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The local (z=0.0315) AGN Mrk 817, was monitored over more than 500 days with space-borne and ground-based instruments as part of a large international campaign AGN STORM 2. Here, we present a comprehensive analysis of the broad-band continuum variations using detailed modeling of the broad line region (BLR), several types of disk winds classified by their optical depth, and new numerical simulations. We find that diffuse continuum (DC) emission, with additional contributions from strong and broad emission lines, can explain the continuum lags observed in this source during high and low luminosity phases. Disk illumination by the variable X-ray corona contributes only a small fraction of the observed continuum lags. Our BLR models assume radiation pressure-confined clouds distributed over a distance of 2-122 light days. We present calculated mean-emissivity radii of many emission lines, and DC emission, and suggest a simple, transfer-function-dependent method that ties them to cross-correlation lag determinations. We do not find clear indications for large optical depth winds but identify the signature of lower column density winds. In particular, we associate the shortest observed continuum lags with a combination of tau(1 Ryd) approx. 2 wind and a partly shielded BLR. Even smaller optical depth winds may be associated with X-ray absorption features and with noticeable variations in the width and lags of several high ionization lines like HeII and CIV. Finally, we demonstrate the effect of torus dust emission on the observed lags in the i and z bands., Comment: 23 pages, 18 figures. Corrected typographical error in the title of the paper as it appeared in the Metadata

X-ray reverberation mapping is a powerful technique for probing the innermost accretion disk, whereas continuum reverberation mapping in the UV, optical, and infrared (UVOIR) reveals reprocessing by the rest of the accretion disk and broad-line region (BLR). We present the time lags of Mrk 817 as a function of temporal frequency measured from 14 months of high-cadence monitoring from Swift and ground-based telescopes, in addition to an XMM-Newton observation, as part of the AGN STORM 2 campaign. The XMM-Newton lags reveal the first detection of a soft lag in this source, consistent with reverberation from the innermost accretion flow. These results mark the first simultaneous measurement of X-ray reverberation and UVOIR disk reprocessing lags$\unicode{x2013}$effectively allowing us to map the entire accretion disk surrounding the black hole. Similar to previous continuum reverberation mapping campaigns, the UVOIR time lags arising at low temporal frequencies are longer than those expected from standard disk reprocessing by a factor of 2-3. The lags agree with the anticipated disk reverberation lags when isolating short-timescale variability, namely timescales shorter than the H$\beta$ lag. Modeling the lags requires additional reprocessing constrained at a radius consistent with the BLR size scale inferred from contemporaneous H$\beta$-lag measurements. When we divide the campaign light curves, the UVOIR lags show substantial variations, with longer lags measured when obscuration from an ionized outflow is greatest. We suggest that, when the obscurer is strongest, reprocessing by the BLR elongates the lags most significantly. As the wind weakens, the lags are dominated by shorter accretion disk lags., Comment: 28 pages, 11 figures, 3 tables. Accepted for publication in the Astrophysical Journal

We present the results of the XMM-Newton and NuSTAR observations taken as part of the ongoing, intensive multi-wavelength monitoring program of the Seyfert 1 galaxy Mrk 817 by the AGN Space Telescope and Optical Reverberation Mapping 2 (AGN STORM 2) Project. The campaign revealed an unexpected and transient obscuring outflow, never before seen in this source. Of our four XMM-Newton/NuSTAR epochs, one fortuitously taken during a bright X-ray state has strong narrow absorption lines in the high-resolution grating spectra. From these absorption features, we determine that the obscurer is in fact a multi-phase ionized wind with an outflow velocity of $\sim$5200 km s$^{-1}$, and for the first time find evidence for a lower ionization component with the same velocity observed in absorption features in the contemporaneous HST spectra. This indicates that the UV absorption troughs may be due to dense clumps embedded in diffuse, higher ionization gas responsible for the X-ray absorption lines of the same velocity. We observe variability in the shape of the absorption lines on timescales of hours, placing the variable component at roughly 1000 $R_g$ if attributed to transverse motion along the line of sight. This estimate aligns with independent UV measurements of the distance to the obscurer suggesting an accretion disk wind at the inner broad line region. We estimate that it takes roughly 200 days for the outflow to travel from the disk to our line of sight, consistent with the timescale of the outflow's column density variations throughout the campaign.

The assembly and co-evolution of supermassive black holes (SMBH) and their host galaxy stellar population is a key open questions in galaxy evolution. Stellar mass ($M_\star$) and star formation rate (SFR), are inferred by modeling the spectral energy distribution (SED). For galaxies triggering SMBH activity, the active galactic nucleus (AGN) contaminates the light at all wavelengths, hampering the inference of galaxy parameters. Incomplete AGN templates can lead to systematic overestimates of the stellar mass, biasing our understanding of AGN-galaxy co-evolution. This challenge has gained further impetus with the advent of sensitive wide-area surveys with millions of luminous AGN, including by eROSITA, Euclid and LSST. We aim to estimate the accuracy and bias of AGN host galaxy parameters and improve upon existing techniques. This work makes two contributions: 1) a new SED fitting code, GRAHSP, with a flexible, empirically motivated AGN model including a power law continuum emission lines, a FeII forest and a flexible infrared torus. We verify that our model reproduces published X-ray to infrared SEDs of AGN to better than 20\% accuracy. A fully Bayesian fit with nested sampling includes uncertainties in the model and the data, making the inference highly robust. 2) we created a benchmark photometric dataset where pure quasars are merged with non-AGN pure galaxies into a hybrid (Chimera) object but with known galaxy and AGN properties. Comparing the true and retrieved $M_\star$, SFR and AGN luminosities shows that previous codes systematically over-estimate $M_\star$ and SFR by 0.5 dex with a wide scatter of 0.7 dex, at AGN luminosities above 10^44 erg/s. In contrast, GRAHSP shows no bias on $M_\star$ and SFR. GRAHSP also estimates more realistic uncertainties. GRAHSP enables characterization of the environmental conditions conducive to black hole growth. (abridged), Comment: accepted in A&A

We fit the UV/optical lightcurves of the Seyfert 1 galaxy Mrk 817 to produce maps of the accretion disk temperature fluctuations $\delta T$ resolved in time and radius. The $\delta T$ maps are dominated by coherent radial structures that move slowly ($v \ll c$) inwards and outwards, 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 $\delta T$ maps and find that most of the temperature fluctuations exist over relatively long timescales ($\sim$100s of days). We show how detrending 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 $\sim$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., Comment: 23 pages, 18 figures, submitting to ApJ, comments welcome

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, Accepted for publication in ApJ

We present rest-frame ultraviolet (UV) images of six luminous quasars at $z \sim 4.8$ obtained with the Hubble Space Telescope (HST). These quasars exhibit a wide range of star formation rates (SFRs) and lie in a wide range of environments. We carefully model and subtract the point-like quasar emission and investigate the morphology of the underlying host galaxies at kpc scales. The residual images allowed identification of potential companion sources, which enabled us to explore the role of galaxy merger scenarios in the co-evolution of the quasars and their hosts. We also search for the mechanism driving extreme SFRs in three of the quasars. We find that the rate of detection of potential companions to the host galaxies does not follow trends between high- and low-SFR sources; i.e., the HST imaging suggests that both high- and low-SFR sources are found in both dense and sparse galactic environments. The suggested role of major mergers driving extreme SFRs cannot be supported by the multiwavelength data in hand. Three of four companion sources, previously revealed by sub-millimeter observations, are not detected in the HST images of three of our quasars. An adapted high-resolution imaging strategy focused on high-SFR sources and extended to a larger quasar sample is required to determine the role of mergers in the processes of star formation and supermassive black hole growth at high redshift., Comment: 22 pages, 10 figures; accepted for publication in ApJ

