Types Of Active Galactic Nuclei Research Articles

The Interplay between the Disk and Corona of the Changing-look Active Galactic Nucleus 1ES 1927+654

Time-domain studies of active galactic nuclei (AGNs) offer a powerful tool for understanding black hole accretion physics. Prior to the optical outburst on 2017 December 23, 1ES 1927+654 was classified as a “true” type 2 AGN, an unobscured source intrinsically devoid of broad-line emission in polarized spectra. Through our 3 yr monitoring campaign spanning X-ray to ultraviolet/optical wavelengths, we analyze the post-outburst evolution of the spectral energy distribution (SED) of 1ES 1927+654. Examination of the intrinsic SED and subsequent modeling using different models reveal that the post-outburst spectrum is best described by a combination of a disk, blackbody, and corona components. We detect systematic SED variability and identify four distinct stages in the evolution of these components. During the event the accretion rate is typically above the Eddington limit. The correlation between ultraviolet luminosity and optical to X-ray slope (α OX) resembles that seen in previous studies of type 1 AGNs, yet exhibits two distinct branches with opposite slopes. The optical bolometric correction factor (κ 5100) is ∼10 times higher than typical AGNs, again displaying two distinct branches. Correlations among the corona optical depth, disk surface density, and α OX provide compelling evidence of a disk–corona connection. The X-ray corona showcases systematic variation in the compactness-temperature plot. Between 200 and 650 days, the corona is “hotter when brighter,” whereas after 650 days, it becomes “cooler when brighter.” This bimodal behavior, in conjunction with the bifurcated branches of α OX and κ 5100, offers strong evidence of a transition from a slim disk to a thin disk ∼650 days after the outburst.

Unveiling the quasar main sequence: illuminating the complexity of active galactic nuclei and their evolution

The Eigenvector 1 schema, or the main sequence of quasars, was introduced as an analogous scheme to the HR diagram that would allow us to understand the more complex, extended sources - active galactic nuclei (AGNs) that harbor accreting supermassive black holes. The study has spanned more than three decades and has advanced our knowledge of the diversity of Type-1 AGNs from both observational and theoretical aspects. The quasar main sequence, in its simplest form, is the plane between the FWHM of the broad Hβ emission line and the strength of the optical Fe ii emission to the Hβ. While the former allows the estimation of the black hole mass, the latter enables direct measurement of the metal content and traces the accretion rate of the AGN. Together, they allow us to track the evolution of AGN in terms of the activity of the central nuclei, its effect on the line-emitting regions surrounding the AGN, and their diversity making them suitable distance indicators to study the expansion of our Universe. This mini-review aims to provide (i) a brief history leading up to the present day in the study of the quasar main sequence, (ii) introduce us to the many possibilities to study AGNs with the main sequence as a guiding tool, and (iii) highlight some recent, exciting lines of researches at the frontier of this ever-growing field.

Dust and power: Unravelling the merger-active galactic nucleus connection in the second half of cosmic history

Galaxy mergers represent a fundamental physical process under hierarchical structure formation, but their role in triggering active galactic nuclei (AGNs) is still unclear. We aim to investigate the merger-AGN connection using state-of-the-art observations and novel methods for detecting mergers and AGNs. We selected stellar mass-limited samples at redshift $z<1$ from the Kilo-Degree Survey (KiDS), focussing on the KiDS-N-W2 field with a wide range of multi-wavelength data. We analysed three AGN types, selected in the mid-infrared (MIR), X-ray, and via spectral energy distribution (SED) modelling. To identify mergers, we used convolutional neural networks (CNNs) trained on two cosmological simulations. We created mass- and redshift-matched control samples of non-mergers and non-AGNs. We first investigated the merger-AGN connection using a binary AGN/non-AGN classification. We observed a clear AGN excess (of a factor of $2-3$) in mergers with respect to non-mergers for the MIR AGNs, along with a mild excess for the X-ray and SED AGNs. This result indicates that mergers could trigger all three types, but are more connected to the MIR AGNs. About half of the MIR AGNs are in mergers but it is unclear whether mergers are the main trigger. For the X-ray and SED AGNs, mergers are unlikely to be the dominant triggering mechanism. We also explored the connection using the continuous AGN fraction $f_ AGN $ parameter. Mergers exhibit a clear excess of high $f_ AGN $ values relative to non-mergers, for all AGN types. We unveil the first merger fraction $f_ merger - f_ AGN $ relation with two distinct regimes. When the AGN is not very dominant, the relation is only mildly increasing or even flat, with the MIR AGNs showing the highest $f_ merger $. In the regime of very dominant AGNs ($f_ AGN merger $ shows the same steeply rising trend with increasing $f_ AGN $ for all AGN types. These trends are also seen when plotted against AGN bolometric luminosity. We conclude that mergers are most closely connected to dust-obscured AGNs, generally linked to a fast-growing phase of the supermassive black hole. Such mergers therefore stand as the main (or even the sole) fuelling mechanism of the most powerful AGNs.

