A MULTI-WAVELENGTH STUDY OF THE DISK WINDS AND THEIR ROLE IN THE AGN STUDIES

Active galactic nuclei (AGNs) are located at the centers of massive galaxies and are the most luminous objects in the universe. Each AGN embeds a super-massive black hole which produces outflows of gas, or winds. These winds are important because they provide a reasonable physical basis for the connections between the black hole and the properties of their host galaxy. While AGNs have been extensively studied, several fundamental questions about them are yet to be answered. These include the structure and dynamics of the central source and their winds, and questions regarding the evolution of these galaxies. NGC 5548 is a bright and well-studied AGN that has been the target of many monitoring campaigns since 1987. The most extensive observations were in 2013 and 2014, in which its emission and absorption lines behaved in an anomalous way that had never before been seen. For a two-month period during the observations, emission and absorption lines did not respond to the variations of the continuum – the HST team said that the spectral lines had “gone on holiday”. The main goal of my thesis is to model the pan-spectral data available for the NGC 5548 not only to explain the abnormal holiday, but also to use the data as a laboratory to investigate the inner structure of the AGNs and their evolution. Here I explain the physics by which the variations of a disk wind produce the observed holiday. The disk wind acts as a shield between the central source and the clouds that produce the emission and absorption lines. I simulate the behavior of the wind to explain the holiday, and also investigate and model the general characteristics of such winds to predict their effects on the observations. My newly proposed models lead to novel tools to detect the footprint of the disk winds in the observations and track their evolution. This project is a systematic study of UV and X-ray spectroscopic signatures of the wind in the NGC 5548 and is widely applicable to the family of AGNs. Although the comprehensive data set that is used here belongs to one AGN, the results are applicable to all AGNs

Spot The Odd One Out: Regularized Complete Cycle Consistent Anomaly Detector GAN

This study presents an adversarial method for anomaly detection in real-world applications, leveraging the power of generative adversarial neural networks (GANs) through cycle consistency in reconstruction error. Previous methods suffer from the high variance between class-wise accuracy which leads to not being applicable for all types of anomalies. The proposed method named RCALAD tries to solve this problem by introducing a novel discriminator to the structure, which results in a more efficient training process. Additionally, RCALAD employs a supplementary distribution in the input space to steer reconstructions toward the normal data distribution, effectively separating anomalous samples from their reconstructions and facilitating more accurate anomaly detection. To further enhance the performance of the model, two novel anomaly scores are introduced. The proposed model has been thoroughly evaluated through extensive experiments on six various datasets, yielding results that demonstrate its superiority over existing state-of-the-art models. The code is readily available to the research community at https://github.com/zahraDehghanian97/RCALAD.Comment: under revision of Applied Soft Computing Journa

An Extreme FeLoBAL Outflow in the VLT/UVES Spectrum of Quasar SDSS J1321-0041

Context. Quasar outflows are often analyzed to determine their ability to contribute to active galactic nucleus (AGN) feedback. We have identified a broad absorption line (BAL) outflow in the VLT/UVES spectrum of the quasar SDSS J1321-0041. The outflow shows troughs from Fe II, and is therefore identified as an FeLoBAL. It is quite extreme among that population, as it shows C II and Si II BALs. Aims. Outflow systems require a kinetic luminosity above $\sim0.5\%$ of the quasar's luminosity to contribute to AGN feedback. For this reason, we analyzed the spectrum of J1321-0041 to determine the outflow's kinetic luminosity, as well as the quasar's bolometric luminosity. Methods. We measured the ionic column densities from the absorption troughs in the spectrum, and determined the Hydrogen column density and ionization parameter using those column densities as our constraints. We also determined the electron number density $n_e$ based on the ratios between excited state and resonance state column densities of Fe II and Si II. This allowed us to find the distance of the outflow from its central source, as well as its kinetic luminosity. Results. We determined the kinetic luminosity of the outflow to be $8.4^{+13.2}_{-5.3}\times 10^{45}\text{ erg s}^{-1}$, and the quasar's bolometric luminosity to be $1.72\pm0.13\times10^{47}\text{ erg s}^{-1}$, resulting in a ratio of $\dot{E}_k/L_{Bol}=4.8^{+7.7}_{-3.1}\%$. We conclude that this outflow has sufficient kinetic luminosity to contribute to AGN feedback.Comment: 6 pages, 5 figures, 2 tables. Submitted to A&

Narrow absorption line Outflow in Seyfert 1 galaxy J1429+4518: Outflow's distance from the central source and its energetics

