also discussed within the context of radio galaxies as possible multi-messen-ger sources.

Searching for QPOs in the gamma-ray emission of NGC 1275

Rodrigo Nemmen

Co-authors:

Vasileios Paschalidis, Raniere de Menezes

The centers of galaxy clusters are agitated places where many galaxy mergers occur leading to the formation of the central galaxy. NGC 1275—the central radio galaxy in the Perseus cluster—is no exception: it may have undergone a merger with another galaxy as recently as 300 Myrs ago. NGC1275 is therefore an interesting target for supermassive binary black hole searches. Impor-tantly, NGC 1275 is the brightest gamma-ray emitter among nearby AGN. Here we report an anal-ysis of the gamma-ray variability of NGC1275 observed continuously with the Fermi Large Area Telescope over the last nine years. We applied several time-domain analysis methods including wavelets, Fourier and Bayesian methods, in order to search for quasi-periodic oscillations (QPO) in the gamma-ray emission. We found weak evidence for any periodicity, with the LAT light-curve being consistent with a power-law or red spectral noise. We discuss the perspectives for similar gamma-ray QPO searches in other AGNs.


Rapid Gamma-Ray Variability of NGC 1275

Narek Sahakyan

Co-authors:

Vardan Baghmanyan, Sargis Gasparyan

We will present a detailed analysis of the γ-ray light curve of NGC 1275 using the Fermi LAT data accumulated during 2008-2017. Major γ-ray flares were observed in 2015 October and 2016 De-cember/2017 January when the source reached a daily peak flux of (2.21+/- 0.26) × 10^-6 photon cm^-2 s^-1, achieving a flux of (3.48+/- 0.87)× 10^-6 photon cm^-2 s^-1 within 3 hr, which corre-sponds to an apparent isotropic γ-ray luminosity of ≈ 3.84× 10^45 erg s^-1. The most rapid flare had an e-folding time as short as 1.21+/- 0.22 hr, which had never been previously observed for any radio galaxy in γ-ray band. Also, γ-ray spectral changes were observed during these flares: in the flux versus photon index plane, the spectral evolution follows correspondingly a counterclock-wise and a clockwise loop inferred from the light curve generated by an adaptive binning meth-od. On 2016 December 30 and 2017 January 1 the X-ray photon index softened (Γ_x≈ 1.75-1.77) and the flux increased nearly ~3 times as compared with the quiet state. The observed hour-scale variability suggests a very compact emission region (R_γ ≤5.22× 10^14 (δ /4) cm), implying that the observed emission is most likely produced in the subparsec-scale jet if the entire jet width is responsible for the emission. During the active periods, the γ-ray photon index hardened, shifting the peak of the high-energy spectral component to > GeV, making it difficult to explain the ob-served X-ray and γ-ray data in the standard one-zone synchrotron self-Compton model.


Young radio sources in gamma-rays: 3C 84 and PKS 1718-649

Giulia Migliori

According to theoretical predictions, gamma-ray emission could be produced in the jets and lobes of young extragalactic radio sources. However so far, young radio sources remain elusive in gamma-rays, with only a handful of detections (or candidates) reported with Fermi-LAT. Being a re-started radio source, 3C 84, which belongs to the sample of misaligned AGNs in the third Fermi Gamma-ray LAT Catalog (3FGL), can be considered at the same time old and young. I will discuss 3C 84 and other young sources/gamma-ray candidates, focusing in particular on our gamma-ray study of the Compact Symmetric Object (CSO) PKS 1718-649.


Session 16Gamma-ray observations of 3C 84 and other AGNs (2)

Chair: Monica OrientiFriday, May 18 - Grand Hotel Sofia

Exploring the the radio and GeV-TeV gamma-ray connection in the different blazar sub-classes

Rocco Lico

Co-authors:

Marcello Giroletti, Monica Orienti, Luigi Costamante,Vasiliki Pavlidou, Filippo D’Ammando, Fabrizio Tavecchio

The Fermi-LAT revealed that blazars dominate the census of the gamma-ray sky, and a significant correlation was found between radio and gamma-ray emission in the 0.1-100 GeV energy range. However, the possible connection between radio and very high energy (VHE, E>0.1 TeV) emission still remains elusive, owing to the lack of a homogeneous VHE sky coverage.