Chemical abundances along the quasar main sequence

Context. The main sequence of quasars has emerged as a powerful tool for organizing the observational and physical characteristics of type-1 active galactic nuclei (AGNs). Aims. In this study, we present a comprehensive analysis of the metallicity of the gas in the broad-line region, incorporating both new data and previously published findings, to assess the presence of any trend along the main sequence. Methods. We performed a multicomponent analysis on the strongest ultraviolet (UV) and optical emission lines for a sample of 13 radio quiet quasars in the 0.009 ≤ z ≤ 0.472 redshift range, selected based on the availability of multiwavelength data. We employed UV and optical data obtained from the Hubble Space Telescope (mainly from the Cosmic Origins Spectrograph and Faint Object Spectrograph) and several ground-based observatories, respectively. We then measured ten diagnostic ratios and compared them with the prediction of CLOUDY photoionization simulations, identifying the closest photoionization solution to the data. Results. Our investigation reveals a consistent pattern along the main sequence. We observe a systematic progression in metallicity, ranging from subsolar values to metallicity levels several times higher than solar values. Conclusions. These findings underscore the fundamental role of metallicity in correlating with the main sequence of quasars. Extreme metallicity values, at least several dozen times the solar metallicity, are confirmed in low-z AGNs radiating at a high Eddington ratio, although the origin of the extreme enrichment remains open to debate.

Cold Filaments Formed in Hot Wake Flows Uplifted by Active Galactic Nucleus Bubbles in Galaxy Clusters

Multiwavelength observations indicate that the intracluster medium in some galaxy clusters contains cold filaments, while their formation mechanism remains debated. Using hydrodynamic simulations, we show that cold filaments could naturally condense out of the hot gaseous wake flows uplifted by jet-inflated active galactic nucleus (AGN) bubbles. Consistent with observations, the simulated filaments extend to tens of kiloparsecs from the cluster center, with a representative mass of 108–109 M ⊙ for a typical AGN outburst energy of 1060 erg. They show smooth velocity gradients, stretching typically from inner inflows to outer outflows with velocity dispersions of several hundred kilometers per second. The properties of cold filaments are affected substantially by the jet properties. Compared to kinetic-energy-dominated jets, it is easier for thermal-energy-dominated jets to produce long cold filaments with large masses, as observed. AGN jets with an early turn-on time, a low jet base, or a very high power tend to overheat the cluster center and produce short cold filaments that take a relatively long time to condense out.

The fast transient AT 2023clx in the nearby LINER galaxy NGC 3799 as a tidal disruption of a very low-mass star

