Life Cycles 2018

Contributions for Life Cycles 2018

TALKS

Energetics, structure of jets and radio-galaxy populations

Name: Judith Croston
Contribution: Talk
Title: Particle content, radio galaxy morphology and jet power: all radio-loud AGN are not equal
Abstract: I will present the first systematic comparison of the plasma conditions in Fanaroff & Riley class I and II radio galaxies, which demonstrates conclusively that their internal composition is different. I will discuss the reasons for this difference, and its implications for the jet-power/radio-luminosity relationship. I will also show evidence that lobe composition is unconnected to accretion mode (optical excitation class). I will discuss the implications of this work for interpreting the results of new radio surveys such as the LOFAR Two-Metre Sky Survey, and will also show how these results may provide a method for inferring the environmental conditions of high-redshift radio-loud AGN.

Name: Stas Shabala
Contribution: Talk
Title: Modeling the environmental dependence of radio galaxy populations
Abstract: Feedback from AGN radio jets is held responsible for regulating star formation in the most massive galaxies over the last half of Hubble time. Observations of radio galaxy populations encode important information on feedback energetics and duty cycles, yet interpreting these observations is challenging due to the highly non-linear nature of the mapping between the observable and physical properties of radio jets.
I will present our group’s work on modeling the jet-environment interaction using a combination of analytical and numerical techniques. A major departure from existing dynamical radio source models is in using galaxy clustering to describe environments into which the jets expand; this approach allows jet models to be easily integrated within a semi-analytic galaxy formation framework. We find that the mapping between observables (such as radio luminosity) and physical parameters (such as AGN jet power and age) is strongly environment-dependent, and also evolves substantially over the AGN lifetime. A combination of models, broadband radio and ancillary multi-wavelength data, such as from the ongoing GAMA Legacy ATCA Southern Survey (GLASS), will help us quantify the AGN-environment interaction.

Name: Wendy Williams
Contribution: Talk
Title: The LoTSS first data release
Abstract: The LOFAR Two-metre Sky Survey first data release (LoTTS-DR1) includes direction-dependent calibrated images covering over 400 sq degrees at a resolution of 6 arcsec and down to a noise level of ~70 microJy/beam. The source catalogue contains over 300,000 sources, which we have cross-identified, through a combination of likelihood ratios and visual classification, with Pan-STARRS/WISE optical sources for which we also provide photometric redshifts. I will give a brief update on the data release and also give an update on the recent progress with the survey, in particular with the deeper Tier-2 fields.

Name: Beatriz Mingo
Contribution: Talk
Title: What can the extended sources from the LOFAR HETDEX survey teach us about the life cycles of AGN?
Abstract: I will present the results of our automatic classification of ~10000 extended sources with fluxes above 2 mJy in the LOFAR HETDEX field. With the aid of SDSS data we can separate nearby star-forming galaxies from radio galaxies, use our code to reliably classify the latter as Fanaroff-Riley class I and II, and to identify candidate sources with hybrid morphologies.
I will present the population distributions we obtain with our classifications and the properties of their hosts, and discuss the implications of our results and the potential of this dataset to provide new insight on the duty cycles of AGN and their co-evolution with their host galaxies and large-scale environments.

Name: Martin Bourne
Contribution: Talk
Title: Jet feedback in galaxy clusters
Abstract: Accretion onto supermassive black holes releases large amounts of energy, for example as radio jets, which inflate the X-ray cavities often observed in galaxy clusters. Jets heat and stir the ICM, and influence galaxy and cluster evolution. However, how the mechanical energy of the jets is isotropically communicated to the ICM remains an open question. Detailed observations of galaxy clusters, have shed light on the properties of the ICM and can be used to place constraints on jet-driven feedback in galaxy clusters. From a theoretical standpoint, hydrodynamic simulations provide a key opportunity to test models of jet feedback in galaxy clusters and explore parameter space. However, the large dynamic range in the mechanisms governing AGN feedback and its interaction with galaxy clusters, makes modelling the relevant scales a formidable task. I will present results from a new set of jet feedback simulations, recently performed using the moving mesh code AREPO. The simulations allow us to investigate the interplay between the jet and ICM in both idealised and more realistic conditions. We study the jet lobe inflation and mechanisms that heat the ICM, with particular emphasis placed upon the roles of jet-driven turbulence and pre-existing substructure-driven bulk turbulence within the ICM. I will discuss how our results compare to Hitomi observations of the Perseus cluster and what implications this has for how jet feedback communicates with the ICM.

Name: Gianluigi Bodo
Contribution: Talk
Title: Dynamics of turbulent jets
Abstract: FRI radio sources are traditionally associated with turbulent jets, however very few numerical simulations of such kind of flows have been presented. We have started a systematic numerical investigation of turbulent, low Mach number jets, and I will present the first results discussing
the entrainment properties and the interaction with the ambient medium.

