Local Active Galactic Nuclei Research Articles

A compact symmetric ejection from the low mass AGN in the LINER galaxy NGC 4293

ABSTRACT We conducted a Very Long Baseline Array (VLBA) observation of the low mass active galactic nucleus (AGN) in galaxy NGC 4293 (z = 0.003). The object is associated with a low-ionization nuclear emission-line region (LINER). Its black hole mass is estimated as ∼105 or ${\sim}10^7 \, \mathrm{M}_\odot$. The VLBA 1.5 GHz image shows an inverse symmetric structure with two discrete radio blobs separated by an angular distance of ∼120 mas, corresponding to ∼7 parsec. Furthermore, its integrated radio spectrum has a turnover at the frequency of ∼0.44 GHz. Based on the compactness and spectrum, the nuclear radio source in NGC 4293 belongs to a sample of (megahertz) peaked spectrum (PS/MPS) radio sources with compact symmetric morphologies. NGC 4293 has 1.4 GHz radio power of only ${\sim}10^{20}\, \mathrm{W\, Hz^{-1}}$ with the VLBA observation, which is consistent with local AGNs but lower than the current PS samples. One of the two blobs has a steep radio spectrum α = −0.62 ± 0.08 (Sν ∝ ν+α), while the other one has an inverted spectrum α = 0.32 ± 0.10. The VLBA 1.5 GHz luminosity ratio of the two blobs is 3.23 and both blobs show lateral-flowing structures where the hotspots reside at the edge of each radio lobe. This can be explained as jet interactions with dense circumnuclear medium. We estimate the black hole mass of NGC 4293 through the Fundamental Plane of black hole activity, which constrains the black hole mass to be ${\lesssim}10^6\, \mathrm{M}_\odot$. It supports that the object is a low-mass AGN and a potential candidate for accreting and ejecting IMBHs.

Supermassive black holes at high redshift are expected to be obscured by their massive host galaxies’ interstellar medium

We combine results from deep ALMA observations of massive (M* > 1010 M⊙) galaxies at different redshifts to show that the column density of their interstellar medium (ISM) rapidly increases toward early cosmic epochs. Our analysis includes objects from the ASPECS and ALPINE large programs, as well as individual observations ofz ∼ 6 quasar hosts. When accounting for non-detections and correcting for selection effects, we find that the median surface density of the ISM of the massive galaxy population evolves as ∼(1 + z)3.3. This means that the ISM column density toward the nucleus of az > 3 galaxy is typically > 100 times larger than locally, and it may reach values as high as Compton-thick atz ≳ 6. Remarkably, the median ISM column density is on the same order of what is measured from X-ray observations of large active galactic nucleus (AGN) samples already atz ≳ 2. We have developed a simple analytic model for the spatial distribution of ISM clouds within galaxies, and estimate the total covering factor toward active nuclei when obscuration by ISM clouds on the host scale is added to that of parsec-scale circumnuclear material (the so-called torus). The model includes clouds with a distribution of sizes, masses, and surface densities, and also allows for an evolution of the characteristic cloud surface density with redshift, Σc, * ∝ (1 + z)γ. We show that, forγ = 2, such a model successfully reproduces the increase in the obscured AGN fraction with redshift that is commonly observed in deep X-ray surveys, both when different absorption thresholds and AGN luminosities are considered. Our results suggest that 80–90% of supermassive black holes in the early Universe (z > 6 − 8) are hidden to our view, primarily by the ISM in their hosts. We finally discuss the implications of our results and how they can be tested observationally with current and forthcoming facilities (e.g., VLT, E-ELT, ALMA, and JWST) and with next-generation X-ray imaging satellites. By extrapolating the observed X-ray nebulae around local AGN to the environments of supermassive black holes at high redshifts, we find ≲1″ nebulae impose stringent design constraints on the spatial resolution of any future X-ray imaging Great Observatory in the coming decades.