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 ApJ

Weak emission-line quasars (WLQs) are a subset of Type 1 quasars that exhibit extremely weak Ly$\alpha +$N V $\lambda$1240 and/or C IV $\lambda$1549 emission lines. We investigate the relationship between emission-line properties and accretion rate for a sample of 230 `ordinary' Type 1 quasars and 18 WLQs at $z < 0.5$ and $1.5 < z < 3.5$ that have rest-frame ultraviolet and optical spectral measurements. We apply a correction to the H$\beta$-based black-hole mass ($M_{\rm BH}$) estimates of these quasars using the strength of the optical Fe II emission. We confirm previous findings that WLQs' $M_{\rm BH}$ values are overestimated by up to an order of magnitude using the traditional broad emission-line region size-luminosity relation. With this $M_{\rm BH}$ correction, we find a significant correlation between H$\beta$-based Eddington luminosity ratios and a combination of the rest-frame C IV equivalent width and C IV blueshift with respect to the systemic redshift. This correlation holds for both ordinary quasars and WLQs, which suggests that the two-dimensional C IV parameter space can serve as an indicator of accretion rate in all Type 1 quasars across a wide range of spectral properties., Comment: 17 pages (AASTeX 6.3.1), 5 figures, accepted for publication in ApJ

We present reverberation mapping measurements for the prominent ultraviolet broad emission lines of the active galactic nucleus Mrk817 using 165 spectra obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. Our ultraviolet observations are accompanied by X-ray, optical, and near-infrared observations as part of the AGN Space Telescope and Optical Reverberation Mapping Program 2 (AGN STORM 2). Using the cross-correlation lag analysis method, we find significant correlated variations in the continuum and emission-line light curves. We measure rest-frame delayed responses between the far-ultraviolet continuum at 1180 A and Ly$\alpha$ $\lambda1215$ A ($10.4_{-1.4}^{+1.6}$ days), N V $\lambda1240$ A ($15.5_{-4.8}^{+1.0}$days), SiIV + OIV] $\lambda1397$ A ($8.2_{-1.4}^{+1.4}$ days), CIV $\lambda1549$ A ($11.8_{-2.8}^{+3.0}$ days), and HeII $\lambda1640$ A ($9.0_{-1.9}^{+4.5}$ days) using segments of the emission-line profile that are unaffected by absorption and blending, which results in sampling different velocity ranges for each line. However, we find that the emission-line responses to continuum variations are more complex than a simple smoothed, shifted, and scaled version of the continuum light curve. We also measure velocity-resolved lags for the Ly$\alpha$, and CIV emission lines. The lag profile in the blue wing of Ly$\alpha$ is consistent with virial motion, with longer lags dominating at lower velocities, and shorter lags at higher velocities. The CIV lag profile shows the signature of a thick rotating disk, with the shortest lags in the wings, local peaks at $\pm$ 1500 $\rm km\,s^{-1}$, and a local minimum at line center. The other emission lines are dominated by broad absorption lines and blending with adjacent emission lines. These require detailed models, and will be presented in future work., Comment: Submitted to ApJ. 25 pages, 8 figures, and 6 tables

Post-starburst galaxies are believed to be in a rapid transition between major merger starbursts and quiescent ellipticals. Their optical spectrum is dominated by A-type stars, suggesting a starburst that was quenched recently. While optical observations suggest little ongoing star formation, some have been shown to host significant molecular gas reservoirs. This led to the suggestion that gas depletion is not required to end the starburst, and that star formation is suppressed by other processes. We present NOEMA CO(1-0) observations of 15 post-starburst galaxies with emission lines consistent with Active Galactic Nucleus (AGN) photoionization. We collect post-starburst candidates with molecular gas measurements from the literature, with some classified as classical E+A, while others with line ratios consistent with AGN and/or shock ionization. Using far-infrared observations, we show that systems that were reported to host exceptionally-large molecular gas reservoirs host in fact obscured star formation, with some systems showing star formation rates comparable to ULIRGs. Among E+A galaxies with molecular gas measurements, 7 out of 26 (26\%) host obscured starbursts. Using far-infrared observations, post-starburst candidates show similar SFR-$M_{\mathrm{H_2}}$ and Kennicutt-Schmidt relations to those observed in star-forming and starburst galaxies. In particular, there is no need to hypothesize star formation quenching by processes other than the consumption of molecular gas by star formation. The combination of optical, far-infrared, and CO observations indicates that some regions within these galaxies have been recently quenched, while others are still forming stars in highly obscured regions. All this calls into question the traditional interpretation of such galaxies.

This program is part of QUEST (Quasar/ULIRG Evolutionary Study) and seeks to examine the gaseous environments of z < 0.3 quasars and ULIRGs as a function of host galaxy properties and age across the merger sequence from ULIRGs to quasars. This first paper in the series focuses on 33 quasars from the QUEST sample and on the kinematics of the highly ionized gas phase traced by the N V 1238, 1243 A and O VI 1032, 1038 A absorption lines in high-quality Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) data. N V and O VI outflows are present in about 60% of the QUEST quasars and span a broad range of properties, both in terms of equivalent widths (from 20 mA to 25 A) and kinematics (outflow velocities from a few x 100 km/s up to ~10,000 km/s). The rate of incidence and equivalent widths of the highly ionized outflows are higher among X-ray weak or absorbed sources. The weighted outflow velocity dispersions are highest among the X-ray weakest sources. No significant trends are found between the weighted outflow velocities and the properties of the quasars and host galaxies although this may be due to the limited dynamic range of properties of the current sample. These results will be re-examined in an upcoming paper where the sample is expanded to include the QUEST ULIRGs. Finally, a lower limit of ~0.1% on the ratio of time-averaged kinetic power to bolometric luminosity is estimated in the 2-4 objects with blueshifted P V 1117, 1128 absorption features., Comment: 37 pages, 14 figures, accepted for publication in the Astrophysical Journal

High cadence, high quality observations of active galactic nuclei (AGN) clearly show continuum variations with lags, relative to the shortest observed variable UV continuum, that increase with wavelength ("lag spectra"). These have been attributed to the irradiation and heating of the central accretion disk by the central X-ray emitting corona. An alternative explanation, connecting the observed lag-spectra to line and continuum emission from gas in the broad line region (BLR), has also been proposed. In this paper I show the clear spectral signature of the time-dependent diffuse gas emission in the lag-spectrum of 6 AGN. I also show a new lag-luminosity relationship for 9 objects which is a scaled down version of the well known lag(H-beta)-L(5100A) relationship in AGN. The shape of the lag-spectrum, and its normalization, are entirely consisted with diffuse emission from radiation pressure supported clouds in a BLR with a covering factor of about 0.2. While some contributions to the continuum lag from the irradiated disk cannot be excluded, there is no need for this explanation., Comment: 12 pages, 11 figures, submitted to MNRAS after a referee report