In the HST/COS spectrum of the Seyfert 1 galaxy 2MASX J14292507+4518318, we have identified a narrow absorption line (NAL) outflow system with a velocity of -151 km s$^{-1}$ This outflow exhibits absorption troughs from the resonance states of ions like CIV, NV, SiIV, and SiII, as well as excited states from CII*, and SiII*. Our investigation of the outflow involved measuring ionic column densities and conducting photoionization analysis. These yield the total column density of the outflow to be estimated as $\log N_{H}$=19.84 [cm$^{-2}]$, its ionization parameter to be $\log U_{H}$=$-$2.0 and its electron number density equal to $\log n_{e}$= 2.75[cm$^{-3}$]. These measurements enabled us to determine the mass-loss rate and the kinetic luminosity of the outflow system to be $Mdot$=0.22[$M_{Sun}$$yr^{-1}$] and $\log Edot_{K}$=39.3 [erg s$^{-1}$], respectively. We have also measured the location of the outflow system to be at $\sim$275 pc from the central source. This outflow does not contribute to the AGN feedback processes due to the low ratio of the outflow's kinetic luminosity to the AGN's Eddington luminosity ($Edot_{K}/L_{Edd}\approx 0.00025 \%$). This outflow is remarkably similar to the two bipolar lobe outflows observed in the Milky Way by XMM-Newton and Chandra.Comment: 11 pages, 8 figures, accepted for publication in MNRA

Multiple locations of near-infrared coronal lines in NGC 5548

We present the first intensive study of the variability of the near-infrared coronal lines in an active galactic nucleus (AGN). We use data from a 1-yr-long spectroscopic monitoring campaign with roughly weekly cadence on NGC 5548 to study the variability in both emission line fluxes and profile shapes. We find that in common with many AGN coronal lines, those studied here are both broader than the low-ionizaton forbidden lines and blueshifted relative to them, with a stratification that implies an origin in an outflow interior to the standard narrow line region. We observe for the first time [S VIII] and [Si VI] coronal line profiles that exhibit broad wings in addition to narrow cores, features not seen in either [S IX] or [Si X]. These wings are highly variable, whereas the cores show negligible changes. The differences in both the profile shapes and variability properties of the different line components indicate that there are at least two coronal line regions in AGN. We associate the variable, broad wings with the base of an X-ray heated wind evaporated from the inner edge of the dusty torus. The coronal line cores may be formed at several locations interior to the narrow line region: either along this accelerating, clumpy wind or in the much more compact outflow identified with the obscurer and so emerging on scales similar to the outer accretion disc and broad-line region

AGN STORM 2: V. Anomalous Behavior of the CIV Light Curve in Mrk 817

An intensive reverberation mapping campaign on the Seyfert 1 galaxy Mrk817 using the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST) revealed significant variations in the response of the broad UV emission lines to fluctuations in the continuum emission. The response of the prominent UV emission lines changes over a $\sim$60-day duration, resulting in distinctly different time lags in the various segments of the light curve over the 14 months observing campaign. One-dimensional echo-mapping models fit these variations if a slowly varying background is included for each emission line. These variations are more evident in the CIV light curve, which is the line least affected by intrinsic absorption in Mrk817 and least blended with neighboring emission lines. We identify five temporal windows with distinct emission line response, and measure their corresponding time delays, which range from 2 to 13 days. These temporal windows are plausibly linked to changes in the UV and X-ray obscuration occurring during these same intervals. The shortest time lags occur during periods with diminishing obscuration, whereas the longest lags occur during periods with rising obscuration. We propose that the obscuring outflow shields the ultraviolet broad lines from the ionizing continuum. The resulting change in the spectral energy distribution of the ionizing continuum, as seen by clouds at a range of distances from the nucleus, is responsible for the changes in the line response.Comment: 20 pages, 8 figures, submitted to Ap

