The 3C Extragalactic Radio Sky: Legacy of the Third Cambridge Catalogue

16 Sept 2019, 08:00 → 20 Sept 2019, 19:00 Europe/Rome

Aula Darwin (Torino - Italy)

We decided to organize this conference to commemorate 60 years since the first release of the Third Cambridge Catalogue (3C). The main scientific aims of the meeting are to discuss major advances in studies of interactions between radio sources and their large-scale environments (i.e., feedback processes) in the context of past and anticipated future radio surveys, with special attention devoted to the legacy of the 3C radio sources. Both observational and theoretical points of view will be covered.

Download the conference poster here.

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SCIENTIFIC RATIONALE

Supermassive black holes hosted in active galaxies have a crucial impact on their environment at all scales. The radiatively cooling hot gas in the cores of massive elliptical galaxies is reheated by relativistic jets from the central AGN. This heating could balance radiative losses of the cluster gas which is continuously emitting X-rays. This is only one of the many facets of the feedback process, occurring in radio-loud active galaxies. In fact, the energy produced by the AGN also influences the growth of the host stellar component and it is now an essential ingredient in simulations of galaxy evolution.

In the last decades, significant efforts in observational campaigns, theory, and simulations have been dedicated to unraveling the different aspects of feedback processes. Radio surveys play an instrumental role in investigating the effects of feedback in radio galaxies and their large-scale environments, studying the origin of shocks, relics and halos. Today, an increasing number of X-ray images are revealing cavities in the hot ionized  intergalactic medium permeating the environments of massive galaxies. These cavities are generally filled by the radio extended emission of lobes and  plumes, which provide the energy necessary to maintain the gas in the halo at high temperature thus preventing the cooling and collapsing of the gas onto the galaxy core enhancing star formation.

Thanks to pathfinder instruments (such as LOFAR, ASKAP, MeerKAT, MWA, LWA), surveys are providing an unprecedentedly detailed view of the radio sky, with the much-anticipated Square Kilometer Array on the horizon. These radio surveys provide one of the necessary ingredients in upcoming panchromatic studies with similar angular resolution.

Many of the major discoveries carried out to date have one common denominator: they were made thanks to the study of radio sources  belonging to the Third Cambridge (3C) Catalogue, that since 1959 has had a tremendous influence on our view of the extragalactic radio sky. It pointed out first quasars and radio galaxies, whose early studies ushered in many fields now recognized to be fundamental in high-energy astrophysics.

The main scientific objective of the conference is to celebrate the 60 year anniversary of the 3C catalogue, bringing together an international audience of scientists who are actively addressing open questions on how feedback occurs in active galaxies hosted in galaxy groups and clusters. To provide broad context, connections between the represented smallest- to largest-scale emission will be discussed. We aim to favor interactions between astrophysicists working on different aspects of feedback process, to enable new collaborations, and to pave the path to future observational campaigns. We wish to focus on the legacy value of the 3C catalogue, on what we learned during the past six decades and what we could expect to improve our knowledge in the forthcoming decade.

 

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TOPICS:

• The Third Cambridge catalogue - historical and future perspectives
• Panchromatic view of past and future radio surveys
• Radio-loud AGN & their environments: non-thermal processes, feedback mechanisms - mergers, shocks, and cavities - ISM and ICM - role of BCGs
• Extragalactic jets at all scales: from the central black hole to the interaction with the large scale environments
• New frontiers of MHD simulations on all scales: jets and outflows, and interactions with their surrounding medium
• The most famous 3C sources: beyond 3C405 (Cygnus A), 3C274 (M87), 3C84 (Perseus A) and the others
• Quasars and Blazars: the heritage of 3C273, 3C279, and 3C454.3

 

Image credits: ESA, Steve Gull.

3CSKYcreditcardform.doc

Monday, 16 September

A historical perspective of the Third Cambridge catalogue

1 The 3CR Radio Sources - personal reflections

The early history of the 3CR radio sources and their role in opening up high energy astrophysics will be described. The 3CR sample turned out to have many of the properties which led to current topical issues in galaxy formation and evolution and the role which high energy astrophysics plays in these processes.

Speaker: Prof. Malcom Longair

2 3CR, 3CRR and Jet Physics

Speaker: Dr Robert Laing (SKA)

3 Revisiting the Fanaroff-Riley dichotomy with the LOFAR Two-Metre Sky Survey (LoTSS)

The relative positions of the high and low surface brightness regions of radio-loud active galaxies in the 3CR sample were found by Fanaroff and Riley to be correlated with their luminosity. We use the LOFAR Two-metre Sky Survey (LoTSS) first data release to revisit this canonical relationship. LoTSS is the deepest wide-area survey to date, with sensitivity to both compact and extended structures, allowing us to carry out the largest and most complete radio galaxy morphological analysis for 5805 sources spanning over five orders of magnitude in luminosity.
The LoTSS extended source population shows high diversity. I will discuss whether radio luminosity alone is a reliable proxy for a source appearing as edge-brightened or centre-brightened, and explore the relationship established by Ledlow and Owen where the FRI/II break depends on the optical host magnitude, which is a proxy for small-scale environment. In particular, I will also introduce a population of sources with FRII morphologies and luminosities spanning over two orders of magnitude below the FRI/II break, many of which show signs of ongoing activity.
I will highlight the complexity of the low-luminosity, extended radio source population, and the key role of the jet power/environment dependence. Ours is also a cautionary tale about interpreting the results obtained when using automated techniques to classify radio survey data.

Speaker: Dr Beatriz Mingo (The Open University)

10:30 Coffee Break

4 Observing the 3C Survey of Radio Sources

I am one of the authors of the 3C Catalogue. I observed the Northern part of the Survey called 3C(c) in August-September 1956 as part of my PhD thesis.

Abstract: In 1956, David Edge and I observed the Northern sky using the 4-aerial interferometer from the 2C Survey, with feeds modified for 159 MHz. David’s thesis was the major 3C(a) survey. My observations - just 63 years ago - were the 3C(c) survey at lower culmination in the zone from declination +52 to +70 where the interferometer EW fringes had frequencies from 8 – 12 mHz and a band-pass filter at the output reduced the NS side-fringes which improved the resolution.
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The 3C(c) survey was observed by transit scans between 27 August and 14 September 1956. Analysis took most of 1957, but was complete by November. I confirmed positions and source reality of David’s analysis for the northern scans of the main 3C(a) catalogue and added sources up to declination +70. The 3C(c) survey also showed that source distribution in space - the log N/log S slope and P(D) - in its small area of sky did not support Steady State cosmology.
These results were discussed freely at the Cavendish but not elsewhere … until Ryle, Scheuer and Archer went with others to Paris for the joint IAU/URSI symposium in 1958. The catalogue was submitted to Memoirs RAS for publication in July 1959.

3C was the last Cambridge survey to use paper charts, with pen & ruler analysis, hand drawn contour maps and integration by a chemical balance. We were pre-Sputnik physicists and engineers emerging as astronomers into a violent, extragalactic universe.
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Speaker: Bruce McAdam (University of Sydney)

5 The sequence of events that led to the 1963 publication in Nature of 3C273, the first Quasar and the first extragalactic radio jet

Abstract
The pages of Nature for March 16 1963 carried two short publications which announced the precise radio position, structure, and the optical identification and redshift measurement of the radio source 3C 273, the first quasar (Hazard et. al., 1963; Schmidt, 1963). These discoveries irreversibly changed our understanding of the Universe, and at the same time gave 3C 273 an iconic place in extragalactic astronomy. Fifty plus years later we present here our detailed examination, based on the available evidence, of the circumstances surrounding the observations that led to the these publications in Nature in 1963.

