List of Abstracts

Flows driven by photons have been studied for almost a century, and a quantitative description of the radiative forces on atoms and ions is important for understanding a wide variety of systems. These systems include massive stars, cataclysmic variables, central stars of planetary nebulae, active galactic nuclei (AGN), and a variety of other environments with accretion disks. The colloquially-termed "radiation pressure" of line-driven winds plays an important role in driving outflows in these environments. Quantifying the associated forces is crucial to understanding how these flows enable interactive mechanisms within these environments, such as stellar winds or AGN feedback. Here we provide new calculations of the dimensionless line strength parameter and AGN mass loss rates due to radiation driving. For representative AGN, we calculate the photoionization balance at each step along the LOS to the proposed wind-launching region above the accretion disk. We then use a recently compiled database of approximately 5.6 million spectral lines to compute the strength of the line-driving force on the gas and the mass-loss rates resulting from these outflows. Values of the initial parameters for each model are selected randomly from reasonable ranges. The varied parameters include the black hole mass, the launch radius, the wind velocity at the launch radius, the radius to the observer, and the black hole accretion rate. We also introduce a "shielding factor" that increases the magnitude of the accretion disk column density prior to the launch radius. This shielding factor simulates a proposed inner “failed wind" region that is thought to shield the outflowing gas from becoming over-ionized by the central source. We also revisit and formalize the role of the commonly-used ionization parameter in setting the properties of the accelerating gas.

Observations of the galaxy population throughout cosmic time have suggested an evolutionary scenario where galaxies evolve from blue and star-forming, to red and quiescent as star formation is quenched and gas is consumed in stars or becomes unavailable for stellar synthesis. What happens between these two stages remains mysterious. Though studies have suggested that black holes in the form of AGN and outflows play important roles in this part, the details of how they impact the host galaxies and their interplay with other quenching mechanisms are still not fully understood. In this talk, I’ll present several studies on post-starburst galaxies (PSBs), which have rapidly and recently quenched their star formation within the past 1 Gyr and thus are promising in providing insights into this transition stage. Multiwavelength data provide a more complete view of the on-going activities inside these galaxies. In summary, we found that PSBs commonly show signatures of AGN activities but these AGN appear to be weak and/or heavily obscured. These AGN might be able to drive outflows but those outflows are likely not strong enough to remove gas from the host galaxy. Direct evidence of AGN quenching the star formation of the host galaxy is still missing and AGN likely quench by disturbing rather than expelling the gas.

The central parsec of AGN is a key region for the launching of winds, and near-infrared interferometry is a unique tool for its study. With VLTI/GRAVITY, we can now spatially resolve not just the hot dust continuum on milliarcsecond 'torus' scales through imaging but also the broad-line region on microarcsecond scales through spectro-astrometry. I will present the latest results from our ESO Large Program and associated projects where we have mapped the kinematics of the BLR in five nearby AGN, measured sizes of the hot dust for seventeen AGN, and reconstructed images for two AGN. BLR kinematics can generally be described as a rotating disk and have allowed us to measure the BLR size and supermassive black hole mass independent of 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. The ongoing GRAVITY+ upgrade will greatly enhance the sensitivity and sky coverage of GRAVITY, and first results demonstrate its power for AGN science at z~2 and beyond.

We discuss the dominant importance of plasma injection effects within magnetospheres of black holes for the ensuing dynamics of relativistic winds and jets. Outside the outer light cylinder, where the magnetic field is nearly helical, the magnetically dominated outflows move in fact nearly radially with very large Lorentz factors $\gamma_0 \gg 1 $, imprinted into plasma during pair production within the gaps. Only at large distances, $r \geq \gamma_0 (c/\Omega)$,
the MHD acceleration $\Gamma \propto r$ takes over. One of the implications is that the M87 jet, well resolved at few BH radii, is not produced by the Blandford-Znajek mechanism.

The “quasar mode” (or radiative mode) of AGN feedback, operated through outflows, plays an essential role in the evolution of galaxies. Quasar outflows are detected as blue-shifted broad absorption lines in the UV/optical spectra of quasars. Thanks to the Sloan digital sky survey, ~100,000 broad absorption line quasars are available now for ensemble statistical studies. This rich dataset has also enabled us to identify some peculiar cases of these sources. In this talk, I will review the current understanding of the quasar outflows and present our recent efforts to understand (i) the nature of these sources and (ii) the primary driver for the variability in the absorption lines.