Name: Jeremy Harwood
Contribution: Talk
Title: The identification and analysis of radio galaxies in the era of big data
Abstract: Over the next few years, surveys from SKA precursors such as the LOFAR Two-metre Sky Survey (LoTSS), and the MeerKAT MIGHTEE survey, along with complementary surveys from established telescopes such as AGES-XL, will provide high sensitivity, high-resolution observations with excellent image fidelity for thousands of radio galaxies. The field is therefore set to move away from individual objects and enter an era of determining characteristic properties for the population as a whole. However, the identification and analysis of resolved radio galaxies (particularly rarer objects such as those in the remnant phase) have historically been a manual task relying on serendipitous discoveries, a process which is not feasible with the large volumes of data produced by forthcoming and future surveys.
In this talk I will focus on how emerging techniques that are able to use multiple galaxy properties for identification can be applied to large radio surveys in an automated manner. I will show how machine learning (both supervised and unsupervised) can be used for the identification of remnant radio galaxies and how this is being applied to the HETDEX and Lockman hole fields in order to identify remnant radio galaxies. I will go on to discuss how this may be applied to future surveys in order to identify not only remnants, but a multitude of source types.

Name: Aleksandar Shulevski
Contribution: Talk
Title: The life and times of 3C236
Abstract: The talk focuses on the highest resolution imagery we were able to obtain with LOFAR of this giant radio galaxy. Re-started AGN like 3C 236 offer a unique possibility to constrain their duty cycle. I will elaborate on the new insights we now have into the activity history of 3C236 via broad-band radio studies and put it in context of the broader picture of AGN energetics emerging from the latest studies done with data sets obtained at very low radio frequencies.

Life cycles of radio galaxies

Name: Monica Orienti
Contribution: Talk
Title: Young radio sources and the life-cycle of the radio emission
Abstract: The evolutionary stage of a powerful radio source originated by an AGN is related to its linear size. In this context, compact symmetric objects, which are powerful and intrinsically small objects, should represent the young stage in the individual radio source life. Following the evolution models, these objects would evolve into the population of classical radio galaxies. However, the fraction of young radio sources in flux density-limited sample is much larger than what expected from the number counts of large radio sources, suggesting the existence of short-lived radio sources. With the aim of investigate the incidence of short-lived objects we selected a sample of 18 fader candidates with steep-spectral index. The sources were target of high-resolution multifrequency observations in order to confirm the lack of active regions.
In this presentation I will discuss the physical conditions of young radio sources on the basis of high resolution VLBI observations. In particular I will present preliminary results on VLBA and JVLA observations of the sample of fader candidates and discuss their properties in the context of radio source evolution.

Name: Daniele Dallacasa and Monica Orienti
Contribution: Talk
Title: Young radio sources: truthful or liar objects?
Abstract: From a sample of possibly young radio sources, we show that most of the candidates are something different. This is somehow expected in relative numbers of young (small), middle age (middle size) and old (large) radio sources. Therefore, finding genuinely young radio galaxies is a largely unsuccessful task. Among the few objects which can be termed young, simple assumptions/model fail to describe the evolution of the spectrum as the source grows. We will present a relatively small sample of about 30 young source candidates and discuss their radio spectrum as well as the shape evolution over more than a decade.

Name: Aleksandra Wolowska
Contribution: Talk
Title: Discovery of new radio transients - short-lived radio-loud AGNs
Abstract: Despite the intensive studies of the evolution of radio-loud AGNs we still don't know many details of this process. In the general scenario of the evolution, the younger and smaller Gigahertz-Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources become large-scale FRI and FRII objects. However, a growing number of observations of low power radio sources suggests that the model cannot explain all their properties and there are still some aspects of the evolutionary path that remain unclear. There are indications, that some sources may be short-lived objects on timescales 10^4 - 10^5 years. Those objects represent a new population of active galaxies. Here, we present discovery of several radio transient sources on timescales of 5-20 years, largely associated with renewed AGN (Active Galactic Nucleus) activity. These changing-look AGNs possibly represent behaviour typical for many active galaxies.

Name: Joseph Callingham
Contribution: Talk
Title: Learning lots about radio galaxy evolution from LoTSS: A low luminosity peaked-spectrum sample
Abstract: The LOFAR Two-metre Sky Survey (LoTSS) is a deep 120-168 MHz imaging survey that will eventually cover the entire Northern sky at ~6” resolution and with a sensitivity of ~100 micro-Jy/beam. This survey will produce the most complete low-luminosity (P_1.4GHz < 10^25 W/Hz) peaked-spectrum sample to-date. I will show in this talk that there are many more low-luminosity peaked-spectrum sources than previously expected, and most of them appear to be too weakly powered to break out of their host galaxy and evolve into known massive radio galaxies, such as Centaurus A and Cygnus A.