Speaker: Dr David Jauncey (CSIRO Astronomy & Astrophtsics, and Research School of Astronomy & Astrophysics, Australian National University, Australia)

6 Catalogue with visual morphological classification of 32,616 radio galaxies with optical hosts

We present the catalogue of RadiO sources with Galactic counterparts and Unresolved or Extended morphologies I (ROGUE I), which is the largest handmade catalogue of visually classified radio objects and optical galaxies. It was created by cross-matching galaxies from the Sloan Digital Sky Survey Data Release 7 as well as radio sources from the First Images of Radio Sky at Twenty Centimetre and the National Radio Astronomical Observatory VLA Sky Survey catalogues. ROGUE I contains 32,616 galaxies with a FIRST core within 3'', of the optical position. The results of our classification procedure are:

• the majority of radio sources in the ROGUE I catalogue, i.e. ~93%, have unresolved (compact or elongated) morphologies, while the rest of them exhibit extended morphologies, such as Fanaroff-Riley type I, II, and hybrid, wide-angle tail, narrow-angle tail, head-tail sources, and sources with intermittent or reoriented jet activity, i.e. double-double, X-shaped, and Z-shaped,
• most of the Fanaroff-Riley II radio sources in ROGUE I have low radio luminosities, comparable to the luminosities of Fanaroff-Riley I sources,
• our selection procedure allowed to discover or reclassify a number of objects as giant, double-double, X-shaped, and Z-shaped radio sources,
• the optical host galaxies in ROGUE I have elliptical ($\sim$64%), spiral ($\sim$16%), distorted ($\sim$12%), and lenticular ($\sim$7%) morphologies; the remaining $\sim$1% are ring galaxies and galaxy mergers.

The presented sample can serve as a database for training automatic methods of identification and classification of optical galaxies and radio sources.

Speaker: Natalia Zywucka (Centre for Space Research, North-West University, Potchefstroom, South Africa)

7 Nature vs nurture: what shapes the hybrid jet morphology of radio galaxies?

Hybrid morphology radio sources (HyMoRS) are a rare type of radio galaxy that display distinct Fanaroff-Riley classes on opposite sides of their nuclei. To increase number statistic in the analyses of hybrid morphology radio sources, our team embarked on a large-scale search of these sources within the international citizen science project, the Radio Galaxy Zoo. In the first stage of this study we find 25 new candidate hybrid morphology radio galaxies, at redshifts 0.07 < z < 1.0. In this talk I will present our investigations into the hosts of HyMoRS: for a third of the candidates spectroscopic observations reveal a variety of hosts including quasars, green bean galaxies, and high- and low-excitation galaxies. I will also discuss hybrid radio morphology formation in terms of the radio source environment (nurture) and intrinsically occurring phenomena (nature; activity cessation and amplification), showing that in principle these peculiar radio galaxies can be formed by both mechanisms. Finally, I will present and discuss deep and high resolution follow up radio images of one of our candidates, and the additional information these observations reveal.

Speaker: Anna Kapinska (National Radio Astronomy Observatory (NRAO))

A panchromatic view of past and future radio surveys

12:30 Lunch

8 The HST view of extragalactic 3C radio sources: from the central supermassive black holes to galaxy clusters

We have been using the Hubble Space Telescope for over 2 decades to study the 3C(R) sample of extragalactic radio sources and their environment. We discovered new optical jets, nuclear dusty disks, point-like nuclear sources in low-power radio galaxies that allowed to directly test the FRI-BL Lac unification model. We revealed unexpected complex UV morphologies at low-z, indicative of ongoing star formation and recent galaxy mergers. We found evidence for spectacular ongoing mergers at z>1 that may shed light on the ultimate origin of radio-loud AGN activity. In this talk I will review some of the most important results we obtained thanks to HST observations, and I will briefly discuss future possible follow-up research with JWST.

Speaker: Dr Marco Chiaberge (STSCI)

9 The promise of next-generation RC surveys: Revealing the physics and evolution of galaxies and AGN in the SKA era

A wealth of new data from upgraded and new radio interferometers are rapidly improving and transforming our understanding of the faint extra-galactic radio sky. Indeed the mounting statistics at sub-mJy and μJy flux levels is finally allowing us to get stringent observational constraints on the faint radio population, and on the modeling of its various components. In this talk I will provide a brief overview of the latest results, focusing on star-forming galaxies and (low power) Active Galactic Nuclei (AGN), the two populations dominating the faint extra-galactic radio sky. In particular I will highlight a) the benefit of wide-area deep samples to provide statistically robust constraints on radio source demography and evolution, and b) the added value of sub-arcsec resolution to get an unbiased census of SF, and to address the role of AGN feedback in galaxy evolution.

Speaker: Dr Isabella Prandoni

10 Radio bimodality of Swift/BAT AGNs and SDSS quasars

Comparison of properties of quasars with those of low redshift AGNs with similar BH masses but accreting at much lower accretion rates provides exceptional opportunity to study the dependence of the properties of these massive accretion systems on the specific accretion rate. This particularly concerns abilities of such systems to produce powerful jets. We present here results of comparison of radio loudness distributions and discuss them in the context of investigated in literature scenarios proposed to explain the radio dichotomy of AGN. Our preliminary results indicate that: (1) there is an explicit bimodality in the radio-loudness distributions in both populations; (2) the radio-loud fraction of AGNs accreting at moderate rates is larger than of quasars. These differences are consistent with predictions of the MAD (magnetically-arrested-disk) scenario for the production of strong jets and favor the model according to which central accumulation of magnetic flux proceeds prior to the AGN/quasar event.

Speaker: Katarzyna Rusinek (Nicolaus Copernicus Astronomical Center Polish Academy of Sciences)

15:20 Coffee break

11 X-ray and multi-wavelength observations of z>0.5 3CRR radio galaxies.

The complex nuclear structures of active galactic nuclei (AGN)
lead to strong selection effects in most wavebands, including the X-ray.
Highly obscured AGN are hard to find, and identify. Estimating their
numbers, a function of luminosity and redshift, remains a major quest
both for AGN science, and in understanding the level of accretion
power particularly in the early Universe.
Multi-wavelength observations of the low-frequency, radio-selected 3CR luminous
AGN sample (z>0.5) largely avoid selection biases, revealing the obscured AGN,
and probing both their intrinsic, and orientation-dependent properties.
Chandra, Spitzer, Herschel and multi-wavelength observations confirm that
the FIR (> ~40um) does not depend on orientation and that ~half the sample
is significantly obscured with ~a quarter being Compton thick. This is a
larger fraction than typically estimated for optically- or X-ray-selected,
high-luminosity samples. Once the primary X-ray power-law is obscured, AGN
X-ray spectra are complex, and detecting and estimating X-ray obscuration
levels becomes highly uncertain. This is particularly true for sources close
to the flux limit. The loss or miss-classification of obscured AGN in surveys
also results in large (*10-1000) uncertainties on their intrinsic luminosities.
The use of independent measures of the AGN power, such as the low-frequency
radio, help to counteract such problems, and so to probe the intrinsic AGN
properties.

Speaker: Dr Belinda Wilkes (SAO)

12 Unravelling the origin of extended X-ray emission surrounding FR II radio galaxies

We carried out an extensive X-ray analysis of the surface brightness profiles of a sample of FRII radio galaxies. We aimed at assessing the extension of the X-ray diffuse emission along the radio structure as well as in the cross-cone direction perpendicular to the radio axis. We also addressed the hotspot detection significance over the local X-ray background. To obtain a complete characterization of the selected FRII radio galaxies, we compared X-ray images with radio maps at $\sim100$ MHz and investigated the possible presence of a galaxy cluster/group surrounding them by inspecting optical and infrared observations. The sample of FRII radio galaxies was selected from the radio sources of the Third Cambridge catalog observed during the Chandra snapshot survey. These observations span a range of exposure times between 8 and 20 ks and were obtained during Chandra Cycles A09, A012, A013, A015, A017 and A029. As a preliminary result, we find that around $40 \%$ of the sources clearly show extended X-ray emission up to hundreds of kpc both along the radio axis and in the cross-cone direction. Additionally, the presence of diffuse X-ray emission with no counterparts at radio frequencies $\sim1$ GHz shows tentative evidence of CMB quenching.