With this work we aim to quantify and assess the significance of a possible connection between the radio emission on parsec scale measured by the very long baseline interferometry and GeV-TeV gamma-ray emission in blazars, which is a central issue for understanding the blazar physics. We use two large and unbiased AGN samples extracted from the 1FHL and 2FHL catalogs, and for comparison, we perform the same analysis by using the 3FGL 0.1-300 GeV gamma-ray energy flux.

Overall, the radio and gamma-ray emission above 10 GeV turns out to be uncorrelated for all the blazar sub-classes with the exception of high synchrotron peaked objects. Conversely, when 0.1-300 GeV gamma-ray energies are considered, a strong and significant correlation is found for all of the blazar sub-classes. We interpret these results within the context of the blazar spectral energy distribution properties.


IC 310: Lightning from the Black Hole?

Dorit Glawion

Since the discovery of gamma-ray emission from the active galaxy IC 310 in 2010, this object and the related observational results are an on-going matter of debate. At TeV energies IC 310 showed an impressive bright gamma-ray flare with ultra-fast flux variability on time scales down to a few minutes. The flickering and the hard TeV spectrum ranging over two decades in energy as well as the viewing angle between 10 and 20 degrees, as inferred from radio observations were shown to be inconsistent with the standard shock-in-jet model. Instead, alternative interpretations such as the magnetospheric model were suggested to explain the acceleration of particles and the production of gamma rays.

Here, we will review observations from radio frequencies up to the very high energy regime as well as possible theoretical explanations for the object IC 310 and the observed „black hole light-ning“.


Very High Energy and Neutrino Emission from NGC1275 and IC310: GRMHD Simulations of Magnetic Reconnection and Radiative Transfer/Particle Calculations

Juan Carlos Rodriguez Ramirez

Co-authors:

Elisabete Maria de Gouveia Dal Pino, Rafael Alves Batista, Luis Henrique Kadowaki

Very high energy (VHE) radiation and possibly also neutrinos fluxes have been detected from the NGC1275 and IC310 radio galaxies in the Perseus cluster, and theoretical models involving leptonic and hadronic processes have been proposed to reproduce the measured spectral energy distributions (SEDs).

Most of these works consider cosmic ray (CR) acceleration in shocks at a relativistic jet pointing to the line of sight as the mechanism that generates the VHE. However, other possibilities involv-ing particle acceleration by magnetic reconnection in the accretion disc-coronal plasma have not been exhaustively explored yet.

We here consider this process in the core region of accreting black holes (BHs) and compute nu-merically the resulting VHE and neutrino fluxes produced by hadronic and leptonic processes.

We first perform general relativistic magnetohydrodynamical (GRMHD) simulations of BH ac-cretion disk-coroan seeking for strong magnetic reconnection events and chose the appropriate environment profiles for our emission calculations. We then perform leptonic radiative transfer calculations on the chosen background snapshots in order to obtain the photon field that will be the target for photo-hadronic interactions. Then, we inject high energy protons (according to the characteristics of the plasma in the reconnection regions) and compute photon and neutrino flux-es stemming from the interactions of the injected protons with the background photon and mag-netic fields (using the CRPropa3 code).

We compute the resulting SEDs of gamma-rays and neutrinos in a self-consistent manner and compare our results with the measured spectra of the NGC1275 and IC310. Based on our results, we finally discuss the plausibility of magnetic reconnection as the operating mechanism for VHE emission on these radio galaxies.


Session 17Magnetic fields and relativistic jets

Chair: Keiichi AsadaFriday, May 18 - Grand Hotel Sofia

Magnetic fields in relativistic jets

Denise Gabuzda


An abundance of information about the magnetic (B) fields of relativistic AGN jets has been ob-tained through polarization-sensitive radio observations made on a wide range of scales, from the parsec scales probed by Very Long Baseline Interferometry to the kiloparsec scales probed by in-struments such as the the Jansky Very Large Array and e-MERLIN. The observed radio emission is synchrotron radiation, for which the linear polarization angles in optically thin regions of the jets are orthogonal to the local synchrotron B fields.

The characteristic B field structures observed for these jets will be described. A key question is whether B field structures observed in particular AGN jets come about primarily due to “global” ef-fects such as the intrinsic B field of the jet itself, which is expected to be helical, or local phenom-ena such as shocks, turbulence and shear. Observational criteria that can be used to try to distin-guish between various possible origins for observed B field structures will be described. There is now considerable evidence that the relativistic jets of AGNs do indeed carry helical B fields, with the observed polarization also sometimes appreciably influenced by local effects. Patterns seen in the helical B field components, indicated for example by Faraday rotation observations, provide unique information about the processes involved in the generation of these helical B fields.