We present an extensive analysis of the optical and ultraviolet (UV) properties of AT 2023clx, the closest optical/UV tidal disruption event (TDE) to date ($z=0.01107$), which occurred in the nucleus of the interacting low-ionization nuclear emission-line region (LINER) galaxy, NGC 3799. After correcting for the host reddening ($ h $ = 0.179 mag), we find its peak absolute $g$-band magnitude to be $-18.03 0.07$ mag, and its peak bolometric luminosity to be L_ pk $. AT 2023clx displays several distinctive features: first, it rose to peak within $10.4 days, making it the fastest rising TDE to date. Our SMBH mass estimate of $ M BH ---estimated using several standard methods--- rules out the possibility of an intermediate-mass BH as the reason for the fast rise. Dense spectral follow-up reveals a blue continuum that cools slowly and broad Balmer and He II lines as well as weak He I emission features that are typically seen in TDEs. The early, broad (width $ $) profile of Halpha matches theoretical expectations from an optically thick outflow. A flat Balmer decrement ($L_ H alpha $/$L_ H beta 1.58$) suggests that the lines are collisionally excited rather than being produced via photoionisation, in contrast to typical active galactic nuclei. A second distinctive feature, seen for the first time in TDE spectra, is a sharp, narrow emission peak at a rest wavelength of sim 6353 This feature is clearly visible up to 10\,d post-peak; we attribute it to clumpy material preceding the bulk outflow, which manifests as a high-velocity component of Halpha ($-9\,584 $). Its third distinctive feature is the rapid cooling during the first sim 20 days after peak, reflected as a break in the temperature evolution. Combining these findings, we propose a scenario for AT 2023clx involving the disruption of a very low-mass star ($ with an outflow launched in our line of sight and with disruption properties that led to efficient circularisation and prompt accretion disc formation, observed through a low-density photosphere.

Black Hole–Halo Mass Relation from UNIONS Weak Lensing

This Letter presents, for the first time, direct constraints on the black hole–halo mass relation using weak gravitational-lensing measurements. We construct type I and type II active galactic nucleus (AGN) samples from the Sloan Digital Sky Survey, with a mean redshift of 0.4 (0.1) for type I (type II) AGNs. This sample is cross correlated with weak-lensing shear from the Ultraviolet Near Infrared Optical Northern Survey. We compute the excess surface mass density of the halos associated with 36,181 AGNs from 94,308,561 lensed galaxies and fit the halo mass in bins of black hole mass. We find that more massive AGNs reside in more massive halos. The relation between halo mass and black hole mass is well described by a power law of slope 0.6 for both type I and type II samples, in agreement with models that link black hole growth to baryon feedback. We see no dependence on AGN type or redshift in the black hole–halo mass relation below a black hole mass of 108.5 M ⊙. Above that mass, we find more massive halos for the low-z type II sample compared to the high-z type I sample, but this difference may be interpreted as systematic error in the black hole mass measurements. Our results are consistent with previous measurements for non-AGN galaxies. At a fixed black hole mass, our weak-lensing halo masses are consistent with galaxy rotation curves but significantly lower than galaxy-clustering measurements. Finally, our results are broadly consistent with state-of-the-art hydrodynamical cosmological simulations, providing a new constraint for black hole masses in simulations.

Spectral similarities in galaxies through an unsupervised classification of spaxels

We present the first unsupervised classification of spaxels in hyperspectral images of individual galaxies. Classes identify regions by spectral similarity and thus take all the information into account that is contained in the data cubes (spatial and spectral). We used Gaussian mixture models in a latent discriminant subspace to find clusters of spaxels. The spectra were corrected for small-scale motions within the galaxy based on emission lines with an automatic algorithm. Our data consist of two MUSE/VLT data cubes of JKB 18 and NGC 1068 and one NIRSpec/JWST data cube of NGC 4151. Our classes identify many regions that are most often easily interpreted. Most of the 11 classes that we find for JKB 18 are identified as photoionised by stars. Some of them are known regions, but we mapped them as extended, with gradients of ionisation intensities. One compact structure has not been reported before, and according to diagnostic diagrams, it might be a planetary nebula or a denser region. For NGC 1068, our 16 classes are of active galactic nucleus-type (AGN) or star-forming regions. Their spatial distribution corresponds perfectly to well-known structures such as spiral arms and a ring with giant molecular clouds. A subclassification in the nuclear region reveals several structures and gradients in the AGN spectra. Our unsupervised classification of the MUSE data of NGC 1068 helps visualise the complex interaction of the AGN and the jet with the interstellar medium in a single map. The centre of NGC 4151 is very complex, but our classes can easily be related to ionisation cones, the jet, or H$_2$ emission. We find a new elongated structure that is ionised by the AGN along the N-S axis perpendicular to the jet direction. It is rotated counterclockwise with respect to the axis of the H$_2$ emission. Our work shows that the unsupervised classification of spaxels takes full advantage of the richness of the information in the data cubes by presenting the spectral and spatial information in a combined and synthetic way.