Reverberation mapping (RM) of active galactic nuclei (AGNs) has been used over the past three decades to determine AGN broad-line region (BLR) sizes and central black-hole masses, and their relations with the AGN's luminosity. Until recently the sample of objects with RM data was limited to low-luminosity AGNs ($L_{\rm opt} \lesssim 10^{46}$ ergs s$^{-1}$) and low redshifts ($z \lesssim 0.5$). Here we present results from a reverberation-mapping project of some of the most luminous and highest redshift quasars that have been mapped to date. The study is based on almost twenty years of photometric monitoring of 11 quasars, six of which were monitored spectrophotometrically for 13 years. This is the longest reverberation-mapping project carried out so far on this type of AGNs. We successfully measure a time lag between the CIV$\lambda$1549 broad emission line and the quasar continuum in three objects, and measure a CIII$\lambda$1909 lag in one quasar. Together with recently published data on CIV reverberation mapping, the BLR size is found to scale as the square root of the UV luminosity over eight orders of magnitude in AGN luminosity. There is a significant scatter in the relation, part of which may be intrinsic to the AGNs. Although the CIV line is probably less well suited than Balmer lines for determination of the mass of the black hole, virial masses are tentatively computed and in spite of a large scatter we find that the mass of the black hole scales as the square root of the UV luminosity., Comment: 14 Figures, 27 pages, Accepted for publication in ApJ

E+A galaxies are believed to be a short phase connecting major merger ULIRGs with red and dead elliptical galaxies. Their optical spectrum suggests a massive starburst that was quenched abruptly, and their bulge-dominated morphologies with tidal tails suggest that they are merger remnants. AGN-driven winds are believed to be one of the processes responsible for the sudden quenching of star formation and for the expulsion and/or destruction of the remaining molecular gas. Little is known about AGN-driven winds in this short-lived phase. In this paper we present the first and unique sample of post starburst galaxy candidates with AGN that show indications of ionized outflows in their optical emission lines. Using IRAS-FIR observations, we study the star formation in these systems and find that many systems selected to have post starburst signatures in their optical spectrum are in fact obscured starbursts. Using SDSS spectroscopy, we study the stationary and outflowing ionized gas. We also detect neutral gas outflows in 40\% of the sources with mass outflow rates 10--100 times more massive than in the ionized phase. The mean mass outflow rate and kinetic power of the ionized outflows in our sample ($\dot{M}\sim 1\, \mathrm{M_{\odot}/yr}$, $\dot{E}\sim 10^{41}\, \mathrm{erg/sec}$) are larger than those derived for active galaxies of similar AGN luminosity and stellar mass. For the neutral outflow ($\dot{M}\sim 10\, \mathrm{M_{\odot}/yr}$, $\dot{E}\sim 10^{42}\, \mathrm{erg/sec}$), their mean is smaller than that observed in (U)LIRGs with and without AGN.

We present the first results from the ongoing, intensive, multi-wavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this AGN 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 recovers in the next 42 days of the campaign, as Mrk 817 enters a less obscured state. The short CIV and Ly alpha lags suggest that the accretion disk extends beyond the UV broad line region., Comment: 28 pages, 14 figures, submitted to ApJ. Comments welcome

Post starburst E+A galaxies are systems that hosted a powerful starburst that was quenched abruptly. Simulations suggest that these systems provide the missing link between major merger ULIRGs and red and dead ellipticals, where AGN feedback is responsible for the expulsion or destruction of the molecular gas. However, many details remain unresolved and little is known about AGN-driven winds in this short-lived phase. We present spatially-resolved IFU spectroscopy with MUSE/VLT of SDSS J124754.95-033738.6, a post starburst E+A galaxy with a recent starburst that started 70 Myrs ago and ended 30 Myrs ago, with a peak SFR of $\sim 150\,\mathrm{M_{\odot}/yr}$. We detect disturbed gas throughout the entire field of view, suggesting triggering by a minor merger. We detect fast-moving multi-phased gas clouds, embedded in a double-cone face-on outflow, which are traced by ionized emission lines and neutral NaID \emph{emission} and absorption lines. We find remarkable similarities between the kinematics, spatial extents, and line luminosities of the ionized and neutral gas phases, and propose a model in which they are part of the same outflowing clouds, which are exposed to both stellar and AGN radiation. Our photoionization model provides consistent ionized line ratios, NaID absorption optical depths and EWs, and dust reddening. Using the model, we estimate, for the first time, the neutral-to-ionized gas mass ratio (about 20), the sodium neutral fraction, and the size of the outflowing clouds. This is one of the best ever observed direct connections between the neutral and ionized outflow phases in AGN., Comment: MNRAS accepted

New reverberation mapping (RM) measurements, combined with accurate luminosities and line ratios, provide strong constraints on the location of the line emitting gas in the broad line region (BLR) of active galactic nuclei (AGN). In this paper I present new calculations of radiation pressure and magnetic pressure confined clouds and apply them to a ``generic AGN'' and to NGC 5548. The new calculations are in good agreement with the observed lags of all broad emission lines, and with the luminosities of La, Civ 1549, Ovi 1035 and Heii 1640. They are also in reasonable agreement with the luminosities of Mgii 2798 and the 1990A blend of Ciii] and Siiii] lines for high metallicity gas. They explain the changes in time-lag following an increase in continuum luminosity and their dependencies on the inner and outer boundaries of the BLR. They also predict very strong Balmer and Paschen continua with important implications to continuum RM experiments. However, the calculated Balmer and Paschen line luminosities are too weak, by factors of 2-5. This ``Balmer line crisis'' was noted in several earlier works and is now confirmed and constrained by RM measurements that were not available in the past. It seems that present photoionization codes that use the escape probability formalism, fail to correctly compute the Balmer line luminosities in high density, large optical depth gas., Comment: 14 pages, 5 figures, 4 tables. Accepted for publication in MNRAS

We present ALMA band-7 data of the [CII] $\lambda157.74\,\mu{\rm m}$ emission line and underlying far-infrared (FIR) continuum for twelve luminous quasars at $z \simeq 4.8$, powered by fast-growing supermassive black holes (SMBHs). Our total sample consists of eighteen quasars, twelve of which are presented here for the first time. The new sources consists of six Herschel/SPIRE detected systems, which we define as "FIR-bright" sources, and six Herschel/SPIRE undetected systems, which we define as "FIR-faint" sources. We determine dust masses for the quasars hosts of $M_{dust} \le 0.2-25.0\times 10^8 M_{\odot}$, implying ISM gas masses comparable to the dynamical masses derived from the [CII] kinematics. It is found that on average the MgII line is blueshifted by $\sim 500\,{\rm km\,s}^{-1}$ with respect to the [CII] emission line, which is also observed when complementing our observations with data from the literature. We find that all of our "FIR-bright" subsample and most of the "FIR-faint" objects lie above the main sequence of star forming galaxies at $z \sim 5$. We detect companion sub-millimeter galaxies (SMGs) for two sources, both FIR-faint, with a range of projected distances of $\sim20-60$ kpc and with typical velocity shifts of $\left|\Delta v\right| \lesssim200\,{\rm km\,s}^{-1}$ from the quasar hosts. Of our total sample of eighteen quasars, 5/18 are found to have dust obscured starforming companions., Comment: 26 pages, 10 figures, 6 tables. Submitted after Referee acceptance

The bolometric luminosity of active galactic nuclei (AGN) is difficult to determine and various approximations have been used to calibrate it against different observed properties. Here I combine theoretical calculations of optically thick, geometrically thin accretion disks, and observed X-ray properties of AGN, to provide new bolometric correction factors (\kbol) over a large range of black hole (BH) mass, accretion rate, and spin. This is particularly important in cases where the mass accretion rate cannot be determined from the observed spectral energy distribution, and in cases where luminosity-independent correction factors have been used. Simple powerlaw approximations of \kbol\ are provided for L(5100\AA), L(3000\AA), L(1400\AA), L(2-10 keV) and L(narrow \hb). In all cases the uncertainties are large mostly due to the unknown BH spin. Prior knowledge of the BH mass reduces the uncertainty considerably., Comment: MNRAS accepted; 9 pages, 4 figures, one table

