Department of Physics and Astronomy, George Mason University

International AGN Seminar Series

The International AGN Seminar Series offers an opportunity for researchers studying Active Galactic Nuclei and their students to come together this summer in a series of inspiring and focussed talks given by leaders in the field, followed by informal discussions that can potentially lead to future collaborations. The talks will take place on Tuesdays at 12:00pm ET and be 40 minutes, with 20 minutes for informal discussion and questions.

Click here if you would like to join the email Listserv for this seminar series.

Meeting link

Youtube Channel with recorded talks.

We also plan to have informal lunch meetings once a month for those interested. They will take place on first Thursday of the month at 12:00pm ET starting Sept 1. For Faculty/Research Staff, You can join here: Faculty/Staff lunch meetings. For Postdocs/Grad Students, you can join here: Postdoc/grad student lunch meetings.

6/24/2021Taro Shimizu Resolving the Sub-parsec Structure of AGN with VLTI/GRAVITY

Near-infrared interferometry is a unique tool to study the inner sub-parsec structure of AGN which is inaccessible with current single dish telescopes. With VLTI/GRAVITY, we can now spatially resolve not just the hot dust continuum on milliarcsecond scales through imaging but also the broad-line region on microarcsecond scales through spectro-astrometry. In this seminar, I will review the latest results from our ongoing ESO Large Program where we have mapped the kinematics of the BLR in three nearby AGN, measured sizes of the hot dust for eight AGN, and reconstructed images for two AGN. BLR kinematics have allowed us to independently measure the BLR size and supermassive black hole mass where we find consistent results with reverberation mapping. The hot dust sizes are consistent with previous NIR interferometric results and show larger sizes compared to dust reverberation mapping with evidence for an evolving structure with AGN luminosity. Individual images suggest the hot dust traces a thin inner disk and resolve the sub-pc cloud structure. I will end with an outlook towards the Gravity+ upgrade which will greatly enhance the sensitivity and sky coverage of GRAVITY and allow for observations of AGN out to high redshift.

7/1/2021Stephanie JuneauAGN feedback modulated by host galaxy substructure and kinematics

AGN feedback has been proposed as a key ingredient of galaxy and black hole evolution. In particular, different modes of AGN feedback (radio jets vs. quasar winds) may contribute to regulating galaxy and/or black hole growth in different parts of the parameter space. However, open questions remain such as the origin and impact of AGN-driven outflows. Two complementary approaches can be used: (1) detailed case studies to reveal physical insight; (2) large galaxy population studies to delineate global trends. I will touch on both approaches in this talk. First, I will present findings from a multi-scale analysis of gas ionization and dynamics thanks to 3D spectroscopy with the VLT/MUSE instrument. Interpreted together with radio continuum observations, this work is strongly suggestive of a connection between AGN feedback and the host galaxy substructure. Second, I will describe exciting new opportunities from large galaxy survey experiments such as the Dark Energy Spectroscopic Instrument (DESI) and Euclid, which will yield unprecedented samples of several million galaxy and quasar spectra. The DESI collaboration completed Survey Validation (SV) and the first two months of its survey, which have already yielded over 2 million successful galaxy redshifts! By 2026, we will obtain redshifts for 40 million galaxies and quasars. Leveraging such massive spectroscopic surveys will allow us to perform systematic searches for interesting AGN spectral signatures, and will yield a treasure trove of discoveries and targets for follow-up studies.

7/8/2021Franciso Muller SanchezImpact of AGN outflows in the evolution of galaxies
Important progress into the physical mechanisms governing the coevolution of supermassive black holes and galaxies has recently been made thanks to adaptive optics integral-field spectroscopy of nearby AGN, and observations have shed light on gas inflow, nuclear star formation, the structure of the torus, and outflows. In this talk, I will describe recent work showing how AGN influence their host galaxies. I will focus on our team’s recent results for a large sample of nearby AGN, which include luminous Seyfert galaxies and confirmed dual AGN at z < 0.05. We find that AGN-driven outflows of ionized gas are ubiquitous in both, single and dual AGN, with mass outflow rates ranging from a few solar masses per year in Seyfert galaxies to ~100 M_sun yr-1 in dual AGN. The mass outflow rates in all galaxies are 2-3 orders of magnitude greater than the black hole accretion rates, suggesting that AGN feedback suppresses accretion onto the supermassive black hole. Furthermore, the observations provide direct evidence of the ways in which the AGN outflows interact with the interstellar medium, either by creating cavities of molecular gas, or by launching molecular outflows. Finally, in the prototypical merger system NGC 6240, we observe for the first time simultaneously an AGN-driven outflow of highly-ionized gas and a starburst-driven outflow of ionized hydrogen. This shows that stellar feedback and supermassive black hole feedback can work in tandem to regulate the stellar growth of a galaxy after a merger event.   

