AGN TALK SERIES AT THE IAC

It is well-established that shocks are the key driver for dust destruction in the interstellar medium (ISM). Feedback processes from active galactic nuclei (AGN), such as winds and jets, can generate shocks that create harsh conditions where dust is expected to be destroyed. Surprisingly, recent JWST observations show that dust grains and polycyclic aromatic hydrocarbons (PAHs) can persist in extreme environments (eg, high temperatures, fast winds) that favour grain destruction through sputtering and/or shattering. The processes underlying dust survival and processing in shocks remain poorly understood. In this talk, I will report on JWST/MIRI imaging of extended dust structures aligned with the narrow line region of a number of nearby AGN, where shocks are prevalent. Using simple models, I will demonstrate that not only does dust co-exists with shocks, but is also likely heated by them. To explore this further, I will present results from hydrodynamical simulations run with the Arepo code, to investigate dust survival under thermal sputtering in AGN-driven shocks. These simulations show that conditions such as grain size, shock velocity, gas temperature, and cooling efficiency can significantly influence the sputtering timescale. This has important implications for AGN feedback efficiency and the dust lifecycle, both of which are key to galaxy evolution.

The Vera C. Rubin Observatory is already taking images from Cerro Pachon in Chile. In this talk I will present preparatory work that we have conducted in preparation for this incredible new data set. In particular I will talk about synergies with the eROSITA Space Observatory. The AGN science that will be possible with both instruments and other existing and upcoming datasets will be presented. I will present work on the photometric redshifts for Rubin and how multi-wavelength data can be used to improve accuracy. I will present the Redshift Assessment and Infrastructure Layers (RAIL) code and discuss various methods that have been applied to the problem of photometric redshift estimation for galaxies and AGN. I will discuss prospects for the early science to be conducted with Rubin and how it will take us beyond current understanding.

We use the James Webb Space Telescope Mid-Infrared Instrument medium-resolution spectrometer observations of the double-double active galactic nucleus (AGN) host 3C 293, to probe the warm molecular and ionized gas kinematics. The gas kinematics suggests inflowing material towards the circum-nuclear region, mainly in warm molecular gas. In addition, it shows spatially resolved outflows in the inner 2 kpc, seen in low ionization (traced by the [Ar II] 6.99 μm emission) and in warm molecular gas (traced by the H2 rotational transitions). We find a maximum mass-outflow rate of 4.90 ± 2.04 M ⊙ yr‑1 at ∼900 pc from the nucleus for the warm outflow (198 K ≤ T ≤ 1000 K) and estimate an outflow rate of up to 1.22 ± 0.51 M ⊙ yr‑1 for the hotter gas phase (T > 1000 K). The warm molecular phase outflows by themselves are one order of magnitude greater than those from the ionized phase. These outflows can clear the entire nuclear reservoir of warm molecular gas in about 1 Myr. The derived kinetic power of the molecular outflows leads to coupling efficiencies of 2%–5% of the AGN luminosity, way above the minimum expected for the AGN feedback to be effective in quenching the star formation. Further analysis also shows that the molecular emission has a strong shock component, likely induced by the radio jets.

Galaxy clusters are superb laboratories for studying the baryon cycle that governs the evolution of galaxies. We can observe how the hot intracluster medium (ICM) cools down and fuels star formation in central galaxies, to how this process ultimately leads to the activation and regulatory effects of the universe's most massive supermassive black holes (SMBHs). In this talk, I will present multiwavelength observations from ALMA, MUSE, and SITELLE and Chandra of several massive clusters on central clusters, to show how the AGN feedback cycle regulates the different phases of the interstellar medium, and regulas star formation. In this talk, I will present a a tight positive correlation between the X-ray surface brightness and the Halpha surface brightness of the multiphase gas using Chandra and MUSE observations, in a sample of seven X-ray bright cooling-flow clusters. This discovery was done by using a novel method of blind image decomposition, which allow us to isolated the hot phase of the X-ray interstellar medium, which was blended with the bright diffuse ICM, to unveil its relation with the warm phase.

I will present the first results of an ALMA Band 7 survey of 150 quasars in the Stripe 82 field. These data contribute to our understanding of the multiplicity around far-infrared-bright quasars down to a resolution of 0.8" as a function of redshift, IR fluxes and "balnicity". They also allow for the calibration of the far-infrared-based star formation rates in the hosts of bright quasars. Multiplicities are used to assess the importance of major mergers as triggers of concomitant accretion onto supermassive black holes and extreme star formation. Finally, serendipitous emission line detections will also be presented.