The global influence of AGN-driven outflows remains uncertain, due to a lack of large samples with accurately-determined outflow properties. In the second paper of this series, we determine the mass and energetics of ionized outflows is 234 type II AGN, the largest such sample to date, by combining the infrared emission of the dust in the wind (paper I) with the emission line properties. We provide new general expressions for the properties of the outflowing gas, which depend on the ionization state of the gas. We also present a novel method to estimate the electron density in the outflow, based on optical line ratios and on the known location of the wind. The inferred electron densities, $n_{\mathrm{e}} \sim 10^{4.5}\,\mathrm{(cm^{-3})}$, are two orders of magnitude larger than typically found in most other cases of ionized outflows. We argue that the discrepancy is due to the fact that the commonly-used [SII]-based method underestimates the true density by a large factor. As a result, the inferred mass outflow rates and kinetic coupling efficiencies are $\dot{M}_{\mathrm{out}} \sim 10^{-2}\, \mathrm{(M_{\odot}/yr)}$ and $\epsilon = \dot{E}_{\mathrm{kin}}/L_{\mathrm{bol}} \sim 10^{-5}$ respectively, 1--2 orders of magnitude lower than previous estimates. Our analysis suggests the existence of a significant amount of neutral atomic gas at the back of the outflowing ionized gas clouds, with mass that is a factor of a few larger than the observed ionized gas mass. This has significant implications for the estimated mass and energetics of such flows., Comment: After referee report

Accreting supermassive black holes (SMBHs) can exhibit variable emission across the electromagnetic spectrum and over a broad range of timescales. The variability of active galactic nuclei (AGNs) in the ultraviolet and optical is usually at the few tens of per cent level over timescales of hours to weeks. Recently, rare, more dramatic changes to the emission from accreting SMBHs have been observed, including tidal disruption events, 'changing look' AGNs and other extreme variability objects. The physics behind the 're-ignition', enhancement and 'shut-down' of accretion onto SMBHs is not entirely understood. Here we present a rapid increase in ultraviolet-optical emission in the centre of a nearby galaxy, marking the onset of sudden increased accretion onto a SMBH. The optical spectrum of this flare, dubbed AT 2017bgt, exhibits a mix of emission features. Some are typical of luminous, unobscured AGNs, but others are likely driven by Bowen fluorescence - robustly linked here with high-velocity gas in the vicinity of the accreting SMBH. The spectral features and increased ultraviolet flux show little evolution over a period of at least 14 months. This disfavours the tidal disruption of a star as their origin, and instead suggests a longer-term event of intensified accretion. Together with two other recently reported events with similar properties, we define a new class of SMBH-related flares. This has important implications for the classification of different types of enhanced accretion onto SMBHs., Comment: Published in Nature Astronomy

Large scale outflows of different gas phases are ubiquitous in the host galaxies of active galactic nuclei (AGN). Despite their many differences, they share a common property - they all contain dust. The dust is carried with the outflow, heated by the AGN, and emits at infrared wavelengths. This paper shows that the infrared emission of this dust can be used to detect AGN outflows and derive their properties. We use a sample of about 4000 type II AGN and compare the infrared properties of systems that show spectroscopic signature of ionized gas outflows to systems that do not. We detect an additional mid-infrared emission component in galaxies with spectroscopically discovered winds, and attribute it to the dust in the outflow. This new component offers novel constraints on the outflow properties, such as its mean location and covering factor. We measure the location of the outflow for roughly 1700 systems, with the distribution showing a prominent peak around 500 pc, a tail that extends to large distances (10 kpc), and no objects with a location smaller than 50 pc. The covering factor of the wind shows a wide distribution which is centered around 0.1, with 24% (8%) of the winds showing covering factors larger than 0.2 (0.5). The dust emission is not sensitive to various systematics affecting optically-selected outflows, and can be used to estimate the mass outflow rate in thousands of galaxies with only 1D spectra.

We present Reverberation Mapping (RM) results for 17 high-redshift, high-luminosity quasars with good quality R-band and emission line light curves. We are able to measure statistically significant lags for Ly_alpha (11 objects), SiIV (5 objects), CIV (11 objects), and CIII] (2 objects). Using our results and previous lag determinations taken from the literature, we present an updated CIV radius--luminosity relation and provide for the first time radius--luminosity relations for Ly_alpha, SiIV and CIII]. While in all cases the slope of the correlations are statistically significant, the zero points are poorly constrained because of the lack of data at the low luminosity end. We find that the emissivity weighted distance from the central source of the Ly_alpha, SiIV and CIII] line emitting regions are all similar, which corresponds to about half that of the H_beta region. We also find that 3/17 of our sources show an unexpected behavior in some emission lines, two in the Ly_alpha light curve and one in the SiIV light curve, in that they do not seem to follow the variability of the UV continuum. Finally, we compute RM black hole masses for those quasars with highly significant lag measurements and compare them with CIV single--epoch (SE) mass determinations. We find that the RM-based black hole mass determinations seem smaller than those found using SE calibrations., Comment: Accepted for publication in ApJ. Important changes to Tables 1, 2, 4 and Section 5 respect to previous version

Post starburst E+A galaxies show indications of a powerful starburst that was quenched abruptly. Their disturbed, bulge-dominated morphologies suggest that they are merger remnants. The more massive E+A galaxies are suggested to be quenched by AGN feedback, yet little is known about AGN-driven winds in this short-lived phase. We present spatially-resolved IFU spectroscopy by the Keck Cosmic Web Imager of SDSS J003443.68+251020.9, at z=0.118. The system consists of two galaxies, the larger of which is a post starburst E+A galaxy hosting an AGN. Our modelling suggests a 400 Myrs starburst, with a peak star formation rate of 120 Msun/yr. The observations reveal stationary and outflowing gas, photoionized by the central AGN. We detect gas outflows to a distance of 17 kpc from the central galaxy, far beyond the region of the stars (about 3 kpc), inside a conic structure with an opening angle of 70 degrees. We construct self-consistent photoionization and dynamical models for the different gas components and show that the gas outside the galaxy forms a continuous flow, with a mass outflow rate of about 24 Msun/yr. The gas mass in the flow, roughly $10^9$ Msun, is larger than the total gas mass within the galaxy, some of which is outflowing too. The continuity of the flow puts a lower limit of 60 Myrs on the duration of the AGN feedback. Such AGN are capable of removing, in a single episode, most of the gas from their host galaxies and expelling enriched material into the surrounding CGM., Comment: submitted to MNRAS; comments are welcome!