7/15/2021 Cristina Ramos AlmeidaMulti-scale and multi-phase AGN feedback on pc and kpc scales.

AGN feedback might be capable of regulating the growth of massive galaxies, but the complexity of the parameter space involved makes it difficult to quantify this from the observational point of view. In this context, it is particularly relevant to acknowledge the multi-phase and multi-scale nature of AGN-driven outflows, to then confront their properties with galaxy processes/features varying on the same timescales. In this talk I will summarise recent results from the analysis of infrared and sub-mm observations showing that the circumnuclear material of AGN is complex, episodic and highly dynamic, as well as examples of galaxies in which AGN feedback is shaping the distribution of molecular gas in the close (pc-scale; GATOS survey) and intermediate (kpc-scale; QSOFEED survey) environment of accreting supermassive black holes.

7/22/2021Misty BentzComparing Direct Black Hole Mass Measurements in AGNs

 Supermassive black holes appear to be ubiquitous in galaxy nuclei, and several large-scale galaxy properties have been to found to scale with black hole mass, giving rise to the idea that galaxies and their black holes co-evolve.  There are only a few techniques that can directly constrain the mass of a black hole through its gravitational influence on luminous matter, of which the most commonly applied are reverberation mapping and stellar or gas dynamical modeling. These techniques have been applied to a modest number of black holes, with the vast majority of black hole masses in the literature instead being estimates derived from scaling relationships that are based on these direct results, with black hole masses outside the local universe relying on reverberation mapping scaling relationships and black hole masses in the local universe deriving from dynamical modeling scaling relationships.   To date, however, there are only a handful of black holes with masses that have been constrained through multiple techniques because of their disparate technical requirements.  In AGNs, the situation is even worse because active galaxies are rare and most are too far away to allow the spatial resolution needed for dynamical modeling.  I will describe our ongoing project to directly compare black hole masses from reverberation mapping and stellar dynamical modeling in the nearest Type 1 Seyferts, including our upcoming JWST Early Release Science program.  Both reverberation mapping and stellar dynamical modeling are time- and resource-intensive techniques and the number of galaxies we can study is small, but the results will help uncover potential biases in these direct mass techniques and illuminate any differences in the black hole mass scales that are applied locally versus at cosmological distances. 

7/29/2021Vivian UFeeding and Feedback in Galaxy Mergers

The upcoming decades will present exciting opportunities to explore the physics of merging supermassive black holes from the multi-messenger perspective. The electromagnetic identification of dual and binary candidates with subsequent detailed follow-ups will become routine. Thus, a study of the small-scale environment in galaxy mergers hosting these events provides the necessary groundwork for future investigations in the co-evolution of supermassive black holes and their host galaxies. In this talk, I will highlight published results and ongoing work from our Keck OSIRIS AO LIRG Analysis survey, which probes the nuclear gas kinematics in nearby interacting galaxies in the context of gas feeding and feedback. The power of high-resolution studies in dissecting how galaxy systems evolve will become indispensable as we enter an exciting era of observational astronomy with the imminence of the James Webb Space Telescope, 30-meter class telescopes, and beyond.