The most rapid SMBH growth in the Universe has occurred in luminous quasi-stellar objects (QSOs), making them the perfect laboratories for observing galaxy–SMBH evolution. When we have an unobscured view of the accretion disc, which peaks in the UV, QSOs display very blue UV–optical colours. However, we have recently discovered a hidden population of QSOs, obscured by dust, which are almost completely uncharacterised by previous spectroscopic surveys. These dusty QSOs could represent an important short-lived transitional phase in the evolution of galaxies (a “blow-out” phase). Utilising data from DESI we can now, for the first time, explore a statistically significant sample of these reddened QSOs. Combining DESI spectra with radio data from the LoTSS DR2, we find a striking positive relationship between the amount of dust extinction and the radio detection fraction in DESI QSOs. This demonstrates an intrinsic connection between opacity and the production of radio emission in QSOs. In our latest study, we construct sensitive radio SEDs of 38 QSOs across 0.144-3 GHz frequencies, with additional ~kpc scale e-MERLIN imaging, in order to probe the origin of the enhanced radio emission in dusty QSOs. We find that dusty QSOs tend to display steeper radio spectral slopes compared to typical blue QSOs, which is likely due to outflow-driven shocks on the surrounding ISM. These results are consistent with dusty QSOs representing an important blow-out phase in the evolution of galaxies.

Deep optical imaging studies now provide convincing evidence that galaxy mergers are the dominant, if not sole, triggering mechanism for powerful radio AGN and quasars in the local universe. However, it's difficult to determine the nature of the triggering mergers (e.g. whether major/minor,  gas-rich/gas-poor) using imaging observations alone. This is where observations of the cool ISM (dust and molecular gas) with facilities such as Herschel and ALMA are important: they provide key information about star formation rates, masses of the cool gas reservoirs, as well as gas kinematics and morphologies. In this talk, I will review recent Herschel and ALMA results on the cool ISM for the complete 2Jy sample of local radio AGN. They reveal that the most powerful radio AGN with strong emission lines (e.g. HERGs) are in most cases triggered in modest, rather than major, mergers as the accreted gas settles into a stable dynamical configuration. On the other hand, many of those with weaker emission lines (e.g. LERGs) are triggered by a different mechanism (e.g. accretion of gas from the hot ISM) or gradually fuelled by gas accretion from stable, compact disks in the near-nuclear regions. There are also interesting differences between the cold molecular gas properties of luminous radio AGN and nearby type 2 quasars in the sense that the radio AGN appear to be significantly less gas-rich.

Active galactic nuclei (AGN) drive powerful, multiphase outflows into their host galaxies which are expected to play a key role in galaxy evolution. However, exactly how small-scale accretion disc winds couple to the ISM to drive these outflows remains an open question. In this talk, I will present our AGN in Clumpy DisCs (ACDC) simulations which feature a physically-motivated AGN wind model embedded in an idealised galaxy disc with a resolved ISM, manually distributed in a clumpy substructure. We find that the hot wind causes the cold ISM clumps to fragment and become entrained in the outflow as small cloudlets. This leads to an outflow that differs significantly from commonly-considered shell-like morphologies, which has important implications for observational studies seeking to characterise outflows and infer their impact on the hot galaxy. We also find that mixing between the AGN wind and ISM clouds produces X-ray emission that can be detected above the level from star formation with telescopes such as Chandra or AXIS. This could provide a complementary probe for the total volume of gas that the outflow has interacted with.

The interplay between the nuclear activity and the interstellar medium (ISM) of galaxies plays an important role in their evolution: the gas accreting onto the dormant supermassive black hole turns it into an active galactic nucleus (AGN) and the ensuing activity is believed to starve the host galaxy of the fuel needed to form stars. The contribution of radio-loud AGN to this feedback effect is yet to be well understood. In order to understand the impact of radio AGN, we need to study the jet-ISM interaction in detail at high spatial resolution and also cover a wide range of parameters such as age/morphology, radio power. I will present our results from sub-kpc scale cold atomic gas and kpc-scale molecular gas studies in the central regions of radio galaxies. I will also detail how such studies, in combination with theoretical modelling, provide new insights into the morphology, kinematics and physical condition of gas directly impacted by the radio jets, helping us further quantify the impact of radio jets on the ambient ISM and thereby the evolution of their host galaxies.