Name: Marek Jamrozy
Contribution: Talk
Title: Radio and optical properties of extragalactic radio sources with recurrent jet activity.
Abstract: Active galactic nuclei in general can be classified into a number of separate categories; among others, the radio galaxies with two or more pairs of lobes extending from the core along the same axis, called double-double radio sources. Besides the axial symmetric sources, there is another type of recurrent activity radio galaxies. These are objects exhibiting large-scale diffuse relic radio emission
that is due to an earlier cycle of activity. Such relics can be seen around compact powerful young radio sources. The AGNs with repeated jet activity could affect both the parent galaxy and the diffuse extended radio structure. Therefore, some properties of the objects with multiple activity cycles can be different from the radio galaxies with single activity.
In this talk I will summarise results on radio and optical investigations of a sample of 74 radio sources with recurrent jet activity.

Name: Vijay Mahatma
Contribution: Talk
Title: Determining the Age of Radio Galaxies
Abstract: Radio-loud AGN are the dynamical footprints of accretion onto supermassive blackholes. In determining their global energetics over cosmic time, i.e the jet power-radio luminosity function, a crucial ingredient is the source age. Various methods of extracting source ages from observations have led to discrepancies in the past, and hence inaccurate calculations of jet power. Here, I present a detailed investigation of two powerful radio galaxies and their source dynamics and energetics. We find that the spectral age and dynamical age of a radio galaxy can agree precisely under certain conditions, although some major caveats remain. These studies will be useful in determining individual jet power estimates from upcoming radio surveys (e.g LoTTs, SKA etc). I also present some recent results of larger sample studies of radio galaxies captured during their remnant and restarting phases observed with LOFAR.

Name: Marisa Brienza
Contribution: Talk
Title: Studying the late stages of radio galaxy evolution with LOFAR
Abstract: Low frequency observations have opened the way to the search and study of remnant radio galaxies. These sources represent the last evolutionary stage of radio galaxies, when the jets switch off, and have remained elusive and poorly understood so far.
In this talk we present some first results obtained with LOFAR in this field, i.e. the study of the serendipitous remnant radio galaxy `Blob1' and a systematic search for remnants in the Lockman Hole, a well-studied extragalactic field.
The spectrum of Blob1, with a moderately steep spectral index at low frequency and a sudden steepening above 1400 MHz, has shown that not all remnants have ultra-steep spectra down to MHz frequencies as classically assumed. In light of this, we have performed a systematic search of remnants using, for the first time, a combination of spectral criteria (the classical ultra-steep spectral index and high spectral curvature) and morphological criteria (low radio core prominence and relaxed shapes) to construct a complete sample. We have identified 23 candidates with different characteristics that we propose are related to different stages of the remnant evolution. For ~90% of the radio sources we identified an optical counterpart with redshift information and therefore estimated their physical properties. Interestingly, we find that also at low frequency the fraction of remnants remains low, suggesting a very rapid luminosity evolution of the plasma.
To predict the fraction of remnants expected in radio flux limited samples, we also created mock catalogues of radio galaxies using Monte-Carlo simulations based on known radiative and dynamical evolution models. In this talk we discuss the results of these simulations and in particular how the fraction of mock remnants compares to that observed in the Lockman Hole when different models are used.

Name: Nika Jurlin
Contribution: Talk
Title: Restarting radio galaxies in the Lockman Hole
Abstract: Super massive 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. In particular, the low radio frequencies can be used as fossil record to trace the oldest populations of particles. Therefore, they are ideal tool to study past epochs of jet activity and characterise the active, inactive and restarted phases of radio galaxies.
Restarted sources, which are the focus of my talk, are sources that exhibit remnant plasma from a past AGN activity and, at the same time, new-born jets. In order to broaden the understanding of episodic jet activity and to constrain its time scales, it is important to identify statistically significant samples of restarted radio galaxies.
In this talk, I will present a preliminary sample of candidate restarted radio galaxies that we selected with the LOw Frequency ARray (LOFAR) in the Lockman Hole extragalactic field, which covers 25 square degrees with a resolution of 6 arcsec and a rms noise of 150 uJy/beam. This sample was selected from deep LOFAR images obtained on the basis of spectral criteria, high radio core prominence, and relaxed, diffuse and faint outer emission combined with bright and compact inner structures being used as morphological criteria. I will discuss their rate of occurrence, which provides fundamental information for understanding the duty cycle of radio sources.
The methods for the identification of restarted radio sources developed for this project will soon be applied for selecting larger samples in the LOFAR Two-metre Sky Survey.

Accretion, triggering and multi-wavelengths

Name: Clive Tadhunter
Contribution: Talk
Title: The importance of long-term variability in understanding the radio source population
Abstract: There remains considerable uncertainty about what determines the radio morphologies of radio-loud AGN (e.g. whether FRI or FRII), and how we understand the links between radio and optical activity: is the gaseous environment the most important factor, or is it the rate or mode of accretion onto the central super-massive black hole? In this talk I will explore the idea that a combination of accretion rate and long-term variability largely determine the radio and optical properties of the population of powerful radio sources, with gaseous environment playing a secondary role.