Dwarf AGNs from variability for the origins of seeds (DAVOS): Intermediate-mass black hole demographics from optical synoptic surveys

ABSTRACT We present a phenomenological forward Monte Carlo model for forecasting the population of active galactic nuclei (AGNs) in dwarf galaxies observable via their optical variability. Our model accounts for expected changes in the spectral energy distribution of AGNs in the intermediate-mass black hole (IMBH) mass range and uses observational constraints on optical variability as a function of black hole (BH) mass to generate mock light curves. Adopting several different models for the BH occupation function, including one for off-nuclear IMBHs, we quantify differences in the predicted local AGN mass and luminosity functions in dwarf galaxies. As a result, we are able to model the fraction of variable AGNs as a function of important galaxy host properties, such as host galaxy stellar mass, in the presence of selection effects. We find that our adopted occupation fractions for the ‘heavy’ and ‘light’ initial BH seeding scenarios can be distinguished with variability at the 2–3σ level for galaxy host stellar masses below ∼108M⊙ with data from the upcoming Vera C. Rubin Observatory. We also demonstrate the prevalence of a selection bias whereby recovered IMBH masses fall, on average, above the predicted value from the local host galaxy–BH mass scaling relation with the strength of this bias dependent on the survey sensitivity. Our methodology can be used more broadly to calibrate AGN demographic studies in synoptic surveys. Finally, we show that a targeted ∼ hourly cadence program over a few nights with the Rubin Observatory can provide strong constraints on IMBH masses given their expected rapid variability time-scales.

Measurement of AGN dust extinction based on the near-infrared flux variability of WISE data

ABSTRACT We present the measurement of the line-of-sight extinction of the dusty torus for a large number of obscured active galactic nuclei (AGNs) based on the reddening of the colour of the variable flux component in near-infrared (NIR) wavelengths. We collected long-term monitoring data by Wide-field Infrared Survey Explorer (WISE) for 513 local AGNs catalogued by the Swift/BAT AGN Spectroscopic Survey (BASS) and found that the multi-epoch NIR flux data in two different bands (WISE W1 and W2) are tightly correlated for more than 90 per cent of the targets. The flux variation gradient (FVG) in the W1 and W2 bands was derived by applying linear regression analysis, and we reported that those for unobscured AGNs fall in a relatively narrow range, whereas those for obscured AGNs are distributed in a redder and broader range. The AGN’s line-of-sight dust extinction (AV) is calculated using the amount of the reddening in the FVG and is compared with the neutral hydrogen column density (NH) of the BASS catalogue. We found that the NH/AV ratios of obscured AGNs are greater than those of the Galactic diffuse interstellar medium (ISM) and are distributed with a large scatter by at most two orders of magnitude. Furthermore, we found that the lower envelope of the NH/AV of obscured AGNs is comparable to the Galactic diffuse ISM. These properties of the NH/AV can be explained by increase in the NH attributed to the dust-free gas clouds covering the line of sight in the broad-line region.

A Hidden Population of Massive Black Holes in Simulated Dwarf Galaxies

We explore the characteristics of actively accreting massive black holes (MBHs) within dwarf galaxies in the Romulus25 cosmological hydrodynamic simulation. We examine the MBH occupation fraction, X-ray active fractions, and active galactic nucleus (AGN) scaling relations within dwarf galaxies of stellar mass 108 M ⊙ < M star < 1010 M ⊙ out to redshift z = 2. In the local universe, the MBH occupation fraction is consistent with observed constraints, dropping below unity at M star < 3 × 1010 M ⊙, M 200 < 3 × 1011 M ⊙. Local dwarf AGN in Romulus25 follow observed scaling relations between AGN X-ray luminosity, stellar mass, and star formation rate, though they exhibit slightly higher active fractions and number densities than comparable X-ray observations. Since z = 2, the MBH occupation fraction has decreased, the population of dwarf AGN has become overall less luminous, and as a result the overall number density of dwarf AGN has diminished. We predict the existence of a large population of MBHs in the local universe with low X-ray luminosities and high contamination from X-ray binaries and the hot interstellar medium that are undetectable by current X-ray surveys. These hidden MBHs make up 76% of all MBHs in local dwarf galaxies and include many MBHs that are undermassive relative to their host galaxy’s stellar mass. Their detection relies on not only greater instrument sensitivity but also better modeling of X-ray contaminants or multiwavelength surveys. Our results indicate that dwarf AGN were substantially more active in the past, despite having low luminosity today, and that future deep X-ray surveys may uncover many hidden MBHs in dwarf galaxies out to at least z = 2.