Speaker: Ana Jimenez-Gallardo (Dipartimento di Fisica, Università degli Studi di Torino)

13 Radio morphology-accretion mode link in FRII low-excitation radio galaxies

Radio Galaxies (RG) are Radio-Loud Active Galactic Nuclei (AGN) characterized by powerful relativistic jets, oriented at relatively large inclination angles with respect to the observer’s line of sight. They are extraordinarily relevant to address important issues such as the interaction between Super Massive Black Holes, the radio jets and their environment.
RGs are commonly classified on the basis of their radio morphology into low radio power FRI (core-dominated) and high radio power FRII (lobe-dominated). Almost all FRIIs hide an efficient accretion disk, while the central engine of FRIs is probably an ADAF, suggesting a strong link between ejection of relativistic plasma and accretion. However, there is a group of FRII sources that does not fit into this picture. They exhibit powerful extended radio structures but inefficient accretion, as attested by their low excitation optical spectra.
In order to investigate their nature, an X-ray systematic analysis of all FRIIs belonging to the 3CR sample with z < 0.3 and available Chandra and XMM-Newton observations was performed. We investigate different scenarios and conclude that the evolutionary one is the most probable. FRII-LERGs have indeed intermediate properties (X-ray luminosity, column density and accretion rate in terms of Eddington luminosity) with respect to classical FRIIs and FRIs.
The nuclear power seems to suffer of a depletion of the cold gas reservoir. It is then plausible to think that this information has not yet reached the large-scales radio structures at kpc distances from the central engine. The powerful lobes are the heritage of a past AGN activity at higher efficiency.

Speaker: Duccio Macconi (OAS-Bologna, DIFA Bologna)

14 The composite X-ray spectrum and pc-scale radio structure of 3C RR radio sources

The 3C RR radio catalog is a low-frequency radio-selected sample, and is one of the most well-studied radio samples on multi-band. The uniqueness of the sample enables us to study the emission of AGNs at various aspects. In this talk, we will give our results about the composite X-ray spectrum of 3C RR quasars, and the pc-scale structure of 3C RR radio galaxies. The composite SED of radio-loud quasars differs from that of radio-quiet quasars mainly on radio and X-ray bands, while the former difference may be caused by the jet, the reason of the latter is unclear. The 3C RR sample is low-frequency radio selected sample, therefore, the sample is dominated by the steep-spectrum sources, in which the jet beaming effect will not be severe, ideal for studying the SED of radio-loud quasars. We found that the composite X-ray spectrum of 3C RR quasars is similar to that of radio-loud quasars in the literature, supporting the SED difference between radio-loud and radio-quiet quasars. We will also show the pc-scale structure of a sample of 3C RR radio galaxies by using VLBA data both observed by us and from the literature. The MIR observations are used to constrain the accretion mode in the sample sources. The ps-scale structure and the jet-accretion relation are studied (Yuan, Gu & Chen 2018).

Speaker: Prof. Minfeng Gu (Shanghai Astronomical Observatory, CAS)

17:30 Aperitive

Tuesday, 17 September

Radio-loud active galaxies and their environments: feedback mechanisms - intracluster medium - mergers, shocks and cavities - role of BCGs - non-thermal processes

15 The case for AGN feedback in clusters of galaxies

Clusters of galaxies are fantastic laboratories for understanding the physics of AGN feedback. They play a pivotal role in our understanding of jet-mode feedback by demonstrating that AGN-driven jets can inject profound amounts of energy into their surroundings via shock fronts, sound waves and turbulence, in addition to driving powerful molecular outflows and metals out of galaxies. In this talk, I will review the current state of this field. I will also present new state-of-the-art VLA observations of the Perseus cluster of galaxies, as well as a detailed study that focusses on the statistical properties of large scale radio emission in clusters (known as mini-halos). Both these studies reveal new physics about the nature and properties of non-thermal particles in clusters of galaxies.

Speaker: Prof. Julie Hlavacek-Larrondo

16 A multi-scale low radio frequency view of the Perseus cluster

Among the most notorious sources belonging to the Third Cambridge Catalogue is 3C84, active galactic nuclei of NGC 1275, the Perseus cluster’s brightest galaxy. It is the origin of a complex interaction between radio jets and the cluster’s environment, releasing relativistic particles on large distances. 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-scale low radio frequency (230-470 MHz) observations of the Perseus cluster from the Karl G. Jansky Very Large Array, probing the non-thermal emission from the old particle population of the AGN outflows. Our observations of this nearby relaxed cool core cluster have revealed a multitude of new structures associated with the radio lobes and the mini-halo, which extends on hundreds of kpc in size. The irregular morphology of the mini-halo seems to have been influenced both by the AGN activity and by the sloshing motion of the cluster’s gas. In addition, it has a filamentary structure similar to that seen in radio relics found in merging clusters. Furthermore, the Perseus cluster hosts several interesting head-tail radio galaxies (NGC 1265, NGC 1272, IC310 and CR 15) on which I will also present an analysis of the morphology and spectral index distribution.

Speaker: Marie-Lou Gendron-Marsolais (European Southern Observatory)

17 NuSTAR observations of 3C84 in the Perseus Cluster

This presentation will cover the broad-band observations of one of the 3C sources, namely the radio galaxy 3C84 (a.k.a. NGC1275), which is the central dominant galaxy in the Perseus Cluster. The AGN contains a radio-emitting jet, and is believed to play an important role in providing the feedback to the cluster by energizing large-scale "bubbles" of radio-emitting plasma. In particular, we will discuss the observations of 3C84 with NuSTAR, which reveal strong nonthermal emission associated with the AGN rather than the cluster. We discuss the possible origin of that emission, and implications on the energetics and content of the jet in 3C84.

Speaker: Grzegorz Madejski (SLAC)

18 The Slow Heartbeat of Supermassive Black Hole Fuelling

I will review the observed variability of the low accretion
rate AGN in Brightest Cluster Galaxies (BCGs). Radio/sub-mm
monitoring of a sample of several dozen systems over the past decade
shows most systems have varied by >30% and many by factors of >2.
The implications of this variability, particularly in the sub-mm,
will be discussed.

Speaker: Alastair Edge (Durham University)

10:30 Cofee Break

19 Galaxy clusters at low radio frequencies

Speaker: Prof. Reinout Van Weeren

20 Is AGN activity necessary to power diffuse emission in galaxy clusters?

The presence of relativistic particles and diffuse magnetic field in cluster volumes is unveiled
by the observation of synchrotron radio emission extended on Mpc scales in the form of radio
relics and halos. Their origin is connected with merger processes, but the underlying particle acceleration mechanisms are still debated. A possible scenario calls upon the presence of a fossil population of mildly relativistic electrons that can be re-accelerated by the shock waves generated during the merger.
Such fossil particles could be injected in the intra-cluster medium by AGN. Hence, it is now mandatory to study the AGN and AGN evolution in clusters to understand the cluster diffuse emission.

Radio observation plays a crucial role in the understanding of a possible AGN-relic connection, that would establish a link between radio galaxies and their large-scale environment. While new low frequencies instruments are providing an unprecedentedly detailed view
of steep spectrum sources that can power diffuse cluster radio sources, the presence of a source of relativistic electrons is still
missing for the majority of radio relics, leaving the puzzle unresolved.

I will show the case of the radio relic and AGN in the merging galaxy cluster RXCJ1314 where, using high-resolution JVLA data, we discovered
the presence of a WAT radio galaxy embedded in the diffuse emission. I will discuss the spectral and polarization properties of this system in comparison with a few similar cases found in the literature so far.

Speaker: Chiara Stuardi (Universita' di Bologna)

21 Stormy weather in 3C 196.1: Nuclear Outbursts and Merger Events Shape the Environment of the Hybrid Radio Galaxy 3C 196.1

Active galactic nuclei (AGN) feedback have a dramatic impact on cosmic structure formation and evolution, producing the so-called 'cosmic downsizing', the BH-host scaling relations and the quenching of cooling-flows in cluster cores. In particular, radio-loud AGN are expected to experience the most intense galaxy-scale outflows and feedback in the centre of massive galaxies, with jet/intra-cluster medium interaction in the form of cavities (X-ray) and bubbles (radio).
We here present a detailed multi-wavelength analysis based on archival radio (VLA and GMRT), optical (HST) and X-ray (Chandra) data of the hybrid radio galaxy 3C 196.1, whose host is a z=0.198 BCG embedded in a kT ~ 4 keV cluster.
Chandra snapshot observation allowed us to constrain the physical parameters of the cluster, which has a cool core with a low central temperature ~ 2.8 keV, low central entropy ~ 13 keV cm^2 and a short cooling time of ~ 500 Myr, which is < 0.05 of the age of the Universe at this redshift.
3C 196.1 represents an intriguing example of combined effects on the surrounding cluster environment of both AGN activity and merging events.
Indeed, analysis of the X-ray and radio images reveals cavities located at galactic-scale (~ 10 kpc) and in the cluster outskirts (~ 300 kpc, ~ 0.3 R500), originated by previous AGN outbursts ~ 280 Myrs ago, with energetics of ~ 10^59 and ~ 10^60 erg (respectively).
3C 196.1 also harbours one the biggest and highest energetic bubbles ever measured so far and currently multiwavelength observational efforts have been planned to study it in more details.

