Search

Changing-look active galactic nuclei (CLAGNs) are characterized by extreme variations in line emission over short time-scales, mostly affecting broad H  |$\beta$| lines. While a few hundred CLAGNs are known, a complete sample of turn-on CLAGNs is still elusive. Here, we present a search for turn-on CLAGNs in a complete sample of galaxies, using archival spectra and recent light curves. We obtained light curves from the Asteroid Terrestrial Impact Last Alert System for 16 232 emission-line galaxies, including both star-forming and active galaxies, at |$z< 0.1$| with spectra from the Six-degree Field Galaxy Survey (6dFGS). We first establish typical variability behaviour for different active galactic nucleus (AGN) types, as recorded between 2001 and 2009, and then select outliers from the bulk behaviour as CLAGN candidates. We obtain new spectra for the candidates and identify 12 new turn-on CLAGNs (appearing broad H  |$\beta$| line) and 19 new turn-off CLAGNs (disappearing broad H  |$\beta$| line). We may have missed AGNs that changed and reverted their state over the 15–20 yr since 6dFGS spectra were taken, and thus our CLAGN rates of 1.7 per cent for turn-on and 9.6 per cent for turn-off are lower limits. The turn-on rate is naturally much lower as the type 1.9/2 sample is dominated by obscured AGNs due to orientation, which is not expected to change. However, the number of turn-on (27) and turn-off (24) CLAGNs we find are similar, suggesting that our parent AGN sample is reasonably complete in our search volume at |$z < 0.1$|⁠. [ABSTRACT FROM AUTHOR]

JWST has discovered a large population of active galactic nuclei (AGN) at high redshift, which are weak in the X-rays. Here we present the NIRSpec spectrum of the most extreme of these objects, GN-28074, an AGN at |$z=2.26$| with prominent hydrogen and He  i  broad lines, and with the highest limit on the bolometric to X-ray luminosity ratio among all spectroscopically confirmed AGN in GOODS. This source is also characterized by a mid-IR excess, likely associated with the AGN torus' hot dust. The high bolometric luminosity and moderate redshift of this AGN allow us to explore its properties more in depth relative to other JWST -discovered AGN. The NIRSpec spectrum reveals prominent, slightly blueshifted absorption of H |$\alpha$|⁠ , H |$\beta$|⁠ , and He  i   |$\lambda$| 10830. The Balmer absorption lines require gas with densities of |$n_{\rm H}\gt 10^8~{\rm cm}^{-3}$|⁠ , consistent with clouds in the broad-line region (BLR). This finding suggests that part of the X-ray weakness is due to high (Compton-thick) X-ray absorption by clouds in the BLR, or in its outer regions. GN-28074 is also extremely radio-weak. The radio weakness can also be explained in terms of absorption, as the inferred density of the BLR clouds makes them attenuate the radio emission through free–free absorption. Alternatively, the nuclear magnetic field may be underdeveloped, resulting both in intrinsically weak radio emission and lack of hot corona, hence intrinsic X-ray weakness. Finally, we show that recently proposed scenarios, invoking hyper-dense outflows or Raman scattering to explain the broad H |$\alpha$|⁠ , are ruled out. [ABSTRACT FROM AUTHOR]

We derive the nitrogen and oxygen abundances in the narrow line regions (NLRs) of a sample of 38 local (⁠|$z \: \lt \: 0.4$|⁠) Seyfert 2 nuclei. For that, we consider narrow optical emission line intensities and direct estimates of the electron temperatures (⁠|$T_{\rm e}$| -method). We obtain a new theoretical expression for the nitrogen ionization correction factor [ICF(⁠|$\rm N^{+}$|⁠)] for NLRs. Applying this new ICF, we unexpectedly find that NLRs and disc H  ii regions exhibit similar ICF distributions. We find nitrogen abundances in the range |$7.6 \: \lt \: \rm 12+log(N/H) \: \lt \: 8.6$| (mean value |$8.06\pm 0.22$|⁠) or |$\rm 0.4 \: \lt \: (N/N_{\odot }) \: \lt 4.7$|⁠ , in the metallicity regime |$8.3 \: \lt \: \rm 12+log(O/H) \: \lt \: 9.0$|⁠. Our results indicate that the dispersion in N/H abundance for a fixed O/H value in AGNs of |$\sim 0.2$| dex agrees with that for disc H  ii regions with similar metallicity. We show that Seyfert 2 nuclei follow a similar (N/O)–(O/H) relation to the one followed by star-forming objects. Finally, we find that active galaxies called as ..nitrogen-loud.. observed at very high redshift (⁠|$z \: \gt \: 5$|⁠) show N/O values in consonance with those derived for local NLRs. This result indicates that the main star-formation event is completed in the early evolution stages of active galaxies. [ABSTRACT FROM AUTHOR]

We report on the second observing program of the active galactic nucleus NGC 4151 with simultaneous Imaging X-ray Polarimetry Explorer (IXPE; 750 ks), NuSTAR (∼60 ks), XMM-Newton (∼75 ks), and NICER (∼65 ks) pointings. NGC 4151 is the first Type-1 radio-quiet Seyfert galaxy with constrained polarization properties for the X-ray corona. Despite the lower flux state in which the source was re-observed and the resulting higher contribution of the constant reflection component in the IXPE energy band, our results are in agreement with the first detection. From polarimetric analysis, a polarization degree Π = 4.7 ± 1.3% and polarization angle Ψ = 77° ± 8° east of north (68% c.l.) were derived in the 2.0–8.0 keV energy range. Combining the two observations leads to polarization properties that are more constrained than those of the individual detections, showing Π = 4.5 ± 0.9% and Ψ = 81° ± 6° (with a detection significance of ∼4.6σ). The observed polarization angle aligns very well with the radio emission in this source, supporting, together with the significant polarization degree, a slab or wedge geometry for the X-ray corona. However, a switch in the polarization angle at low energies (37° ±7° in the 2–3.5 keV bin) suggests the presence of another component. When it is included in the spectro-polarimetric fit, a high polarization degree disfavors an interpretation in terms of a leakage through the absorbers, instead pointing to scattering from some kind of mirror. [ABSTRACT FROM AUTHOR]

This study analyses JWST MIRI/MRS observations of the infrared (IR) polycyclic aromatic hydrocarbon (PAH) bands in the nuclear (∼0.4″ at 11 μm; ∼75 pc) and circumnuclear regions (inner ∼kpc) of local active galactic nuclei (AGNs) from the Galactic Activity, Torus, and Outflow Survey (GATOS). We examine the PAH properties in the circumnuclear regions of AGNs and the projected direction of AGN-outflows and compare them to those in star-forming regions and the innermost regions of AGNs. This study employs 4.9–28.1 μm sub-arcsecond angular resolution data to investigate the properties of PAHs in three nearby sources (DL ∼ 30 − 40 Mpc). Our findings are aligned with previous JWST studies, demonstrating that the central regions of AGNs display a larger fraction of neutral PAH molecules (i.e. elevated 11.3/6.2 and 11.3/7.7 μm PAH ratios) in comparison to star-forming galaxies. We find that AGNs might affect not only the PAH population in the innermost region, but also in the extended regions up to ∼kpc scales. By comparing our observations to PAH diagnostic diagrams, we find that, in general, regions located in the projected direction of the AGN-outflow occupy similar positions on the PAH diagnostic diagrams as those of the innermost regions of AGNs. Star-forming regions that are not affected by the AGNs in these galaxies share the same part of the diagram as star-forming galaxies. We also examined the potential of the PAH-H2 diagram to disentangle AGN-versus-star-forming activity. Our results suggest that in Seyfert-like AGNs, the illumination and feedback from the AGN might affect the PAH population at nuclear and kpc scales, particularly with respect to the ionisation state of the PAH grains. However, PAH molecular sizes are rather similar. The carriers of the ionised PAH bands (6.2 and 7.7 μm) are less resilient than those of neutral PAH bands (11.3 μm), which might be particularly important for strongly AGN-host coupled systems. Therefore, caution must be applied when using PAH bands as star-formation rate indicators in these systems even at kpc scales, with the effects of the AGN being more important for ionised ones. [ABSTRACT FROM AUTHOR]