8/5/2021Erin Hicks Tracing the Cycle of AGN Feeding and Feedback

Near-infrared integral field spectroscopic surveys of local AGN have established that their circumnuclear regions (~100pc) contain a large reservoir of molecular gas and that inflows and outflows are frequently present.  On ~10pc scales ALMA observations tracing cold gas components have revealed a rotating, turbulent, and inhomogeneous disk-like structure, while mid-infrared studies show polar elongated structures indicative of dusty outflows.  A new picture is therefore emerging where, in contrast to a static “torus”, the obscuring central structure is dynamic and central to a cycle of gas flowing inward from the host galaxy supporting the growth of the central black hole and outward driven by AGN feedback.  I will present results from multiple surveys of local active galaxies that build additional support for a dynamic central obscuring structure in AGN.  I will also highlight how JWST will provide a unique probe of the AGN circumnuclear region with critical insight into the feeding and feedback of AGN in the context of galaxy evolution.

10/5/2021Jonelle WalshDynamical Measurements of Supermassive Black Holes in Nearby Galaxies

Supermassive black holes are fundamental components of galaxies, as demonstrated by the empirical correlations between the masses of black holes and large-scale host galaxy properties. Despite progress over the past two decades, the local black hole mass census remains highly incomplete. Obtaining a more complete picture of black hole demographics and a deeper understanding of the physical mechanisms that drive black hole – galaxy co-evolution requires the precise measurements of black holes in a wider range of galaxies with varied evolutionary pasts. In this talk, I will describe a Gemini Large and Long Program aimed at addressing a bias in the types of galaxies for which black hole mass measurements have been made. I will also discuss an ALMA program where we are obtaining gas-dynamical black hole mass measurements for massive early-type galaxies, including a population of local galaxies that show remarkable similarities to galaxies observed at earlier epochs in the Universe.

10/19/2021Xin LiuThe Hunt for Binary Supermassive Black Holes: New Opportunities with Large Synoptic Surveys

When galaxies frequently merge in the hierarchical universe, their central black holes (BHs) pair and form binary supermassive BHs. The merger of binary BHs provides a means of growth; the abundance on sub-galactic scales may be used to constrain the nature of dark matter particles; the final coalescence should produce the loudest sirens in the low-frequency gravitational wave sky. Despite significant merits, however, direct observational evidence for binary supermassive BHs has remained elusive to date. The primary hurdle to detecting binary supermassive BHs on sub-galactic scales is spatial resolution. I will talk about our efforts using temporal information to break the angular resolution limit, analogous to detecting stellar binaries and exoplanets. Our pilot work has discovered many promising candidates, and the time is ripe for capitalizing on the unprecedented sensitivity, volume, and time baseline offered by ongoing and upcoming large photometric and spectroscopic time-domain surveys to break this subject open.

11/02/2021Mallory MolinaIdentifying Massive Black Holes in Dwarf Galaxies via [Fe X] Coronal-Line Emission

Characterizing the black hole (BH) population in dwarf galaxies can provide important constraints on the BH seed population and the evolution of dwarf galaxies. In this talk, I will present the first systematic search for active galactic nuclei (AGNs) in dwarf galaxies using the [Fe X] optical coronal line. I identified 81 [Fe X]-emitting dwarf galaxies in the SDSS, whose [Fe X] luminosities indicate the presence of accreting massive BHs from AGNs or tidal disruption events (TDEs). Approximately 50% of these objects show additional evidence for AGN activity. Furthermore, these BH candidates are found in lower-mass, bluer galaxies typically missed by other selection techniques. I will present the BH candidate sample and its properties, and discuss the implications for the dwarf galaxy BH population.

11/16/2021Laura BlechaTitle: The Dynamics & Multi-messenger Signatures of Supermassive Black Hole Evolution
Abstract: Supermassive black holes (SMBHs) are of great interest both as critical components in galaxy evolution and as the dominant sources of low-frequency gravitational waves (GWs). The detection of such GWs with pulsar timing arrays (PTAs) may be imminent, and in the coming years, the Laser Interferometer Space Antenna (LISA) could detect SMBH merger events. I will discuss recent work using galactic- to cosmological-scale hydrodynamics simulations to quantify the role of galaxy mergers in SMBH fueling. I will also describe recent progress in constraining the dynamics and multi-messenger signatures of BH pairs, binaries, and GW recoils, utilizing results from simulations coupled with SMBH binary inspiral and spin evolution models. Electromagnetic detections of such systems in the coming years will be crucial counterparts for the likely imminent detection of GWs by pulsar timing arrays, and they will provide key constraints on LISA event rates. I will conclude by mentioning some ongoing work to constrain the formation of SMBH “seeds” in the early Universe, which will be key for understanding the LISA source population