Speaker: Dr Federica Ricci

12:10 Group photo

12:30 Lunch

The most famous 3C sources

22 Recent results from JVLA Observations of Cygnus A

Speaker: Dr Rick Perley (NRAO)

23 X-ray Observations of Cygnus A: a Powerful Radio Galaxy in a Dense Environment

Cygnus A, the archetype of powerful Fanaroff-Riley class II radio galaxies, is hosted by the central galaxy of a cool core cluster, in a dense, high pressure environment. I will focus on what deep Chandra observations of Cygnus A have revealed about the radio galaxy and interactions with its environment. Measuring properties of its cocoon shocks has revealed that the pressure is relatively uniform within the radio cocoon. It has also provided estimates approaching 10^{46} erg/sec for the average jet power. Simple modeling implies that the jets are light, with negligible kinetic power and momentum carried by rest mass. Diffuse X-ray emission from the lobes is dominated by Compton scattered radio synchrotron emission. I will discuss new results on the properties of the hotspots and a "hole" found in the X-ray emission of the eastern lobe, around the primary hotspot.

Speaker: Paul Nulsen (Harvard-Smithsonian Center for Astrophysics)

24 Feeding and feedback in radio galaxies: an X-ray perspective

Observations performed in the last decades have shown that supermassive black holes (SMBHs) and cosmic structures are not separate elements of the Universe. While galaxies have sizes roughly ten orders of magnitude larger than SMBHs, black holes would not exist without matter feeding them, and cosmic structures would not be the same without feedback from SMBHs. Powerful winds/jets in active galactic nuclei (AGN) may be the basis of this co-evolution. X-ray observations trace both the cold/feeding and hot/ionized feedback phases. We show the Chandra HETG spectral analysis of two radio galaxies, 3C 390.3 and 3C 120. Complex emission/absorption features are present in the soft X-rays and Fe K band. We detect a hot gas with temperature kT~0.5-1keV from broad ionized Fe L-shell lines which may originate from a ~kpc scale shocked bubble inflated by the wind/jet. Moreover, the shape and strength of the neutral Fe K line, along with partial covering observed with XMM-Newton in PKS 2251+11, suggest that the material feeding the accretion disk, or torus, may be in the form of Compton-thick, clumpy clouds. Such systems may likely be late stage mergers and they allow us to extend the parameter space traced by winds in Seyferts and ULIRGs.

Speaker: Francesco Tombesi (University of Rome "Tor Vergata")

25 The Quasi-Quasar 3C 120

The broad-line radio galaxy 3C 120 has the properties of a Seyfert galaxy at optical through X-ray frequencies, and a quasar-like blazar at radio frequencies. It is one of a very small number - and probably the best - of active galaxies suitable for probing the relationship between the accretion disk/corona and a relativistic jet. We recently monitored 3C 120 with Swift at optical/UV/X-ray frequencies alongside our long-standing VLBA monthly imaging program and monitoring of the 37 GHz flux at the Metsahovi Radio Observatory. The changing optical-UV spectrum reveals the presence of a component with an inverted spectrum, which may be synchrotron radiation from electrons with a nearly mono-energetic (roughly 10 GeV) distribution. A flare from
optical to X-ray frequencies appears to have originated near the radio core 0.5-1.3 pc from the black hole. Analysis of the optical-X-ray light curves disfavors the proposal that the inner accretion disk is disrupted prior to the launch of a superluminal knot seen in the VLBA images.

This research was supported in part by NASA through the Swift and Fermi guest investigator programs, grants NNX16AN69G and 80NSSC17K0649, and by the National Science Foundation via grant AST-1615796.

Speaker: Alan Marscher (Boston University)

15:30 Coffee break

26 M87 (aka 3C274; Virgo A): The interaction between M87’s black hole and its environment

Speaker: Dr William Forman

27 Detection of Proper Motions in the Knots of the M87 (3C 274) Jet with the Chandra X-ray Observatory

We present results from two observations of the M87 jet taken with the Chandra High Resolution Camera (HRC) separated by ~5 years. We detect proper motions in knot HST-1 and knot D of 24.1pm1.6 mas/yr and 9.2pm2.6 mas/yr, respectively. This corresponds to superluminal velocities of 6.3pm0.4c and 2.4pm0.6c, respectively, along the axis of the jet. These velocities are consistent with the previously measured motions of the optical, ultraviolet, and radio components. Comparison of the multi-epoch X-ray and HST observations show that the knots are co-moving in the two bands. There are significant variations in the X-ray fluxes of these knots between the two observations with no corresponding variations in the optical. Assuming synchrotron losses, we estimate the magnetic fields of knots HST-1 and D to be ~420 and ~230 microG, respectively, consistent with the equipartition estimates. We conclude that synchrotron loss is the primary mechanism responsible for the changes in X-ray fluxes of these knots, and that the proper motions of the knots reflect the underlying velocity of the jet. In this presentation, we will describe our observations, discuss our results and implications for our understanding of the M87 jet, and outline future work.

Speaker: Dr Ralph Kraft (SAO)

28 Exploring new data and imaging frontiers with the Event Horizon Telescope

The Event Horizon Telescope (EHT) is a global array built to resolve the innermost region of the supermassive black hole candidates at the Galactic Center and the center of the M87 galaxy. The EHT reached an angular resolution of 25 uas at a wavelength of 1.3 mm in the 2017 science campaign, joined for the first time by the highly sensitive phased Atacama Large Millimeter/submillimeter Array (ALMA). The EHT however faces many challenges: in addition to the difficulty of campaign coordination and acquisition of VLBI data, the heterogeneity of the array and its susceptibility to weather and atmospheric turbulence make the data calibration particularly arduous. The sparsity of the array also causes an additional difficulty: the ‘missing information problem’, plaguing high frequency VLBI, hinders the imaging process and requires more sophisticated tools and analysis than what is typically done for interferometric imaging. In this talk, I will present the data processing and imaging techniques developed and used by the EHT to overcome these challenges and achieve its science goal: obtaining the first image of a black hole.

Speaker: Dr Sara Issaoun

29 M87 black hole mass from observations of a jet shape break

The change in a boundary shape of a jet in M87 was discovered first by Asada and Nakamura (2012). This jet is characterized by the initially quasi-parabolic flow changing into the approximately conical one. We propose that the change in a jet boundary shape is due to a transition of an outflow from the Poynting dominated to particle-dominated (equipartition) regime. We propose a model with an electric current closed inside a jet (Beskin et al. 2017). This assumption ensures the absence of a current sheet at the jet boundary, which may affect a jet stability in a positive way. Within this model, we are able to reproduce exactly the observed jet boundary shape behavior adopting the ambient pressure is due to a Bondi accretion flow. Assuming the presence of a dynamically important magnetic field, we are able to find the mass and spin of a super massive black hole in M87. The obtained mass is larger than accepted so far, while the spin has a moderate value of ~0.1.