Name: Martin Krause
Contribution: Talk
Title: Powerful radio jets are linked to binary black holes and galaxy mergers
Abstract: Where gas accretion produces powerful jets, this may reveal any binary nature of supermassive black holes via the geodetic precession induced of the black hole spins. In a complete sample of powerful jet sources with high resolution VLA maps, we find the majority are precessing. The precession periods typically suggest binaries with separations of less than a parsec, similar to expectations from galaxy merger simulations. Complementary evidence corroborates this finding.
This connects powerful jets to close binary black holes and corroborates the idea that powerful jet episodes might be linked to galaxy mergers.

Name: Dan Dicken
Contribution: Talk
Title: The dust masses of powerful radio galaxies: clues to the triggering of their activity
Abstract: As part of our continuing effort to study the triggering of powerful radio AGN, we present the results of the latest Herschel infrared imaging campaign of the southern 2Jy sample of 46 powerful radio galaxies (z$<$0.7). With an excellent detection rate across the Herschel PACS and SPIRE bands (100-500 microns) we revisit the question of non-thermal contamination of the thermal infrared signature from dust. Because the latter traces activity from the AGN and star formation, accounting for the non-thermal infrared component is important for the correct interpretation of the data. In addition, following on from previous work, we use the far-infrared imaging data to estimate the dust and gas content of the sample. We compare techniques for estimating the dust mass from infrared photometry in order to check our conclusions and cross match the dust mass results for our radio galaxy sample with ULIRGs and local elliptical galaxies. The results confirm that radio-galaxies lie in a unique range of dust masses below that of ULIRGS but above that of elliptical galaxies. This has important consequences for understanding the triggering of powerful radio AGN.

Name: Hannah Stacey
Contribution: Talk
Title: Extreme dust-obscured star-formation in quasar host galaxies revealed through gravitational lensing
Abstract: Investigating the connection between star formation and AGN growth in the high redshift Universe is challenging due to limitations in sensitivity and resolution of observational data. Previous studies have revealed high levels of star formation in quasar host galaxies, but studies of individual quasars have inevitably focused on a few bright sources. By targeting quasars that are gravitationally-lensed we probe intrinsically lower luminosities, allowing us to study more typical quasars and construct a more complete sample of the population. We have derived FIR luminosities and SFRs for the 104 gravitationally-lensed quasars observed with Herschel/SPIRE, the largest such sample ever studied. We find evidence for dust-obscured star formation in 72% of the sample, a result is in line with current models of quasar evolution but suggests that most quasars have coexistence of extreme dust-obscured star-formation and accretion. A more complete understanding of this result requires detailed observations of individual objects. In this respect, high-resolution follow-up of lensed quasars from within our sample will be important as it will allow the radio jets, host galaxy, heated dust and gas to be mapped on small angular-scales. In addition to the Herschel study, we present the initial results of our high-resolution studies of the FIR emission as traced by ALMA, which resolve the AGN- and star-formation-heated dust on scales of 10-200 parsecs in combination with sophisticated gravitational lens modelling techniques.

Name: Vanessa Moss
Contribution: Talk
Title: Connecting HI and soft X-ray absorption in distant AGN with next-generation telescopes
Abstract: Recent studies of young radio galaxies have revealed the presence of dense and dusty gas near the active nucleus traced by both 21cm HI absorption and soft X-ray absorption (e.g. Ostorero et al. 2010, Siemiginowska et al. 2016, Glowacki et al. 2017, Moss et al. 2017), offering new insight into the physical nature of the circumnuclear medium in these distant galaxies. I will detail our findings so far and the significance of our results, as well as current work that is being conducted as part of ASKAP Early Science, within the scope of the SEAFOG project (Studies with eRosita And FLASH of Obscured Galaxies). I will also highlight how these pilot observations reflect the future prospects of all-sky radio/X-ray complementarity in this space, particularly in the context of synergy between telescopes such as ASKAP, eRosita, Athena and the Square Kilometre Array.

Name: James Allison
Contribution: Talk
Title: The cold gas reservoir feeding a distant interacting young radio galaxy
Abstract: While some radio galaxies show stong emission lines in the optical, characteristic of an active galactic nucleus, others do not. We have substantial circumstantial evidence that this dichotomy is the result of the mode in which gas is accreted onto the nucleus. However, the exact mechanisms by which high and low excitation radio galaxies are nourished can only be determined through direct observation of the gas. A powerful method for measuring the kinematics of gas deep into the centres of radio-loud AGN is through detection of the HI 21-cm hyperfine and CO rotational lines in absorption. The ASKAP telescope, in its commissioning and early science phase, has been very successful in detecting HI absorption in radio galaxies at intermediate cosmological redshifts. In followup observations using ALMA we have detected CO(2-1) absorption in PKSB1740-517, a young powerful radio galaxy at z=0.5 that is seen to be interacting with its companions. I will discuss the results of this work, including how we can disentangle the line-of-sight ambiguities from absorption and what we learn about the system by combining the ASKAP, ALMA and multiwavelength ancillary data.