The determination of outflow physical properties is important to assess the possible effects of Active Galactic Nuclei feedback on host galaxies and to compare observed outflow properties with model predictions. However, current estimates are based on simplified assumptions and do not take into account many observational aspects like projection effects and spatial resolution.
I present a new 3D method to model the kinematics and orientation of outflows allowing to reconstruct in a tomographic way the outflow features, including the observed kinematical maps, even in presence of very clumpy and irregular emission and kinematics.
At variance with previous works, this model does not assume a distribution of the observed gas emission flux but uses a novel procedure to derive it directly from observations, reproducing a 3D distribution of the emitting clouds and providing accurate estimates of the outflows physical properties, e.g. the outflow and energy rate as a function of distance from the galaxy nucleus.
I have successfully tested the performance of the method with both nearby Seyfert-II galaxies observed with the Multi Unit Spectroscopic Explorer at VLT and high redshift sources observed by JWST, showing that the very complex kinematical features observed can be ascribed to the clouds clumpiness in a very simple radial velocity field, accounted by a suitable geometry.

Since the early sixties our view of radio galaxies and quasars has been drastically shaped by discoveries made thanks to observations of radio sources listed in the Third Cambridge catalog and its revised version (3CR). However the largest fraction of data collected to date on 3CR sources is mainly performed with relatively old instruments, rarely updated, and the 3CR lists objects lying in the Northern Hemisphere only, thus having limited access to innovative astronomical facilities (e.g., ALMA, VLT with MUSE and ERIS, ELT, SKA, LSST). To mitigate these limitations we built a new catalog of powerful radio sources visible from the Southern Hemisphere, extracted from the G4Jy catalog and based on the same selection criteria as the 3CR. This new catalog, named G4Jy-3CRE, lists 264 radio sources that will be primary targets for SKA and are all located at declination below -5 deg and with 9 Jy limiting sensitivity at nearly 178 MHz. I will present here results (i) on the search for optical counterparts and the comparison with mid-infrared analyses; (ii) on the optical spectroscopic campaign and (iii) an overview of the X-ray emission for several radio sources listed in the G4Jy-3CRE. Finally, I will highlight preliminary results achieved and achievable in the future with multifrequency observations to investigate the physics of jets, outflows and their interaction with the large scale environments where powerful radio sources born, grow and die.

The wealth of spectroscopic observations of outflows in local AGN led to various attempts to correlate the mass outflow rate and kinetic power with source luminosity and feedback efficiency. I will review new results about type-II AGN and show why some of these estimates over-predict the mass outflow rate, especially for the ionized gas, and why neutral and molecular gas outflows are more efficient yet highly uncertain. I will also show that in many low-z systems, quenching of star formation is not as efficient as deduced from standard star formation rate estimates.

Active Galactic Nuclei (AGN) significantly impact the evolution of their host galaxies by expelling large fractions of gas with wide-angle outflows. The X-ray band is key to understanding how these winds affect their environment, because they are heated to high, X-ray temperatures. In this talk, I will introduce our Bayesian framework for characterizing AGN outflows, which provides substantial improvements in our ability to explore parameter space and perform robust model selection. We applied this framework to the new and archival deep Chandra HETG observation of the Seyfert galaxy NGC 4051. We detected six components, spanning velocities from 100s to 10,000s km/s, and mapped their evolution across an eight year period. The most significant wind component is collisionally, rather than photo-, ionized and remains remarkably stable between the two epochs. This is the first detection in absorption of such an AGN outflow, which, critically, was enabled by using a Bayesian approach. Furthermore, for one of the fast components, we obtain one of the tightest wind density measurements to date, log n/[cm^−3]=13.0+/-0.015, and determine that it is located at ∼240 gravitational radii. We will demonstrate how, within a Bayesian framework, such precise density measurements are possible by properly accounting for free-free heating and infrared radiation. The potential of our method will be fully realized with the next generation of X-ray gratings and microcalorimeters, such as XRISM, Athena, LEM, and Arcus.

Winds located at different spatial scales and with different properties are found both in radio-loud (RL) and in radio-quiet (RQ) AGN, suggesting that winds and jet may co-exist. Within the accretion and ejection paradigm, several questions are still to be answered, such as how are jets and winds formed and connected to the accretion flow, if they are they a phase of every AGN life and how their feedback is acting in galaxies. Winds and jets are radio emitters, sometimes clearly distinguishable in their emission features, sometimes not. I will discuss possible ways to investigate the role of radio emission of winds and jets together with their multi-frequency counterparts, within the current and forthcoming generation of high sensitive radio arrays.