BASS. XXI. The Data Release 2 Overview

The BAT AGN Spectroscopic Survey (BASS) is designed to provide a highly complete census of the key physical parameters of the supermassive black holes (SMBHs) that power local active galactic nuclei (AGNs) (z ≲ 0.3), including their bolometric luminosity (L bol), black hole (BH) mass (M BH), accretion rates (L bol/L Edd), line-of-sight gas obscuration (N H), and the distinctive properties of their host galaxies (e.g., star formation rates, masses, and gas fractions). We present an overview of the second data release of BASS (DR2), an unprecedented spectroscopic AGN survey in spectral range, resolution, and sensitivity, including 1449 optical (∼3200 Å–1 μm) and 233 near-IR (1–2.5 μm) spectra for the brightest 858 ultrahard X-ray (14–195 keV) selected AGNs across the entire sky and essentially all levels of obscuration. This release provides a highly complete set of key measurements (emission-line measurements and central velocity dispersions), with 99.9% measured redshifts and 98% BH masses estimated (for unbeamed AGNs outside the Galactic plane). The BASS DR2 AGN sample represents a unique census of nearby powerful AGNs, spanning over 5 orders of magnitude in AGN bolometric luminosity (L bol ∼ 1040–1047 erg s−1), BH mass (M BH ∼ 105–1010 M ⊙), Eddington ratio (L bol/L Edd ≳ 10−5), and obscuration (N H ∼ 1020–1025 cm−2). The public BASS DR2 sample and measurements can thus be used to answer fundamental questions about SMBH growth and its links to host galaxy evolution and feedback in the local universe, as well as open questions concerning SMBH physics. Here we provide a brief overview of the survey strategy, the key BASS DR2 measurements, data sets and catalogs, and scientific highlights from a series of DR2-based works pursued by the BASS team.

BASS. XXX. Distribution Functions of DR2 Eddington Ratios, Black Hole Masses, and X-Ray Luminosities

We determine the low-redshift X-ray luminosity function, active black hole mass function (BHMF), and Eddington ratio distribution function (ERDF) for both unobscured (Type 1) and obscured (Type 2) active galactic nuclei (AGNs), using the unprecedented spectroscopic completeness of the BAT AGN Spectroscopic Survey (BASS) data release 2. In addition to a straightforward 1/V max approach, we also compute the intrinsic distributions, accounting for sample truncation by employing a forward-modeling approach to recover the observed BHMF and ERDF. As previous BHMFs and ERDFs have been robustly determined only for samples of bright, broad-line (Type 1) AGNs and/or quasars, ours are the first directly observationally constrained BHMF and ERDF of Type 2 AGNs. We find that after accounting for all observational biases, the intrinsic ERDF of Type 2 AGNs is significantly more skewed toward lower Eddington ratios than the intrinsic ERDF of Type 1 AGNs. This result supports the radiation-regulated unification scenario, in which radiation pressure dictates the geometry of the dusty obscuring structure around an AGN. Calculating the ERDFs in two separate mass bins, we verify that the derived shape is consistent, validating the assumption that the ERDF (shape) is mass-independent. We report the local AGN duty cycle as a function of mass and Eddington ratio, by comparing the BASS active BHMF with the local mass function for all supermassive black holes. We also present the logN−logS of the Swift/BAT 70 month sources.

Optical and JWST Mid-IR Emission Line Diagnostics for Simultaneous IMBH and Stellar Excitation in z ∼ 0 Dwarf Galaxies*

