List of Posters

Narrow-line Seyfert 1 galaxies (NLS1s) are suggested to be an earlier phase of active galactic nuclei (AGN). They are usually characterized by a high Eddington ratio, where AGN-driven outflows are likely more prevalent. We present a 1-9 GHz radio spectral analysis for a sample of NLS1s observed with VLASS and ATCA. The radio spectra flatten at lower frequencies in most of the objects and suggest a median spectral turnover of ~ 1 GHz, which implies synchrotron self-absorption in a source with a size of only a fraction of 1 pc, possibly a compact wind or a weak jet. Other spectral shapes, for instance, flat or inverted slopes may indicate a compact optically thick source likely a relativistic jet or coronal emission, a significant spectral steepening may suggest relic emission from past AGN activity, and a single spectral slope may be consistent with star-forming activity.

The spectroscopic analysis of stellar-mass black hole wind absorption lines can give important information on these structures. However many questions on the wind launching mechanism and its geometry remain open; the recent developments in X-ray polarimetry can let us look at this topic in a new light.
In this work, we analyze the polarization signature expected from a magnetically-driven disk wind, using magnetohydrodynamic (MHD) calculations to constrain the wind geometry and density structure. Using the photoionization code CLOUDY we investigate the ionization structure of the stratified wind along several lines of sight; then we run the Monte-Carlo code STOKES to compute the polarized radiative transfer of photons interacting with the wind, and to determine the polarization properties of the outcoming radiation.

V.L. Oknyansky (University of Haifa, Israel/SAI MSU Moscow, Russia)
C.M.Gaskell (University of California, Santa Krus, USA)
We show that, contrary to simple predictions, most AGNs show at best only a small increase of lags inthe J, H, K, and L bands with increasing wavelength. We suggest that a possible cause of this near simultaneity of the variability from the near-IR to the mid-IR is that the hot dust is in a hollow bi-conical outflow of which we only see the near side. In the proposed model sublimation or recreation of dust in some cloud along our line of sight in the hollow cone could be a factor in explaining the changing look phenomenon of an AGN. The relative wavelength independence of IR lags simplifies the use of IR lags for estimating cosmological parameters.

AGN-driven galaxy-scale outflows are an important component of galaxy evolution models, but the details of how they affect the host galaxy's interstellar medium (ISM) and star formation are not fully understood. To better understand these processes, we need to study the properties of the AGN, outflow, and SF in the host galaxy and disentangle their various contributions to the optical spectra. We discuss spectroscopic approaches for characterizing and detecting outflows in integral field unit (IFU) data, including a multi-dimensional variant of BPT diagrams. We will also consider a few intriguing galaxies where we have identified the strong impact of large-scale outflows and/or jets on the ISM and star formation using MaNGA data. By combining optical spectroscopic results with radio results, we obtained a multi-wavelength picture of these systems.

Given a binary system consisting of a stellar-mass black hole (BH) and a massive star, the star bloats the envelope at the later evolutionary phase and transports a certain fraction of its mass to the companion BH. Such mass transfer phenomena are crucial in collapsing the binary orbit to leave close binary BHs that would finally merge through emitting gravitational waves. Then, decay rates of the orbital separation depend on how rapidly the orbital angular momentum is carried away by gas outflowing from the binary. While powerful outflows would be driven by UV and X-ray radiation produced in the accretion disk, the actual effect is still poorly understood. Therefore, we have performed the first three-dimensional radiation hydrodynamics simulations of mass transfer in a close binary system that self-consistently solves the production and diffusion of thermal photons in the accretion disk. Our poster will briefly summarize our simulation results and show how significant radiation-driven outflows occur in mass-transferring binaries.

Authors: M. Sniegowska, S. Panda, P. Marziani, K. Garnica

Abstract:
High Eddington active galactic nuclei (AGN) are of particular interest for the galaxy evolution since, during such a phase, the central black hole mass undergoes a fast growth phase. Recent work indicates extremely high metallicity values for super-Eddington quasars. The evidence of high metallicity is based on an analysis that involves lines emitted by ionic species of Silicon and Aluminium, two elements that are greatly enhanced in core collapse supernovae with very massive progenitors. Repeated supernova explosions in the outer AGN accretion disks were already suggested in the literature. In quasars, Silicon and Aluminium line emission is predominantly due to a virialized low ionization sub-region of the Broad Line Regions. We isolate a component of the emission lines due to outflowing gas, and we repeat the metallicity estimates using different diagnostic ratios, and upper limits from relevant emission features (including optical FeII) for four sources. We derive lower abundance values for the outflowing component relative to the core component in these lines, and we discuss whether supernova pollution might be at the origin of the discrepancy.

We present a new analysis of the old ~ 900 ks high-resolution RGS XMM-Newton observations of the nearby Seyfert galaxy Mrk 509. The physically motivated warm absorber model proposed by us is a stratified medium in constant total pressure (CTP) regime. Our models allow us to fit continuum shapes bounded together with the line profiles, which gives additional constraints on the gas structure of the warm absorber in this source. A grid of synthetic absorbed spectra were computed with photoionization code- TITAN assuming the system to be under CTP. As an illuminated spectral energy distribution (SED) we used the most actual multi-wavelength observations available for Mrk 509. CTP gas with ionization parameter (log \xi_{0}) ~ 1.7 defined at the cloud surface is capable of fitting the data. We discuss these results, and compare them with the standard approach employing constant density components, highlighting the limitations of previous prior results.