We present Reverberation Mapping results after monitoring a sample of 17 high-z, high-luminosity quasars for more than 10 years using photometric and spectroscopic capabilities. Continuum and line emission flux variability is observed in all quasars. Using cross-correlation analysis we successfully determine lags between the variations in the continuum and broad emission lines for several sources. Here we present a highlight of our results and the determined radius--luminosity relations for Ly_alpha and CIV., Comment: Contributed talk at conference "Quasars at all cosmic epochs", held in Padova 2-7 April 2017, published in Frontiers in Astronomy and Space Sciences

We present a long-term, multi-wavelength project to understand the epoch of fastest growth of the most massive black holes by using a sample of 40 luminous quasars at z~4.8. These quasars have rather uniform properties, with typical accretion rates and black hole masses of L/L_Edd~0.7 and M_BH~10^9 M_sol. The sample consists of "FIR-bright" sources with a previous Herschel/SPIRE detection, suggesting SFR > 1000 M_sol/yr, as well as of "FIR-faint" sources for which Herschel stacking analysis implies a typical SFR of ~400 M_sol/yr. Six of the quasars have been observed by ALMA in [CII]{\lambda}157.74 micron line emission and adjacent rest-frame 150 micron continuum, to study the dusty cold ISM. ALMA detected companion, spectroscopically confirmed sub-mm galaxies (SMGs) for three sources - one FIR-bright and two FIR-faint. The companions are separated by ~14-45 kpc from the quasar hosts, and we interpret them as major galaxy interactions. Our ALMA data therefore clearly support the idea that major mergers may be important drivers for rapid, early SMBH growth. However, the fact that not all high-SFR quasar hosts are accompanied by interacting SMGs, and their ordered gas kinematics observed by ALMA, suggest that other processes may be fueling these systems. Our analysis thus demonstrates the diversity of host galaxy properties and gas accretion mechanisms associated with early and rapid SMBH growth., Comment: 5 pages of text, 4 figures. Proceeding of the meeting "Quasars at All Cosmic Epochs" (Padova, April 2017). Published in "Frontiers in Astronomy and Space Science" (available at http://www.frontiersin.org/articles/10.3389/fspas.2017.00049)

We present a new analysis of the PG quasar sample based on Spitzer and Herschel observations. (I) Assuming PAH-based star formation luminosities (L_SF) similar to Symeonidis et al. (2016, S16), we find mean and median intrinsic AGN spectral energy distributions (SEDs). These, in the FIR, appear hotter and significantly less luminous than the S16 mean intrinsic AGN SED. The differences are mostly due to our normalization of the individual SEDs, that properly accounts for a small number of very FIR-luminous quasars. Our median, PAH-based SED represents ~ 6% increase on the 1-243 micron luminosity of the extended Mor & Netzer (2012, EM12) torus SED, while S16 find a significantly larger difference. It requires large-scale dust with T ~ 20 -- 30 K which, if optically thin and heated by the AGN, would be outside the host galaxy. (II) We also explore the black hole and stellar mass growths, using L_SF estimates from fitting Herschel/PACS observations after subtracting the EM12 torus contribution. We use rough estimates of stellar mass, based on scaling relations, to divide our sample into groups: on, below and above the star formation main sequence (SFMS). Objects on the SFMS show a strong correlation between star formation luminosity and AGN bolometric luminosity, with a logarithmic slope of ~ 0.7. Finally we derive the relative duty cycles of this and another sample of very luminous AGN at z = 2 -- 3.5. Large differences in this quantity indicate different evolutionary pathways for these two populations characterised by significantly different black hole masses., Comment: Accepted for publication in MNRAS

Post starburst E+A galaxies are thought to have experienced a significant starburst that was quenched abruptly. Their disturbed, bulge-dominated morphologies suggest that they are merger remnants. We present ESI/Keck observations of SDSS J132401.63+454620.6, a post starburst galaxy at redshift z = 0.125, with a starburst that started 400 Myr ago, and other properties, like star formation rate (SFR) consistent with what is measured in ultra luminous infrared galaxies (ULRIGs). The galaxy shows both zero velocity narrow lines, and blueshifted broader Balmer and forbidden emission lines (FWHM=1350 +- 240 km/s). The narrow component is consistent with LINER-like emission, and the broader component with Seyfert-like emission, both photoionized by an active galactic nucleus (AGN) whose properties we measure and model. The velocity dispersion of the broad component exceeds the escape velocity, and we estimate the mass outflow rate to be in the range 4-120 Mo/yr. This is the first reported case of AGN-driven outflows, traced by ionized gas, in post starburst E+A galaxies. We show, by ways of a simple model, that the observed AGN-driven winds can consistently evolve a ULIRG into the observed galaxy. Our findings reinforce the evolutionary scenario where the more massive ULIRGs are quenched by negative AGN feedback, evolve first to post starburst galaxies, and later become typical red and dead ellipticals., Comment: Submitted to MNRAS, after referee's comments

In this work, which is a continuation of Castell\'o-Mor et al. (2016), we present new X-ray and infrared (IR) data for a sample of active galactic nuclei (AGN) covering a wide range in Eddington ratio over a small luminosity range. In particular, we rigorously explore the dependence of the optical-to-X-ray spectral index $\alpha_{OX}$ and the IR-to-optical spectral index on the dimensionless accretion rate, $\dot{\mathcal{M}}=\dot{m}/\eta$ where $\dot{m}=L_{AGN}/L_{Edd}$ and $\eta$ is the mass-to-radiation conversion efficiency, in low and high accretion rate sources. We find that the SED of the faster accreting sources are surprisingly similar to those from the comparison sample of sources with lower accretion rate. In particular: i) the optical-to-UV AGN SED of slow and fast accreting AGN can be fitted with thin AD models. ii) The value of $\alpha_{OX}$ is very similar in slow and fast accreting systems up to a dimensionless accretion rate $\dot{\mathcal{M}}_{c}\sim$10. We only find a correlation between $\alpha_{OX}$ and $\dot{\mathcal{M}}$ for sources with $\dot{\mathcal{M}} > \dot{\mathcal{M}}_{c}$. In such cases, the faster accreting sources appear to have systematically larger $\alpha_{OX}$ values. iii) We also find that the torus in the faster accreting systems seems to be less efficient in reprocessing the primary AGN radiation having lower IR-to-optical spectral slopes. These findings, failing to recover the predicted differences between the SEDs of slim and thin ADs within the observed spectral window, suggest that additional physical processes or very special geometry act to reduce the extreme UV radiation in fast accreting AGN. This may be related to photon trapping, strong winds, and perhaps other yet unknown physical processes., Comment: Accepted for publication on MNRAS, 14 pages, 7 figures

We present new ALMA band-7 data for a sample of six luminous quasars at z~4.8, powered by fast-growing supermassive black holes (SMBHs) with rather uniform properties: the typical accretion rates and black hole masses are L/L_Edd~0.7 and M_BH~10^9 M_sol. Our sample consists of three "FIR-bright" sources, which were individually detected in previous Herschel/SPIRE observations, with star formation rates of SFR>1000 M_sol/yr, and three "FIR-faint" sources for which Herschel stacking analysis implies a typical SFR of ~400 M_sol/yr. The dusty interstellar medium in the hosts of all six quasars is clearly detected in the ALMA data and resolved on scales of ~2 kpc, in both continuum (\lambda_rest ~150 um) and [C II]157.74 um line emission. The continuum emission is in good agreement with the expectations from the Herschel data, confirming the intense SF activity in the quasar hosts. Importantly, we detect companion sub-millimeter galaxies (SMGs) for three sources -- one FIR-bright and two FIR-faint, separated by ~14-45 kpc and <450 km/s from the quasar hosts. The [C II]-based dynamical mass estimates for the interacting SMGs are within a factor of ~3 of the quasar hosts' masses, while the continuum emission implies SFR(quasar)~(2-11)xSFR(SMG). Our ALMA data therefore clearly support the idea that major mergers are important drivers for rapid early SMBH growth. However, the fact that not all high-SFR quasar hosts are accompanied by interacting SMGs and the gas kinematics as observed by ALMA suggest that other processes may be fueling these systems. Our analysis thus demonstrates the diversity of host galaxy properties and gas accretion mechanisms associated with early and rapid SMBH growth., Comment: This version matches the one published in ApJ. 21 pages, 9 figures