12/07/2021David RosarioTitle: AGN in a cold Universe: how gas and dust connect galaxies and their supermassive black holes

 The cold material in the interstellar medium (ISM) is the essential raw material for the growth of both galaxies and supermassive black holes. We have learned a great deal about the interplay of the various components of the ISM with AGN. In this talk, I will begin by reviewing some key results from the last decade that outline these relationships and what they tell us about the crucial process of galaxy-black hole co-evolution. I will then zoom into a particular phase in the lives of powerful QSOs when they are reddened by dust along the line of sight. Recent work has identified peculiar properties for this population, which suggests that they are caught in a special time in their evolution. I will present evidence that the nature of red QSOs is best explained by the presence of dusty nuclear winds, rather than obscured starbursts. Finally, I will introduce an up-coming JWST program designed to find and characterise dusty winds in nearby AGN, which promises to revolutionise our understanding of the mechanisms by which AGN carry energy into their host galaxies.

01/18/2022Mitchell RevalskiTitle: The Dynamics of Radiatively Driven Outflows in Nearby Active Galaxies

Active galactic nuclei (AGN) can launch powerful outflows of ionized gas, and precise, spatially-resolved studies are required to fully understand their role in galaxy evolution. Observations from the Hubble Space Telescope (HST) have revolutionized our understanding in this area, but numerous questions remain: How common are outflows, what mechanisms drive them, where are they launched from, and how far do they extend into their host galaxies? Further, what are the most accurate techniques for measuring their masses and energetics? In this seminar, I will describe our efforts over the last decade to answer these questions for the ionized, narrow line region outflows in nearby Seyfert galaxies. Using spatially-resolved spectroscopy from HST and ground-based facilities, we have modeled the geometry and kinematics of these systems and found prevalent outflows in at least half of the galaxies, whose kinematics are consistent with radiatively driven gas launched from multiple radii. We have also created photoionization models to precisely measure gas masses and outflow rates, which tightly constrain the energetic impact of the outflows on their host galaxies. These studies have provided insight into the range of densities and ionization states within the outflows, which we are using to model larger samples and build a more complete picture of feeding and feedback in the nearby universe.

02/01/2022Giacomo VenturiTitle: AGN outflows versus compact, low-power jets: A detailed study of their properties and effects on their host galaxies

Outflows of gas driven by active galactic nuclei (AGN) are believed to play a major role in shaping the properties and evolution of their host galaxies, by depleting their gas reservoir and affecting their star formation activity. However, the limited spatial resolution and quality of observations generally leads to large uncertainties on the outflow properties, making it hard to put constraints on the outflow models.
I will present our work on ionised gas outflows in local AGN carried out with the optical integral field spectrograph MUSE at VLT. The key combination of vicinity of the targets, providing spatial resolutions of ~10-100 pc, and MUSE capabilities (1’x1’ wide FOV plus spectral coverage of the main optical emission-line diagnostics) allowed us to investigate the ionised gas conditions, kinematics and excitation in great detail.
We could map ubiquitous AGN-ionised bi-conical outflows, dissect their properties (velocity, density, mass outflow rate, energetics etc…) and investigate their acceleration mechanisms. We also studied the effect of compact (<1 kpc), low-power (<10^44 erg/s) radio jets on their host galaxy interstellar medium (ISM), finding that they are able to strongly perturb the ISM in the direction perpendicular to their path. In line with recent simulations, our results demonstrate that not only powerful, extended jets but also low-power, compact ones are capable of affecting their host galaxies.