Speaker: Elena Nokhrina (Moscow Institute of Physics and Technology)

Social Dinner at "La Piazza dei mestieri"

30 The 3C Survey - A personal perspective

Speaker: Dr Alastair Edge

Wednesday, 18 September

Frontiers of MHD simulations at all scales: jets, outflows, and intracluster medium

31 Frontiers in Computational Plasma Astrophysics: connecting small and large scales

Speaker: Prof. Andrea Mignone

32 How relativistic jets from AGNs affect the host galaxy and its environment

Relativistic jets from AGNs are an important driver of feedback in galaxies with an active black hole. They first interact with the host galaxy's ISM before breaking out to larger scales, significantly affecting the galaxy's morphology and evolution. Cosmological simulations predict that massive galaxies undergo several such episodes in the course of their evolution. However, large scale simulations are unable to probe the impact of such AGN activity on the ISM of the host galaxy due to limited resolution. I shall present the results of our recent 3D relativistic (magneto) hydrodynamic simulations, performed on scales of several kpc, of AGN jets interacting with the dense turbulent ISM and the ambient CGM. The young relativistic jets initially couple strongly with the dense clouds in the ISM, driving fast moving lateral outflows. The resultant outflows though strong, do not escape the galaxy, supporting a galactic fountain scenario of feedback, rather than a blow out phase as envisaged in earlier models. We have performed a suite of simulations of different jet powers, ISM conditions and morphologies. While AGN activity can potentially quench star formation by driving outflows or inducing turbulence, we find that they can also potentially enhance star formation (positive feedback) in localised patches. In another new effort, we have developed a novel new technique of estimating the evolution of the energy of non-thermal relativistic electrons in the jet, duly accounting for energy losses due to radiative processes (synchrotron + inverse compton) and enhancements due to diffusive shock acceleration at shocks. We perform this in-situ in our relativistic magneto-hydrodynamic framework of PLUTO to create realistic maps of synchrotron emission, estimate particle age and identify potential sites of acceleration of particles. The results of our simulations show qualitative and quantitative similarities with observed results of jet-ISM interaction in several galaxies which I will discuss in the talk.

Speaker: Dr Dipanjan Mukherjee (Observatory of Torino (INAF))

33 Jets, Blobs, and Circular Polarization: Using PLUTO to Model Time Domain Variability in Blazars

Extragalactic jets are highly collimated beams of relativistic plasma that emanate from the centers of Active Galactic Nuclei (AGN). Despite decades of dedicated observation and study the underlying plasma composition of these relativistic outflows remains largely unknown. The polarized emission emanating from relativistic jets, however, can now be imaged on micro arcsecond scales using Global mm-wave Very Long Baseline Interferometry (VLBI). These polarimetric observations provide us with a powerful probe of the underlying nature of the jet plasma. In parallel to this observational advance, modern computational resources have allowed for increasingly sophisticated numerical jet simulations. Relativistic magnetohydrodynamic (RMHD) jet models are able to reproduce many of the observed macroscopic features of these plasma flows (e.g., recollimation shocks, jet sheaths & spines, bow shocks, & enshrouding jet cocoons). This talk presents a study of the variability in the circular polarization produced by a blob of relativistic plasma passing through a standing recollimation shock within a jet. This is accomplished through the use of the PLUTO code in concert with full Stokes polarized radiative transfer carried out (post-process) with the ray-tracing code RADMC-3D.

Speaker: Nicholas MacDonald (Max Planck Institute for Radio Astronomy (MPIfR))

34 Self-consistent modeling of particle acceleration and evolution of spectral distribution in blazars.

Blazar emission models are challenged by recent multiwavelength and multi-messenger observations. The only way to transform these observational evidences into an advance of the understanding of the physical phenomena behind, is to build models that are as much as possible reproducible, robust, and with a solidly connection to the phenomenology. I will give some examples of this approach using the JetSeT framework, an open source code able to reproduce radiative and accelerative processes acting in relativistic jets, and to fit the numerical models to observed data. In particular I will review some of the main phenomenological signatures of acceleration acting in the relativistic jets of blazars, and I will show how it is possible to constrain models, linking predictions from Monte Carlo simulations and from the numerical solutions of the diffusion equation in momentum space, to the spectral features observed in the multi-wavelength SED of blazars. I will focus on the spectral evolution and spectral curvature in the X-ray/hard X-ray data and in the TeV data, and the implications on the acceleration mechanisms. Finally, I will discuss the formation of pile-up during strong flares.

Speaker: Andrea Tramacere (Astronomy Department of the University of Geneva,)

tramacere_3C_Torino_2019.pdf

10:30 Coffee break

35 What makes a good jet?

Speaker: Prof. Alexander Tchekhovskoy

36 Hot Relativistic Jets

Comparable energy contents of radio lobes in FR II sources calculated
using their luminosities and their confinement by external medium seem
to exclude possibility of their energy domination by protons.
This suggests that the jets powering the lobes are pair dominated.
Large pair content of jets is indicated also by blazar models, which
for the electron-proton plasma predict much larger jet powers than obtained
using energetics of their radio lobes.
However, noting the very efficient cooling of electrons/positrons in
blazars, the energy flux of jets at sub-parsec distances from a black hole is
expected to be dominated by protons and magnetic fields rather than by pairs.
Neglecting the leptonic contribution to the jet energy flux also at kpc scales
would imply very efficient conversion of kinetic energy of cold protons to
internal energy of electrons and positrons in terminal shocks. This however is
rather difficult to accomplish and, therefore, we propose that energetical
domination of pairs over protons is already achieved prior to the jet
termination. We investigate conditions required to form such hot,
pair-dominated jets and provide some additional observational and theoretical
arguments in favor of their existence.

Speaker: Marek Sikora (N. Copernicus Astronomical Center)

37 Theory vs. observations: Unraveling black hole accretion physics with the Event Horizon Telescope

The Event Horizon Telescope (EHT) is a global VLBI array with the capability to study millimetre wave emission from extragalactic radio sources with an unprecedented micro-arcsecond resolution. In a 2017 observing run, the EHT observed M87 and Sgr A* - the two primary EHT targets - alongside several other AGN sources. Eight telescopes participated in this observing session, including the phased-up Atacama Large Millimeter/submillimeter Array.
In this talk, I will present a novel synthetic data generation pipeline designed for the EHT, called SYMBA. This pipeline is able to accurately predict EHT measurements for any theoretical source model as it creates realistic data corruption effects and passes the synthetic data through the full EHT calibration and imaging machinery. SYMBA is used to directly compare EHT observations with general relativistic magnetohydrodynamics (GRMHD) simulations. First, I will showcase the current capabilities of the array to resolve the shadow of the supermassive black hole in the center of M87. Then, I will predict how an increase in sensitivity and resolving power will soon enable the EHT to probe the electron distribution function of hot emitting plasma surrounding the central nucleus of M87. The necessary enhancement will already arrive in 2020 with the addition of the Greenland Telescope, Kitt Peak station, and phased IRAM NOEMA interferometer to the EHT array.

Speaker: Mr Michael Janssen (Radboud University)

38 Reconnection and Associated Flares in Global Relativistic Jets Containing Helical Magnetic Fields with PIC Simulations

In the study of relativistic jets one of the key open questions is their interaction with the environment on the microscopic level. Here, we study the evolution of both electron–proton and electron–positron relativistic jets containing helical magnetic fields, focusing on their interaction with an ambient plasma. We have performed simulations of “global” jets containing helical magnetic fields in order to examine how helical magnetic fields affect kinetic instabilities such as the Weibel instability, the kinetic Kelvin-Helmholtz instability (kKHI) and the Mushroom instability (MI) using a larger jet radius. In our simulation study these kinetic instabilities are suppressed and new types of instabilities can grow. In the electron-proton jet simulation a recollimation-like instability occurs near the center of jet. In the electron-positron jet simulation mixed kinetic instabilities grow and the jet electrons are accelerated. The evolution of electron-proton jets shows that helical magnetic fields are untangled and electrons are accelerated rapidly. We also investigate mechanisms of flares possibly due to reconnection.

Speaker: Prof. Kenichi Nishikawa (Alabama A&M University)

14:00 Tour Buses Departure from Conference Venue

Thursday, 19 September

Extragalactic jets at all scales: from the central supermassive black hole to their interaction with the large scale environments

39 Powerful Radio Galaxies: The Heavy Lifters of the Universe

Speaker: Prof. Brian McNamara

40 The cool ISM reservoirs of powerful radio galaxies: a new window on fuelling and triggering

Although radio AGN play a key role in galaxy evolution through their feedback effect, we still do not fully understand how they are triggered and fuelled. Possibilities range from major, gas-rich mergers on the one hand, to direct accretion of the hot gas from the X-ray haloes of the host galaxies and clusters on the other. The cool ISM reservoirs of the host galaxies provide key information on triggering events. Here I present the results of deep Herschel observations of the 2Jy and 3CR samples which allow the dust masses – a proxy for the cool ISM contents -- to be quantified for the first time in substantial numbers of radio galaxies. The results demonstrate that the cool ISM masses of the majority of FRII radio galaxies are an order of magnitude lower than those of ULIRGs (representing gas-rich major mergers), but an order of magnitude higher than those of quiescent elliptical galaxies. Combined with existing information on detailed host galaxy morphologies, environments and star formations rates , this is consistent with triggering in galaxy mergers that are relatively minor in their gas contents in most cases. In contrast, the cool ISM masses of the majority of FRI radio galaxies are substantially lower than their FRII counterparts, consistent with fuelling via direct hot gas accretion or cold gas accretion at low rates from dynamically settled disks. I discuss these results in the context of recent ALMA observations that detect molecular gas disks in some nearby radio galaxies.