In the context of an evolutionary model, the outflow phase of an active galactic nucleus (AGN) occurs at the peak of its activity, once the central supermassive black hole (SMBH) is massive enough to generate sufficient power to counterbalance the potential well of the host galaxy. This outflow feedback phase plays a vital role in galaxy evolution. I will present results from my two recent papers and what I am currently up to. In the first study, we develop an approach to select powerful AGNs in the feedback phase using optical/IR colours, and optical and X-ray spectral properties from the eROSITA Final Equatorial-Depth Survey (eFEDS). We trace and characterise outflows using SDSS spectroscopy, and explore the link between AGN luminosity and outflow properties.  We find that the X-ray selection (eROSITA) is a powerful tool to select AGN in the feedback phase and this X-ray active phase is the best tracer of fast winds. We find a weak correlation between AGN bolometric luminosity and outflow velocity and ~30% of our sample have kinetic coupling efficiencies within 1-10%. In the second study, we perform a spatially resolved analysis of a red, X-ray obscured and X-ray luminous quasar, ID608 at a redshift of z=0.6031. Our analysis reveals that the quasar resides in an interacting system with 3 companion galaxies with outflows that extend up to 9.5 kpc and move at high velocities exceeding 1000 km/s. 

Radio-loud active galactic nuclei (RL AGN), a subset of AGN where a significant portion of their output is emitted through synchrotron jets, play a crucial role in models of galaxy formation and evolution. These AGN are believed to inject the energy needed to prevent the cooling of hot baryonic matter, thus slowing or halting the growth of the most massive galaxies. Using the LOw Frequency Array (LOFAR) Two-metre Sky Survey (LoTSS), we are studying RL AGN in the local universe at low frequencies, where LOFAR’s advanced capabilities provide a less biased view of AGN structures compared to previous surveys. However, these new observations also bring challenges, such as understanding a newly emerging population of low-luminosity, compact active nuclei in galaxies. In my talk, I will present our findings as we use high-frequency Jansky VLA observations to constrain the morphologies of these compact sources, selected from the LOFAR AGN population, on sub-kiloparsec scales. Additionally, I will demonstrate how tools like the power/linear size (P-D) diagram are instrumental in classifying radio-selected AGN.

Galaxy evolution is one of the main topics of modern-day Astrophysics. The details of how galaxies evolve are still not fully understood from both theoretical and observational perspectives. Galaxy mergers, fast star formation, and active galactic nuclei (AGN) are believed to be crucial in shaping galaxies to their current evolutionary stage. These phenomena peaked at the time known as cosmic noon (z~2) where Ultra-Luminous Infrared Galaxies ((U)LIRGs, galaxies with LIR≥1011Lsun) are also prevalent. In the local Universe (U)LIRGs are also observed, allowing the detailed study of their physical properties in conditions analogous to those in the higher redshift population. In my talk I will explore the results from the JWST ERS program, focusing on the NGC 7469 galaxy. NGC 7469 is a nearby (z=0.016) Sy 1.5 galaxy classified as an LIRG with a prominent star-forming ring. Its face-on morphology makes it an ideal target to study the interplay between star formation regions and AGN.  We used JWST spectroscopic capabilities to study the high ionization emission lines, the molecular gas, and the dust content revealing the role of the supermassive black hole feeding and feedback in this galaxy. I will also highlight the recent results of another JWST GO program where we observed the first spatially resolved warm molecular gas outflows in a radio galaxy and talk about the preliminary results of a survey of such outflow and molecular gas properties in nearby (U)LIRGs. 

The study of BH accretion physics in AGNs poses challenges for theorists. Analytical models are limited in their ability to account for complex systems involving magnetized plasma within curved spacetime. In recent decades, numerical simulations have provided valuable insights into these systems, but a full understanding of BH physics remains a work in progress. In this presentation, I will discuss my recent work on modelling hot accretion flows around BHs using various numerical simulation approaches. During accretion, substantial mass, momentum, and energy are expelled via relativistic jets and AGN winds. My research aims to characterize the properties of these outflows and assess their potential impact on the SMBH environment through AGN feedback, influencing certain aspects of the host galaxy.