Abstract Current observational facilities have yet to conclusively detect 103–104 M ⊙ intermediate-mass black holes (IMBHs) that fill in the evolutionary gap between seed black holes in the early universe and z ∼ 0 supermassive black holes. Dwarf galaxies present an opportunity to reveal active IMBHs amidst persistent star formation. We introduce photoionization simulations tailored to address key physical uncertainties: coincident versus noncoincident mixing of IMBH and starlight excitation, open versus closed geometries of surrounding gas clouds, and different shapes of the spectral energy distribution of active galactic nuclei (AGN). We examine possible AGN emission line diagnostics in the optical and mid-IR, and find that the diagnostics are often degenerate with respect to the investigated physical uncertainties. In spite of these setbacks, and in contrast to recent work, we are able to show that [O iii]/Hβ typically remains bright for dwarf AGN powered by IMBHs down to 103 M ⊙. Dwarf AGN are predicted to have inconsistent star-forming and Seyfert/LINER classifications using the most common optical diagnostics. In the mid-IR, [O iv] 25.9 μm and [Ar ii] 6.98 μm are less sensitive to physical uncertainties than are optical diagnostics. Based on these emission lines, we provide several diagrams of mid-IR emission line diagnostic diagrams with demarcations for separating starbursts and AGN with varying levels of activity. The diagrams are valid over a wide range of ionization parameters and metallicities out to z ∼ 0.1, so will prove useful for future JWST observations of local dwarf AGN in the search for IMBHs. We make our photoionization simulation suite freely available.

Short-timescale X-ray spectral variability in the Seyfert 1 galaxy NGC 3783

Aims. We report on the X-ray time-resolved spectral analysis of XMM-Newton observations of NGC 3783. Our main goal is to detect transient features in the Fe K line complex in order to study the dynamics of the innermost accretion flow. Methods. We reanalyse archival observations of NGC 3783, a bright local active galactic nucleus, for which a transient Fe line was reported, complementing this data set with new available observations. This results in a long set of observations which can allow us to better assess the significance of transient features and possibly test their recurrence time. Moreover, as the new data catch the source in an obscured state, this analysis allows also to test whether the appearance and disappearance of transient features is linked to the presence of obscuring gas. Results. We detect discrete features at the ≥90% significance level both in emission and in absorption at different times of the observations, split into 5 ks time-resolved spectra. The overall significance of individual features is higher in the obscured dataset. The energy distribution of the detections changes between the two states of the source, and the features appear to cluster at different energies. Counting the occurrences of emission and absorption lines at the same energies, we identify several groups of ≥3σ detections: emission features in the 4–6 keV band are present in all observations and are most likely due to effects of the absorber present in the source; an emission line blend of neutral Fe Kβ and ionised Fe Kα is present in the unobscured dataset; absorption lines produced by gas at different outflowing velocities and ionisation states show an increase in energy between the two epochs, shifting from ∼6.6 keV to ∼6.7 − 6.9 keV. The representation of the features in a time–energy plane via residual maps highlights a possible modulation of the Fe Kα line intensity linked to the clumpiness of the absorbing medium.

Constraints on Cosmic Ray Acceleration Capabilities of Black Holes in X-ray Binaries and Active Galactic Nuclei

Rotating black holes (BHs) are likely the largest energy reservoirs in the Universe as predicted by BH thermodynamics, while cosmic rays (CRs) are the most energetic among particles detected on Earth. Magnetic fields surrounding BHs combined with strong gravity effects, thanks to the spacetime symmetries, turn the BHs into powerful accelerators of charged particles. At the same time, in the age of multi-wavelength and multi-messenger astronomy, BHs and their environments have not yet been probed with CR messengers, despite being observed across most of the electromagnetic spectrum, and neutrino and gravitational waves. In this paper, we probe the acceleration capabilities of BHs in 8 galactic X-ray binaries and 25 local active galactic nuclei (AGNs) within 100 Mpc, based on the ultra-efficient regime of the magnetic Penrose process of a BH energy extraction combined with observational data. We find that the maximum energy of the galactic BHs can reach only up to the knee of the CR spectrum, including supermassive BH Sgr A* at the Galactic Center. On the other hand, for supermassive BHs in AGNs, we find that the mean energy of primary CRs is of the order of 1019 eV. It is therefore likely that local supermassive BHs give sufficient contribution to the ankle—a sharp change in the slope of the cosmic ray spectrum around 1018.6 eV energy. We also discuss the energy losses of primary CRs close to the acceleration zones. In the galactic BH cases, it is likely dominated by synchrotron radiation losses.