The correlation between magnetic flux and jet power

Elena Nokhrina

Magnetic field threading a black hole ergosphere is believed to play the key role in both driving the powerful relativistic jets observed in active galactic nuclei and extracting the rotational energy from a black hole via Blandford-Znajek process. The magnitude of magnetic field and the magnetic flux in the vicinity of a central black hole is predicted by theoretical models. On the other hand, the magnetic field in a jet can be estimated through measurements of either the core shift effect or the brightness temperature. In both cases the obtained magnetic field is in the radiating domain, so its direct application to the calculation of the magnetic flux needs some theoretical assumptions. We address the issue of estimating the magnetic flux contained in a jet using the measurements of a core shift effect and of a brightness temperature for the jets, directed almost at the observer. The accurate account for the jet transversal structure allow us to express the magnetic flux through the observed values and an unknown rotation rate of magnetic surfaces. If we assume the sources are in a magnetically arrested disk state, the lower limit for the rotation rate can be obtained. On the other hand, the flux estimate may be tested against the total jet power predicted by the elec-tromagnetic energy extraction model. The resultant expression for power depends logarithmically weakly on an unknown rotation rate. We test our model on 36 observed AGN jets. We show that the total jet power estimated through the magnetic flux is in good agreement with the observed power. Comparing the obtained magnetic field with the magnetic flux given by the MAD model we either obtain the extremely slow rotation rates, or we conclude that this is an indication that the majority of the sources considered are not in the magnetically arrested disk state.


Discrepancies in estimates of the blazar jet powerExtended-jet models of broad-band spectra of BL Lacs

Andrzej Zdziarski

Co-authors:

Patryk Pjanka, Marek Sikora, Lukasz Stawarz


In the first part of this talk, I will present and discuss the results of measurements of the jet power in blazars by three different methods, based on radio lobes, spectral fitting and core shifts. The found strong discrepancies between the first vs. the last two can be reconciled if jets contain, in addition to ions, electron-positron pairs.

In the second part, I will present a new model for broad-band spectra of BL Lac objects. Usual modelling of both broad-band and high-energy emission of blazars is by a one-zone moving-blob model. Those fits do nor reproduce the radio emission, which is postulated to be from a different component. However, the radio spectra usually join smoothly on to the IR ones. We have devel-oped an analytical model for calculating the broad-band, radio to VHE gamma-rays, spectra of BL Lac objects. In this model, we calculate partially self-absorbed and optically thin synchrotron and self-Compton emission from an extended jet, taking into account electron energy losses as well as their transport along the jet. As an example, we apply this model and obtain a good fit to the quiescent spectrum of Mrk 421.

Why only a small fraction of quasars are radio loud?

Xinwu Cao

It is still a mystery why only a small fraction of active galactic nuclei (AGNs) contain relativistic jets. A strong magnetic field is a necessary ingredient for jet formation, however, the advection of the external field in a geometrically thin disk is inefficient. Gas with a small angular velocity may fall from the Bondi radius R_B nearly freely to the circularization radius R_c, and a thin accretion disk is formed within R_c. We suggest that the external magnetic field is substantially enhanced in this region, and the magnetic field at R_c can be sufficiently strong to drive outflows from the disk if the angular velocity of the gas is low at R_B. The magnetic field is efficiently dragged in the disk, because most angular momentum of the disk is removed by the outflows that lead to a signif-icantly high radial velocity. The strong magnetic field formed in this way may accelerate jets in the region near the black hole, either by the Blandford-Payne or/and Blandford-Znajek mechanisms. We suggest that the radio dichotomy of AGNs predominantly originates from the angular velocity of the circumnuclear gas. An AGN will appear as a radio-loud (RL) one if the angular velocity of the circumnuclear gas is lower than a critical value at the Bondi radius, otherwise, it will appear as a radio-quiet (RQ) AGN. This is supported by the observations that RL nuclei are invariably hosted by core galaxies. Our model suggests that the mass growth of the black holes in RL quasars is much faster than that in RQ quasars with the same luminosity, which is consistent with the fact that the massive black holes in RL quasars are systematically a few times heavier than those in their RQ counterparts.