EPOCHS Paper – VIII. An insight into MIRI-selected galaxies in SMACS-0723 and the benefits of deep MIRI photometry in revealing AGN and the dusty universe

ABSTRACT We present the analysis of the stellar population and star formation history of 181 MIRI selected galaxies at z = 0 − 3.5 in the massive galaxy cluster field SMACS J0723.3–7327, commonly referred to as SMACS0723, using the JWST Mid-Infrared Instrument (MIRI). We combine the data with the JWST Near Infrared Camera (NIRCam) catalogue, in conjunction with the Hubble Space Telescope (HST) WFC3/IR and ACS imaging. We find that the MIRI bands capture PAH features and dust emission, significantly enhancing the accuracy of photometric redshift and measurements of the physical properties of these galaxies. The median photo-z’s of galaxies with MIRI data are found to have a small 0.1 per cent difference from spectroscopic redshifts and reducing the error by 20 per cent. With MIRI data included in SED fits, we find that the measured stellar masses are unchanged, while the star formation rate is slightly lower by 0.1 dex. We also fit the median SED of active galactic nuclei (AGNs) and star-forming galaxies (SFG) separately. MIRI data provides tighter constraints on the AGN contribution, reducing the typical AGN contributions by ∼15 per cent. In addition, we also compare the median SED obtained with and without MIRI, and we find that including MIRI data yields steeper optical and UV slopes, indicating bluer colours, lower dust attenuation, and younger stellar populations. In the future, MIRI/MRS will enhance our understanding by providing more detailed spectral information and allowing for the study of specific emission features and diagnostics associated with AGN.

AGN Feedback Signatures in UV Emission

Supermassive black holes (SMBH) are believed to influence galaxy evolution through AGN (active galactic nuclei) feedback. Galaxy mergers are key processes of galaxy formation that lead to AGN activity and star formation. The relative contribution of AGN feedback and mergers to star formation is not yet well understood. In radio-loud objects, AGN outflows are dominated by large jets. However, in radio-quiet objects, outflows are more complex and involve jet, wind, and radiation. In this review, we discuss the signatures of AGN feedback through the alignment of radio and UV emissions. Current research on AGN feedback is discussed, along with a few examples of studies such as the galaxy merger system MRK 212, the radio-quiet AGN NGC 2639, and the radio-loud system Centaurus A. Multi-frequency observations of MRK 212 indicate the presence of dual AGN, as well as feedback-induced star-forming UV clumps. The fourth episode of AGN activity was detected in radio observations of the Seyfert galaxy NGC 2639, which also showed a central cavity of 6 kpc radius in CO and UV maps. This indicates that multi-epoch jets of radio-quiet AGN can blow out cold molecular gas, which can further reduce star formation in the center of the galaxies. Recent UV observations of Cen A have revealed two sets of stellar population in the northern star-forming region, which may have two different origins. Recent studies have shown that there is evidence that both positive and negative feedback can be present in galaxies at different scales and times. High-resolution, multi-band observations of large samples of different types of AGN and their host galaxies are important for understanding the two types of AGN feedback and their effect on the host galaxies. Future instruments like INSIST and UVEX will be able to help achieve some of these goals.

Observational properties of active galactic nucleus obscuration during the peak of accretion growth

ABSTRACT We investigated the gas obscuration and host galaxy properties of active galactic nuclei (AGNs) during the peak of cosmic accretion growth of supermassive black holes at redshift 0.8–1.8 using X-ray-detected AGNs with mid-infrared and far-infrared detection. The sample was classified as type-1 and type-2 AGNs using optical spectral and morphological classification while the host galaxy properties were estimated with multiwavelength spectral energy distribution fitting. For type-1 AGNs, the black hole mass was determined from MgII emission lines while the black hole mass of type-2 AGNs was inferred from the host galaxy’s stellar mass. Based on the derived parameters, the distribution of the sample in the absorption hydrogen column density (NH) versus Eddington ratio diagram is examined. Among the type-2 AGNs, 28 ± 5 per cent are in the forbidden zone, where the obscuration by dust torus cannot be maintained due to radiation pressure on dusty material. The fraction is higher than that observed in the local universe from the Burst Alert Telescope AGN Spectroscopic Survey data release 2 (BASS DR2) (11 ± 3 per cent). The higher fraction implies that the obscuration of the majority of AGNs is consistent with the radiation pressure regulated unified model but with an increased incidence of interstellar matter (ISM)-obscured AGNs. We discuss the possibility of dust-free absorption in type-1 AGNs and heavy ISM absorption in type-2 AGNs. We also find no statistical difference in the star-formation activity between type-1 and type-2 AGNs which may suggest that obscuration triggered by a gas-rich merging is not common among X-ray detected AGNs in this epoch.