Speaker: Clive Tadhunter (University of Sheffield)

41 The MURALES survey: a MUse RAdio Loud Emission lines Snapshot

We report the first results of the MURALES survey, a program of MUSE observations of 40 nearby (z<0.3) 3C radio galaxies. The MUSE data, combined with the unique multiband dataset available for these sources adds a key ingredient for our understanding of the radio-loud AGN feedback. We already fully modelled the MUSE data obtained for all the sources. The line emission images of unprecedented depth reveals the widespread presence of filamentary structures extending several tens of kpc in almost all the FRIIs. Only in a few cases we have evidence that the ionised gas is related to the expansion of the relativistic jet. In 3C317 and 3C277.3 we observe ionised gas around the X-ray cavities, a clear manifestation of the AGN feedback. In other cases the dense gas filaments are oriented perpendicularly to the radio jets, likely the remnants of the gas rich mergers which triggered the AGN. High velocity outflows of ionised gas, when revealed, remains confined in the inner region of the galaxy and it seems not to have a significative effect on the host galaxy.

Speaker: Barbara Balmaverde (INAF - Osservatorio astronomico di Brera)

42 Feedback in local radio galaxies using optical IFS

This presentation resume our results using optical integral field spectroscopy of four nearby (z < 0.07) radio galaxies obtained with GMOS in Gemini North and South telescopes (Couto et al. 2013, 2016, 2017,in prep), a series of studies of the gas excitation and kinematics of the sample. The field-of-view probes a circumnuclear region of ~3.5”x5”, with average spatial resolution of ~0.6”. The galaxies in our sample, Arp 102B, Pictor A, 3C 33 and 4C +29.30 present extended radio jets and have in common signatures of interactions or merger events. For Pictor A, e.g., we find unusually low [N II]6584/Hα ratio (0.15 - 0.25), indicating low metallicity of the gas, not expected in AGNs (Active Galactic Nuclei). This suggests an accretion of gas through an interaction event, in agreement with the tidal tail observed by Gentry et al. (2015). The presence of more than one kinematic component in the galaxies of our sample indicate that feedback is disturbing the gas in the central regions, and this is usually traced by high velocity dispersion and high line ratios. Although we estimate low energetic input of the radio jet in the circumnuclear gas (outflow kinetic power of Ė< 1% Lbol), jet-cloud interaction seems to be connected with extended emission-line regions. 3C 33 present clear signatures of ionized gas being pushed perpendicularly by the radio jet, in a region where high line ratios and an increase of electron temperature and velocity dispersion is observed. We also present resolved diagnostic diagrams for these galaxies using the optical emission-lines, and the comparison with shocks and photoionization models, which suggests more presence of shocks in regions closer to the radio jet, but also contribution of photoionization.

Speaker: Guilherme Couto (Universidad de Antofagasta)

10:30 Coffee break

Special Session A,B,C

Lunch

Extragalactic jets at all scales: from the central supermassive black hole to their interaction with the large scale environments

43 Dynamical modelling of powerful radio galaxies and their environmental impact

The basic principles of the dynamical evolution of powerful radio sources have been known for over 40 years but the details, and particularly the details of their interaction with their environments, continue to be an interesting topic. I'll discuss the current state of the art of radio source dynamics based on the latest observations and on numerical and analytical models.

Speaker: Martin Hardcastle (University of Hertfordshire)

44 Life-cycle of radio galaxies seen by LOFAR

Supermassive black holes at the centre of galaxies can cycle through periods of activity (in this phase known as active galactic nuclei, AGN) and quiescence. Quantifying the duty cycle of AGN is crucial for understanding the energetic impact they have on the host galaxy. In radio AGN this duty cycle can be investigated by using the characteristics of the radio spectrum and the morphology of the radio emission. The low radio frequencies can be used as fossil record to trace the oldest populations of particles. We have used deep LOFAR images of the Lockman Hole extragalactic field to select a sample of objects in the restarting phase of this cycle.
In this talk, I will present samples of candidate remnants and restarted radio galaxies that we selected using criteria based on the core prominence and the spectral index. I will discuss their radio properties and the optical properties of their host galaxies, as well as their rate of occurrence, which provides fundamental information for understanding the duty cycle of radio sources. The results will be discussed in the context of models of the evolution of the radio sources that we are developing.
The methods for the identification of remnant and restarted radio sources developed for this project will be applied for selecting larger samples in the LOFAR Two-metre Sky Survey.

Speaker: Raffaella Morganti (ASTRON and Kapteyn Institute (NL))

45 Resolved spectral studies in the SKA era: radio galaxies and the AGES-XL survey

Powerful radio galaxies are known to play a key role in determining the evolutionary path of galactic populations; however, much of the physics that underlie these important sources remains poorly understood. One of the most pressing questions in radio galaxy physics today is determining the age, life expectancy, and duty cycle of these sources and how this evolves over cosmic time. A detailed understanding of the spectrum these sources produce potentially provides the key to answering these questions, but to date detailed studies on well-resolved scales have remained limited to a handful of bright, nearby objects, leaving our knowledge of the wider population limited. The broad-bandwidth, high resolution, large area observations provided by forthcoming surveys such as MeerKAT MIGHTEE, and ultimately those performed with the SKA, gives us the first opportunity to fully address these questions.

In preparation for these large data volumes we have performed a targeted survey of 30 of the brightest radio galaxies in the XMM-LSS field; the VLA GHz survey of extragalactic sources in the XMM-LSS field (AGES-XL). AGES-XL provides the largest sample of radio galaxies to date with the data quality required to perform a detailed spectral analysis (e.g. spectral curvature) on well-resolved scales, as well as addressing outstanding issues in the particle acceleration processes that drive these powerful sources. In this talk, we present the latest results from AGES-XL, the methods used to analyse the spectrum of a large samples of well-resolved radio galaxies, and the outstanding challenges that remain when dealing with the extremely large data volumes that the SKA and its precursors will produce.

Speaker: Jeremy Harwood (University of Hertfordshire)

46 Resolved spectral ageing in 3C320 and 3C444

Relativistic radio jets create large-scale lobes -- the extragalactic footprints of accretion onto supermassive black holes, central to radio-loud active galaxies. In these dynamic and energetic structures, the phenomenon of spectral ageing occurs -- the progressive steepening of the radio spectrum in the lobes due to radiative losses. Recent advances in computing capabilities have enabled this physical process to become a tool that can be used to calculate the age of radio galaxies -- an important parameter used to determine their jet power (the time averaged kinetic feedback into the environment). In building the jet power function for all radio galaxies, accurate sources ages are required. Spectral ages, however, are almost always underestimated relative to the dynamical ages
of radio galaxies. In this talk I will present a detailed investigation of spectral and dynamical ages of two powerful cluster-centre 3C radio galaxies, using broad-band VLA data at multiple frequencies, and deep X-ray observations with Chandra and XMM-Newton of the surrounding shocked environment driven by the jets. Combined with an analytic model, we find that equipartition magnetic fields systematically underestimate the spectral age, revealing that the lobes of radio galaxies are truly a departure from minimum energy. Spectral ages can therefore be found accurately with true magnetic field estimates and accounting for electron mixing in the lobes. These findings will be key to building future tools to determine jet powers of all radio-loud AGN, which will be observed in the dawn of deep radio surveys such as the SKA, and will lead to information on the total power output of radio galaxies over all cosmic time.