02/15/2022David RupkeTitle: Integral Field Spectroscopy of Galactic Winds From the Ground Up… to JWST

Intense star formation and rapid black hole accretion in the centers of galaxies produce energy that propels gas outward. These galactic winds affect the evolution of their host galaxies, self-regulate the future growth of stars and black holes, and populate the enormous reservoirs of gas surrounding them. In the past decade, optical and near-IR integral field spectroscopy (IFS) from the ground has revolutionized the study of galaxy-scale outflows that reach into the their surroundings. The unprecedented infrared sensitivity, spatial resolution, and spectral coverage of the JWST IFUs will be in turn be transformative for studying outflows from galaxies. For quasars in particular, PSF contamination will be an issue when studying underlying extended emission. Through our Early Release Science program Q3D, we are providing the community with a Python-based PSF decomposition and spectral analysis package–q3dfit–for high dynamic range JWST IFU observations, allowing the user to create science-ready maps of relevant spectral features. Luminous quasars, with their bright central source (quasar) and extended emission (host galaxy), are excellent test cases for this software. I will discuss existing and planned IFS observations of galactic winds driven by star formation and black holes that probe their extent and properties and illuminate the connection between galaxies and their surroundings.

03/01/2022Sara EllisonTitle: AGN triggering and star formation quenching in post-merger galaxies

For two decades, we have adopted a picture of the role of galaxy mergers motivated by simulations:  interactions cause tidal disturbances, trigger star formation, fuel AGN and then feedback quenches the merger remnant.  However, this picture is based on simulations that use only limited suites of idealized, binary merger configurations with out-dated physical models (particularly with regards to the AGN).  A further limitation in our understanding of the complete merger cycle is that simulations and observations alike have tended to focus on the pre-coalescence regime of the interaction.  In this talk, I will focus on the little studied post-merger regime, looking both at predictions of AGN fuelling and subsequent feedback/quenching in the IllustrisTNG simulation as well as the largest observational post-merger sample currently available. 

04/05/2022Mar MezcuaTitle: The seeds of the first supermassive black holes
Supermassive black holes of 10^10 solar masses already existed at z~6-7, when the Universe was less than 1 Gyr old. To reach this mass in such a short time they should have started as seed intermediate-mass black holes (IMBHs) of 100-10^6 solar masses at z > 8.
I will show that a population of actively accreting IMBHs exists in local dwarf galaxies and that they can be detected out to z~3 with the use of deep multiwavelength surveys. Whether these are the relics of those early seed black holes that did not grow into supermassive is still a matter of debate, since processes such as dwarf galaxy mergers and black hole feedback can have a very strong impact on black hole growth. The next generation of observational facilities such as the SKA could open a new window by detecting seed IMBHs at birth. 
05/03/2022Anne MedlingTitle: Tracking Black Hole Fueling and Feedback with Adaptive Optics and ALMA: Observational Constraints for Physical Models
I will present KOALA: the Keck OSIRIS AO LIRG Analysis, an adaptive optics-assisted near-infrared integral field spectroscopy campaign of 30+ nearby gas-rich galaxy merger nuclei.  Our dataset traces stellar and gas kinematics and properties at few 10s of pc resolution, providing an excellent laboratory for studying the fueling and feedback associated with the central supermassive black holes and nuclear starbursts.  These data have shown that 50-500 pc nuclear disks are a nearly ubiquitous mechanism for funneling gas to the black holes.  High central dynamical masses suggest that black holes may ‘claim their mass’ early in a merger, but that that material takes much of the merger timescale to find its way through the accretion process.  This gas pileup scenario is supported by recent ultra-longbaseline ALMA observations and presents a significant challenge to current common sub-grid black hole accretion rate prescriptions.  Our dataset also reveals high ratios of shock-excited molecular gas (H_2 2.12 micron emission) compared to ionized hydrogen (Br gamma emission) reveal star formation- and AGN-driven nuclear outflows that in some cases can be traced out to several kpc scales.  For more information on the survey and access to our data, visit

8/30/2022Almudena PrietoTitle: Dust in the Central Parsecs of AGNs

I will discuss the new challenges that parsec-scale observations in the IR, when combined with comparable physical scales in radio, millimetre, optical, UV and X-ray of the nearest AGN, are posing to us regarding the nature of the nuclear emission, the ubiquitous presence of nuclear dust filaments, and the role of these filaments as accretion drivers. The way these observations challenge the requirement of a torus and question one of its fundamental attributes which is the collimation of the nuclear radiation, will be discussed.