To test RNLRs−LO3 relation for narrow emission line regions of AGNs through low-redshift Type-2 AGNs in SDSS

ABSTRACT Sizes of narrow emission line regions (NLRs) of active galactic nuclei (AGNs) could be estimated by [O iii] line luminosity LO3 through the known RNLRs−LO3 empirical relations. Unfortunately, it is not convenient to test the RNLRs− LO3 empirical relations through structure properties of spatially resolved NLRs of large samples of AGNs. In this manuscript, a method is proposed to test the $R_{\mathrm{ NLRs}}\!\!-\!\!L_{\mathrm{ O3}}^{\sim 0.25}$ empirical relations for AGN NLRs through Sloan Digital Sky Survey (SDSS) Type-2 AGNs having few orientation effects on NLR sizes expected by the AGN unified model, after considering sizes Rfib of SDSS fibre-covered regions. Comparing Rfib and RNLRs estimated by LO3, Type-2 AGNs with Rfib > RNLRs (Sample-II) and with Rfib < RNLRs (Sample-I) should have different physical properties of NLRs. Accepting electron density gradients in AGN NLRs, statistically higher electron densities (traced by lower flux ratio RS2 of [S ii] λ6717 Å to [S ii] λ6731 Å) could be expected for the Type-2 AGNs in the Sample-I. Then, through the collected 1062 SDSS Type-2 AGNs in the Sample-I and 3658 SDSS Type-2 AGNs in the Sample-II, statistically lower RS2 for the Type-2 AGNs in the Sample-I can be confirmed with confidence level higher than 5σ, even after considering necessary effects. Therefore, the results in this manuscript can provide strong clues to support that the reported $R_{\mathrm{ NLRs}}~\propto ~L_{\mathrm{ O3}}^{0.25}$ empirical relation is preferred to estimate NLR sizes of SDSS AGNs through SDSS fibre spectroscopic results, and also to support the commonly expected electron density gradients in AGN NLRs.

High energy gamma-ray sources in the VVV survey - II. The AGN counterparts

ABSTRACT We identified Active Galactic Nuclei (AGN) candidates as counterparts to unidentified gamma-ray sources (UGS) from the Fermi-LAT Fourth Source Catalogue at lower Galactic latitudes. Our methodology is based on the use of near- and mid-infrared photometric data from the VISTA Variables in the Vía Láctea (VVV) and Wide-field Infrared Survey Explorer (WISE) surveys. The AGN candidates associated with the UGS occupy very different regions from the stars and extragalactic sources in the colour space defined by the VVV and WISE infrared colours. We found 27 near-infrared AGN candidates possibly associated with 14 Fermi-LAT sources using the VVV survey. We also found 2 blazar candidates in the regions of 2 Fermi-LAT sources using WISE data. There is no match between VVV and WISE candidates. We have also examined the Ks light curves of the VVV candidates and applied the fractional variability amplitude (σrms) and the slope of variation in the Ks passband to characterise the near-infrared variability. This analysis shows that more than 85 per cent of the candidates have slopes in the Ks passband >10−4 mag/day and present σrms values consistent with a moderate variability. This is in good agreement with typical results seen from type-1 AGN. The combination of YJHKs colours and Ks variability criteria was useful for AGN selection, including its use in identifying counterparts to Fermi γ-ray sources.