Context. Extreme continuum variability in extragalactic nuclear sources can indicate extreme changes in accretion flows onto supermassive black holes. Aims. We explore the multiwavelength nature of a continuum flare in the Seyfert LCRS B040659.9−385922. The all-sky X-ray surveys conducted by the Spectrum Roentgen Gamma (SRG)/extended ROentgen Survey with an Imaging Telescope Array (eROSITA) showed that its X-ray flux increased by a factor of roughly five over six months, and concurrent optical photometric monitoring with the Asteroid Terrestrial-impact Last Alert System (ATLAS) showed a simultaneous increase. Methods. We complemented the eROSITA and ATLAS data by triggering a multiwavelength follow-up monitoring program (X-ray Multi-Mirror Mission: XMM-Newton, Neutron star Interior Composition Explorer: NICER; optical spectroscopy) to study the evolution of the accretion disk, broad-line region, and X-ray corona. During the campaign, X-ray and optical continuum flux subsided over roughly six months. Our campaign includes two XMM-Newton observations, one taken near the peak of this flare and the other taken when the flare had subsided. Results. The soft X-ray excess in both XMM-Newton observations was power law-like (distinctly nonthermal). Using a simple power law, we observed that the photon index of the soft excess varies from a steep value of Γ ∼ 2.7 at the flare peak to a relatively flatter value of Γ ∼ 2.2 as the flare subsided. We successfully modeled the broadband optical/UV/X-ray spectral energy distribution at both the flare peak and post-flare times with the AGNSED model, incorporating thermal disk emission into the optical/UV and warm thermal Comptonization in the soft X-rays. The accretion rate falls by roughly 2.5, and the radius of the hot Comptonizing region increases from the flaring state to the post-flare state. Additionally, from the optical spectral observations, we find that the broad He IIλ4686 emission line fades significantly as the optical/UV/X-ray continuum fades, which could indicate a substantial flare of disk emission above 54 eV. We also observed a redshifted broad component in the Hβ emission line that is present during the high flux state of the source and disappears in subsequent observations. Conclusions. A sudden strong increase in the local accretion rate in this source manifested itself via an increase in accretion disk emission and in thermal Comptonized emission in the soft X-rays, which subsequently faded. The redshifted broad Balmer component could be associated with a transient kinematic component distinct from that comprising the rest of the broad-line region. [ABSTRACT FROM AUTHOR]

Context. Active galactic nuclei (AGNs) are known to be variable across all wavelengths. Significant observational efforts have been invested in the last decade in studying their ultraviolet (UV) and optical variability. Long and densely sampled, multi-wavelength monitoring campaigns of numerous Seyfert galaxies have been conducted with the aim of determining the X-ray/UV/optical continuum time lags. Time-lag studies can be used to constrain theoretical models. The observed time lags can be explained by thermal reprocessing of the X-rays illuminating the accretion disc (known as the X-ray reverberation model). However, the observed light curves contain more information that can be used to further constrain physical models. Aims. Our primary objective is to investigate whether, in addition to time lags, the X-ray reverberation model can also explain the UV/optical variability amplitude of nearby Seyferts. Methods. We measured the excess variance of four sources (namely Mrk 509, NGC 4151, NGC 2617, and Mrk 142) as a function of wavelength using data from archival long, multi-wavelength campaigns with Swift, and ground-based telescopes. We also computed the model excess variance in the case of the X-ray reverberation model by determining the disc's transfer function and assuming a bending power law for the X-ray power spectrum. We tested the validity of the model by comparing the measured and model variances for a range of accretion rates and X-ray source heights. Results. Our main result is that the X-ray thermal reverberation model can fit both the continuum, UV/optical time lags, as well as the variance (i.e. the variability amplitude) in these AGNs, for the same physical parameters. Our results suggest that the accretion disc is constant and that all the observed UV/optical variations, on timescales of days and up to a few weeks, can be fully explained by the variable X-rays as they illuminate the accretion disc. [ABSTRACT FROM AUTHOR]

We explore the relations between the gas-phase metallicity radial profiles (few hundred inner parsec) and multiple galaxy properties for 15 Seyfert galaxies from the active galactic nuclei integral field spectroscopy sample using optical integral field unit observations from Gemini Multi-Object Spectrograph (GMOS) and Multi Unit Spectroscopic Explorer (MUSE) processed archival data. The data were selected at |$z \lesssim 0.013$| within black hole mass range |$\left[6\lt \log \left(M_{\rm BH}/{\rm M_\odot } \right)\lt 9\right]$| with moderate 14–150-keV X-ray luminosities |$\left[42\, \lesssim \, \log L_X (\rm erg\, s^{-1})\, \lesssim \, 44\right]$|⁠. We estimated the gas-phase metallicity using the strong-line methods and found mean values for the oxygen-dependent (⁠|$Z \sim 0.75\, \mathrm{Z}_\odot$|⁠) and nitrogen-dependent (⁠|$Z \sim 1.14\, \mathrm{Z}_\odot$|⁠) calibrations. These estimates show excellent agreement with |$\Delta Z \approx 0.19$| and 0.18 dex between the mean values from the two strong-line calibrations for GMOS and MUSE, respectively, consistent with the order of metallicity uncertainty via the strong-line methods. We contend that our findings align with a scenario wherein local Seyferts have undergone seamless gas accretion histories, resulting in positive metallicity profiles over an extended period of time, thereby providing insights into galaxy evolution and the chemical enrichment or depletion of the universe. Additionally, we argue that metal-poor gas inflow from the local interstellar medium and accreted through the circumgalactic medium on to the galaxy systems regulates the star formation processes by diluting their central metallicity and inverting their gas-phase metallicity radial gradients, producing a more prominent anticorrelation between gas-phase metallicity and Eddington ratio. [ABSTRACT FROM AUTHOR]

In the era of massive photometric surveys, we explore several approaches to estimate the masses of supermassive black holes (SMBHs) in active galactic nuclei (AGNs) from optical ground-based imaging, in each case comparing to the independent SMBH mass measurement obtained from spectroscopic data. We select a case-study sample of 28 type 1 AGN hosted by nearby galaxies from the Galaxy And Mass Assembly (GAMA) survey. We perform multicomponent spectral decomposition, extract the AGN component, and calculate the SMBH mass from the broad H |$\alpha$| emission line width and luminosity. The photometric g and i band data is decomposed into AGN+spheroid(+disc)(+bar) components with careful surface brightness fitting. From these, the SMBH mass is estimated using its relation with the spheroid Sérsic index or effective radius (both used for the first time on ground-based optical imaging of AGN); and the more widely used scaling relations based on bulge or galaxy stellar mass. We find no correlation between the H |$\alpha$| -derived SMBH masses and those based on the spheroid Sérsic index or effective radius, despite these being the most direct methods involving only one scaling relation. The bulge or galaxy stellar mass based methods both yield significant correlations, although with considerable scatter and, in the latter case, a systematic offset. We provide possible explanations for this and discuss the requirements, advantages, and drawbacks of each method. These considerations will be useful to optimize strategies for upcoming high quality ground-based and space-borne sky surveys to estimate SMBH masses in large numbers of AGN. [ABSTRACT FROM AUTHOR]

Active galactic nuclei (AGN) are extremely variable in the X-ray band down to very short timescales. However, the driver behind the X-ray variability is still poorly understood. Previous results suggest that the hot corona responsible for the primary Comptonized emission observed in AGN is expected to play an important role in driving the X-ray variability. In this work, we investigate the connection between the X-ray amplitude variability and the coronal physical parameters; namely, the temperature (kT) and optical depth (τ). We present the spectral and timing analysis of 46 NuSTAR observations corresponding to a sample of 20 AGN. For each source, we derived the coronal temperature and optical depth through X-ray spectroscopy and computed the normalized excess variance for different energy bands on a timescale of 10 ks. We find a strong inverse correlation between kT and τ, with correlation coefficient of r < −0.9 and negligible null probability. No clear dependence was found among the temperature and physical properties, such as the black hole mass or the Eddington ratio. We also see that the observed X-ray variability is not correlated with either the coronal temperature or optical depth under the thermal equilibrium assumption, whereas it is anticorrelated with the black hole mass. These results can be interpreted through a scenario where the observed X-ray variability could primarily be driven by variations in the coronal physical properties on a timescale of less than 10 ks; whereas we assume thermal equilibrium on such timescales in this work, given the capability of the currently available hard X-ray telescopes. Alternatively, it is also possible that the X-ray variability is mostly driven by the absolute size of the corona, which depends on the supermassive black hole mass, rather than resulting from any of its physical properties. [ABSTRACT FROM AUTHOR]