This work presents the properties of 42 objects in the group of the most luminous, highest star formation rate LINERs at z = 0.04 - 0.11. We obtained long-slit spectroscopy of the nuclear regions for all sources, and FIR data (Herschel and IRAS) for 13 of them. We measured emission line intensities, extinction, stellar populations, stellar masses, ages, AGN luminosities, and star-formation rates. We find considerable differences from other low-redshift LINERs, in terms of extinction, and general similarity to star forming (SF) galaxies. We confirm the existence of such luminous LINERs in the local universe, after being previously detected at z ~ 0.3 by Tommasin et al. (2012). The median stellar mass of these LINERs corresponds to 6 - 7 $\times$ 10$^{10}$M$_{\odot}$ which was found in previous work to correspond to the peak of relative growth rate of stellar populations and therefore for the highest SFRs. Other LINERs although showing similar AGN luminosities have lower SFR. We find that most of these sources have LAGN ~ LSF suggesting co-evolution of black hole and stellar mass. In general among local LINERs being on the main-sequence of SF galaxies is related to their AGN luminosity., Comment: submitted to MNRAS

This is the third paper in a series describing the spectroscopic properties of a sample of 39 AGN at $z \sim 1.5$, selected to cover a large range in black hole mass ($M_{BH}$) and Eddington ratio ($L/L_{Edd}$). In this paper, we continue the analysis of the VLT/X-shooter observations of our sample with the addition of 9 new sources. We use an improved Bayesian procedure, which takes into account intrinsic reddening, and improved $M_{BH}$ estimates, to fit thin accretion disc (AD) models to the observed spectra and constrain the spin parameter ($a_*$) of the central black holes. We can fit 37 out of 39 AGN with the thin AD model, and for those with satisfactory fits, we obtain constraints on the spin parameter of the BHs, with the constraints becoming generally less well defined with decreasing BH mass. Our spin parameter estimates range from $\sim$$-$0.6 to maximum spin for our sample, and our results are consistent with the "spin-up" scenario of BH spin evolution. We also discuss how the results of our analysis vary with the inclusion of non-simultaneous GALEX photometry in our thin AD fitting. Simultaneous spectra covering the rest-frame optical through far-UV are necessary to definitively test the thin AD theory and obtain the best constraints on the spin parameter., Comment: 17 pages, 10 figures, accepted for publication in MNRAS

The typical optical-UV continuum slopes observed in many type 1 AGN are redder than expected from thin accretion disk models. A possible resolution to this conundrum is that many AGN are reddened by dust along the line of sight. To explore this possibility, we stack 5000 SDSS AGN with luminosity L~10^45erg/s and redshift z~0.4 in bins of optical continuum slope alpha_opt and width of the broad H$\beta$ emission line. We measure the EW of the NaID absorption feature in each stacked spectrum. We find a linear relation between alpha_opt and EW(NaID), such that EW(NaID) increases as alpha_opt becomes redder. In the bin with the smallest H$\beta$ width, objects with the bluest slopes that are similar to accretion disk predictions are found to have EW(NaID)=0, supporting the line-of-sight dust hypothesis. This conclusion is also supported by the dependence of the $H\alpha/H\beta$ line ratio on alpha_opt. The implied relationship between alpha_opt and dust reddening is given by E(B-V)~0.2(-0.1-alpha_opt), and the implied reddening of a typical type 1 AGN with alpha_opt=-0.5 is E(B-V)~0.08mag. Photoionization calculations show that the dusty gas responsible for reddening is too ionized to produce the observed features. Therefore, we argue that the sodium absorption arises in regions of the host ISM which are shielded from the AGN radiation, and the correlation with alpha_opt arises since ISM columns along shielded and non-shielded sightlines are correlated. This scenario is supported by the similarity of the E(B-V)-NaID relation implied by our results with the relation in the Milky-Way found by previous studies., Comment: accepted for publication in ApJ

The absence of intrinsic broad line emission has been reported in a number of active galactic nuclei (AGN), including some with high Eddington ratios. Such "true type 2 AGN" are inherent to the disk-wind scenario for the broad line region: Broad line emission requires a minimal column density, implying a minimal outflow rate and thus a minimal accretion rate. Here we perform a detailed analysis of the consequences of mass conservation in the process of accretion through a central disk. The resulting constraints on luminosity are consistent with all the cases where claimed detections of true type 2 AGN pass stringent criteria, and predict that intrinsic broad line emission can disappear at luminosities as high as about 4x$10^{46}$ erg s$^{-1}$ and any Eddington ratio, though more detections can be expected at Eddington ratios below about 1%. Our results are applicable to every disk outflow model, whatever its details and whether clumpy or smooth, irrespective of the wind structure and its underlying dynamics. While other factors, such as changes in spectral energy distribution or covering factor, can affect the intensities of broad emission lines, within this scenario they can only produce true type 2 AGN of higher luminosity then those prescribed by mass conservation., Comment: To appear in MNRAS. The L and M columns were inadvertently switched in the original version (Thank you Giovanni Miniutti for catching). Corrected in this version

This is the second in a series of papers aiming to test how the mass ($M_{\rm BH}$), accretion rate ($\dot{M}$) and spin ($a_{*}$) of super massive black holes (SMBHs) determine the observed properties of type-I active galactic nuclei (AGN). Our project utilizes a sample of 39 unobscured AGN at $z\simeq1.55$ observed by VLT/X-shooter, selected to map a large range in $M_{\rm BH}$ and $L/L_{\rm edd}$ and covers the most prominent UV-optical (broad) emission lines, including H$\alpha$, H$\beta$, MgII, and CIV. This paper focuses on single-epoch, "virial" $M_{\rm BH}$ determinations from broad emission lines and examines the implications of different continuum modeling approaches in line width measurements. We find that using a "local" power-law continuum instead of a physically-motivated thin disk continuum leads to only slight underestimation of the FWHM of the lines and the associated $M_{\rm BH}\left({\rm FWHM}\right)$. However, the line dispersion $\sigma_{\rm line}$ and associated $M_{\rm BH}\left(\sigma_{\rm line}\right)$ are strongly affected by the continuum placement and provides less reliable mass estimates than FWHM-based methods. Our analysis shows that H$\alpha$, H$\beta$ and MgII can be safely used for virial $M_{\rm BH}$ estimation. The CIV line, on the other hand, is not reliable in the majority of the cases, this may indicate that the gas emitting this line is not virialized. While H$\alpha$ and H$\beta$ show very similar line widths, the mean ${\rm FWHM\left(MgII\right)}$ is about 30% narrower than ${\rm FWHM\left(H\beta\right)}$. We confirm several recent suggestions to improve the accuracy in CIV-based mass estimates, relying on other UV emission lines. Such improvements do not reduce the scatter between CIV-based and Balmer-line-based mass estimates., Comment: 26 Pages, 15 figures, Accepted for publication in MNRAS