The properties of supermassive black holes and their host galaxies for type 1 and 2 active galactic nuclei in the eFEDS and COSMOS fields

In this study, our primary objective is to compare the properties of supermassive black holes (SMBHs) and their host galaxies between type 1 and type 2 active galactic nuclei (AGNs). In our analysis, we use X-ray detected sources in two fields, namely the eFEDS and the COSMOS-Legacy. To classify the X-ray sources, we performed a spectral energy distribution (SED) fitting analysis, using the CIGALE code. The robustness of our analysis was paramount so, to ensure this, we imposed stringent selection criteria. Thus, only sources with extensive photometric data across the optical, near- and mid-infrared part of the spectrum and reliable host galaxy properties and classifications were included. The final sample consists of 3312 AGNs, of which 3049 are classified as type 1 and 263 as type 2. The sources span a redshift range of 0.5 < z < 3.5 and encompass a wide range of X-ray luminosities, falling within 42 < log,[LX,2−10 keV(erg s−1)] < 46. Our results show that type 2 AGNs exhibit a tendency to inhabit more massive galaxies, by 0.2 − 0.3 dex (on a logarithmic scale), compared to type 1 sources. Type 2 AGNs also display, on average, lower specific black hole accretion rates, a proxy of the Eddington ratio, compared to type 1 AGNs. These differences persist across all redshifts and LX considered within our dataset. Moreover, our analysis uncovers that type 2 sources tend to have lower star formation rates compared to type 1 AGNs at z < 1. This picture reverses at z > 2 and log,[LX,2−10 keV(erg s−1)] > 44. Similar patterns emerge when we categorize AGNs based on their X-ray obscuration levels (NH). However, in this case, the observed differences are pronounced only for low-to-intermediate LX AGNs and are also sensitive to the NH threshold applied for the AGN classification. These comprehensive findings enhance our understanding of the intricate relationships governing AGN types and their host galaxy properties across diverse cosmic epochs and luminosity regimes.

USING SUPERVISED MACHINE LEARNING MODELS TO FIND ACTIVE GALACTIC NUCLEI IN MULTIWAVELENGTH DATASETS

Active galactic nuclei (AGN) are unique astronomical sources that emit intense radiation over the entire electromagnetic (EM) spectrum from radio to gamma ray frequencies. They are estimated to be vastly under classified with only 0.1% of them predicted to have been discovered (Padovani). A major contributing factor to this is that in the past high-quality data was not available for sources across multiple wavelengths. It is often not possible to classify a body as an AGN looking at just one section of the EM spectrum due to the variance in emissions from different sources. This implies looking at just one wavelength will lead to under-coverage in all but one type of AGN. With the emergence of new telescopes and technologies, this paper has managed to collate multi-wavelength data on galactic and extragalactic sources from the XMM-Newton and Gaia, and eROSITA telescopes. Applying various supervised learning models, such as random forests and histogram-based boosting on these sources, has allowed us to classify the AGN in these surveys with a ~97% accuracy using only emission data i.e. without including redshifts. These findings indicate that applying similar models to data collected from these telescopes should help overcome the current under-coverage in AGN.

From Sub-Solar to Super-Solar Chemical Abundances along the Quasar Main Sequence

The 4D (four-dimensional) eigenvector 1 (E1) sequence has proven to be a highly effective tool for organizing observational and physical properties of type-1 active galactic nuclei (AGNs). In this paper, we present multiple measurements of metallicity for the broad line region gas, from new and previously-published data. We demonstrate a consistent trend along the optical plane of the E1 (also known as the quasar main sequence), defined by the line width of Balmer hydrogen Hβ profile and by a parameter measuring the prominence of singly-ionized iron emission. The trend involves an increase from sub-solar metallicity in correspondence with extreme Population B (weak Feii emission, large Hβ FWHM (full width at half maximum)) to metallicity several tens the solar value in correspondence with extreme Population A (strongest Feii optical emission, narrower Hβ profiles). The data establish the metallicity as a correlate of the 4DE1/main sequence. If the considerably high metallicity (Z≳10Z⊙, solar metallicity) gas is expelled from the sphere of influence of the central black hole, as indicated by the widespread evidence of nuclear outflows and disk wind in the case of sources radiating at a high Eddington ratio, then it is possible that the outflows from quasars played a role in chemically enriching the host galaxy.

The Application of Machine Learning to Quasar and Seyfert Classification

Machine learning can be utilized to classify spectra flagged as Active Galactic Nuclei (AGNs) belonging to Seyferts or Quasars, expediting data collection and aiding in analyzing the AGN types. While many properties of Seyferts and Quasars can be used as feature points in training a machine learning model, one relatively available property with high information density is the spectra of the AGN types. This paper aims to describe the training and results of a K-Nearest Neighbors and a Dense Neural Network machine learning model built to classify AGNs as Seyfert type 1s, Seyfert type 2s, or Quasars.