9/13/2022Dale KocevskiTitle: Measuring AGN Hosts Properties at z>3 with JWST

AGN have become key components of most galaxy evolution models, yet several open issues remain in our understanding of how the link between galaxies and their SMBHs is established and maintained.  Among these are the mechanism(s) responsible for fueling the bulk of SMBH growth across cosmic time and the role that AGN play in quenching the star formation activity of the first generation of massive quiescent galaxies. I will present recent results from the CEERS survey, which is using the James Webb Space Telescope (JWST) to determine the morphologies and stellar populations of AGN hosts at z > 3 for the first time.  Surprisingly, we find AGN hosts at these redshifts have optical colors consistent with a quenched or post-starburst stellar population.  The presence of AGN in passively evolving galaxies at z > 3 is significant because a rapid feedback mechanism is required in most cosmological simulations to explain the growing population of massive quiescent galaxies observed at these redshifts.  I will also discuss what the morphologies of these galaxies tell us about the processes driving their nuclear activity.

9/27/2022Ismael G. BerneteTitle: A high angular resolution view of the PAH emission in Seyfert galaxies using the James Webb Space Telescope

Abstract: Nowadays, there is evidence that most galaxies can host supermassive black holes. It also is widely accepted that most galaxies undergo an active phase in their evolution. The impact of the energy released by active galactic nuclei (AGN) in the interstellar medium (ISM) of the host galaxy has been proposed as a key mechanism responsible for regulating star formation (SF). The mid-infrared (IR) is the ideal spectral range to investigate the nuclear/circumnuclear regions of AGN since dust extinction is significantly lower compared to the visible range. In addition, it provides unique tracers to study the AGN-SF connection such as H2 rotational lines, fine structure lines and Polycyclic Aromatic Hydrocarbons (PAHs).

PAH molecules are made up of multiple aromatic rings, mainly containing carbon and hydrogen. They are well known on Earth as a by-product of incomplete combustions (e.g. roasted coffee). PAHs are ubiquitous and abundant in space and are amongst the most widespread organic compounds in the Universe. PAH features are also a powerful tool to characterize the interstellar medium (ISM) in different astrophysical objects and environments. However, our understanding of the effect of the hardness of the radiation field on these molecules is limited.

In this talk, I will summarise our first results on the PAH properties of AGN using new James Webb Space Telescope data.  In this work, we used JWST/MIRI MRS spectroscopy of 3 Seyferts to compare their nuclear PAH emission with that of star-forming regions. Our results showed that a suite of PAH features is present in the innermost parts of luminous Seyfert galaxies. We found that the nuclear regions of AGN lie at different positions of the PAH diagnostic diagrams, whereas the SF regions are concentrated around the average values of SF galaxies. The nuclear PAH emission mainly originates in neutral PAHs. In contrast, PAH emission originating in the SF regions favours small ionised PAH grains. Therefore, our results provide evidence that the AGN have a significant impact on the ionization state and size of the PAH grains on scales of ~142-245 pc.

10/11/2022Kristina NylandTitle: Newborn Quasar Jets

Abstract: Radio jets/lobes associated with quasars are among the most energetic, long-lived objects in the universe.  Powered by actively feeding supermassive black holes (SMBHs), radio quasar jets may grow to scales of 100’s of kpc or more over millions of years, extending far beyond the stellar light of their host galaxies.  These large-scale jets play a major role in the regulation of galaxy and SMBH growth by preventing hot halos of gas around galaxies from cooling and forming new stars.  However, the role of energetic feedback driven by younger, small-scale (< 1 kpc) jets that are still confined within their host galaxies remains unknown.  State-of-the-art simulations suggest that small-scale jets may also influence their environments, but systematic observational studies are needed to test this idea. Identifying jets in the early stages of their evolution by directly resolving their morphologies remains unfeasible, particularly at high redshift.  An alternative approach is to identify them by comparing data taken years to decades apart.  In this talk, I will present a sample of candidate newborn quasar jets that were recently discovered in the Very Large Array Sky Survey (VLASS) to have brightened dramatically in the past 10-20 years.  I will new discuss implications for our understanding of radio AGN and quasars, their connection to galaxy evolution, and exciting opportunities for further advancements with new and forthcoming radio telescopes/surveys of the dynamic radio sky.