We present new Very Large Telescope Interferometer (VLTI)/GRAVITY near-infrared interferometric measurements of the angular size of the innermost hot dust continuum for 14 type 1 active galactic nuclei (AGNs). The angular sizes are resolved on scales of ∼0.7 mas and the inferred ring radii range from 0.028 to 1.33 pc, comparable to those reported previously and a factor of 10−20 smaller than the mid-infrared sizes in the literature. Combining our new data with previously published values, we compiled a sample of 25 AGNs with bolometric luminosity ranging from 1042 to 1047 erg s−1, with which we studied the radius-luminosity (R − L) relation for the hot dust structure. Our interferometric measurements of radius are offset by a factor of 2 from the equivalent relation derived through reverberation mapping. Using a simple model to explore the dust structure's geometry, we conclude that this offset can be explained if the 2 μm emitting surface has a concave shape. Our data show that the slope of the relation is in line with the canonical R ∝ L0.5 when using an appropriately non-linear correction for bolometric luminosity. In contrast, using optical luminosity or applying a constant bolometric correction to it results in a significant deviation in the slope, suggesting a potential luminosity dependence on the spectral energy distribution. Over four orders of magnitude in luminosity, the intrinsic scatter around the R − L relation is 0.2 dex, suggesting a tight correlation between the innermost hot dust structure size and the AGN luminosity. [ABSTRACT FROM AUTHOR]

We present observations of the type-2 Seyfert NGC 7172 obtained with the medium-resolution spectrometer (MRS) of the Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST). This galaxy hosts one of the lowest ionised gas mass outflow rates (Ṁout ∼ 0.005 M⊙ yr−1) in a sample of six active galactic nuclei (AGN) with similar bolometric luminosities (log Lbol ∼ 44 erg s−1) within the Galactic Activity, Torus, and Outflow Survey (GATOS). We aim to understand the properties of the ionised gas outflow and its impact on the host galaxy. We mainly used the ionised gas emission lines from the neon transitions, which cover a broad range of ionisation potentials (IPs) from ∼20 eV to ∼130 eV. We applied parametric and non-parametric methods to characterise the line emission and kinematics. The low excitation lines (IP < 25 eV, e.g. [Ne II]) trace the rotating disc emission. The high excitation lines (IP > 90 eV, e.g. [Ne V]), which are likely photoionised exclusively by the AGN, are expanding in the direction nearly perpendicular to the disc of the galaxy, with maximum projected velocities in the range of ∼350–500 km s−1. In particular, [Ne V] and [Ne VI] lines reveal a biconical ionised gas outflow emerging north-south from the nuclear region, extending at least ∼2.5″ N and 3.8″ S (projected distance of ∼450 and 680 pc, respectively). Most of the emission arising in the northern part of the cone was not previously detected due to obscuration. Given the almost face-on orientation of the outflow and the almost edge-on orientation of the galaxy, NGC 7172 may be a case of weak coupling. Nevertheless, we found evidence of positive feedback in two distinct outflowing clumps at projected distances of 3.1″ and 4.3″ (i.e. ∼560 and 780 pc) south-west of the AGN. We estimated a star formation rate in these regions using the [Ne II] and [Ne III] luminosities of 0.08 M⊙ yr−1, which is ∼10% of that found in the circumnuclear ring. The star formation activity might have been triggered by the interaction between the ionised gas outflow and the interstellar medium of the galaxy. [ABSTRACT FROM AUTHOR]

Context. Detections of the X-ray spectra of active galactic nuclei (AGNs) typically reveal a noticeable excess of soft X-rays beyond the extrapolation of the power-law trend observed between 2 and 10 keV. However, the cause of this surplus remains unclear. In the scenario of soft Comptonization, observations suggest a warm corona temperature, ranging from 0.1 to 1 keV, and an optical depth of approximately 10 to 30. Furthermore, according to radiative constraints derived from spectral analyses employing Comptonization models, it has been suggested that most of the accretion power is released within the warm corona. At the same time, the disk beneath it is largely non-dissipative, mainly emitting the reprocessed radiation from the corona. Aims. We tested the dissipative warm corona model using the radiative transfer code TITAN-NOAR on a sample of 82 XMM-Newton EPIC-pn observations of 21 AGNs. Based on a spectral modeling of the X-ray data, we aim to estimate the total amount of internal heating inside the warm corona on top of the accretion disk. Methods. By modeling the 0.3–10 keV EPIC-pn spectra with the TITAN-NOAR model component, we estimated the internal heating and optical depth of the warm corona and checked their correlations with such global parameters as the hot corona spectral index, black hole mass, and accretion rate. From the model normalization, we computed the radial extent of the warm corona on top of the cold accretion disk. Results. Our model infers the presence of dissipative warm corona, with optical depths distributed across the range of ∼6–30 and a total internal heating in the range of ∼1–29 × 10−23 erg s−1 cm3. We do not detect any variation between these properties and global properties, such as the black hole mass and accretion rate. The extent of the warm corona is spread across a broad range, from 7–408 gravitational radii, and we find that the warm corona is more extended for higher accretion rates. Conclusions. Soft excess emission is ubiquitous across a wide mass range and accretion rate in AGNs. We confirm that the warm corona responsible for producing the soft X-ray excess is highly dissipative with greater optical depths being associated with lower internal heating and vice versa. The cold standard accretion disk regulates the extent of the warm corona. [ABSTRACT FROM AUTHOR]

Context. Short-term X-ray variability in active galactic nuclei (AGNs) can be explained as being due to varying X-ray absorption induced by the temporary occultation of the primary X-ray source, when moving absorbing clouds cross the line of sight to the X-ray source itself. Earlier work suggests that these absorbing clouds have physical properties similar to those of broad-line region (BLR) emitting clouds and are located in the same spatial region. Aims. We intend to extract physical information on each individual absorber associated with any given occultation event detected in our sample and to analyse general properties of the cloud ensemble whose components can produce X-ray eclipses. Methods. From the analysis of previously detected occultation events, two 'observables' characterising each single occultation event can be derived: the peak fractional hardness ratio variation (ΔHR/HR) and the duration of the event normalised by a characteristic eclipse timescale evaluated for each AGN source. To determine the eclipsing cloud properties, we devised a procedure a) based on simplifying assumptions on the geometry of both the X-ray source and the cloud-like gas condensations, and on the cloud X-ray absorbing properties in the energy range of interest (2–10 keV), and b) relying on a set of simulated instrumental responses from both XMM and Suzaku relevant instruments to different incoming X-ray spectra, absorbed with varying absorber column density and maximum covering factor during the occultation. Thus, we derived information on the individual cloud producing any given occultation event, determining the cloud radius normalised to that of the X-ray source, the spatial location of the cloud, and an estimate of the cloud gas number density for reasonable values of the equivalent absorber column density. Results. The physical properties of eclipsing clouds that we obtained are consistent with those of BLR clouds. We can exclude the dominance, in the ensemble cloud size distribution, of clouds larger than about 10–12 times the Schwarzschild radius characterising each AGN, and we do not find any significant dependence of the cloud physical size on the distance from the central black hole, in agreement with the results of our previous work. As for the number density of these gas condensations, with our procedure we obtained values within a range of ∼109 − 1011 cm−3, which is consistent with the estimates derived from broad emission line analysis. [ABSTRACT FROM AUTHOR]