The mid-infrared range contains a unique set of spectral features (H2 transitions, ionized gas tracers, molecular bands and coronal lines) that can quantify the impact of AGN feedback on the ISM of galaxies particularly in dust obscured environments. In this talk, I will focus on two examples of feedback processes observed by JWST: the radio jet-ISM interaction in the Sy2 NGC7319 (Sy2 AGN in the Stephan's Quintet); and the fast molecular outflows seeing with the CO and H2O molecular ro-vibrational bands.

The James Webb Space Telescope (JWST) has opened a new window into the first billion years of cosmic time through unprecedented, sensitive  imaging and spectroscopy. JWST provides access to rest-frame optical emission at z>4, impossible to get with ground-based facilities. Since its launch, one of the major areas of research with JWST has been the quest for the first massive black holes. Black holes with masses in excess of millions to billions of solar masses are found in all massive galaxies in the local Universe, yet their formation and growth mechanisms remain a conundrum. I will present results from the JWST/NIRSpec GTO team on massive black holes during the first billion years, and their impact on their young host galaxies in the form of powerful outflows and ionizing radiation. I will also discuss observational constraints on early black hole growth, and the prospect for future advances.

Quasars present during the epoch of reionization (within 1 Gyr, or at redshift z>5.5) challenge theories of black hole formation as they host supermassive black holes (SMBH) of up to 10^9 solar masses. Radio jets can increase the black hole accretion rates and are thus a possible mechanism aiding the growth of these SMBHs in such a short time. We investigate P352-15, an extreme radio emitter at the edge of reionization (redshift z=5.832) presenting evidence of an extended radio jet on kpc scales (~1.6 kpc). We demonstrate how this quasar is an ideal laboratory to study the black hole and jet timescales. We first used submillimeter and radio observations from ALMA, NOEMA, GMRT, and the VLA to study the spectral energy distribution (SED) of the quasar. The analysis reveals a strong synchrotron break in the SED suggesting shocks between the jet and the interstellar medium, affecting the dust-dominated continuum emission from the host galaxy. Using these observations, we calculate the jet’s dynamical age to be <10,000 years, implying a recent jet ejection. We compare this jet timescale to the quasar's lifetime (tQ) derived from the analysis of the proximity zone in the rest-UV/optical spectrum, which indicates the duration of the most recent black hole accretion event. We find that tQ is consistent with the jet’s timescale. We are therefore observing evidence for the first time of the black hole - jet co-evolution of a quasar in the first Gyr of the universe.

While the full AGN zoo presents a large variety of classifications, the local (z < 0.1) AGN population can be divided into two main categories: radiative- and kinetic-mode AGN. These are also often identified as high-luminosity (quasar- or Seyfert-like) and low-luminosity (LINER-like) AGN, respectively. According to the most popular scenario, objects in these two classes are intrinsically distinct, differentiated not only by the black hole accretion rate and corresponding type of energetic output, but also by the physical process through which the accretion occurs. In this talk, I will present the recent discovery of a tight correlation between the nuclear ALMA millimetre luminosities, SMBH masses, and 2-10 keV X-ray luminosities that is found to hold for both low- and high-luminosity AGN. This has been dubbed as the "millimetre fundamental plane of BH accretion”. Crucially - for all AGN types - spectral energy distribution (SED) models for advection-dominated accretion flows (ADAFs) naturally explain the existence of the relation, which is instead not reproduced by the standard torus-thin accretion disc models usually applied at least to high-luminosity AGN. I will discuss the implications of this discovery for our understanding of BH accretion in different AGN types, as well as its potential as rapid method to (indirectly) estimate SMBH masses.

Recent observational studies have found that, contrary to the standard thought, feedback from active galactic nuclei (AGN) can play an important role in the evolution of low-mass dwarf galaxies. We investigate the effect of black hole feedback on dwarf galaxies within the AURIGA cosmological magneto-hydrodynamical simulations. We use a set of 12 dwarf galaxies that have been run with and without AGN feedback and the same initial conditions, which allow us to make a direct comparison of the impact of the AGN feedback in dwarf galaxies. We show that we can satisfactorily reproduce several scaling relations, including the Mbh-Mstar, Mbh-sigma and the baryonic TF relation. We found differences in the star formation history of the galaxies with AGN compared to  the ones in which the AGN has been turned-off, suggesting that AGN is a viable way of suppressing SF, even though none of our galaxies is quenched by z=0.  We show, for the first time, a tight correlation between SFR and AGN properties in dwarfs. Moreover, we find that the two galaxies harbouring the largest BHs have suffered a considerable (up to ∼65 %) reduction in their central dark matter density, pinpointing the role of AGNs in determining the final dark matter mass distribution within dwarf galaxies. This pilot study highlights the importance of modelling AGN feedback at the lowest mass scales and the impact this can have on dwarf galaxy evolution.