Determination of supermassive black hole spins in local active galactic nuclei

AbstractWe estimated the radiative efficiency and spin value for a number of local active galactic nuclei (AGNs) with using three popular models connecting the radiative efficiency with such parameters of AGNs as mass of supermassive black hole (SMBH), angle between the line of sight and the axis of the accretion disk and bolometric luminosity. Analysis of the obtained data shows that the spin value decreases with cosmic time, which is in agreement with results of theoretical calculations for low‐redshift AGNs of other authors. Also, we found that the spin value increases with the increasing mass of SMBH and bolometric luminosity. This is the expected result that corresponds to theoretical calculations. Analysis of the distribution of the spin values shows a pronounced peak in the distribution in range. ∼40% of objects have spin and ∼50% of objects have spin . These results are in good agreement with our previous results and with the results of other authors.

Stellar populations in local AGNs: evidence for enhanced star formation in the inner 100 pc

ABSTRACT In modern models and simulations of galactic evolution, the star formation in massive galaxies is regulated by an ad hoc active galactic nuclei (AGN) feedback process. However, the physics and the extension of such effects on the star formation history of galaxies is matter of vivid debate. In order to shed some light in the AGN effects over the star formation, we analysed the inner 500 × 500 pc of a sample of 14 Seyfert galaxies using GMOS and MUSE integral field spectroscopy. We fitted the continuum spectra in order to derive stellar age, metallicity, velocity, and velocity dispersion maps in each source. After stacking our sample and averaging their properties, we found that the contribution of young SP, as well as that of AGN featureless continuum both peak at the nucleus. The fraction of intermediate-age SPs is smaller in the nucleus if compared to outer regions, and the contribution of old SPs vary very little within our field of view (FoV). We also found no variation of velocity dispersion or metallicity within our FoV. Lastly, we detected an increase in the dust reddening towards the center of the galaxies. These results lead us to conclude that AGN phenomenon is usually related to a recent star formation episode in the circumnuclear region.

Mid‐infrared properties of a sample of the most compact radio galaxies

AbstractWe present an analysis of the mid‐infrared properties of the youngest radio galaxies, based on low‐resolution data provided by the WISE satellite. We restrict our analysis to sources with available X‐ray data that constitute the earliest phase of radio galaxy evolution, that is, those classified as gigahertz peaked spectrum and/or compact symmetric objects. We compare the MIR color distribution in our sample to that in the general population of local active galactic nuclei (AGN), in the population of evolved FR II radio galaxies, and also in the population of radio galaxies with recurrent jet activity. We conclude that the triggering of radio jets in AGN does not differentiate between elliptical hosts with substantially different fractions of young stars; instead there is a relationship between the jet duty cycle and the ongoing star formation.

A Local Baseline of the Black Hole Mass Scaling Relations for Active Galaxies. IV. Correlations Between M BH and Host Galaxy σ, Stellar Mass, and Luminosity

Abstract The tight correlations between the mass of supermassive black holes (M BH) and their host-galaxy properties have been of great interest to the astrophysical community, but a clear understanding of their origin and fundamental drivers still eludes us. The local relations for active galaxies are interesting in their own right and form the foundation for any evolutionary study over cosmic time. We present Hubble Space Telescope optical imaging of a sample of 66 local active galactic nuclei (AGNs); for 14 objects, we also obtained Gemini near-infrared images. We use state-of-the-art methods to perform surface photometry of the AGN host galaxies, decomposing them into spheroid, disk, and bar (when present), and inferring the luminosity and stellar mass of the components. We combine this information with spatially resolved kinematics obtained at the Keck Telescopes to study the correlations between M BH (determined from single-epoch virial estimators) and host galaxy properties. The correlations are uniformly tight for our AGN sample, with intrinsic scatter 0.2–0.4 dex, smaller than or equal to that of quiescent galaxies. We find no difference between pseudo and classical bulges or barred and nonbarred galaxies. We show that all the tight correlations can be simultaneously satisfied by AGN hosts in the 107–109 M ⊙ regime, with data of sufficient quality. The M BH–σ relation is also in agreement with that of AGN with M BH obtained from reverberation mapping, providing an indirect validation of single-epoch virial estimators of M BH.