Name: Barbara Balmaverde
Contribution: Talk
Title: The MURALES survey: a MUse RAdio Loud Emission lines Snapshot.
Abstract: We report the first results of the MURALES survey, a complete program of MUSE observations of nearby (z<0.3) 3C radio galaxies. The MUSE data can be combined with the unique multiband dataset available for these sources, produced with all major observing facilities at all accessible wavelengths, adding a key ingredient for our understanding of the radio-loud AGN phenomenon. It is now possible to explore the gas kinematics, its relationship with the relativistic outflows, and unveil jet-triggered star forming regions, enabling us to explore quantitatively the feedback process. We already fully modelled the MUSE data obtained for the first 20 (out of 40) sources. The line emission images of unprecedented depth revealed the widespread presence of filamentary structures extending several tens of kpc, preferentially oriented perpendicularly to the radio jets, likely the remnants of the gas rich mergers which triggered the AGN. We also found a dual AGN associated to 3C459, formed by a radio-loud AGN and a Seyfert 2, separated by 4 kpc.

Name: Filippo Maccagni
Contribution: Talk
Title: ALMA observations of AGN fuelling: the case of the young radio source PKS 1718-649
Abstract: Active Galactic Nuclei (AGN) are powered by the accretion of material onto the supermassive black hole in the centre of a galaxy. Finding direct evidence of this accretion has proven to be a particularly difficult task and has been successful only for very few sources. One of the best candidates to study the mechanisms of triggering and fuelling of AGN is the “baby” radio source PKS B1718-649, an AGN of only 100 years old.
In this talk, I will present a multi-wavelength study of the cold gas of PKSB 1718-649. In this young (100 years) radio source, we detected two HI absorption lines tracing gas that may fuel the central black hole. Follow-up SINFONI observations allowed us to detect warm molecular hydrogen that also may contribute fuelling the AGN. Recent ALMA observations allowed us to trace the cold molecular gas (using carbon monoxide, CO) with unprecedented spatial resolution, on large scales but also down to the very centre of the galaxy, less than 100 pc from the black hole. In particular, against the compact radio emission of the source (r~2pc), we detected CO gas in absorption at red-shifted velocities with respect to the systemic velocity (v = +365 ±22 km/s). This CO (2-1) absorption line could trace molecular clouds falling onto the central super-massive black hole. These clouds are likely located within the innermost 75 pc of the radio source. The ALMA observations of PKS 1718-649 provide one of the best indications a population of cold clouds is falling towards a radio AGN, likely fuelling its activity, and allow us to better understand how radio sources are born.

Radio-quiet and weak radio sources

Name: Alessandro Capetti
Contribution: Talk
Title: Exploring the properties of FR0 radio galaxies
Abstract: Samples of radio galaxies with high flux limits provide us with an incomplete view of radio-loud AGN. Indeed the bulk of this population is dominated by objects lacking of large scale (>10 kpc) radio structures. They have been called "FR0" as a convenient way to connect them into the canonical
Fanaroff-Riley classification scheme. The questions that arise are: why only a minority of radio-galaxies show large scale radio-structures despite the similarity in the hosts and central AGN properties? What is the link between FR0s and the extended radio-galaxies? The available radio data for these galaxies are limited, of insufficient spatial resolution to explore their morphology and without any spectral information.
We recently obtained multiband high resolution JVLA observations of a sample of 18 FR0s. Only three of them are resolved, with symmetric emission extending a few kpc and with a FRI-like morphology. The remaining sources are still unresolved at a resolution of 100-200 pc. I will discuss the implications of these results, considering also the spectral properties.

Name: Preeti Kharb
Contribution: Talk
Title: A Multi-scale Study of Outflows from Low Luminosity AGN
Abstract: I will present the findings from our multi-scale study of low luminosity AGN (LLAGN) comprising Seyfert and LINER galaxies. We have been observing LLAGN on parsec-scales with Very Long Baseline Interferometry (VLBI), as well as on kiloparsec-scales with the VLA and GMRT. These observations are revealing a host of complicated radio structures ranging from weak bases of coronal winds or jets, to lobes with combined AGN and starburst contributions, and relic lobes from previous episodes of AGN activity. I will briefly discuss these results and attempt to arrive at a comprehensive picture.

Name: Ranieri D. Baldi
Contribution: Talk
Title: LeMMINGS: the eMERLIN radio legacy survey of nearby galaxies
Abstract: I will present the first data release of high-resolution 1.5-GHz radio observations of 103 nearby galaxies with the eMERLIN array. The sample consists of active and non-active galaxies, taken from the Palomar sample. The radio images reveal a broad variety of morphologies: one/two-sided jets, double-lobed jets, complex structures and star formation regions on a typical scale of ~100 pc, down to a radio luminosity of 10^32 erg/s. By dividing the sample into optical classes, LINERs show more core-brightened radio morphologies and appear to be the scaled-down version of FRI radio galaxies; Seyferts show less collimated jets than LINERs; HII galaxies and Absorption-line galaxies are a mixed population of weakly active and silent black holes. In addition, I also find that that jetted radio sources follow the optical fundamental plane of black hole activity, suggesting a common disc-jet relationship.