Speaker: Vijay Mahatma

47 A study of different orientation of jet axes in DDRGs

Double-double Radio Galaxies (DDRGs) consist of a pair of double radio sources with a common central AGN. They are unique observational evidence of recurrent jet activity in AGN. In most cases, the diffuse outer double lobes appear reasonably well aligned with the inner ones and they maintain long-term steadiness in bipolar relativistic jet outflows. There are a few examples of “misaligned DDRGs” which undergo different axis orientation for two epochs. The reorientation of the jet axis in these misaligned DDRGs may be caused by an axis precession of the AGN. Influence of a nearby galaxy or the coalescence of massive black holes may trigger a new jet with sufficient axis rotation. In order to understand the possible mechanisms of axis reorientation and the timescales of their duty cycle, we performed multi-frequency radio observations of a few misaligned DDRGs. Study of their optical host galaxies also suggests that they are often associated with past or ongoing galaxy interactions. Here we present the main results from our radio and optical observations and discuss on the possible scenarios responsible for the intermittent jet activity with axis rotation in the case of misaligned DDRGs.

Speaker: Sumana Nandi (Indian Institute of Astrophysics)

15:50 Coffee break

48 A new class of radio structures: hybrid ICM/radio tails

We introduce a new class of "hybrid" radio structures associated with tailed
sources in clusters of galaxies. These hybrid structures do not appear consistent
with models or simulations of material that originated in the outflowing jets.
At the same time, they are not random features of the ICM, e.g., from old radio
galaxies, because they are structurally connected to tailed sources. Their
spectra appear consistent, to first order, with the steeper regions in their
associated tail. We will briefly explore the challenges to be solved in
explaining these sources, identify other cluster radio structures that may
be related, and future work. This work is supported, in part, by U.S. National Science Foundation grant AST 17-14205 to the University of Minnesota.

Speaker: Prof. Lawrence Rudnick (University of Minnesota)

49 A low frequency view on the restarted radio galaxy 3C388

Radio loud Active Galactic Nuclei are episodic in nature, cycling through periods of activity and quiescence. The study of this duty cycle is essential for quantifying the feedback of radio jets on the host galaxy, which is a key parameter in galaxy evolution models. Evidence of this recurrence is observed in restarted radio galaxies, where large-scale old plasma is seen together with a pair of new-born jets. These sources provide a unique opportunity to get constraints on the timescale of the jet activity.

In this talk I present recent results on the well-known restarted radio galaxy 3C388. While most of the known restarted sources have been identified from their morphology, 3C388 represents a unique case where multi-epoch activity has been pointed out from a sharp discontinuity in the radio spectral index distribution of its lobes at GHz frequencies. Thanks to new generation instruments we have been able to expand the investigation of this source in the MHz regime for the first time. In particular, we have complemented the published data at GHz frequencies with new dedicated LOFAR observations at 150 MHz, JVLA observations at 350 MHz and archival GMRT data at 610 MHz.

I will show how the new broad radio spectral coverage allows us to probe the radiative age of the lobes and make a step forward in the understanding of the nature of this well-known radio galaxy. Moreover, I will show the incredible prospects of combining new generation radio data at different frequencies to perform systematic studies of the spatially resolved spectral properties of restarted radio galaxies, and radio galaxies in general.

Speaker: Marisa Brienza (IRA-INAF Bologna)

50 A correlation between supermassive black holes and the hot atmospheres of host galaxies

The masses of central supermassive black holes are known to correlate with the bulge components of their host galaxies, suggesting a coevolution of the two. Here, we report the discovery of a tight correlation between the temperatures of the hot atmospheres permeating brightest cluster/group galaxies (BCGs) and the masses of their central supermassive black holes, making the atmospheric gas temperature the best known proxy for the black hole mass in these systems. The atmospheric gas temperature is set primarily by the underlying gravitational potential and our hydrostatic analysis reveals a linear correlation between the total masses of BCGs and the masses of their central supermassive black holes. In the scenario of a simultaneous growth of the central black holes and their host galaxies through mergers, the observed linear correlation is a natural consequence of the central limit theorem.

Speaker: Prof. Norbert Werner (MTA-ELTE Lendulet Hot Universe Research Group)

51 POSTER HAIKUS

17:45 Aperitive and Poster session

Friday, 20 September

Quasars and Blazars: the heritage of 3C273, 3C279, and 3C454.3

52 Legacy of Monitoring Parsec-Scale Jets of the Quasars 3C279, 3C273, and 3C454.3

I will present results of studying the parsec-scale jets of the three most famous blazars from the 3C catalog, 3C279, 3C273, and 3C454.3, from the earliest days of VLBI up to the most recent highest resolution observations. I will discuss properties of jets (kinematics, timescales of variability,
magnetic field, jet contents, and jet environment) and stress the importance of radio monitoring in understanding the multi-wavelength behavior and physics of blazars.

The research is supported by NASA grant 80NSSC17K0649 and NSF grant AST-1615796.

Speaker: Dr Svetlana Jorstad (IAR, Boston University)

53 Centimeter-band Variability in 3C 273, 3C 279, and 3C 345 as a Probe of Jet Evolution

The very bright, active quasars 3C 273, 3C 279, and 3C 345 are key objects in variability studies across the electromagnetic spectrum, and the first report of large fractional variations in radio emission in 1965 was based on observations of these 3 sources obtained with the University of Michigan 26-meter paraboloid. These structurally-complex 3C objects were subsequently monitored for over 40 years with the Michigan dish (UMRAO) providing a continuous record of total flux density variability at 8 GHz over 4 decades, and of all Stokes variability at 14.5, 8.0, and 4.8 GHz since the late 1970s. The resulting archival data set provides information on the simultaneous spectral evolution of the total and polarized flux on decadal timescales over multiple, consecutive outbursts occurring in the parsec-scale jet flow, yielding clues to the origin of changes in the underlying jet properties. Complementary VLBA 15 GHz images from MOJAVE during the last decade of UMRAO operation permit resolving the emission contributions from core and jet components, and the combined single dish and VLBI data provide insights into the effects of changes in inner jet orientation on the observed source-integrated emission (geometric effects). Investigations have included searches for periodic behavior, potentially indicative of jet precession, and identification of temporal changes in the magnetic field orientation relative to the jet flow direction. I discuss major results and their implications.

Speaker: Margo Aller (University of Michigan)

54 Multiwavelength behaviour of the blazar 3C 279: decade-long studies from $\gamma$-rays to radio.

We report the results of the decade-long (2008--2018) monitoring of the blazar 3C 279 from $\gamma$-rays to 1 GHz radio frequencies, including Fermi and Swift data, obtained within the frames of an intensive GASP-WEBT collaboration campaign as well as polarimetric and spectroscopic data, collected during the same time interval. We have found that: 1) the X-ray and $\gamma$-ray light curves correlate remarkably well, with no delay $\ge 3$ hours, implying co-spatiality of the regions; 2) the $\gamma$-ray flux - optical flux relation depends on the source activity state, with a slope of the relation changing from a linear to a higher degree dependence; 3) Stokes parameters behaviour at optical and radio wavelengths, including imaging with the VLBA at 43 GHz, supports either a dominance of helical structure in the magnetic field configuration or motion of the radiating plasma along a spiral path. We analysed the temporal behaviour of MgII emission line and found that the line flux in "blue" and "red" wings of that line correlate with the continuum flux density. In radio bands we see progressive shifts of the most prominent light curve details with decreasing frequency, corresponding to the growth of the $\tau=1$ surface. In addition, some details in the radio light curve emerge and disappear with the decreasing frequency that suggests different Doppler boosting of stratified radio-emitting zones in the jet.

Speaker: Valeri Larionov (St.Petersburg University)

55 Exploring the Dominant Gamma-Ray Emission Mechanism using Multiwavelength Variability Analysis. Case Study: 3C 279

In this contribution, I will present the results of a paper on the Flat Spectrum Radio Quasar 3C 279. We use light curves that cover a time-frame of six years, at different wavelengths: Gamma-rays, X-rays, UV 3000 Å continuum, optical V band, Near-Infrared (NIR) JHK bands, 1mm, as well as optical spectropolarimetry. By applying cross-correlation analysis, We find that the UV continuum, optical, and NIR bands are correlated with delay zero. This correlation suggests that the emission regions are co-spatial. We also find a correlation between the UV continuum and the 1mm emission, implying that the dominant emission mechanism is synchrotron, and therefore the same is true for the optical and NIR. This is supported by the high optical polarization degree observed. Based on the behaviour of the gamma-ray light curve, we identified three different activity periods (A, B, and C), and we repeated the cross-correlations between the different light curves, on each different period. The results for activity period A suggest that the gamma-ray emission is dominated by Synchrotron Self-Compton. The results for activity period C imply that External Inverse Compton is the dominant gamma-ray emission mechanism. Meanwhile, activity period B shows flares in all bands, with the exception of the gamma-rays which appear to not have any significant activity on this period. We propose that the lack of gamma-ray activity during period B is caused by an increase in the electron-positron pair production. In order to test this, we developed an analytical model to calculate the interaction cross-sections for both, inverse Compton scattering and electron-positron pair production. Our results state that an increase in Lorentz factor can cause the pair production cross- section to increase at higher rates than the inverse Compton. This makes our theory plausible. This is the first time that observational proof has been published, that the dominant gamma-ray emission mechanism in blazars changes with time.