We present a novel implementation for active galactic nucleus (AGN) feedback through ultrafast winds in the code GIZMO. Our feedback recipe accounts for the angular dependence of radiative feedback on black hole spin. We self-consistently evolve in time (i) the gas-accretion process from resolved scales to a smaller scale unresolved (subgrid) AGN disk, (ii) the evolution of the spin of the massive black hole (MBH), (iii) the injection of AGN-driven winds into the resolved scales, and (iv) the spin-induced anisotropy of the overall feedback process. We tested our implementation by following the propagation of the wind-driven outflow into an homogeneous medium, and here we present a comparison of the results against simple analytical models. We also considered an isolated galaxy setup, where the galaxy is thought to be formed from the collapse of a spinning gaseous halo, and there we studied the impact of the AGN feedback on the evolution of the MBH and of the host galaxy. We find that: (i) AGN feedback limits the gas inflow that powers the MBH, with a consequent weak impact on the host galaxy characterized by a suppression of star formation by about a factor of two in the nuclear (≲kpc) region; (ii) the impact of AGN feedback on the host galaxy and on MBH growth is primarily determined by the AGN luminosity rather than by its angular pattern set by the MBH spin (i.e., more luminous AGNs more efficiently suppress central star formation (SF), clearing wider central cavities and driving outflows with larger semiopening angles); (iii) the imprint of the angular pattern of AGN radiation emission is detected more clearly at high (i.e., Eddington) accretion rates. At such high rates, the more isotropic angular patterns, as occur for high spin values, sweep away gas in the nuclear region more easily, therefore causing a slower MBH mass and spin growths and a higher quenching of SF. We argue that the influence of spin-dependent anisotropy of AGN feedback on MBH and galaxy evolution is likely to be relevant in those scenarios characterized by high and prolonged MBH accretion episodes and by high AGN wind–galaxy coupling. Such conditions are more frequently met in galaxy mergers and/or high-redshift galaxies. [ABSTRACT FROM AUTHOR]

A well-known calibrator source in radio astronomy, 3C 286 (⁠|$z=0.85$|⁠), is a compact steep-spectrum (CSS) radio source and spectroscopically classified as a narrow-line Seyfert 1 (NLS1) galaxy. It is also known for its damped Ly |$\alpha$| system from an intervening galaxy at |$z=0.692$| detected in both ultraviolet (UV) and radio spectra. In addition, despite being a misaligned active galactic nuclei (AGN), 3C 286 is also detected in |$\gamma$| -rays by Fermi. Thus, this unique object combines the characteristics of CSS sources, NLS1 galaxies, and |$\gamma$| -ray emitters with misaligned jets, providing an excellent laboratory for extending our knowledge of AGN disc–jet coupling. Despite its significance, 3C 286 has been rarely observed in X-rays. In this study, we present our deep XMM–Newton and Chandra observations of 3C 286. The results reveal that the X-ray spectrum can be well-described by models including an intervening absorber with redshift and column density consistent with previous UV and radio observations. The most important finding is that the spectrum cannot be described by a single power law, but a soft excess is required which is parametrized by a blackbody. Furthermore, we find evidence suggesting the presence of off-nuclear X-ray emission at a radius that corresponds to the location of the radio lobes. While further theoretical work is still needed, our findings offer new clues to understand the specific mechanism for |$\gamma$| -ray emission from this unique object. [ABSTRACT FROM AUTHOR]

Polar dust has been discovered in a number of local active galactic nuclei (AGN), with radiation-driven torus models predicting a wind to be its main driver. However, little is known about its characteristics, spatial extent, or connection to the larger scale outflows. We present the first JWST /MIRI study aimed at imaging polar dust by zooming on to the centre of ESO 428-G14, part of the Galaxy Activity, Torus, and Outflow Survey (GATOS) survey of local AGN. We detect extended mid-infrared (MIR) emission within 200 pc from the nucleus. This polar structure is co-linear with a radio jet and lies perpendicular to a molecular gas lane that feeds and obscures the nucleus. Its morphology bears a striking resemblance to that of gas ionized by the AGN in the narrow-line region. We demonstrate that part of this spatial correspondence is due to contamination within the JWST filter bands from strong emission lines. Correcting for the contamination, we find the morphology of the dust continuum to be more compact, though still clearly extended out to |$r\approx 100 \, \rm pc$|⁠. We estimate the emitting dust has a temperature of |$\sim 120\, \rm K$|⁠. Using simple models, we find that the heating of small dust grains by the radiation from the central AGN and/or radiative jet-induced shocks is responsible for the extended MIR emission. Radiation-driven dusty winds from the torus is unlikely to be important. This has important implications for scales to which AGN winds can carry dust and dense gas out into their host galaxies. [ABSTRACT FROM AUTHOR]

We report on the discovery of one of the most extreme cases of high-frequency radio variability ever measured in active galactic nuclei (AGNs), observed on time-scales of days and exhibiting variability amplitudes of 3–4 orders of magnitude. These sources, all radio-weak narrow-line Seyfert 1 (NLS1) galaxies, were discovered some years ago at Aalto University Metsähovi Radio Observatory (MRO) based on recurring flaring at 37 GHz, strongly indicating the presence of relativistic jets. In subsequent observations with the Karl G. Jansky Very Large Array (JVLA) at 1.6, 5.2, and 9.0 GHz no signs of jets were seen. To determine the cause of their extraordinary behaviour, we observed them with the JVLA at 10, 15, 22, 33, and 45 GHz, and with the Very Long Baseline Array (VLBA) at 15 GHz. These observations were complemented with single-dish monitoring at 37 GHz at MRO, and at 15 GHz at Owens Valley Radio Observatory (OVRO). Intriguingly, all but one source either have a steep radio spectrum up to 45 GHz, or were not detected at all. Based on the 37 GHz data, the time-scales of the radio flares are a few days, and the derived variability brightness temperatures and variability Doppler factors are comparable to those seen in blazars. We discuss alternative explanations for their extreme behaviour, but so far no definite conclusions can be made. These sources exhibit radio variability at a level rarely, if ever, seen in AGN. They might represent a new type of jetted AGN, or a new variability phenomenon, and thus deserve our continued attention. [ABSTRACT FROM AUTHOR]

Despite the evidence that supermassive black holes (SMBHs) co-evolve with their host galaxy, and that most of the growth of these SMBHs occurs via merger-free processes, the underlying mechanisms which drive this secular co-evolution are poorly understood. We investigate the role that both strong and weak large-scale galactic bars play in mediating this relationship. Using 48 871 disc galaxies in a volume-limited sample from Galaxy Zoo DESI, we analyse the active galactic nucleus (AGN) fraction in strongly barred, weakly barred, and unbarred galaxies up to |$z = 0.1$| over a range of stellar masses and colours. After controlling for stellar mass and colour, we find that the optically selected AGN fraction is |$31.6 \pm 0.9$| per cent in strongly barred galaxies, |$23.3 \pm 0.8$| per cent in weakly barred galaxies, and |$14.2 \pm 0.6$| per cent in unbarred disc galaxies. These are highly statistically robust results, strengthening the tantalizing results in earlier works. Strongly barred galaxies have a higher fraction of AGNs than weakly barred galaxies, which in turn have a higher fraction than unbarred galaxies. Thus, while bars are not required in order to grow an SMBH in a disc galaxy, large-scale galactic bars appear to facilitate AGN fuelling, and the presence of a strong bar makes a disc galaxy more than twice as likely to host an AGN than an unbarred galaxy at all galaxy stellar masses and colours. [ABSTRACT FROM AUTHOR]

We present a comprehensive analysis of approximately 15 years (2006–2021) of X-ray observations of UGC 6728, a low-mass bare AGN, for the first time. Our study encompasses both spectral and temporal aspects of this source. The spectral properties of this source are studied using various phenomenological and physical models. We conclude that (a) the observed variability in X-ray luminosity is not attributed to the hydrogen column density (N H) as UGC 6728 exhibits a bare nucleus, implying a negligible N H contribution along the line of sight, and (b) the spectral slope in the X-ray band demonstrates a systematic variation over time, indicating a transition from a relatively hard state to a comparatively soft state. We propose that the underlying accretion dynamics around the central object account for this behaviour. By performing X-ray spectral fitting, we estimate the mass of the central supermassive black hole (SMBH) in UGC 6728 to be |$M_{\rm BH}=(7.13\pm 1.23)\times 10^5$|  M |$_\odot$|⁠. Based on our spectral and temporal analysis, we suggest that UGC 6728 lacks a prominent Compton hump or exhibits a very subtle hump that remains undetectable in our analysis. Furthermore, the high-energy X-ray photons in this source are likely to originate from the low-energy X-ray photons through inverse Compton scattering in a Compton cloud, highlighting a connection between the emission in two energy ranges. We noticed a strong soft excess component in the initial part of our observations, which was later reduced substantially. This variation of soft excess is explained in view of accretion dynamics. [ABSTRACT FROM AUTHOR]