Session 18Simulations of jets and winds

Chair: Gabriele GiovanniniFriday, May 18 - Grand Hotel Sofia

Black hole accretion and relativistic jets

Alexander Tchekhovskoy

Black holes are responsible for a wide variety of astrophysical phenomena. They devour stars, eject relativistic jets, affect star formation and galaxy evolution, and enrich the Universe with heavy elements. I will discuss how global general relativistic magnetized fluid dynamics numerical simu-lations allow us to use this activity to quantitatively probe strong-field gravity and constrain black hole physics in various astrophysical contexts.


Ratio of kinetic-to-bolometric luminosity at the “cold” disk accretion onto black holes

Sergey Bogovalov

Co-authors:

Ivan Tronin

Disk accretion onto black holes is accompanied by ejection of highly collimated jets. In many AGNs the kinetic luminosity of jets well exceeds the bolometric luminosity of disks. We argue that this happens in the case when the wind from the disk carries out almost all the angular momen-tum and gravitational energy of the accreted material. In this case the bolometric luminosity of the disk appears much less the bolometric luminosty in the conventional Shakura-Sunyaev theory of the thick accretion disks. This regime is called as “cold” accretion. We present results of the nu-merical simulation of the “cold” accretion. But the main objective of the work is estimation of the ratio of the kinetic-to-bolometric luminosity of the disks at the accretion onto black holes. All the basic characteristics of the disks in the regime of “cold” accretion have been calculated in frame-works of the theory of $\alpha$ disks by Shakura \& Sunyaev. The main parameter which define this value is the ratio of magnetic field pressure inside the disk to the magnetic field pressure at the base of the wind from the disk. The dependence of this parameter on the accretion rate has been estimated empirically from Fundamental plane of black holes. Application of the obtained equations to the jets from M87 demonstrates good agreement with observations. In the case of Sgr A* the obtained equations allow us to estimate the kinetic energy flux from the disk around galactic black hole.


Monte-Carlo emission modelling of hydrodynamic AGN jet simulations

Izak van der Westhuizen

Co-authors:

Brian van Soelen, Pieter Meintjes

Radio-loud Active Galactic Nuclei (AGN) emit variable emission over most of the electromagnetic spectrum. The spectral energy distribution (SED) of these sources show dominant components of synchrotron and Inverse-Compton emission produced within relativistic jets originating from the nucleus. To model the large scale dynamics of these jets, relativistic hydrodynamic (RHD) simu-lations can be used. In this study we present two such simulations of relativistic jets. The PLUTO RHD code was used to investigate the parameters required to reproduce structures consistent with both FR I and FRII jets. In the first simulation a Lorentz factor of 10 and supersonic flow of Mach 300 was chosen, while for the second simulation a Lorentz factor of 1.0014 with a supersonic flow of Mach 4 was used. Over similar distances scales the first case shows a well collimated beam with a strong shock at the interface between the jet and ambient medium while the second case shows a less stable beam and larger cocoon. To determine whether the physical structures simulated by the PLUTO code is consistent with the observable FR I/II structures, the synchrotron emission has been calculated to produce radio maps at a single frequency of 1.5 GHz. The first case showed emission structures similar to that of FR II radio galaxies with hotspots at the head of the jet while the second case was more consistent to that of an FR I source with the highest intensity occurring within the beam of the jet. Calculating the multi-wavelength (radio - gamma-ray) SED of a synchro-tron self-Compton model for these simulations is very computationally intensive. We are, there-fore, currently investigating the use of Monte-Carlo codes in conjunction with the hydrodynamical simulations. These codes can provide us with a time-dependent, multi-zone emission model to compare to observations. Our progress thus far is also presented.


Hybrid Framework for modelling non-thermal emission and particle acceleration from magnetised relativistic flows

Bhargav Vaidya

Co-authors:

Andrea Mignone, Gianluigi Bodo,Paola Rossi, Silvano Massaglia

Magnetised and relativistic large scale flows in form of jets are a common observational feature seen for example in active galactic nuclei (AGNs), Gamma-ray bursts and micro-quasars.The dominant emission is originated by non-thermal processes from high energy particles.Multi-wavelength observations covering a wide spectrum from Radio wavelengths to TeV Gamma ray emission provides valuable insights into the micro-physical processes that occur in jets and lead to the observed radiation.The length scales associated with these micro-physical processes are many orders of magnitude smaller than the physical jet scales that can range up to few tens of kilo-parsec.Connecting a bridge between these scales poses a serious challenge to theoretical modelling of the emission from AGN jets. In this talk, I will present our recent hybrid numerical framework de-veloped for PLUTO code to quantitatively connect such disjoint scales by simulating multi-dimen-sional flow pattern treating small-scale plasma processes in a sub-grid manner.In particular, I will emphasise on the role of magnetised shocks, commonly observed in AGN jets, in accelerating particles and its influence in governing the emission and polarisation due to non-thermal processes.