10/25/2022David LawTitle: JWST ERO observations of NGC 7319

Stephan’s Quintet is a well known example of interacting galaxies, whose tidal interactions trigger large scale gas flows.  These gas flows have been revealed in spectacular detail by recent observations from the James Webb Space Telescope, from galaxy-scale molecular gas arcs to high-powered outflows driven by the AGN in the center of NGC 7319.  We will discuss the multi-wavelength evidence for highly ionized outflows driven by this AGN through a surrounding molecular gas reservoir, and a preliminary analysis of the kinematics of this complex system. 

11/8/2022Hanae InamiTitle: AGN or starburst? An off-nuclear deeply embedded compact source in IIZw096

Local luminous infrared galaxies (LIRGs) provide an ideal laboratory for detailed investigations of extreme phenomena such as active galactic nuclei (AGN) and starbursts induced by mergers. IIZw096 is one such system with infrared emission that peaks outside of the two merging nuclei. This region is completely embedded by dust and no emission is detected in the UV and optical with HST. Previous observations with Spitzer have hinted that most of the mid- and far-infrared emission of the whole system is from a single source in the region. However, its exact location could not be nailed down due to the limited spatial resolution, and its energy source has also been unknown. In this talk, I will present some results from new JWST imaging observations of the dust embedded region in IIZw096. Thanks to the superb resolution and sensitivity of JWST, we have finally pinpointed the exact source that is responsible for the bulk of the infrared emission and constrained its infrared luminosity density. At the current time, it is not clear whether this source is powered by an AGN or a starburst. I’ll discuss the intriguing nature of this red compact source.

11/22/2022Miguel Pereria SantaellaTitle:  JWST/MIRI MRS view of the jet-ISM interaction in NGC 7319. Missing jet energy?

Feedback from AGN plays a central role in the evolution of galaxies according to simulations. In particular, radio-jet/kinetic mode AGN feedback, which takes place in low accretion AGN, can be an important evolution driver for the majority of galaxies.  Contrary to high-power radio jets, which easily pierce the ISM, low-power radio jets are expected to remain for a longer time trapped in the ISM around the AGN affecting larger gas volumes, thus potentially having a much larger impact on the nuclear regions.  MIRI/MRS mid-IR spectroscopy of NGC7319 (the largest spiral in the Stephan’s Quintet which hosts a type 2 Seyfert AGN with a low-power radio jet) was obtained as part of the JWST Early Release Observations.  In this talk I will present the initial analysis of the MIRI data which, for the first time, spatially resolve the interaction between the radio jet and the ISM.  We detect extended high-ionization emission ([MgV], [NeVI], and [NeV]) close to the jet axis and enhanced warm/hot molecular H2 and ionized gas emission at the radio hotspots.    The mechanical energy of these gas phases at the radio hotspots is <1% of the jet energy, well below the expected value from relativistic jet simulations. I will discuss possible scenarios to explain this result which is apparently at odds with the predictions of simulations

12/13/2022Enrique Lopez RodriguezTitle: On the origin of radio-loudness in active galactic nuclei using far-infrared polarimetric observations

To explain the transfer of energy surrounding supermassive black holes (SMBH), most of the theoretical models, if not all, must incorporate magnetic fields (B-fields). As matter rotates and gets closer to the black hole, the outgoing radiation results in the extraction of energy from the SMBH— matter rotating around an SMBH must have a B-field to account for the loss of angular momentum. This is the main physical mechanism for powering the core of galaxies that contain active nuclei. Although this process can explain the dynamics of matter at sub-pc scales around the black hole, there are still no clear observations of how the matter from the host galaxy, which contains kpc-scale B-fields in close equipartition with the diffuse interstellar medium, feeds the central SMBHs at scales of 10-100 pc.