This study investigates the properties of two gas structures of X-ray selected active galactic nuclei (AGNs), that is, dusty and dust-free gas components, by separating them with the line-of-sight dust extinction (⁠|$A_V$|⁠) and the neutral gas column density (⁠|$N_{\mathrm{H}}$|⁠). The typical column density of the dusty and dust-free gas differs depending on the Seyfert type, indicating that both structures have anisotropic column density distributions. The number of targets with the dusty gas column density (⁠|$N_{\mathrm{H,d}}$|⁠) of |$\log N_{\mathrm{H,d}}\ [\mathrm{cm^{-2}}]\gt 23$| is much smaller than that with the same column density of the dust-free gas. This result indicates that the optically thick part of the dusty gas structure is very thin. There are very few targets with a larger Eddington ratio (⁠|$f_{\mathrm{Edd}}$|⁠) than the effective Eddington limit of the dusty gas and the covering factor of the dusty gas with |$22\le \log N_{\mathrm{H,d}}\ [\mathrm{cm^{-2}}]\lt 24$| exhibits a clear drop at the effective Eddington limit. These results support the scenario wherein the covering factor of the dusty torus decreases in a high Eddington ratio owing to the radiation-driven dusty gas outflow. The covering factor of the dust-free gas with the column density (⁠|$N_{\mathrm{H,df}}$|⁠) of |$22\le \log N_{\mathrm{H,df}}\ [\mathrm{cm^{-2}}]\lt 24$| similarly exhibits the decrease in high Eddington ratio, although it may be owing to the dust-free gas outflow driven by certain other mechanisms than the radiation pressure. Finally, we propose an updated picture of the AGN gas structure based on our results and the literature. [ABSTRACT FROM AUTHOR]

Context. Ultra-fast outflows (UFOs) have been revealed in a large number of active galactic nuclei (AGN) in the past two decades. Their extreme velocities and high ionization states make them a promising candidate for AGN feedback on the evolution of the host galaxy. However, their exact underlying driving mechanism is not yet fully understood. Aims. Given that the variability of UFOs may be used to distinguish among different launching mechanisms, we aim to search for and characterize the responses of the UFO properties to the variable irradiating luminosity. Methods. We perform a high-resolution time- and flux-resolved spectroscopy of archival XMM-Newton observations on six highly accreting narrow-line Seyfert 1 (NLS1) galaxies, selected by UFO detection and sufficient exposure times. The state-of-the-art methods of the blind Gaussian line scan and photoionization model scan are used to identify UFO solutions. We search for ionized winds and investigate the structure of ionized winds and their responses to the luminosity variations. The location, density, and kinetic energy of UFOs are estimated as well. Results. The powerful photoionization model scan reveals three previously unreported UFOs in RE J1034+396, PG 1244+026 and I ZW 1 with a detection significance above 3σ, and two new warm absorbers (WAs) in RE J1034+396. Five out of six (83%) AGN in our sample host multi-phase ionized winds, where outflows in I ZW 1 are energy-conserved. The relatively low-ionization entrained UFOs are discovered in four (66%) AGN of our sample, supporting the shocked outflow interpretation for ionized winds in AGN. We notice that two out of seven (28%) UFOs in our sample seem to respond to the radiation field and three (43%) UFOs hint at a radiatively accelerated nature, requiring further observations. Combined with published works, we do not find any correlations between UFO responses and AGN properties except for a tentative (∼1.8σ) anti-correlation between the UFO acceleration and the Eddington ratio, to be confirmed by further observations and an enlarged sample. The kinetic energy of UFOs, mostly detected in soft X-rays, is found to have a large uncertainty. We, therefore, cannot conclude whether soft X-ray UFOs have sufficient energy to drive the AGN feedback, although they are very promising based on some reasonable assumptions. The primary UFO in I ZW 1 (detected in the hard X-ray) is the only case in our sample to possess conclusively sufficient energy to affect the host galaxy. [ABSTRACT FROM AUTHOR]

The optical spectroscopic classification of active galactic nuclei (AGN) into type 1 and type 2 can be understood in the frame of the AGN unification models. However, it remains unclear which physical properties are driving the classification into intermediate sub-types (1.0, 1.2, 1.5, 1.8, 1.9). To shed light on this issue, we present an analysis of the effect of extinction and AGN and host galaxy luminosities on sub-type determination for a sample of 159 X-ray selected AGN with a complete and robust optical spectroscopic classification. The sample spans a rest-frame 2–10 keV X-ray luminosity range of 1042–1046 erg s−1 and redshifts between 0.05 and 0.75. From the fitting of their ultraviolet-to-mid-infrared spectral energy distributions, we extracted the observed AGN over total AGN+galaxy contrast, optical/ultraviolet line-of-sight extinction, as well as host galaxy and AGN luminosities. The observed contrast exhibits a clear decline with sub-type, distinguishing two main groups: 1.0–5 and 1.8–2. This difference is partly driven by an increase in extinction following the same trend. Nevertheless, 50% of 1.9s and 2s lack sufficient extinction to explain the lack of detection of broad emission lines, unveiling the necessity of an additional effect. Our findings show that 1.8–2s preferentially live in host galaxies with higher luminosities while displaying similar intrinsic AGN luminosities to 1.0–5s. Consequently, the AGN to host galaxy luminosity ratio diminishes, hindering the detection of the emission of the broad emission lines, resulting in the 1.8–2 classification of those with insufficient extinction. Thus, the combination of increasing extinction and decreasing AGN over galaxy luminosity ratio, mainly driven by an increasing host galaxy luminosity, constitutes the main reasons behind the sub-type classification into 1.0–5 and 1.8–2. [ABSTRACT FROM AUTHOR]

We present the results of a joint XMM-Newton and NuSTAR campaign on the active galactic nucleus (AGN) IC 4329A, consisting of 9 × 20 ks XMM-Newton observations, and 5 × 20 ks NuSTAR observations within nine days, performed in August 2021. Within each observation, the AGN is not very variable, and the fractional variability never exceeds 5%. Flux variations are observed between the different observations on timescales of days, with a ratio of 30% of the minimum and maximum 2–10 keV flux. These variations follow the softer-when-brighter behavior typically observed in AGN. In all observations, a soft excess is clearly present. Consistently with previous observations, the X-ray spectra of the source exhibit a cutoff energy between 140 and 250 keV that is constant within the error in the different observations. We detected a prominent component of the 6.4 keV Fe Kα line consistent with being constant during the monitoring, consisting of an unresolved narrow core and a broader component likely originating in the inner accredion disk. We find that the reflection component is weak (Rmax = 0.009 ± 0.002) and most likely originates in distant neutral medium. We also found a warm absorber component together with an ultrafast outflow. Their energetics show that these outflows have enough mechanical power for significant feedback on the environment of the AGN. [ABSTRACT FROM AUTHOR]

NGC 1068 is a nearby, widely studied Seyfert II galaxy presenting radio, infrared, X-ray, and γ-ray emission, along with strong evidence for high-energy neutrino emission. Recently, the evidence for neutrino emission was explained in a multimessenger model, whereby the neutrinos originate from the corona of the active galactic nucleus. In this environment, γ-rays are strongly absorbed, so that an additional contribution is necessary, for instance, from the circumnuclear starburst ring. In this work, we discuss whether the radio jet can be an alternative source of the γ-rays between about 0.1 and 100 GeV, as observed by Fermi-LAT. In particular, we include both leptonic and hadronic processes, namely, accounting for inverse Compton emission and signatures from pp as well as pγ interactions. In order to constrain our calculations, we used VLBA and ALMA observations of the radio knot structures, which are spatially resolved at different distances from the supermassive black hole. Our results show that the best leptonic scenario for the prediction of the Fermi-LAT data is provided by the radio knot closest to the central engine. For that to be the case, a magnetic field strength of ∼1 mG is needed as well as a strong spectral softening of the relativistic electron distribution at (1 − 10) GeV. However, we show that neither such a weak magnetic field strength, nor such a strong softening is expected for that knot. A possible explanation for the ∼10 GeV γ-rays could potentially be provided by hadronic pion production in case of a gas density ≳104 cm−3. Nonetheless, this process is not found to contribute significantly to the low-energy end of the Fermi-LAT range. We conclude that the emission sites in the jet are not sufficient to explain the γ-rays across the whole Fermi-LAT energy band. [ABSTRACT FROM AUTHOR]