AGN STORM 2. IV. Swift X-ray and ultraviolet/optical monitoring of Mrk 817

The AGN STORM 2 campaign is a large, multiwavelength reverberation mapping project designed to trace out the structure of Mrk 817 from the inner accretion disk to the broad emission line region and out to the dusty torus. As part of this campaign, Swift performed daily monitoring of Mrk 817 for approximately 15 months, obtaining observations in X-rays and six UV/optical filters. The X-ray monitoring shows that Mrk 817 was in a significantly fainter state than in previous observations, with only a brief flare where it reached prior flux levels. The X-ray spectrum is heavily obscured. The UV/optical light curves show significant variability throughout the campaign and are well correlated with one another, but uncorrelated with the X-rays. Combining the Swift UV/optical light curves with Hubble UV continuum light curves, we measure interband continuum lags, $\tau(\lambda)$, that increase with increasing wavelength roughly following $\tau(\lambda) \propto \lambda^{4/3}$, the dependence expected for a geometrically thin, optically thick, centrally illuminated disk. Modeling of the light curves reveals a period at the beginning of the campaign where the response of the continuum is suppressed compared to later in the light curve - the light curves are not simple shifted and scaled versions of each other. The interval of suppressed response corresponds to a period of high UV line and X-ray absorption, and reduced emission line variability amplitudes. We suggest that this indicates a significant contribution to the continuum from the broad line region gas that sees an absorbed ionizing continuum.Comment: 20 pages, 13 figures, 3 tables, accepted for publication in Ap

AGN STORM 2. I. First results: A Change in the Weather of Mrk 817

We present the first results from the ongoing, intensive, multiwavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this active galactic nucleus was, in part, selected for its historically unobscured nature, we discovered that the X-ray spectrum is highly absorbed, and there are new blueshifted, broad, and narrow UV absorption lines, which suggest that a dust-free, ionized obscurer located at the inner broad-line region partially covers the central source. Despite the obscuration, we measure UV and optical continuum reverberation lags consistent with a centrally illuminated Shakura–Sunyaev thin accretion disk, and measure reverberation lags associated with the optical broad-line region, as expected. However, in the first 55 days of the campaign, when the obscuration was becoming most extreme, we observe a de-coupling of the UV continuum and the UV broad emission-line variability. The correlation recovered in the next 42 days of the campaign, as Mrk 817 entered a less obscured state. The short C IV and Lyα lags suggest that the accretion disk extends beyond the UV broad-line region. Unified

AGN STORM 2. IV. Swift X-Ray and Ultraviolet/Optical Monitoring of Mrk 817

The AGN STORM 2 campaign is a large, multiwavelength reverberation mapping project designed to trace out the structure of Mrk 817 from the inner accretion disk to the broad emission line region and out to the dusty torus. As part of this campaign, Swift performed daily monitoring of Mrk 817 for approximately 15 months, obtaining observations in X-rays and six UV/optical filters. The X-ray monitoring shows that Mrk 817 was in a significantly fainter state than in previous observations, with only a brief flare where it reached prior flux levels. The X-ray spectrum is heavily obscured. The UV/optical light curves show significant variability throughout the campaign and are well correlated with one another, but uncorrelated with the X-rays. Combining the Swift UV/optical light curves with Hubble Space Telescope UV continuum light curves, we measure interband continuum lags, τ(λ), that increase with increasing wavelength roughly following τ(λ) ∝ λ 4/3, the dependence expected for a geometrically thin, optically thick, centrally illuminated disk. Modeling of the light curves reveals a period at the beginning of the campaign where the response of the continuum is suppressed compared to later in the light curve—the light curves are not simple shifted and scaled versions of each other. The interval of suppressed response corresponds to a period of high UV line and X-ray absorption, and reduced emission line variability amplitudes. We suggest that this indicates a significant contribution to the continuum from the broad-line region gas that sees an absorbed ionizing continuum

AGN STORM 2. VI. Mapping Temperature Fluctuations in the Accretion Disk of Mrk 817

We fit the UV/optical lightcurves of the Seyfert 1 galaxy Mrk 817 to produce maps of the accretion disk temperature fluctuations δ T resolved in time and radius. The δ T maps are dominated by coherent radial structures that move slowly (v ≪ c) inward and outward, which conflicts with the idea that disk variability is driven only by reverberation. Instead, these slow-moving temperature fluctuations are likely due to variability intrinsic to the disk. We test how modifying the input lightcurves by smoothing and subtracting them changes the resulting δ T maps and find that most of the temperature fluctuations exist over relatively long timescales (hundreds of days). We show how detrending active galactic nucleus (AGN) lightcurves can be used to separate the flux variations driven by the slow-moving temperature fluctuations from those driven by reverberation. We also simulate contamination of the continuum emission from the disk by continuum emission from the broad-line region (BLR), which is expected to have spectral features localized in wavelength, such as the Balmer break contaminating the U band. We find that a disk with a smooth temperature profile cannot produce a signal localized in wavelength and that any BLR contamination should appear as residuals in our model lightcurves. Given the observed residuals, we estimate that only ∼20% of the variable flux in the U and u lightcurves can be due to BLR contamination. Finally, we discus how these maps not only describe the data but can make predictions about other aspects of AGN variability