Recent observations have established that dwarf galaxies can host black holes of intermediate mass (IMBHs). With modern numerical models, we would like to test the evolutionary impact of IMBHs. Our novel subsolar-mass (0.8 solar mass) resolution simulations of dwarf galaxies have a resolved three phase ISM and account for non-equilibrium heating, cooling, and chemistry processes. The stellar IMF is fully sampled from 0.08 – 150 solar masses while massive stars can form HII regions and explode as - well resolved - supernovae.  The stellar dynamics around the IMBH is integrated accurately with a regularization scheme. We present a viscous accretion disk model for the IMBH with momentum, energy, and mass conserving mechanical feedback – in line with broad-line region observations of dwarf galaxies. We demonstrate how the IMBH can grow from accretion of the clumpy cold gas phase and how the presence of the IMBH and its feedback impacts the gas phase structure and the formation of a nuclear star cluster. Overall, the IMBH accretion rates are low and the growth times are long, in agreement with observational estimates from X-ray observations. We discuss general implications on IMBH formation and growth.

We study disks and jets in various accretion states (SANE and MAD) using novel, GPU-accelerated general-relativistic magneto-hydrodynamic (GR-MHD) code which we developed, based on HARM. This code, written in CUDA-c and uses OpenMP to parallelize multi-GPU setups, allows high resolution simulations of accretion disks and the formation and structure of jets without the need of multi-node supercomputer infrastructure. A 256^3 simulation is well within the reach of an Nvidia DGX-V100 server, with the computation being a factor about 100 times faster if only the CPU was used.

We use this code to examine several disk structures, wind and jet properties in the MAD and SANE states.
In the MAD state, we find that the magnetic flux threading the horizon only depends on the spin of the BH, while is independent on the disk size or initial configuration. This implies that the jet structure is a strong function of the spin, with non-spinning BHs have the widest jets. We further find that non-zero spins, the jets are wider for prograde than retrograde spins. This is due to pressure balance, where for non-spinning BHs the azimuthal component of the magnetic field (B_phi) can be neglected. The poloidal magnetic field component inside the jet is higher for prograde BH spins, implying a wider jets.

In the SANE state, we find that: (i) increasing the magnetic field does not affect the mass accretion rate; (ii) Simultaneous increase of the disk size and the magnetic field, while keeping the ratio of energies fixed, lead to the destruction of the jet once the magnetic flux through the horizon decrease below a certain limit. This demonstrates that the existence of the jet is not a linear function of the initial magnetic field strength; (iii) the structure of the jet is a weak function of the adiabatic index of the gas, with relativistic gas tend to have a wider jet.

Non-relativistic and massive outflows (so-called winds) exist in all black hole systems. In this talk I will mainly focus on the ones observed in BH Low Mass X-ray Binaries, the outflows observed in AGN being discussed in the invited talk of D. Kazanas. The winds in XrB are much highly ionized compared to those observed in AGN and they are mainly traced by the presence of blue-shifted absorption features due to ionized iron lines (e.g., Fexxv and/or Fexxvi). These are massive equatorial outflows that can be dynamically important for the evolution of the XrB systems. High-inclination sources show these powerful disk winds especially during the soft state. The X-ray signatures are typically absent during the hard states but there are growing evidences of wind signatures in the opt/IR suggesting the presence of wind during the entire outburst. Nonetheless, a large variety of wind signatures (generally strongly variable) and behaviors exist, revealing a complex connection among winds, jets and the states of the accretion disk. I will review in this talk our present knowledge of these winds, the possible physical mechanisms that produce them and the expected advances in this domain from future instruments (e.g., XRISM, Athena).

We will report the first highly significant detection of the polarization of the X-rays from the accretion disk of a black hole in an X-ray binary. The Imaging X-ray Polarization Explorer (IXPE) caught the X-ray binary 4U 1630-47 in the thermal emission state, in which the classical theory of geometrically thin, optically thick accretion disks pioneered by Shakura and Sunyaev in 1973 is believed to give an excellent description of the properties of the accretion flow. However, the IXPE observations reveal unexpectedly high polarization degrees exceeding the predictions of the thin-disk theory. The observations either require extreme fine-tuning of the parameters describing the black hole spacetime and the emitting plasma or significant deviations from the standard scenario, such as a geometrically thick disk or the presence of anisotropic mildly relativistic electrons close to the accretion disk. Simultaneous NICER observations also show absorption lines indicating accretion disk wind outflow, which could be modeled by an MHD wind model. Further, both polarization modeling and accretion disk wind modeling indicate a high inclination angle.