LLAMA: Stellar populations in the nuclei of ultra-hard X-ray-selected AGN and matched inactive galaxies

The relation between nuclear (≲50 pc) star formation and nuclear galactic activity is still elusive; theoretical models predict a link between the two, but it is unclear whether active galactic nuclei (AGNs) should appear at the same time, before, or after nuclear star formation activity. We present a study of this relation in a complete, volume-limited sample of nine of the most luminous (log L14 − 195 keV &gt; 1042.5 erg s−1) local AGNs (the LLAMA sample), including a sample of 18 inactive control galaxies (six star-forming; 12 passive) that are matched by Hubble type, stellar mass (9.5 ≲ log M⋆/M⊙ ≲ 10.5), inclination, and distance. This allows us to calibrate our methods on the control sample and perform a differential analysis between the AGN and control samples. We performed stellar population synthesis on VLT/X-shooter spectra in an aperture corresponding to a physical radius of ≈150 pc. We find young (≲30 Myr) stellar populations in seven out of nine AGNs and in four out of six star-forming control galaxies. In the non-star-forming control population, in contrast, only two out of 12 galaxies show such a population. We further show that these young populations are not indicative of ongoing star formation, providing evidence for models that see AGN activity as a consequence of nuclear star formation. Based on the similar nuclear star formation histories of AGNs and star-forming control galaxies, we speculate that the latter may turn into the former for some fraction of their time. Under this assumption, and making use of the volume completeness of our sample, we infer that the AGN phase lasts for about 5% of the nuclear starburst phase.

AGNIFS survey of local AGN: GMOS-IFU data and outflows in 30 sources

ABSTRACT We analyse optical data cubes of the inner kiloparsec of 30 local (z ≤ 0.02) active galactic nucleus (AGN) hosts that our research group, AGNIFS, has collected over the past decade via observations with the integral field units of the Gemini Multi-Object Spectrographs. Spatial resolutions range between 50 and 300 pc and spectral coverage is from 4800 or 5600 to 7000 Å, at velocity resolutions of ≈50 $\rm ~km~s^{-1}$. We derive maps of the gas excitation and kinematics, and determine the AGN ionization axis – which has random orientation relative to the galaxy – and the kinematic major axes of the emitting gas. We find that rotation dominates the gas kinematics in most cases, but is disturbed by the presence of inflows and outflows. Outflows have been found in 21 nuclei, usually along the ionization axis. The gas velocity dispersion is traced by W80 (velocity width encompassing 80 per cent of the line flux), adopted as a tracer of outflows. In seven sources, W80 is enhanced perpendicularly to the ionization axis, indicating lateral expansion of the outflow. We have estimated mass-outflow rates $\dot{M}$ and powers $\dot{E}$, finding median values of $\log \, [\dot{M}/({\rm \, M_\odot \, yr^{-1}})]=-2.1_{-1.0}^{+1.6}$ and $\log \, [\dot{E}/({\rm \, erg\, s^{-1}})]=38.5_{-0.9}^{+1.8}$, respectively. Both quantities show a mild correlation with the AGN luminosity (LAGN). $\dot{E}$ is of the order of 0.01 LAGN for four sources, but much lower for the majority (nine) of the sources, with a median value of $\log \, [\dot{E}/L_{\rm AGN} ]=-5.34_{-0.9}^{+3.2}$, indicating that typical outflows in the local Universe are unlikely to significantly impact their host galaxy evolution.

Local Active Galactic Nuclei with Large Broad-Hα Variability Reside in Red Galaxies

Abstract Inspired by our serendipitous discovery of six active galactic nuclei (AGNs) with varying broad-Hα fluxes over years from our search for intermediate-mass black holes (IMBHs), we conduct a systematic investigation of changing-look (CL) and large-variability AGNs. We collect all the CL AGNs at z &lt; 0.15 and the reverberation-mapped AGNs with strongly variable broad Hα and perform careful decomposition fittings to both their images and spectra. We find two observational facts: (1) The host galaxies of local CL and large-variability AGNs, mainly being Seyferts, are in the red (gas-poor) tail of the general Seyfert galaxy population. (2) In contrast, there is a significant trend that their more luminous counterparts, namely CL and extremely variable quasars (CLQs and EVQs), are different: CLQs are generally in blue galaxies; in terms of the diagram of star formation rate and M *, local CL Seyfert galaxies are located in the green valley, whereas CLQ hosts are in the star-forming main sequence. We propose explanations for those strongly variable Seyferts and quasars, respectively, under the assumption that accretion disks broadly depend on nuclear fueling modes. Local large-variability and CL Seyferts are in nuclear famine mode, where cold-gas clumps can be formed stochastically in the fueling flow, and their episodic infall produces sharp peaks in the accretion-rate curve. CLQs and EVQs are in feast fueling mode, which may account for both their preference for blue galaxies and their variability pattern (high-amplitude tail of the continuous distribution). Lastly, we propose a new thinking: to search for IMBHs by optical variability in red galaxies.