Wind production from central black hole accretion flow and region beyond AGNs

Defu Bu

Co-authors:

Feng Yuan

Observations of Low-luminosity AGNs (LLAGNs) show that wind is present. I will talk about ob-servations, theory and numerical simulations of wind generation from LLAGNs. In LLAGNs, wind can be driven by the combination of magnetic pressure gradient, gas pressure gradient and cen-trifugal forces. I will also talk about wind generation beyond AGNs. In the region outside of AGNs, the gas can be irradiated and heated by the central X-ray photons and wind can be thermally driv-en. The possible application of wind in AGN feedback study is also discussed.


Symposium concluding remarks

Friday, May 18 - Grand Hotel Sofia

Social Programme

May, 13 - 18 - IAUS 342

– SUNDAY, MAY 13.Welcome cocktail at Grand Hotel Sofia. It will be open to all participants and accompanying per-sons free of cost.

– MONDAY, MAY 14.After the science sessions at the Tina di Lorenzo theatre, the company “Il cuore di Argante” will perform a stage show based on the myth of Perseus. It will be a short emotional play suitable for an international audience. It will be open to all participants and accompanying persons.

– TUESDAY, MAY 15. A tour of the city visiting Baroque palaces in historic downtown Noto. The cost for accompanying persons will be 5€. At 9pm there will be a public lecture in Italian by Dr. Stefania Varano: you are welcome to attend it at CUMO (https://goo.gl/maps/PfuSCnSuoEE2), yet note this will be mainly an event organised for the local general public

– WEDNESDAY. MAY 16. Social trip and dinner. At the time of writing (May 4th) we are considering two options for the trip. One tour will go to historic Syracuse, with a visit to San John’s catacombs from the fourth century AD, and to the island of Ortigia, the historical nucleus of the city, where walking through the city streets you can admire a small part of the archaeological and architectural heritage of what was the birthplace of Archimedes. The other option is to relax on San Lorenzo beach, about 20 km from Noto, also with a chance to visit the Villa Romana del Tellaro on the way. Based on the preferences expressed by participants, we will later decide the final program (ie we may keep both trips in pa

https://goo.gl/maps/PfuSCnSuoEE2

rallel or only make one). After the trip, we will go directly for the social dinner at Dafne restaurant. The cost for accompanying persons will be 50€ for trip and dinner together.

– THURSDAY, MAY 17. After the science sessions, we will visit the INAF 32m radio telescope near Noto and have a dinner with traditional dishes there. The cost for accompanying persons will be 20€.

– FRIDAY, MAY 18, AND LATER. At the end of the conference on Friday afternoon, the week end of the Infiorata will begin in Noto: a cascade of thousands of flowers, expertly arranged on the road, making the vision of baroque city full of scents and colours. For trips on Saturday and Sunday, feel free to get in touch with Shou-gun agency ([email protected]) who can organise trips for you (at your own cost). The area is rich in history (from ancient Greek and Roman ruins and theatres, to baroque cities), nature (beautiful coast, and mount Etna, the highest active volcano in Europe topping 3000m), food-and-wine in ne-arby villages.

Infiorata di Noto

May, 18 - 20 - IAUS 342

The Infiorata di Noto, one of the most colourful festivals anywhere in the world, takes place every year over the third weekend of May.For two and a half days, Via Nicolaci, one of Noto's many delightful streets, is taken over by local and foreign artists who work together on a set theme to create a kaleidoscopic carpet of petal mosaics using flowers grown especially for the event.

They set up shop and begin work on their allotted pieces of pavement on Friday and the "exhibition" is open to allcomers on Saturday and Sunday.A variety of other activities, including parades and sideshows, add to the general carnival atmosphere and the delightful, ingenious Baroque palazzi and churches of Noto provide a perfect backdrop.Monday morning is the day of the town's children, who are let loose to run through the temporary artworks in a symbolic display of destruction and renewal.