Fierce Feedback in an Obscured, Sub-Eddington State of the Seyfert 1.2 Markarian 817

Mrk 817 is a bright and variable Seyfert 1.2 active galactic nucleus (AGN). X-ray monitoring of Mrk 817 with the Neil Gehrels Swift Observatory in 2022 revealed that the source flux had declined to a lower level than recorded at any prior point in the then 19 yr mission. We present an analysis of deep XMM-Newton and NuSTAR observations obtained in this low flux state. The spectra reveal a complex X-ray wind consisting of neutral and ionized absorption zones. Three separate velocity components are detected as part of a structured ultrafast outflow (UFO), with v/c=0.043−0.003+0.007 , v/c=0.079−0.0008+0.003 , and v/c=0.074−0.005+0.004 . These projected velocities suggest that the wind likely arises at radii that are much smaller than the optical broad-line region. In order for each component of the outflow to contribute significant feedback, the volume filling factors must be greater than f ≃ 0.009, f ≃ 0.003, and f ≃ 0.3, respectively. For plausible, data-driven volume filling factors, these limits are passed, and the total outflow likely delivers the fierce feedback required to reshape its host environment, despite a modest radiative Eddington fraction of λ ≃ 0.008–0.016 (this range reflects plausible masses). UFOs are often detected at or above the Eddington limit; this result signals that black hole accretion has the potential to shape host galaxies even at modest Eddington fractions and over a larger fraction of a typical AGN lifetime. We discuss our findings in terms of models for disk winds and black hole feedback in this and other AGN.

Morphological Study of Active Galaxies based on SDSS Images. Preliminary Results

Activity in galaxies has mainly two major forms: Active Galactic Nuclei (AGN) and Starburst (SB). Moreover, different types of AGN have different morphology. However, this question has not yet been properly investigated and due to old low-quality images, the morphology of many galaxies is not well described. SDSS images give a good possibility to homogeneously classify galaxies and investigate differences by the activity types. The concentration of the central part and the ratio between the central bulge and the total flux is a subject for detailed study. We use SDSS images to classify different types of active galaxies (both AGN and Starburst) and understand differences between QSOs, Seyferts 1 and 2, LINERS and Composites, as well as Starburst galaxies. The best expectation from our study will be the preliminary classification of active galaxies into activity types based on the images and before having their spectral types.

Are There Higher Electron Densities in Narrow Emission Line Regions of Type-1 AGNs than in Type-2 AGNs?

In the manuscript, we check properties of electron densities n e traced by flux ratio R sii of [S ii]λ6716 Å to [S ii]λ6731 Å in narrow emission line regions (NLRs) between Type-1 active galactic nucleus (AGN) and Type-2 AGN in SDSS Data Release 12 (DR12). Under the framework of unified model considering kiloparsec-scale structures, similar n e in NLRs should be expected between Type-1 AGN and Type-2 AGN. Based on reliable measurements of the [S ii] doublet with measured parameters at least 5 times larger than corresponding uncertainties, there are 6039 Type-1 AGN and 8725 Type-2 AGN (excluding the Type-2 LINERs and the composite galaxies) collected from SDSS DR12. Then, lower R sii (higher n e ) in NLRs can be well confirmed in Type-1 AGN than in Type-2 AGN, with the confidence level higher than 5σ, even after considering the necessary effects including effects of electron temperatures traced by [O iii]λ4364,4959,5007 Å on estimating n e in NLRs. Two probable methods are proposed to explain the higher n e in NLRs in Type-1 AGN. First, the higher n e in NLRs of Type-1 AGN could indicate longer time durations of AGN activities in Type-1 AGN than in Type-2 AGN, if AGN activities triggering galactic-scale outflows leading to more electrons injecting into NLRs were accepted to explain the higher n e in NLRs of Type-2 AGN than H ii galaxies. Second, the lower n e in NLRs of Type-2 AGN could be explained by stronger star-forming contributions in Type-2 AGN, considering lower n e in H ii regions. The results provide interesting challenges to the commonly and widely accepted unified model of AGN.