We have observed the signature of magnetically aligned dust grains at infrared/sub-mm wavelengths in a sample of radio-loud (RL) and radio-quiet (RQ) active galactic nuclei (AGN). We found that RQ AGN are low polarized (<0.4%), while RL AGN are highly polarized (5-11%) at 10-100 um. These results are particularly interesting because the dusty torus represents the AGN accretion flow on pc-scales, and our result, besides the radio differences, may be the most telling and dramatic empirical difference between RL versus RQ AGN. For RL AGN, the magnetic fields at 5-120 pc-scales may be able to compress and sustain the dusty torus, which extends the inflow/outflow processes from sub-pc scales to pc-scales and links the inflow and outflow with the dynamics of the host galaxy. These findings have profound implications for how we classify and study the evolution of active galaxies, the production of their jets, and their AGN-host connection.


3/14/2023Anil SethTitle: Revealing Low Luminosity AGN with JWST

Most galaxies in the local Universe accrete at rates far below their Eddington limit.  JWST is the most sensitive telescope for detecting these low-luminosity AGN, but identifying them requires quantifying their unique signatures.  JWST can also probe the changes in AGN structure that occur at low luminosities through both the IR continuum as well as coronal lines that are formed from the UV ionizing spectrum.  ReveaLLAGN is a a study of 7 nearby low-luminosity AGN with IFUs on NIRSpec and MIRI;  these objects will serve as templates for more distant objects, and provide a first look at the SED and emission line properties of low-luminosity AGN in the mid-IR.  We present initial results from Sombrero and NGC1052 in this talk, contrasting these objects with Spitzer observations of higher luminosity AGN and the JWST observation of NGC7319.

4/11/2023Yiqing SongTitle: What powers the hearts of local luminous infrared galaxies? Insights from the Very Large Array

Luminous and Ultra-luminous Infrared Galaxies (U/LIRGs) are the most extreme star-forming galaxies in the local Universe, and they are primarily triggered by interacting and mergers of gas-rich galaxies. As such, they provide excellent local laboratories to study in detail the physical processes that could be associated with the hierarchical transformation of star-forming galaxies into elliptical galaxies. However, the dusty nature of U/LIRGs poses great challenges in accurately characterizing their properties at UV/optical wavelengths. In this talk, I will introduce a recently completed multi-band survey of a representative sample of 68 local U/LIRGs conducted with the Karl G. Jansky Very Large Array (VLA), which provides a relatively extinction-free view of the energetics in these extreme local systems. Using arcsecond-resolution observations for the survey, we find tight correlations between the 3 – 33 GHz radio continuum and mid- and far-IR emission on kpc scales, with no clear distinction between AGN and star forming activity. However, compared to star-forming activity, AGN tend to show steeper spectral slopes towards higher radio frequencies. High-resolution continuum observations at 15 and 33 GHz reveal diverse nuclear morphologies in these systems within the central kpc, with which we identify and characterize over 100 compact regions of radio continuum emission at ~100pc scales that are associated with star formation and/or AGN activity. We identify a sample of radio-bright galactic nuclei that are forming stars near the maximal capacity as predicted by theoretical models for star-forming disks supported by dust-reprocessed radiation pressure. Several of these nuclei have been identified to host AGN, and the rest may be going through a key phase of heavily obscured co-evolution between supermassive black holes and circumnuclear star formation. I will briefly discuss ongoing and future multi-wavelength efforts to further investigate the nature of these compact nuclei.  

5/9/2023Steph LaMassaTitle: Unveiling Luminous Obscured Black Hole Growth with the Wide-Area Multi-Wavelength Stripe 82X Survey

Luminous obscured AGN represent a key phase in the cosmic growth history of supermassive black holes. Since these AGN are rare, they can only be adequately sampled via wide-area surveys that probe a large volume of the Universe. “Stripe 82X”, an X-ray survey covering ~30 deg^2 of the rich multi-wavelength Sloan Digital Sky Survey Stripe 82 field, is designed to uncover this population and constrain their evolution and impact on their host galaxies. In this talk, I will summarize the AGN demographics discovered in Stripe 82X and how they compare with AGN identified from wide-area optical and mid-infrared surveys. I will discuss what we have learned about the host galaxies of these luminous AGN and how the obscured AGN fraction evolves with redshift and luminosity. Finally, I will mention exciting future prospects for learning more about the cosmic evolution of rare (yet important!) high-redshift, high luminosity obscured AGN.