In X-ray the presence of highly ionized outflowing gas with mildly relativistic velocities (0.05 - 0.4c), named Ultra-Fast Outflows (UFOs), has been observed in many Active Galactic Nuclei (AGNs) based on the detection of absorption lines in the Iron K band. Within the SUBWAYS project we characterized these winds in 22 quasars at z ~ 0.2 (Matzeu et al., 2022), and compared the results with those from similar studies on local Seyfert galaxies (i.e., 42 radio-quiet AGNs at z < 0.1; Tombesi et al., 2010) and high redshift quasars (i.e., 14 AGNs at z ≥ 1.4; Chartas et al., 2021). In this talk, we will present the results of our extensive statistical analysis on the main physical parameters of the sources (e.g. black hole mass, bolometric luminosity, accretion rates, and SEDs) and of the UFOs (e.g. column density, ionization parameter, outflow velocity, and energetics), as well as the key correlations found across our sample.

Understanding radiatively-driven outflows in quasars is fundamental to studying the co-evolution of galaxies and their central supermassive black holes. Broad UV emission lines, such as CIV, can be used to trace radiatively driven winds, with emission line blueshifts generally considered a signature of outflows. Furthermore, the direct recombination mechanism by which the HeII line emits makes HeII equivalent width an ideal indicator of the SED hardness. Recently it has been suggested that a larger fraction of luminous quasars at z>6 show strong signatures of outflows when compared to quasar populations of more modest redshift, which could suggest that AGN feedback is more prevalent in the early Universe. Using a statistically significant sample of ~2500 quasars at z~4, we investigate for the first time how the CIV and HeII emission line properties of quasars evolves from z~2 to z~4. We find that the trends in line properties with fundamental parameters such as luminosity, black hole mass and Eddington ratio are remarkably consistent across the entire redshift range investigated. There is no evolution in CIV emission line blueshifts between z=2 and z=4 when the samples are matched in UV-luminosity. We show that the samples of quasars at z~5-7 however have systematically lower black hole masses and higher accretion rates compared to the z~2-4 population. Thus, matching these quasars in luminosity to their lower redshift counterparts, as has been done in previous work, is ineffective in selecting populations with the same distribution of black hole mass and accretion rate. This could at least partially explain the observed evolution in UV emission line properties seen in the very high-redshift Universe. Larger samples at z~6 with black hole mass measurements, will enable us to understand whether the difference in their masses and accretion rates is physical or as a result of selection biases in current observed samples.

In this work, we performed detailed broadband spectral and timing analysis of a small flaring event of ~120 ks in a narrow-line Seyfert 1 galaxy NGC 4051 using simultaneous XMM-Newton and NuSTAR observations. The ~300 ks long NuSTAR observation and the overlapping XMM-Newton exposure were segregated into pre-flare, flare and post-flare segments. We found that during the flare, the NuSTAR count rate peaked at 2.5 times the mean count rate before the flare. We explored the variation of X-ray emission in different time scales using various phenomenological and physical models. The 0.3 − 50 keV X-ray spectrum of the source can be described by a composite model consisting of a primary continuum, reprocessed emission, warm absorber and ultra-fast outflows. From the spectral analysis, we found that the reflection fraction drops significantly during the flare, accompanied by the increase in the coronal height to ~12.2 Rg from ~9.6 Rg (during the pre-flare phase) above the disc. The spectrum became softer during the flare supporting the "softer when brighter" nature of the source. After the alleviation of the flare, the coronal height drops to ~7.4 Rg, and the corona heats up to the temperature of ~228 keV. This indicates that there could be inflation of the corona during the flare. We did not find any significant change in the inner accretion disc or the seed photon temperature. These results suggest that the flaring event occurred due to the change in the coronal properties rather than any notable change in the accretion disc.

Roche lobe overflow from a donor star onto a compact object binary companion can evolve to a phase of unstable runaway mass transfer, before eventually culminating in a common-envelope event. The hyper-Eddington accretion rates achieved during this brief phase are accompanied by an intense mass loss through disk winds, analogous to, but even more extreme than ultraluminous X-ray sources in the nearby universe. This expanding outflow will inflate a compact and energetic bubble of plasma into the circumbinary medium (a "hypernebula"). Embedded within this hypernebula are relativistic electrons heated at the termination shock of the winds from the inner accretion flow. We have developed a time-dependent, radiative, multi-messenger model for the X-ray, synchrotron radio, and high energy neutrino emission (100 TeV-PeV, as seen by IceCube) from hypernebulae. If episodic, relativistic jets are sources of (periodically) repeating fast radio bursts (Sridhar+21b), such hypernebulae could generate a persistent radio emission and contribute large and time-variable Faraday rotation measure to the bursts, consistent with the observations. Hypernebulae can be discovered through large area radio surveys, such as VLASS, as off-nuclear point sources. They presage energetic transients from common envelope mergers, and can act as signposts to future gravitational wave (LISA) events.