The connection between X-ray weakness and powerful X-ray outflows is both expected in a scenario where outflows are connected with radiation-driven winds, and observed in several sources, both in the local Universe and at high redshift. Here I present the first results of a new study of this possible connection based on a search for SDSS quasars with weak X-ray emission in serendipitous XMM-Newton observations. The selected objects have a "normal" optical/UV blue continuum, but a flat and extraordinarily weak X-ray spectrum. The availability of rest-frame optical/UV spectra allows to check for the signature of outflows in the absorption lines and/or in the profiles of the emission lines. This method could reveal the presence of a population of so-far overlooked outflowing quasars and confirm the connection between winds and X-ray weakness in quasars.

Authors: M. H. Naddaf, M. L. Martinez-Aldama, P. Marziani, S. Panda, M. Sniegowska, and B. Czerny

Broad Absorption Line Quasars (BAL QSOs) show signatures of massive energetic outflows from the underlying source which play an important role in the feedback process in Active Galactic Nuclei (AGN) and in turn in the evolution of the central black hole and galactic bulge. We test a theoretical model of dust-driven wind based on the failed radiatively accelerated dusty outflow (FRADO) model of Czerny & Hryniewicz. Considering a certain range of black hole masses, Eddington ratios, and metallicities, we model BAL QSO as sources viewed along the outflowing stream and calculate the probabilities of seeing the BAL phenomenon as functions of these global parameters, which later were compared with those seen in the observational data from the SDSS DR7. We also include considerations on the presence/absence of obscuring torus. We found that both in the model and in the data the BAL phenomenon mostly happens for sources with black hole masses larger than 10^8 solar masses, the effect gets stronger with accretion rate, and also high metallicities are more likely in QSOs showing BAL features if the presence of torus is taken into account. The consistency of the model with the data provides support for the interpretation of the BAL phenomenon as the result of the orientation of the source instead a temporary stage of AGN life.

Despite that quasar-driven, galaxy-scale outflows are regularly evoked in galaxy evolution models and detected in observations, it is unclear how quasars drive such outflows – either via a hot bubble of shocked nuclear wind, via radiation pressure, or via some other mechanism. I will argue that the nature of this driving mechanism sets the physical conditions in the narrow emission line region (NLR), and hence emission line observations carry information which can be used to constrain how quasar wind-driving works. I will present novel hydrodynamic simulations of NLR clouds subject to either radiation-pressure feedback or shocked-wind feedback, with sufficient resolution to predict the emitted line spectrum. I will then compare the distinct predictions of the different mechanisms with emission line observations.

One commonly-invoked launching mechanism for AGN outflows is radiation line driving. This mechanism depends closely on the SED of the ionizing continuum, and so is inherently linked to the structure of the accretion flow. Theories of radiation line-driven winds therefore provide testable predictions as a function of black hole (BH) mass and accretion rate.
In this work we confront these predictions using the ultraviolet emission line properties of 190,000 quasars from SDSS DR17. We quantify how the shape of CIV 1549A and the equivalent width (EW) of HeII 1640A depend on the BH mass and Eddington ratio inferred from MgII 2800A. The blueshift of the CIV emission line is commonly interpreted as a tracer of quasar outflows, while the HeII EW traces the strength of the 10-100eV continuum which photo-ionizes the ultraviolet emission line regions.
Above L/LEdd>0.2, there is a strong mass dependence in both CIV blueshift and HeII EW. Large CIV blueshifts are observed only in regions with both high BH mass and high accretion rate, consistent with predictions for radiation line driven winds. The observed trends in HeII and 2 keV X-ray strength are broadly consistent with theoretical models of AGN SEDs, where the ionizing SED depends on the accretion disc temperature and the strength of the soft excess. At L/LEdd < 0.2, we find a dramatic switch in behaviour: the ultraviolet emission properties show much weaker trends, and no longer agree with SED models, hinting at changes in the structure of the broad line region. Overall the observed emission line properties are generally consistent with the radiation line driving scenario, where quasar winds are governed by the SED, which itself results from the accretion flow and hence depends on both the SMBH mass and accretion rate.

Traditionally, AGN feedback is thought to operate through either kinetically powerful (>10^45 erg/s), extended (10s kpc) jets or massive gas outflows. Recent observational work and simulations suggest that also low-power (<10^45 erg/s) jets may play an important role, but little is known so far about their actual effect on their galaxy hosts.
I will present recent results on the interplay between low-power radio jets and their host galaxies, by exploiting VLT/MUSE optical integral field observations of low and intermediate z galaxies. We found evidence for a novel phenomenon, consisting in turbulent, high-velocity dispersion gas in the direction perpendicular to the jets and to the AGN ionisation cones. Based on our analysis, the most likely origin for this perpendicular high-velocity dispersion gas appears to be the strong interaction of the low-power jets with the gas in the host galaxy disc, perturbing and shocking the disc material, in accordance with predictions from hydrodynamic simulations of jet-disc interaction. Moreover, we found a correlation between the mass and the energetics of the high velocity dispersion gas and the power of the radio jet, supporting that jets may be responsible for the enhancement of turbulence. and could represent a significant mechanism of AGN feedback in luminous sources. This phenomenon, being observed in a growing number of objects, could potentially represent an important additional channel of AGN feedback to be taken into account.