We employ optical and UV observations to present SEDs for two reverberation-mapped samples of super-Eddington and sub-Eddington AGN with similar luminosity distributions. The samples are fitted with accretion disc models in order to look for SED differences that depend on the Eddington ratio. The fitting takes into account measured BH mass and accretion rates, BH spin and intrinsic reddening of the sources. All objects in both groups can be fitted by thin AD models over the range 0.2-1$\,\mu$m with reddening as a free parameter. The intrinsic reddening required to fit the data are relatively small, $E(B-V)\leq0.2$~mag, except for one source. Super-Eddington AGN seem to require more reddening. The distribution of $E(B-V)$ is similar to what is observed in larger AGN samples. The best fit disc models recover very well the BH mass and accretion for the two groups. However, the SEDs are very different, with super-Eddington sources requiring much more luminous far-UV continuum. The exact amount depends on the possible saturation of the UV radiation in slim discs. In particular, we derive for the super-Eddington sources a typical bolometric correction at 5100\AA{} of 60-150 compared with a median of $\sim$20 for the sub-Eddington AGN. The measured torus luminosity relative to $\lambda L_{\lambda}(5100\AA{}$) are similar in both groups. The $\alpha_{OX}$ distribution is similar too. However, we find extremely small torus covering factors for super-Eddington sources, an order of magnitude smaller than those of sub-Eddington AGN. The small differences between the groups regarding the spectral range 0.2-22$\,\mu$m, and the significant differences related to the part of the SED that we cannot observed may be consistent with some slim disc models. An alternative explanation is that present day slim-disc models over-estimate the far UV luminosity of such objects by a large amount., Comment: 21 pages, 10 figures, 4 tables, Accepted for publication in MNRAS

The origin of short timescale (weeks/months) variability of AGN, whether due to intrinsic disc variations or reprocessing of X-ray emission by a surrounding accretion disc, has been a puzzle for many years. However recently a number of observational programmes, particularly of NGC5548 with Swift, have shown that the UV/optical variations lag behind the X-ray variations in a manner strongly supportive of X-ray reprocessing. Somewhat surprisingly the implied size of the accretion disc is ~3x greater than expected from a standard, smooth, Shakura-Sunyaev thin disc model. Although the difference may be explained by a clumpy accretion disc, it is not clear whether the difference will occur in all AGN or whether it may change as, eg, a function of black hole mass, accretion rate or disc temperature. Measurements of interband lags for most AGN require long timescale monitoring, which is hard to arrange. However for low mass (<1 million solar mass) AGN, the combination of XMM-Newton EPIC (X-rays) with the optical monitor in fast readout mode allows an X-ray/UV-optical lag to be measured within a single long observation. Here we summarise previous related observations and report on XMM-Newton observations of NGC4395 (mass ~100x lower and accretion rate ~20x lower than for NGC5548). We find that the UVW1 lags the X-rays by ~470s. Simultaneous observations at 6 different ground based observatories also allowed the g-band lag (~800s) to be measured. These observations are in agreement with X-ray reprocessing but initial analysis suggests that, for NGC4395, they do not differ markedly from the predictions of the standard thin disc model., Comment: 6 pages, 16 figures, accepted for publication in Astronomische Nachrichten

We report herschel observations of 100 very luminous, optically selected AGNs at z=2-3.5 with log(LUV)(erg/sec)> 46.5, where LUV=L1350A. The distribution in LUV is similar to the general distribution of SDSS AGNs in this redshift and luminosity interval. We measured SF luminosity, LSF, and SFR in 34 detected sources by fitting combined SF and WISE-based torus templates. We also obtained statistically significant stacks for the undetected sources in two luminosity groups. The sample properties are compared with those of very luminous AGNs at z>4.5. The main findings are: 1) The mean and the median SFRs of the detected sources are 1176 and 1010 Msun/yr, respectively. The mean SFR of the undetected sources is 148 Msun/yr. The ratio of SFR to BH accretion rate is approximately 80 for the detected sources and less than 10 for the undetected sources. There is no difference in LAGN and only a very small difference in L(torus) between detected and undetected sources. 2) The redshift distribution of LSF and LAGN for the most luminous, redshift 2-7 AGNs are different. The highest LAGN are found at z=~3. However, LSF of such sources peaks at z=~5. Assuming the objects in our sample are hosted by the most massive galaxies at those redshifts, we find many of them are below the main-sequence of SF galaxies at z=2-3.5. 3) The SEDs of dusty tori at high redshift are similar to those found in low redshift, low luminosity AGNs. Herschel upper limits put strong constraints on the long wavelength SED ruling out several earlier suggested torus templates. 4) We find no evidence for a luminosity dependence of the torus covering factor in sources with log(LAGN)=44-47.5. This conclusion is based on the highly uncertain and non-uniformally treated LAGN in many earlier studies. The median covering factors over this range are 0.68 for isotropic dust emission and 0.4 for anisotropic emission., Comment: 53 pages, 10 diagrams, accepted by ApJ

This review describes recent developments related to the unified model of active galactic nuclei (AGN). It focuses on new ideas about the origin and properties of the central obscurer (torus), and the connection with its surrounding. The review does not address radio unification. AGN tori must be clumpy but the uncertainties about their properties are still large. Todays most promising models involve disk winds of various types and hydrodynamical simulations that link the large scale galactic disk to the inner accretion flow. IR studies greatly improved the understanding of the spectral energy distribution of AGNs but they are hindered by various selection effects. X-ray samples are more complete. A basic relationship which is still unexplained is the dependence of the torus covering factor on luminosity. There is also much confusion regarding "real type-II AGNs" that do not fit into a simple unification scheme. The most impressive recent results are due to IR interferometry, which is not in accord with most torus models, and the accurate mapping of central ionization cones. AGN unification may not apply to merging systems and is possibly restricted to secularly evolving galaxies., Comment: To appear in Annual Review of Astronomy and Astrophysics (ARAA) vol. 53 (2015)

We have completed two years of photometric and spectroscopic monitoring of a large number of active galactic nuclei (AGNs) with very high accretion rates. In this paper, we report on the result of the second phase of the campaign, during 2013--2014, and the measurements of five new H$\beta$ time lags out of eight monitored AGNs. All five objects were identified as super-Eddington accreting massive black holes (SEAMBHs). The highest measured accretion rates for the objects in this campaign are $\dot{\mathscr{M}}\gtrsim 200$, where $\dot{\mathscr{M}}= \dot{M}_{\bullet}/L_{\rm Edd}c^{-2}$, $\dot{M}_{\bullet}$ is the mass accretion rates, $L_{\rm Edd}$ is the Eddington luminosity and $c$ is the speed of light. We find that the H$\beta$ time lags in SEAMBHs are significantly shorter than those measured in sub-Eddington AGNs, and the deviations increase with increasing accretion rates. Thus, the relationship between broad-line region size ($R_{_{\rm H\beta}}$) and optical luminosity at 5100\AA, $R_{_{\rm H\beta}}-L_{5100}$, requires accretion rate as an additional parameter. We propose that much of the effect may be due to the strong anisotropy of the emitted slim-disk radiation. Scaling $R_{_{\rm H\beta}}$ by the gravitational radius of the black hole, we define a new radius-mass parameter ($Y$) and show that it saturates at a critical accretion rate of $\dot{\mathscr{M}}_c=6\sim 30$, indicating a transition from thin to slim accretion disk and a saturated luminosity of the slim disks. The parameter $Y$ is a very useful probe for understanding the various types of accretion onto massive black holes. We briefly comment on implications to the general population of super-Eddington AGNs in the universe and applications to cosmology., Comment: 53 pages, 12 figures, 7 tables, accepted for publication in The Astrophysical Journal