Ionized gas kinematics of cluster AGN at z ∼ 0.8 with KMOS

ABSTRACT We present an integral field spectroscopy study of two active galactic nuclei (AGN) in the galaxy cluster RXJ0152–137 at z = 0.84. We have combined integrated and 3D spectra with HST images to perform a complete morpho-kinematical analysis of each galaxy. For G557, we detect narrow and broad H α and [N ii] emission. The broad H α component is redshifted by v ∼ 939 km s−1 concerning the narrow component. The kinematics analysis and VLT/FORS2 data indicate that G557 presents evidence of radial outflows. For G300, it was possible to detect only the broad H α emission. The spectral properties of both galaxies are equivalent to those of local AGN. We also compare the results obtained for each AGN with their location within the cluster. We found a possible connection of the environment with the properties inferred for each of them, and the possible interaction of G557 with an unconfirmed neighboring galaxy, for which a bridge-like structure is observed in the HST images. This work shows evidence of how the same type of AGN can show differences in their spectroscopic properties depending on the region of the cluster in which they develop, which is important to understand how the environment affects AGN and, consequently, the evolution of galaxies.

Subarcsecond Mid-infrared View of Local Active Galactic Nuclei. IV. The L- and M-band Imaging Atlas*

Abstract We present the largest currently existing subarcsecond 3–5 μm atlas of 119 local (z &lt; 0.3) active galactic nuclei (AGNs). This atlas includes AGNs of five subtypes: 22 are Seyfert 1; five are intermediate Seyferts; 46 are Seyfert 2; 26 are low-ionization nuclear emission regions; and 20 are composites/starbursts. Each active galactic nucleus was observed with the Very Large Telescope Infrared Spectrometer and Array Camera (ISAAC) in the L and/or M bands between 2000 and 2013. We detected at 3σ confidence 92 sources in the L band and 83 sources in the M band. We separated the flux into unresolved nuclear flux and resolved the flux through two-Gaussian fitting. We report the nuclear flux, extended flux, apparent size, and position angle of each source, giving 3σ upper limits for sources that are undetected. Using Wide-field Infrared Survey Explorer (WISE) W1- and W2-band photometry we derived relations predicting the nuclear L and M fluxes for Sy1 and Sy2 AGNs based on their W1–W2 color and WISE fluxes. Lastly, we compare the measured mid-infrared colors to those predicted by dusty torus models SKIRTOR, CLUMPY, CAT3D, and CAT3D-WIND, finding the best agreement with the latter. We find that models including polar winds best reproduce the 3–5 μm colors, indicating that it is an important component of dusty torus models. We found that several AGNs are bluer than models predict. We discuss several explanations for this and find that it is most plausibly stellar light contamination within the ISAAC L-band nuclear fluxes.

Rejuvenation triggers nuclear activity in nearby galaxies

ABSTRACT Feedback, in particular from active galactic nuclei (AGNs), is believed to play a crucial role in the evolution of galaxies. In the local Universe, many galaxies with an AGN are indeed observed to reside in the so-called green valley, usually interpreted as a transition phase from a blue star-forming to a red quenched state. We use data from the Sloan Digital Sky Survey to show that such an interpretation requires substantial revision. Optically selected nearby AGN galaxies follow exponentially declining star formation histories, as normal galaxies of similar stellar and dark matter halo mass, reaching in the recent past (∼0.1 Gyr ago) star formation rate levels consistent with a quiescent population. However, we find that local AGN galaxies have experienced a sudden increase in their star formation rate, unfolding on time-scales similar to those typical of AGN activity, suggesting that both star formation and AGN activity were triggered simultaneously. We find that this quenching followed by an enhancement in the star formation rate is common to AGN galaxies and more pronounced in early-type galaxies. Our results demonstrate that local AGN galaxies are not just a simple transition type between star-forming and quiescent galaxies as previously postulated.