Name: Isabella Prandoni
Contribution: Talk
Title: The role of AGN feedback in galaxy evolution
Abstract: Feedback processes associated with active galactic nuclei (AGN) are claimed to have important impacts on the circumgalactic environment and the subsequent evolution of the host galaxy. Two main variants of feedback are commonly discussed: radiative and kinetic. The former requires a radiatively efficient (quasar-like) AGN; the latter an energetic outflow or jet. These generic processes can occur together, or one may dominate. To properly understand the detailed process of galaxy formation and evolution there is an urgent need to identify and quantify the role of AGN feedback, not only through detailed studies in the local Universe, but also at high redshifts, where most of the accretion occurred.
In this talk I will present results from two radio-selected AGN samples.
The first is a volume-limited (z<0.03) representative sample of massive, radio-loud (RL) early-type galaxies (ETG; mainly FRI radio galaxies). A systematic study of the various gas phases (ionised and molecular) and of the stellar and dust components in this sample, in comparison with local samples of radio-quiet (RQ) ETGs (e.g. ATLAS3D) will enable a better understanding of the feeding of AGNs and will isolate the role played by jet-induced feedback (likely the dominant feedback mode in local, massive ETGs) in the overall formation and evolution of ETGs.
The second, extracted from a deep (uJy), high (sub-arcsec) resolution, radio survey of the GOODS-N region, is mainly aimed at a better understanding of the interplay between star formation and black-hole accretion at the epoch when both peak (z~1-3). This is done through a radio spectro-morphological comparative study of star-forming galaxies, RQ and RL AGNs.

Name: Miranda Jarvis
Contribution: Talk
Title: Prevalence of radio jets associated with quasar outflows and feedback
Abstract: We have identified radio jet structures in ~70% of a sample z<0.2 type~2 `obscured’ quasars that host kpc-scale ionized gas outflows. This is despite our targets being classified as `radio quiet’ with moderate radio luminosities (logL[1.4GHz]=23.3-24.4 W/Hz) and expected to be associated with `quasar mode’ feedback. I will present our results on the pilot sample of 10 objects that combine high resolution (~0.3-1 arcsec) radio imaging at 1-6GHz with IFU observations. Our initial results demonstrate that is it extremely common for jets to be spatially and kinematically linked to kpc-scale ionized gas kinematics in such quasars. Therefore, radio jets may be an important driver of outflows during `quasars feedback’ which appears to blur the lines between traditional divisions of feedback modes. Based on a recently accepted VLA proposal our sample should reach ~50 quasars in 2018 and I will outline our on-going multi-wavelength campaign to obtain multi-phase gas tracers for a full picture of how low-z quasars impact upon their host galaxies.

Name: Jonathon Pierce
Contribution: Talk
Title: Exploring the properties of AGNs with intermediate radio powers
Abstract: Though often overlooked, high-excitation radio galaxies (HERGs) with intermediate radio powers represent a large proportion of the local radio AGN population and show evidence for particularly strong jet-induced outflows that have a notable effect on the gas kinematics in their hosts. A good understanding of this population is hence crucial for providing a better representation of the role of AGN feedback in galaxy evolution.
In this talk, I will present evidence that a smaller proportion of this population display tidal features in deep optical images when compared to their high-radio-power counterparts, indicative of a reduced importance in triggering via mergers and interactions. I will also explain how future high-resolution VLA observations will allow us to map the radio emission of these sources on the ~1 - 10 kpc scales of galaxy bulges, to investigate its detailed morphological structure and the potential extent of the associated feedback effects.

Jet-environment interaction

Name: Geoffrey Bicknell
Contribution: Talk
Title: AGN Feedback and the Lifecycle of Radio Galaxies
Abstract: Gigahertz Peak Spectrum and Compact Steep Spectrum sources represent an early phase in the lifecycle of radio galaxies. We have also proposed that they represent an important phase of AGN feedback by relativistic jets, which inject a large amount of energy and momentum into the interstellar medium, either stimulating or quenching star formation. Our recent simulations show that the turnover in the radio spectrum and the low frequency spectral slope may be explained by free-free absorption by the inhomogeneous and turbulent interstellar medium (ISM). Therefore, radio studies of GPS and CSS sources form a valuable complement to optical-IR observations in that they provide information on the structure and extent of the ISM. The duty cycle of these sources is also important for modelling of the star formation - feedback cycle. In addition, those sources which do not break free of the confining ISM probably become FR0 sources, which also play a role in inhibiting star formation via the turbulence that they produce.