For more information: Comune di NotoTurist informations

http://www.comune.noto.sr.it/news/headernews/2018/05/08/infiorata-di-noto-2018-3534/

http://www.comune.noto.sr.it/il-turista/

http://www.comune.noto.sr.it/files/noto/images/stories/attualita18/ProgrammaInfiorata2018.pdf

Noto Radio Telescope

May, 13 - 18 - IAUS 342

The Noto VLBI Station is a radio observatory located on Sicily, southern Italy, outside the city of Noto. The facility is operated by the Istituto di Radioastronomia. It was inaugurated on October 28, 1988.

Optical configuration· Primary mirror dish (D): 32 m (paraboloid) with an active surface system consisting of 244 actuators· Secondary mirror dish (d): 3.2 m (hyperboloid)

Primary mirror focal length (F1) = 10.259 m - Focal Ratio (F1/D) = 0.33Cassegrain Focal length (F2) = 97.36 m - Focal Ratio (F2/D) = 3.04

Total Surface Accuracy (RSS): 350÷400x10-4 m (antenna efficiency is quite constant vs. elevation, due to the primary mirror active surface system which compensates for the gravitational deformations).

Aperture Efficiency (theoretical maximum, i.e. not including surface effects ≈ 58%)· 57% @ 5 GHz (measured);· 50% @ 22 GHz (measured);· 40% @ 43 GHz (measured).

Pointing AccuracyOn both the azimuth and elevation axes, 0.002 degrees RMS. Thanks to an accurate pointing model, the pointing doesn’t need to be calibrated during standard antenna operations.

Frequency AgilityIt is possible to change the observation configuration of the antenna by switching among receivers, as reported in the following:· the interchange among them must be scheduled to be done during working hours and it takes about 4 hours;· between Primary focus receivers to Cassegrain focus receivers (or vice versa) is possiblewithin 4 minutes.

Focal Position F1 (Primary focus)In the Primary focus position a box is installed, hosting a coaxial, uncooled, S/X-band receiver.Focal Position F2 (Cassegrain focus)In the Cassegrain Focus position, four receivers are available:· Clow-band receiver, mono-feed, cryogenic;· Chigh-band receiver, mono-feed, not cooled;· K-band receiver, mono-feed, cryogenic;· Q-band receiver, mono-feed, cryogenic.

More information at: www.noto.ira.inaf.it

http://www.noto.ira.inaf.it/

Public Utility Telephone Numbers

May,13 - 18 - IAUS 342

Calling the following numbers from a fixed line is free of charge:

118: Ambulance 115: Fire-brigade 113*: Polizia (Police) 112*: Carabinieri (military police) 117: Finance Guard 1500: Call centre for health emergencies managed by the Department of Health which gives information to the population in case of health emergencies, notably information about SARS, flu syndro mes, bioterrorist threat or information about the risk of excessively warm weather. The service is active only in some periods of the year. 1515: Woodland fire service, managed by the State Forestry Department 1518: Traffic and road conditions, managed by the Road Safety Information Co-ordinating Centre (CCISS Viaggiare Informati) 530: Blue number for sea emergencies, managed by the Corps of the Port Captaincies – Coast Guard (whose own number is: 800-090090)

* The functions of the Carabinieri and the Polizia in Italian society are overlapping. The Carabinieri are a sort of local branch of military Polizia derived from the ancient Corps of the Royal Carabinieri. The Carabinieri have the dual function of national defence and policing, and they have special powers and prerogatives. Carabinieri offices are located in many villages across Italy, and there is more of a Carabinieri presence than a Polizia presence in Italy. In fact, if you’re driving in the country and are nearing a collection of villages, you’ll see signs directing you to the village where the Carabinieri office is located with the emergency number printed below. In some cities, you can call both numbers (112 and 113) and they will be answered by the same person. However, you should probably address the police before the Carabinieri.

Italy international phone code is 0039

-Trigona Hospital +39.0931.890111

-Grand Hotel Sofia +39.0931.835057

-Netum Hotel +39.0931.835835

Enjoy Sicily and IAUS 342

http://www.asp.sr.it/default.asp?id=41

http://www.grandhotelsofia.it/

https://www.hotelnetumnoto.com/?lang=en

Noto, May 13-18 2018 IAU Symposium 342 · To Giacomo Cuttone, Director of INFN - Laboratori...

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