The detection of a high-velocity (∼0.3 c) inflow of highly ionized matter during an extended XMM–Newton observation of the luminous Seyfert galaxy PG1211+143 in 2014 provided the first direct evidence of a short-lived accretion event, and an explanation for the powerful winds (UFOs) now recognized as a common property of many luminous Seyfert galaxies. Although the ultra-fast inflow observed at a redshift of 0.483 was detected in only one of seven spacecraft orbits, weaker (lower column) but more persistent absorption is seen at a redshift of 0.123 in the high-exposure soft X-ray (RGS) spectra summed over all seven individual spacecraft orbits. Similar stacking of the higher energy (pn camera) spectra reveals underlying absorption at a redshift of 0.148. Interpreted, conventionally, as a Doppler redshift, the RGS observation indicates a line-of-sight inflow velocity v ∼ 0.038 c and (free-fall) radial location at 1400  Rg , with the higher redshift and ionization in pn camera spectra perhaps detecting that inflow closer to the black hole. A very different explanation would be absorption in matter subject to the strong gravity close to the SMBH, an interpretation supported by the launch of a new UFO in the final spacecraft orbit. [ABSTRACT FROM AUTHOR]

In terms of the variable nature of normal active galaxy nuclei (AGN) and luminous quasars, a so-called flux variation gradient (FVG) method has been widely utilized to estimate the underlying non-variable host galaxy fluxes. The FVG method assumes an invariable AGN color, but this assumption has been questioned by the intrinsic color variation of quasars and local Seyfert galaxies. Here, using an up-to-date thermal fluctuation model to simulate multi-wavelength AGN variability, we theoretically demonstrate that the FVG method generally overestimates the host galaxy flux; that is, it is more significant for brighter AGN/quasars. Furthermore, we observationally confirm that the FVG method indeed overestimates the host galaxy flux by comparing it to that estimated through other independent methods. We thus caution that applying the FVG method should be performed carefully in the era of time-domain astronomy. [ABSTRACT FROM AUTHOR]

Spectral energy distribution (SED) fitting is one of the most commonly used techniques to study the dust properties in active galactic nuclei (AGN). Works implementing this technique commonly use radiative transfer models that assume a variety of dust properties. Despite the key role of this aspect, limited effort has been put forward to explore the chemical composition, the role of different optical properties, and the grain size distribution of dust, all of which can have a substantial impact on the theoretical radiative transfer calculations. In this work, we explore the role of the dust chemical composition in the AGN dusty torus through SED fitting to Spitzer /IRS spectra of a sample of 49 nearby AGN with silicate features in emission. We implement a mineralogy model including the popular astronomical silicates and a set of oxides and amorphous silicates with different grain sizes. Wefind that best fits use principally porous alumina, periclase, and olivine. In terms of mass fractions, |$\sim 99~{{\ \rm per\ cent}}$| of the dust is composed of dust grains of size |$\rm {0.1 \, \mu m}$|⁠ , with a |$\lt 1~{{\ \rm per\ cent}}$| contribution from |$\rm {3 \, \mu m}$| grains. Moreover, the astronomical silicates have a very low occurrence in the best fits, suggesting that they are not the most suited dust species to reproduce the silicate features in our sample. [ABSTRACT FROM AUTHOR]

Sizes of narrow emission line regions (NLRs) of active galactic nuclei (AGNs) could be estimated by [O  iii ] line luminosity L O3 through the known R NLRs− L O3 empirical relations. Unfortunately, it is not convenient to test the R NLRs− L O3 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 R fib of SDSS fibre-covered regions. Comparing R fib and R NLRs estimated by L O3, Type-2 AGNs with R fib > R NLRs (Sample-II) and with R fib < R NLRs (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 R S2 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 R S2 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. [ABSTRACT FROM AUTHOR]

The fourth-DR3 version (4FGL-DR3) of the Fermi -LAT catalogue of γ-ray sources contains ∼1000 objects at a galactic latitude | b | > 10° that are not identified with an optical counterpart. We performed a systematic study of these sources, focusing on 190 objects that have a unique X-ray counterpart in the available Swift /XRT observations. Optical counterparts were then selected, and optical spectra were found in the literature for 33 sources. We found that 21 could be classified as BL Lac objects. Among these, we were able to provide the redshift for eight of them, while for two others we established a lower limit to the redshift by detecting intervening absorption. The other 12 objects display optical spectra with prominent emission lines (0.036 <  z  < 1.65). These spectra are characterized by both broad and narrow emission lines, with the exception of three sources. One of these displays only broad emission lines, while the other two exclusively exhibit narrow lines. On the basis of the radio/optical flux ratio, all BL Lac objects in this study are radio-loud. Four sources out of the 12 with prominent emission lines can be classified as radio-loud, while at least five of the 12 sources with prominent lines are radio-quiet. This is somewhat unexpected, given the radio-loudness distribution of 4FGL-associated blazars. [ABSTRACT FROM AUTHOR]

NGC 4395 is a dwarf type 1 Seyfert galaxy with a possible intermediate-mass black hole of several |$\rm {10^4}$| solar masses in its centre. As a well-studied object, its broad-line region size has been measured via H  |$\rm {\alpha }$| time lag in numerous spectroscopic reverberation mapping (SRM) and narrow-band photometric reverberation mapping (PRM) campaigns. Here, we present its H  |$\rm {\alpha }$| time lag measurement using broad-band photometric data, with the application of our newly developed ICCF-Cut (Interpolation and Cross-Correlation Function - Cut) method as well as the javelin (Just Another Vehicle for Estimating Lags In Nuclei) and χ2 methods. Utilizing the minute-cadence multiband light curves obtained from the |$\rm {2}$| -m Faulkes Telescope North and |$\rm {10.4}$| -m Gran Telescopio Canarias telescopes in recent works, we measured its H  |$\rm {\alpha }$| lag as approximately 40–90 min from broad-band PRM. With the H  |$\rm {\alpha }$| emission line velocity dispersion, we calculated its central black hole mass as |$M_{\rm BH} = (8\pm 4) \times 10^3\ \mathrm{ M}_{\rm \odot }$|⁠. These results are comparable with previous results obtained by narrow-band PRM and SRM, providing further support to an intermediate-mass black hole in NGC 4395. In addition, our study also validates the ICCF-Cut as an effective method for broad-band PRM, which holds the potential for widespread application in the era of large multi-epoch, high-cadence photometric surveys. [ABSTRACT FROM AUTHOR]

We present the results of a search for extended emission-line regions (EELRs) ionized by extant or recently faded active galactic nuclei (AGNs), using [O III] narrow-band imaging and spectroscopic follow-up. The sample includes 198 galaxies in 92 strongly interacting or merging galaxy systems in the range of z  = 0.009–0.0285. Among these, three systems have EELRs extended beyond 10 kpc in projection from the nucleus detected in previous studies. We identify a single new distant emission region, projected 35 kpc from UGC 5941. Our optical spectrum does not detect He II, but its strong-line ratios put this in the same class as securely characterized EELR clouds. The nucleus of UGC 5941 is dominated by recent star formation, preventing detection of any weak ongoing AGN. Overall counts of distant EELRs in this and the previous TELPERION samples give incidence 2–5 per cent depending on galaxy and AGN selection, 20–50 times higher than the Galaxy Zoo EELR survey with its higher surface-brightness threshold and much larger input sample. AGNs in interacting and merging systems have an increased detection rate of 12 ± 6 per cent, while none are detected around non-interacting AGNs. Some of these AGNs are at luminosity low enough to require additional X-ray or far-infrared information to tell whether the EELR ionization level suggests long-term fading. [ABSTRACT FROM AUTHOR]