Speaker: Dr Victor Manuel Patiño Alvarez

10:30 Coffee Break

56 Analysis of 3C 279 Orphan Gamma-Ray Flare

Consistent multiwavelength observations of the blazar 3C 279 can be attributed at least in part to the legacy of the Third Cambridge Catalogue. The monitoring campaign during Dec 2013 discovered a very bright, 12-hour, orphan gamma-ray flare with a uniquely hard FermiLAT spectrum and high Compton dominance. We apply a novel theoretical model in the one-zone, leptonic tradition, which now reproduces this unique flaring behavior. We develop a simplified analytic electron energy distribution of the primary radiative cooling region in the relativistic jet to provide intuition about how individual acceleration processes shape blazar emission spectra. Understanding contributions of individual physical processes in relativistic, astrophysical jets is fundamental to elucidating the energy budget near supermassive black holes and the that involved in AGN feedback as the jet impacts the surrounding environment. We rule out the possibility that significant acceleration occurs via magnetic reconnection due to the very low magnetization parameter, and constraints on the maximum Larmor radius for the jet geometry. Our analysis suggests that the flare is initiated by an increase in the particle energies due to shock acceleration, which also increases the stochastic acceleration. The higher energy particle preferentially occupy the outer jet, along the sheath, which decreases the apparent magnetic field and synchrotron radiation, while increasing electron exposure to the BLR photon fields, driving up the external Compton emission.

Speaker: Dr Tiffany Lewis (University of Haifa/Tel Aviv Univeristy)

57 Acceleration of AGN jets on parsec-to-kiloparsec scales.

We probe jets kinematics in 11 radio-loud AGN without relying on multi-epoch VLBI kinematics analysis. The method is based on measuring multi-frequency total flux density time delay and core shift in the jets. Our estimates of the apparent jet speed are consistent with the highest velocities seen by VLBI. We derive Doppler factors, Lorentz factors and viewing angles of the jets, as well as the corresponding de-projected distance from the jet base to the core. The results support evidence for acceleration of the jets with bulk motion Lorentz factor $\Gamma\propto R^{1/2}$ on de-projected scales $R$ of $0.5-500$ parsecs.

Speaker: Alexander Kutkin (ASC LPI)

58 The radio properties of FR0 radio galaxies

There is compelling observational evidence that an emerging group of
compact radio galaxies, which lack of extended radio emission,
dominate in number the radio-loud AGN population in the local Universe. We call
these sources 'FR0' in opposition to the other Fanaroff-Riley classes
to emphasize their lack of prominent extended radio emission. They
are compact on a scale of < 5 kpc, within the host galaxy. Their host
and nuclear properties are indistinguishable from the FRI radio
galaxies, but more abundant and with smaller jets than classical
FRIs. I will present high and low-resolution observations down to low
radio frequencies (from EVN, eMERLIN, VLA, LOFAR and GMRT) to
reconstruct the radio spectral properties and then the history of this
abundant population. Considering the whole properties of the FR0s, we
speculate their possible origins (young radio sources or more exotic
nature) and the possible cosmological scenarios they imply.

Speaker: Dr Ranieri Diego Baldi (University of Southampton)

59 UNVEILING THE PARTICLE ACCELERATION REGIONS IN 3C HOT SPOTS

The discovery of diffuse optical and X-ray synchrotron emission in a number of low-power radio hotspot requires a revision of the standard scenario of particles accelerated by a single strong shock generated at the jet termination. High energy electrons like those responsible for the X-ray emission should arise from very small regions because their short lifetime should limit their emission to a narrow emitting disk. We present the results of our multi-wavelength campaign on a small sample of hot spots of the 3C catalogue. The high-sensitivity JVLA, near-infrared and optical observations allowed us to probe the small-scale structure of the hot spots, unveiling the presence of compact ($<$hundreds pc) features, and to resolve the distribution of the magnetic field across the hot spot. We discuss these finding in the framework of the mechanisms accelerating particles and producing the broadband radio-to-X-ray hot spot emission.

Speaker: Giulia Migliori (DIFA-INAF/IRA)

60 Peering Into the Extended X-ray Emission on Megaparsec Scale in 3C 187

We present an imaging and spectral analysis of Chandra data for the radio galaxy 3C 187 (z = 0.465). The diffuse X-ray emission around 3C 187 in the 0.5-3 keV band is found to extend up to ~ 900 kpc along the radio lobe direction and ~ 700 kpc in the cross-cone direction. Spectral X-ray analysis in combination with radio data yields a possible interpretation of the emission observed in the lobes as IC/CMB radiation. In a thermal scenario, the emission from the cones can be interpreted as thermal radiation from hot gas with temperatures of ~ 2.2 keV and ~ 5.4 keV, respectively. Using NOMAD optical data we found that 3C 187 belongs to a red-sequence of 14 optical sources whose color distribution differs significantly from background sources. Although this can be an indication that 3C 187 belongs to a cluster of galaxies, whose ICM can be responsible for the emission observed in the north lobe and cross-cone region, deeper X-ray observations and optical spectroscopic data are needed to get a clearer picture of this source.

Speaker: Alessandro Paggi (INAF-OATo)

12:40 Lunch

61 Special Session Summary: Radio Galaxy Classification

Speaker: Prof. Lawrence Rudnick

62 Special Session Summary: Multi-wavelength perspective of the 3C radio sources

Speaker: Barbara Balmaverde (INAF - Osservatorio astronomico di Brera)

63 Special Session Summary: Polarimetry

Speaker: Prof. Alan Marscher

15:20 Coffee break

64 Radio galaxies in gamma rays

The third Cambridge catalogue (3C) includes several sources detected at gamma-ray energies. While blazars outnumber radio galaxies in the Fermi Large Area Telescope (LAT) catalogues by nearly two orders of magnitudes, counts are more balanced among the bright, steep spectrum sources composing the 3C. Starting with a focus on the gamma-ray detected 3C radio galaxies, we will present a summary of the properties of misaligned active galactic nuclei (M-AGN) included in the fourth catalogue of AGNs detected by the LAT (4LAC). We will report on the number of sources and their distributions in gamma-ray luminosity, photon index, FR type, and multi-wavelength properties. We will also discuss the implications in terms of location and emission processes for the high energy emission. Finally, we will present the prospects offered by future observations in gamma rays with LAT and the Cherenkov Telescope Array, as well as in radio with the new facilities eventually leading to the Square Kilometre Array.

Speaker: Marcello Giroletti (INAF Istituto di Radioastronomia)

65 Gamma-emission and variability: Beaming in Radiogalaxies

Unification suggests that Blazars are beamed, jet-on oriented radio-galaxies.
The phenomenological distinction between Blazars and Radiogalaxies was originally established before gamma-ray observations revealed efficient Compton-cooling in Blazars. A growing sample of radio-galaxies with extended jets that do not appear highly beamed in radio-studies have been detected at very high gamma-ray energies and exhibit variability comparable to typical Blazars. This leads to a reassessment of estimates of relativistic beaming in radio-galaxies. Gamma-ray spectra and variability properties of radio-galaxies are compared to beaming models, suggesting that the common opening angle of emitting zones in single sources is considerably wider then suggested in unification models.

Speaker: Stefan Wagner (LSW, U. Heidelberg)

66 Closing lecture

Speaker: Prof. Diana Worrall

67 Concluding remarks

Speaker: Prof. Francesco Massaro

Farewell