This is the third in a series of papers reporting on a large reverberation-mapping campaign aimed to study the properties of active galactic nuclei (AGNs) with high accretion rates. We present new results on the variability of the optical Fe II emission lines in 10 AGNs observed by the Yunnan Observatory 2.4m telescope during 2012--2013. We detect statistically significant time lags, relative to the AGN continuum, in nine of the sources. This accurate measurement is achieved by using a sophisticated spectral fitting scheme that allows for apparent flux variations of the host galaxy, and several narrow lines, due to the changing observing conditions. Six of the newly detected lags are indistinguishable from the Hbeta lags measured in the same sources. Two are significantly longer and one is slightly shorter. Combining with Fe II lags reported in previous studies, we find a Fe II radius--luminosity relationship similar to the one for Hbeta, although our sample by itself shows no clear correlation. The results support the idea that Fe II emission lines originate in photoionized gas which, for the majority of the newly reported objects, is indistinguishable from the Hbeta-emitting gas. We also present a tentative correlation between the lag and intensity of Fe II and Hbeta and comment on its possible origin., Comment: 14 pages, 10 figures, accepted for publication in The Astrophysical Journal

We use a suite of hydrodynamical simulations of galaxy mergers to compare star formation rate (SFR) and black hole accretion rate (BHAR) for galaxies before the interaction ('stochastic' phase), during the `merger' proper, lasting ~0.2-0.3 Gyr, and in the `remnant' phase. We calculate the bi-variate distribution of SFR and BHAR and define the regions in the SFR-BHAR plane that the three phases occupy. No strong correlation between BHAR and galaxy-wide SFR is found. A possible exception are galaxies with the highest SFR and the highest BHAR. We also bin the data in the same way used in several observational studies, by either measuring the mean SFR for AGN in different luminosity bins, or the mean BHAR for galaxies in bins of SFR. We find that the apparent contradiction or SFR versus BHAR for observed samples of AGN and star forming galaxies is actually caused by binning effects. The two types of samples use different projections of the full bi-variate distribution, and the full information would lead to unambiguous interpretation. We also find that a galaxy can be classified as AGN-dominated up to 1.5 Gyr after the merger-driven starburst took place. Our study is consistent with the suggestion that most low-luminosity AGN hosts do not show morphological disturbances., Comment: MNRAS Letters, in press

We present a new suite of hydrodynamical simulations and use it to study, in detail, black hole and galaxy properties. The high time, spatial and mass resolution, and realistic orbits and mass ratios, down to 1:6 and 1:10, enable us to meaningfully compare star formation rate (SFR) and BH accretion rate (BHAR) timescales, temporal behaviour and relative magnitude. We find that (i) BHAR and galaxy-wide SFR are typically temporally uncorrelated, and have different variability timescales, except during the merger proper, lasting ~0.2-0.3 Gyr. BHAR and nuclear (<100 pc) SFR are better correlated, and their variability are similar. Averaging over time, the merger phase leads typically to an increase by a factor of a few in the BHAR/SFR ratio. (ii) BHAR and nuclear SFR are intrinsically proportional, but the correlation lessens if the long-term SFR is measured. (iii) Galaxies in the remnant phase are the ones most likely to be selected as systems dominated by an active galactic nucleus (AGN), because of the long time spent in this phase. (iv) The timescale over which a given diagnostic probes the SFR has a profound impact on the recovered correlations with BHAR, and on the interpretation of observational data., Comment: Accepted for publication in MNRAS

We present results from a fifteen-month campaign of high-cadence (~ 3 days) mid-infrared Spitzer and optical (B and V ) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). We find that the 3.6 $\mu$m and 4.5 $\mu$m flux variations lag behind those of the optical continuum by $37.2^{+2.4}_{-2.2}$ days and $47.1^{+3.1}_{-3.1}$ days, respectively. We report a cross-correlation time lag between the 4.5 $\mu$m and 3.6 $\mu$m flux of $13.9^{+0.5}_{-0.1}$ days. The lags indicate that the dust emitting at 3.6 $\mu$m and 4.5 $\mu$m is located at a distance of approximately 1 light-month (~ 0.03 pc) from the source of the AGN UV-optical continuum. The reverberation radii are consistent with the inferred lower limit to the sublimation radius for pure graphite grains at 1800 K, but smaller by a factor of ~ 2 than the corresponding lower limit for silicate grains; this is similar to what has been found for near-infrared (K-band) lags in other AGN. The 3.6 and 4.5 $\mu$m reverberation radii fall above the K-band $\tau \propto L^{0.5}$ size-luminosity relationship by factors $\lesssim 2.7$ and $\lesssim 3.4$, respectively, while the 4.5 $\mu$m reverberation radius is only 27% larger than the 3.6 $\mu$m radius. This is broadly consistent with clumpy torus models, in which individual optically thick clouds emit strongly over a broad wavelength range., Comment: 13 pages, 9 figures

The physics of active super massive black holes (BHs) is governed by their mass (M_BH), spin (a*) and accretion rate ($\dot{M}$). This work is the first in a series of papers with the aim of testing how these parameters determine the observable attributes of active galactic nuclei (AGN). We have selected a sample in a narrow redshift range, centered on z~1.55, that covers a wide range in M_BH and $\dot{M}$, and are observing them with X-shooter, covering rest wavelengths ~1200-9800 \AA. The current work covers 30 such objects and focuses on the origin of the AGN spectral energy distribution (SED). After estimating M_BH and $\dot{M}$ based on each observed SED, we use thin AD models and a Bayesian analysis to fit the observed SEDs in our sample. We are able to fit 22/30 of the SEDs. Out of the remaining 8 SEDs, 3 can be fit by the thin AD model by correcting the observed SED for reddening within the host galaxy and 4 can be fit by adding a disc wind to the model. In four of these 8 sources, Milky Way-type extinction, with the strong 2175\AA\ feature, provides the best reddening correction. The distribution in spin parameter covers the entire range, from -1 to 0.998, and the most massive BHs have spin parameters greater than 0.7. This is consistent with the "spin-up" model of BH evolution. Altogether, these results indicate that thin ADs are indeed the main power houses of AGN, and earlier claims to the contrary are likely affected by variability and a limited observed wavelength range., Comment: 23 pages, 14 figures, accepted for publication in MNRAS

This is the second in a series of papers reporting on a large reverberation mapping (RM) campaign to measure black hole (BH) mass in high accretion rate active galactic nuclei (AGNs). The goal is to identify super-Eddington accreting massive black holes (SEAMBHs) and to use their unique properties to construct a new method for measuring cosmological distances. Based on theoretical models, the saturated bolometric luminosity of such sources is proportional to the BH mass which can be used to obtain their distance. Here we report on five new RM measurements and show that in four of the cases we can measure the BH mass and three of these sources are SEAMBHs. Together with the three sources from our earlier work, we now have six new sources of this type. We use a novel method based on a minimal radiation efficiency to identify nine additional SEAMBHs from earlier RM-based mass measurements. We use a Bayesian analysis to determine the parameters of the new distance expression, and the method uncertainties, from the observed properties of the objects in the sample. The ratio of the newly measured distances to the standard cosmological ones has a mean scatter of 0.14 dex, indicating that SEAMBHs can be use as cosmological distance probes. With their high luminosity, long period of activity and large numbers at high redshifts, SEAMBHs have a potential to extend the cosmic distance ladder beyond the range now explored by type Ia supernovae., Comment: 15 pages, 7 figures, 4 tables, to appear in ApJ