The soft excess in active galactic nuclei (AGNs) may arise through a combination of relativistic reflection and the effects of a warm corona at the surface of the accretion disc. Detailed examination of the soft excess can therefore constrain models of the transport and dissipation of accretion energy. Here, we analyse 34 XMM–Newton observations from 14 type 1 AGNs with the reXcor spectral model that self-consistently combines emission from a warm corona with relativistic reflection assuming a lamppost corona. The model divides accretion energy between the disc, the warm corona, and the lamppost. The XMM–Newton observations span a factor of 188 in Eddington ratio (λobs) and 350 in black hole mass, and we find that a warm corona is a significant contributor to the soft excess for 13 of the 14 AGNs with a mean warm corona heating fraction of 0.51. The reXcor fits reveal that the fraction of accretion energy dissipated in the lamppost is anticorrelated with λobs. In contrast, the relationship between λobs and both the optical depth and the heating fraction of the warm corona appears to transition from an anticorrelation to a correlation at λobs,t ≈ 0.15. Therefore, at least one other physical process in addition to the accretion rate is needed to explain the evolution of the warm corona. Overall, we find that a warm corona appears to be a crucial depository of accretion energy in AGNs across a broad range of λobs and black hole mass. [ABSTRACT FROM AUTHOR]

Aims. We study the X-ray power spectrum of active galactic nuclei (AGN) in order to investigate whether Seyfert I and II power spectra are similar or not and whether AGN variability depends on the mass and accretion rate of black holes as well as to compare the power spectra of AGN with the power spectra of Galactic X-ray black hole binaries. Method. We used 14–195 keV band light curves from the 157-month Swift/BAT hard X-ray survey, and we computed the mean power spectrum and excess variance of AGN in narrow black hole mass and AGN luminosity bins. We fitted a power-law model to the AGN power spectra, and we investigated whether the power spectrum parameters and the excess variance depend on the black hole mass, luminosity, and accretion rate of AGN. Results. We found the Seyfert I and Seyfert II power spectra to be identical, in agreement with AGN unification models. The mean AGN X-ray power spectrum has the same power-law like shape, with a slope of −1 in all AGN irrespective of their luminosity and black hole mass. We did not detect any flattening to a slope of zero at frequencies as low as 10−9 Hz. We detected an anti-correlation between the power spectral density function (PSD) amplitude and the accretion rate, similar to what has been seen in the past in the 2–10 keV band. This implies that the variability amplitude in AGN decreases with an increasing accretion rate. The universal AGN power spectrum is consistent with the mean 2–9 keV band Cyg X-1 power spectrum in its soft state. We detected a small difference in amplitude, but this is probably due to the difference in energy. Conclusions. The mean low-frequency AGN X-ray power spectrum is consistent with the extension of the mean 0.01–25 Hz Cyg X-1 power spectrum in its soft state to lower frequencies. We cannot prove that the mean AGN PSD is analogous to the mean Cyg X-1 PSD in its soft state, as we do not know the location of the high-frequency break in the hard X-ray AGN PSDs. However, if this is the case, then the accretion disc in AGN probably extends to the radius of the innermost circular stable orbit (as is probably the case with the black hole binaries in their soft state). The X-ray corona will then be located on top, illuminating the disc and producing the X-ray reflection and disc reverberation phenomena commonly observed in these objects. Furthermore, the agreement between the PSD amplitude in AGN and the Cyg X-1 (either in the soft or the hard state) over many decades in frequency indicates that the X-ray variability process is probably the same in all accreting objects, irrespective of the mass of the compact object. We plan to investigate this issue further in the near future. [ABSTRACT FROM AUTHOR]

Near IR spectroscopic reverberation of Active Galactic Nuclei (AGN) potentially allows the infrared (IR) broad line region (BLR) to be reverberated alongside the disc and dust continua, while the spectra can also reveal details of dust astro-chemistry. Here, we describe results of a short pilot study (17 near-IR spectra over a 183 d period) for Mrk 509. The spectra give a luminosity-weighted dust radius of 〈 R d,lum〉 = 186 ± 4 light-days for blackbody (large grain dust), consistent with previous (photometric) reverberation campaigns, whereas carbon and silicate dust give much larger radii. We develop a method of calibrating spectral data in objects where the narrow lines are extended beyond the slit width. We demonstrate this by showing our resultant photometric band light curves are consistent with previous results, with a hot dust lag at >40 d in the K band, clearly different from the accretion disc response at <20 d in the z band. We place this limit of 40 d by demonstrating clearly that the modest variability that we do detect in the H and K band does not reverberate on time-scales of less than 40 d. We also extract the Pa β line light curve, and find a lag which is consistent with the optical BLR H β line of ∼70–90 d. This is important as direct imaging of the near-IR BLR is now possible in a few objects, so we need to understand its relation to the better studied optical BLR. [ABSTRACT FROM AUTHOR]

The article titled "Correction to: Characterizing X-ray, UV, and optical variability in NGC 6814 using high-cadence Swift observations from a 2022 monitoring campaign" published in the Monthly Notices of the Royal Astronomical Society discusses a correction to a previous study on NGC 6814. The authors discovered that an outdated Calibration Database (CALDB) version was used in the original study, leading to significantly larger UV flux densities. The updated results show that the intrinsic AGN variability spectrum aligns with a standard accretion disc, except in the U band. The authors also discuss the inter-band continuum lags and suggest that a significant contribution from diffuse continuum emission in NGC 6814 may explain the observed discrepancies. The corrected data is publicly available through the NASA HEASARC Archive and Swift observatory websites. [Extracted from the article]

Supermassive black holes require a reservoir of cold gas at the centre of their host galaxy in order to accrete and shine as active galactic nuclei (AGN). Major mergers have the ability to drive gas rapidly inwards, but observations trying to link mergers with AGN have found mixed results due to the difficulty of consistently identifying galaxy mergers in surveys. This study applies deep learning to this problem, using convolutional neural networks trained to identify simulated post-merger galaxies from survey-realistic imaging. This provides a fast and repeatable alternative to human visual inspection. Using this tool, we examine a sample of ∼8500 Seyfert 2 galaxies (⁠|$L[\mathrm{O\, {\small III}}] \sim 10^{38.5 - 42}$|  erg s−1) at z < 0.3 in the Sloan Digital Sky Survey and find a merger fraction of |$2.19_{-0.17}^{+0.21}$|  per cent compared with inactive control galaxies, in which we find a merger fraction of |$2.96_{-0.20}^{+0.26}$|  per cent, indicating an overall lack of mergers among AGN hosts compared with controls. However, matching the controls to the AGN hosts in stellar mass and star formation rate reveals that AGN hosts in the star-forming blue cloud exhibit a ∼2 × merger enhancement over controls, while those in the quiescent red sequence have significantly lower relative merger fractions, leading to the observed overall deficit due to the differing M *–SFR distributions. We conclude that while mergers are not the dominant trigger of all low-luminosity, obscured AGN activity in the nearby Universe, they are more important to AGN fuelling in galaxies with higher cold gas mass fractions as traced through star formation. [ABSTRACT FROM AUTHOR]

We present a long-term X-ray study of a nearby Active Galactic Nucleus Mrk 6, utilizing observations from XMM–Newton, Suzaku, Swift , and NuSTAR observatories, spanning 22 years from 2001 to 2022. From timing analysis, we estimated variance, normalized variance, and fractional rms amplitude in different energy bands.The temporal study shows fractional rms amplitude (F var) below 10 per cent for the shorter time-scale (∼60 ks) and above 20 per cent for the longer time-scale (∼weeks). A complex correlation is observed between the soft (0.5–3.0 keV) and hard (3.0–10.0 keV) X-ray bands of different epochs of observations. This result prompts a detailed investigation through spectral analysis, employing various phenomenological and physical models on the X-ray spectra. Our analysis reveals a heterogeneous structure of the obscuring material surrounding Mrk 6. A partially ionized absorber exhibits a rapid change in location and extends up to the narrow-line regions or torus. In contrast, another component, located far from the central engine, remained relatively stable. During the observation period, the source luminosity in the 3.0–10.0 keV range varies between (3–15) × 1042 erg s−1. [ABSTRACT FROM AUTHOR]