In this presentation, I will discuss the physics of the multiphase gas in local active galaxies and the impact of the Active Galactic Nucleus (AGN) on the host galaxy evolution. AGNs can generate winds and jets that interact with the host galaxy interstellar medium (ISM). My focus will be on the warm ionized gas, cold dust, cold molecular gas and radio properties, using VLT/MUSE, ALMA and VLA data. To begin, I will introduce a detailed dynamical modeling of the gas component through which we can reconstruct the distribution and kinematics of the discs, winds, jets and their interaction. Through a comparison of high resolution radio and sub-mm data of the central region we are able to infer the presence of compact radio-jets, star formation activity and dust emission on sub-kpc scales. Further, I will explore the correlation between the star formation rate and the cold molecular gas mass surface densities, commonly referred to as the Kennicutt-Schmidt star formation (SF) law. This relation plays a pivotal role in galaxy evolution and determines the efficiency with which galaxies convert their gas reservoirs into stars. This study aims at investigating how the gas and SF properties change across the galaxy and understanding whether the activity of the AGN plays a role. ALMA continuum and CO emission line maps are employed to trace the dust and cold molecular gas properties, respectively. Radio VLA data will be utilized to estimate the star formation rate. I will illustrate the application of this approach to a sample of local hard-X-ray selected Seyfert galaxies.

In this talk, I will present a) the results from a study of normal galaxies using data from the first complete all-sky scan of the eROSITA X-ray survey (eRASS1), and b) new galactic activity diagnostics for the identification of AGN and star-forming galaxies. eRASS1 provides the first unbiased X-ray census of local normal galaxies allowing us to study the X-ray emission (0.2-8.0 keV) from X-ray binaries (XRBs) and the hot interstellar medium in the full range of stellar population parameters present in the local Universe. 

By combining the updated version of the Heraklion Extragalactic Catalogue (HECATE v2.0) value-added catalogue of nearby galaxies (z<0.048) with the X-ray data obtained from the eRASS1, we study the integrated X-ray emission from normal galaxies as a function of their stellar population parameters (i.e. SFR, M⭑, Metallicity, and stellar population age). Stringent optical and mid-infrared AGN diagnostics, developed using machine learning methods, are applied to ensure the star-forming nature of our galaxy sample. 

Our analysis reveals a sub-population of very X-ray luminous starburst galaxies (up to ~2dex excess with respect to that expected from the current scaling relations) with higher specific SFRs, lower metallicities, and younger stellar populations. This excess is not the result of the contribution by hot gas, low-mass X-ray binaries. We discuss the role of  background AGN, and low-luminosity AGN (including tidal disruption events), or stochastic sampling of the X-ray binary X-ray luminosity function. This population drives upwards the X-ray scaling relations for star-forming galaxies, and has important implications for understanding the population of X-ray binaries contributing in the most X-ray luminous galaxies in the local and high-redshift Universe.

These results demonstrate the power of large blind surveys such eRASS1 which can provide a more complete picture of the X-ray emitting galaxy population and their diversity, revealing rare populations of objects and recovering unbiased underlying correlations. 

The morphology of a galaxy results from secular and environmental processes during its evolutionary history. As such, it is an important tracer of galaxy evolution. 

In this talk, I present the first visual classification of morphologies based solely on the molecular gas distribution for a large sample of 79 nearby main-sequence galaxies, using 1" resolution CO(2-1) ALMA observations taken as part of the PHANGS survey. 

We devised a morphology classification scheme for different types of bars, spiral arms (grand-design, flocculent, multi-arm and smooth), rings (central and non-central rings) similar to the well-established optical ones, and further introduced classes to describe the shape of bar lanes. I will present our results on spiral arms and stellar bars, and their (dis-)agreement with literature classifications based on the stellar distribution.  In addition, we find that more curved bar lanes show a shorter radial extent in molecular gas and have lower molecular to stellar mass ratios than those with straighter geometries. Since these bar lanes consist of gas being efficiently funnelled to the centers of galaxies, I further show results on inflows to and outflows from the centres of PHANGs galaxies, as well as the central rings that can result from the funneling.