Name: Giulia Migliori
Contribution: Talk
Title: A Galactic perspective: (micro)quasar X-ray jets
Abstract: While difficult to catch, large-scale jets of microquasars offer a unique point of view on the physics of the jet interactions with the ambient medium. I will review the main results of the observational campaign targeting the large scale jets of the microquasar XTE J1550-564 in the radio and X-ray bands, and discuss what we can learn on the dynamics, structure and emission of the galactic (and extragalactic) jets.

Name: Dipanjan Mukherjee
Contribution: Talk
Title: Impact of relativistic jets on the ISM of their host galaxy
Abstract: Relativistic jets from AGNs are an important driver of feedback in galaxies. Although primarily considered in the context of energy deposition at scales of ~100 kpc, the jets first interact with the host galaxy's ISM before breaking out to larger scales. Our recent 3D relativistic hydrodynamic simulations, performed on scales of several kpc, investigates the interaction of such jets with an inhomogeneous turbulent ISM within the potential of a galaxy. These simulations address the local gas physics, which is often missed in large scale cosmological simulations due to lack of sufficient resolution. The jets are found to couple strongly with the turbulent ISM, driving fast moving lateral outflows of multi-phase gas. 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 previously. We compare the effect of jet power and ISM density on the feedback efficiency. We show that low power jets remain confined within the host for a longer time driving shocks through the ISM, potentially quench star formation on a large scale. I will discuss the implications of these results on the evolution of the host galaxy, and the effects on observable diagnostics such as thermal and line emission from shocked gas and synchrotron emission in radio wavelengths.

Name: Robert Schulz
Contribution: Talk
Title: The parsec-scale jet-driven HI outflows in powerful radio galaxies
Abstract: Massive outflows of neutral atomic hydrogen in powerful radio galaxies are a striking signature of AGN feedback and considered to be largely driven by the relativistic jets pushing through the interstellar medium. However, information on the complex interplay on parsec-scales is extremely limited but can be retrieved using Very Long Baseline Interferometry (VLBI). We have been conducting a study to locate and characterise the outflow of neutral gas on parsec scales in a small, but diverse sample of young and recently restarted radio galaxies comprising 4C12.50, 3C236, 4C52.37, and 3C293. In this talk, I will compare the differences and similarities of the properties of the HI gas in our sample which will provide important input for theoretical models. Our results indicate that the selected sources could represent different stages of evolution in jet-ISM interaction which shows the need for future larger sample study to enable a more detailed statistical analysis.

Name: Pierre Guillard
Contribution: Talk
Title: Molecular Gas, Turbulence and Star Formation in and out of Powerful Radio-Galaxies
Abstract: Radio and infrared observations of molecular gas in powerful radio-galaxies allows us to describe the energetics of the dense gas heated by AGN feedback processes. I will briefly give an overview of these observations, with a focus on a population of sources revealing unusually strong ratios of C+ and H2 to far-infrared, with very broad linewidths up to 1500 km/s, as well as the recent discovery of a massive and turbulent reservoir of CO and CI emitting gas in the halo of the Spiderweb radio galaxy. I will discuss the impact of turbulence and cosmic-rays on the chemo-dynamical state of the molecular gas and star formation efficiency in and out of those radio-galaxies. Those results have consequences on our interpretation of cooling lines at high-redshifts and on our understanding of dissipation of energy, feedback and energetics of galaxy formation in general.

Name: Stas Shabala
Contribution: Talk
Title: Intermittent jet-mode feedback in hydrodynamical simulations
Abstract: [On behalf of Patrick Yates (UTAS PhD student)]
The radio galaxy duty cycle is observed to scale strongly with host galaxy mass and environment. However, it is currently unclear what (if any) implications this intermittency of the radio galaxy phenomenon has for our understanding of AGN feedback.
We investigate this question through a suite of 2D axisymmetric, non-relativistic simulations of intermittent jets under different energy injection scenarios. The jet kinetic power and total injected energy are kept constant in all simulations. We find that radio lobe size and morphology can be substantially altered due to disturbances in the ambient gas from previous jet outbursts. By comparing the same jets in group and cluster environments, we find that the efficiency with which jet energy can couple to the gas is environment-dependent. Finally, we generate synthetic radio continuum maps and show that environment also plays a key role in setting the observable properties of radio lobes, with lobes in poor environments having lower surface brightness at the same jet power.

POSTERS

Name: Paola Rossi
Contribution: Poster
Title: MODELLING NON-THERMAL EMISSION FROM RELATIVISTIC MAGNETISED FLOWS IN THE PLUTO CODE
Abstract: We describe a new hybrid framework to self-consistently model non-thermal spectral signatures from highly energetic
particles embedded in a large-scale classical or relativistic MHD flow. Our method makes use of Lagrangian particles moving through an Eulerian grid where the (relativistic) MHD equations are solved concurrently. Lagrangian particles follow fluid streamlines and represent ensembles of (real) relativistic particles with a finite energy distribution. The spectral distribution of each particle is updated in time by solving the relativistic cosmic ray transport equation based on local fluid conditions. The evolved distribution from each Lagrangian particle is further used to produce
observational signatures like emission maps and polarization signals. This framework has been implemented in the PLUTO code.