A high energy power law is a common feature in the spectra of many astrophysical objects. We show that
the photons in an unmagnetized relativistic plasma, outflowing from an astrophysical system composed of electrons and protons with a variable Lorentz factor (or a velocity shear) go through repeated scattering with electrons to gain energy. The escaped population of photons naturally produces a power-law-shaped spectrum making it a photons’ analogue to the conventional Fermi acceleration mechanism for charged particles. Thus, this mechanism provides a natural alternative to
current explanations of high energy power-law spectra via synchrotron or thermal Comptonization. The model is applicable to any relativistic plasma beam with an arbitrary Lorentz factor profile around black holes. We implement the theory to relativistic jets and show that the obtained range of the photon indices is compatible with the observed values in such objects and the results of Monte Carlo simulations that we carry out independently. Therefore, the observed high energy spectral indices provide a unique indicator of the jet structure.

Compact obscured nuclei (CONs) are thought to exist in as many as 40% of nearby (U)LIRGs. These compact (~100 pc) nuclear structures are characterized by their extreme nuclear column densities, n_H2 >10^25cm^-2, which make them almost invisible at mid-IR, optical and X-ray wavelengths due to the heavy attenuation. As a result, CONs are notoriously difficult to find, identified only via a rare transition of vibrationally excited HCN, nu_2 = 1f (HCN-VIB). All known CONs show signatures of a past gas-rich merger and evidence for molecular outflows (and in several cases, inflows) in HCN and/or CO. These features are consistent with a key obscured starburst phase in which remnant material is ejected from the center of the galaxy, making CONs critical in understanding the role of nuclear feedback in galaxy evolution. The nature of CONs however remains unknown, with both AGN activity and an extreme starburst appearing as plausible nuclear power sources. Using new IFU data from MUSE, I will present several newly discovered features of the CON galaxy NGC4418 uncovering clues to its nature, including the presence of [OIII] knots throughout the galaxy which appear to have been ionized by an AGN. Furthermore, I will present the surprising first detection of permitted iron lines in a Seyfert 2 galaxy (NGC4418), along with two other LIRG CONs. I will discuss the potential implications of this in the context of CONs and the Seyfert galaxy unification model.

We here present 0.02–0.04 arcsec (5–12 pc) resolution ALMA observation of the obscured active galactic nucleus of IRAS 17578-0400. We found an extremely optically thick torus with a characteristic radius of 4 pc, with a temperature gradient from the inner to the outer torus. We found collimated outflow along the minor axis of the torus traced by multiple dense gas tracers such as the HCN(3-2) and HCO+(3-2) lines. The inner ~7pc radius dense gas disk traced by 13CO(1-0) shows the inner gas disk and blue- and red-shifted tails where the gas is connected with the launching region of the collimated dense gas outflow. By examining the PV plots of HCN(3-2), we found a flared inflowing disk with a radius of ~62pc and a thickness of up to ~ 20pc at the outer edge. Perpendicular to the flared disk, the collimated outflow shows an overall stable rotation with a speed of 110 km s−1 throughout the 100 pc scale along the minor axis. The projected outflow speed is about 80 km s−1. Assuming an inclination angle of 80 deg, the outflow speed reaches ~700 km s−1. The outflow is slowing down at a very low rate, which is unlikely dominated by gravity. The inflowing gas on the flared disk is likely the driving force of the collimated rotating outflow of the dense gas. Additionally, upon examining the JVLA Ka and Ku band high-spatial-resolution images, we found the radio emission is located at the kinematic center of the dense gas, where synchrotron and free-free emission is dominated.

Most supermassive black hole in the universe is accreting in the mode of hot accretion. In the past decade, MHD numerical simulations have convincingly shown the existence of strong wind from black hole hot accretion flows and we are also accumulating more and more observational evidences. In this talk, I will review our current understanding of hot wind, including the theoretical and observational evidences of wind, its main physical properties such as mass flux, velocity, spatial distribution, fluxes of energy and momentum as a function of mass accretion rate, black hole spin, and accretion mode (SANE or MAD), and the comparison between wind and jet. The role of hot wind played in AGN feedback will also be briefly discussed.