Name: Judith Ineson
Contribution: Poster
Title: Jet environments and energetics, and prospects for finding galaxy groups with new radio surveys
Abstract: The jets of radio-loud AGN heat and disrupt the surrounding plasma and so play an important role in galaxy and cluster evolution. In order to quantify the effect, we need to know the properties of the both the radio galaxy and its large-scale environment. Modern radio interferometers are providing large surveys of deep radio data, but radio galaxies tend to inhabit galaxy groups rather than clusters and estimating group properties at high redshift is problematic.
We used the luminosity of the intracluster medium as a proxy for total cluster mass for a large sample of radio galaxies. We found a strong relationship between radio luminosity and cluster luminosity for Low Excitation galaxies, suggesting that radio luminosity could be used to estimate group/cluster mass for that class of radio galaxies. This correlation is not evident for High Excitation galaxies, which typically reside in groups and weak clusters.
We estimated the internal conditions of the lobes of the FRII galaxies in our sample, and found them to be not far from equipartition and also near pressure balance with their external environment at mid-lobe. We also found that if we assumed these results and also that the environment followed a universal pressure profile, we could predict cluster luminosity using radio data alone. This could give us a way to estimate the properties of low mass groups and clusters hosting FRII galaxies at higher redshifts.

Name: Brendan Webster
Contribution: Poster
Title: Finding low-power radio-loud active galaxies using LOFAR
Abstract: The unparalleled sensitivity and angular resolution of the LOFAR telescope is revolutionizing our view of the universe in the low-frequency radio regime. This makes it the ideal tool for discovering and studying the currently under-researched population of low power radio-loud active galaxies. Whilst current research has generally focussed on the effects that large scale jets have upon the evolution of their host galaxies, far less is known about the effects that small, galaxy-scale, jets can have upon their hosts making this a vital area of research. I will describe the morphological analysis developed to discover these galaxy-scale radio jets and their hosts using LOFAR. I will also present the preliminary analysis of the relationships between the jet and host galaxy properties for the galaxy scale jets found within the wide-area survey of the HETDEX field.

Name: Magdalena Kunert-Bajraszewska
Contribution: Poster
Title: Radio galaxies with LOFAR: Relic emission from opposites scales
Abstract: Different in their age, scale and distance, the radio galaxies (RGs) are one of the imprints of the active galactic nuclei (AGNs). One of the still open issues related to these objects concerns their life cycle. We already know that during the life of a radio galaxy, multiple phases of activity can be observed. However, when and why one phase of activity stops and a new one starts is still unclear. The history of recurrent activity and interaction with the host galaxy medium of a single RG is recorded in the extended steep spectrum radio emission which LOFAR can probe. Here we present our current work, which is focusing on the study of individual objects belonging to the two extremes of the RGs. 4C33.33 is a giant double-double radio galaxy where the recurrent activity is clearly visible. On the other hand, we suspect that in the case of many weak radio sources their development and jet propagation can be halted on scales of tens of parsecs. Thus, we are also looking for faint diffuse emission present on arcsecond scales in some compact AGNs.

Name: Francesco Santoro
Contribution: Poster
Title: Probing the efficiency of the AGN feedback in young AGN: the case of PKS1934-63
Abstract: Classical galaxy formation models require the efficiency of the AGN feedback mechanism (e.g. the energy deposited in outflows by the AGN divided by its bolometric luminosity) to be around 5-10%. Efficiencies form the most powerful outflows seem to confirm this prediction, however there is increasing observational evidence of low efficiencies (less than 1%).
Estimating the efficiency of the AGN feedback is not an easy task and is usually subject to large uncertainties. This is especially true for the electron density of the warm ionised gas.
Compact radio sources represent the first stages of the evolution of classical radio galaxies. They are still embedded in a dense ambient ISM and host AGN-driven outflows of warm ionised, atomic and molecular gas. They are thus ideal to test the efficiency of the AGN in removing gas from the host galaxy.
I will present the results obtained from X-Shooter observations of the compact radio galaxy PKS1934-63. The warm ionised gas shows a complex kinematics and part of the gas is outflowing due to the interaction with the AGN. Regardless of its small mass I find that the outflowing gas stands out in terms of its physical properties. It has extreme densities and shows clear signs of being ionised by AGN-driven shocks. The AGN feedback efficiency we find is lower than the predictions of models and there are no signs of outflowing gas in the warm molecular or neutral phase.
To conclude I will outline a possible evolutionary scenario to explain the properties of the different gas phases for this source and show preliminary results coming from a bigger sample of young radio sources.

E-mail: secretaryastronomy@astron.nl

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