Variability studies of active galactic nuclei are a powerful diagnostic tool in understanding the physical processes occurring in disc-jet regions, unresolved by direct imaging with currently available techniques. Here, we report the first attempt to systematically characterize intra-night optical variability (INOV) for a sample of seven apparently radio-quiet narrow-line Seyfert 1 galaxies (RQNLSy1s) that had shown recurring flaring at 37 GHz in the radio observations at Metsähovi Radio Observatory, indicating the presence of relativistic jets in them, but no evidence for relativistic jets in the recent radio observations of Karl G. Jansky Very Large Array at 1.6, 5.2, and 9.0 GHz. We have conducted a total of 28 intra-night sessions, each lasting ≥3 h for this sample, resulting in an INOV duty cycle (⁠|$\overline{\mathrm{ DC}} ~\sim$| 20 per cent) similar to that reported for γ-ray-NLSy1s (DC ∼ 25 per cent–30 per cent), that display blazar-like INOV. This in turn infers the presence of relativistic jet in our sample sources. Thus, it appears that even lower mass (M BH ∼ 106 M⊙) RQNLSy1 galaxies can maintain blazar-like activities. However, we note that the magnetic reconnection in the magnetosphere of the black hole can also be a viable mechanism to give rise to the INOV from these sources. [ABSTRACT FROM AUTHOR]

X-ray properties of active galactic nuclei (AGNs) depend on their underlying physical parameters, particularly the accretion rate. We identified eight reverberation-mapped AGNs with some of the largest known accretion rates without high-quality X-ray data. We obtained new Chandra ACIS-S X-ray observations and nearly simultaneous optical spectrophotometry to investigate the properties of these AGNs with extreme super-Eddington accreting massive black holes (SEAMBHs). We combined our new X-ray measurements with those of other reverberation-mapped AGNs, which have the best-determined masses and accretion rates. The trend of the steepening of the spectral slope between X-ray and optical-UV, αox, with increasing optical-UV luminosity, |$L_{\rm 2500{\mathring{\rm A}}}$|⁠ , holds true for even the most extreme SEAMBHs. One of our new SEAMBHs appears X-ray-weak for its luminosity, perhaps due to absorption associated with orientation effects involving a slim disc thought to be present in highly accreting systems. The correlation of the |$\rm 2\!-\!8~ keV$| X-ray photon index with the accretion rate also holds for the extreme SEAMBHs, which show some of the largest photon indices reported for AGNs. [ABSTRACT FROM AUTHOR]

Spatially resolved MaNGA's optical spectra of 1072 present-day lenticular (S0) galaxies, dimensionally reduced from a principal component analysis (PCA), are used to determine their radial activity structure shaped by any possible nebular ionization source. Activity profiles within |$1.5\,$| R e are examined in tandem with the mass, age, ellipticity, and kinematics of the stars, as well as environmental density. Among the results of this comparison, we find that the sign of the radial activity gradient of S0s is tightly related to their PCA classification, BPT designation, and star formation status. PCA-passive lenticulars often show low-level, flat activity profiles, although there is also a significant number of systems with positive gradients, while their less common active counterparts generally have negative gradients, usually associated with high SSFRs and, sometimes, moderate Seyfert emission. A fraction of the latter also shows radial activity profiles with positive gradients, which become more abundant with increasing stellar mass regardless of environmental density. Our analysis also reveals that the subset of active S0s with negative gradients experiences at all galactocentric radii a systematic reduction in its median activity level with stellar mass, consistent with expectations for main-sequence galaxies. In contrast, passive S0s with positive gradients show the opposite behaviour. Furthermore, systems whose activity is dominated by star formation are structurally rounder than the rest of S0s, while those classified as Seyfert exhibit higher rotational support. The possibility that negative and positive activity gradients in S0s may result from rejuvenation by two distinct types of minor mergers is raised. [ABSTRACT FROM AUTHOR]

It has been argued that SDSS J1430+2303 possesses a supermassive black hole binary that has been predicted to merge within a few months or three years from 2022 January. We have conducted follow-up optical spectroscopic observations of SDSS J1430+2303 with the KOOLS-IFU on the Seimei Telescope in 2022 May, June, and July, and 2023 April. The observed spectrum around Hα shows a central broad component ∼103 km s−1 blueshifted from the narrow Hα line, as well as a broader double-peaked component with a separation of ∼± 5 × 103 km s−1, similar to the spectrum reported in 2022 January. We investigate the variability of the complex broad Hα emission line relative to the continuum over the observation period. The continuum-normalized relative flux of the central broad component shows an increasing trend from 2022 May to July, which is interpreted to be caused by the decrease of the continuum; this is also supported by damping of the X-ray, UV, and optical light curves observed for the same period. From 2022 July to 2023 April, however, the central broad component decreased significantly. For the relative flux of the broader double-peaked component, no significant change appears at any epoch. These results suggest that the complicated broad line profile of SDSS J1430+2303 is generated from at least two distinct regions. While the central broad component originates from a broad-line region, the broader double-peaked component arises in the vicinity of the continuum source. [ABSTRACT FROM AUTHOR]

In the Hubble Space Telescope /Cosmic Origins Spectrograph spectrum of the Seyfert 1 galaxy 2MASX J14292507+4518318, we have identified a narrow absorption line outflow system with a velocity of −151 km s−1. This outflow exhibits absorption troughs from the resonance states of ions like C  iv , N  v , S  iv , and Si  ii , as well as excited states from C  ii * and Si  ii *. Our investigation of the outflow involved measuring ionic column densities and conducting photoionization analysis. These allow the total column density of the outflow to be estimated as log  N H = 19.84 cm−2, its ionization parameter to be log  U H = −2.0, and its electron number density to be log  n e = 2.75 cm−3. These measurements enabled us to determine the mass-loss rate and the kinetic luminosity of the outflow system to be |$\dot{M}$|  = 0.22  |$\mathrm{ M}_{\odot } \, \mathrm{ yr}^{-1}$| and |$\log \dot{E_{\mathrm{ K}}}$|  = 39.3 erg s−1, respectively. We have also measured the location of the outflow system to be at ∼275 pc from the central source. This outflow does not contribute to the active galactic nucleus (AGN) feedback processes due to the low ratio of the outflow's kinetic luminosity to the AGN's Eddington luminosity (⁠|$\dot{E_{\mathrm{ K}}}/{L_{\mathrm{ Edd}}}\approx 0.00025 {{\, \rm per\, cent}}$|⁠). This outflow is remarkably similar to the two bipolar lobe outflows observed in the Milky Way by XMM–Newton and Chandra. [ABSTRACT FROM AUTHOR]

We analyse the validity of optical diagnostic diagrams relying on emission-lines ratios and in the context of classifying Active Galactic Nuclei (AGNs) according to the cosmic metallicity evolution in the redshift range |$0 \le z \le 11.2$|⁠. In this regard, we fit the results of chemical evolution models (CEMs) to the radial gradients of the N/O abundances ratio derived through direct estimates of electron temperatures (T e-method) in a sample of four local spiral galaxies. This approach allows us to select representative CEMs and extrapolate the radial gradients to the nuclear regions of the galaxies in our sample, inferring in this way the central N/O and O/H abundances. The nuclear abundance predictions for theoretical galaxies from the selected CEMs, at distinct evolutionary stages, are used as input parameters in AGN photoionization models built with the Cloudy code. We found that standard BPT diagnostic diagrams are able to classify AGNs with oxygen abundances |$\rm 12+\log (O/H) \gtrsim 8.0$| [ |$(Z/Z_{\odot }) \gtrsim 0.2$| ] at redshift |$z \lesssim 4$|⁠. On the other hand, the He  ii λ4685/Hβ versus [N  ii ]λ6584/Hα diagram produces a reliable AGN classification independent of the evolutionary stage of these objects. [ABSTRACT FROM AUTHOR]

Narrow-line Seyfert 1 (NLSy1) galaxies are an enigmatic class of active galactic nuclei (AGN) that exhibit peculiar multiwavelength properties across the electromagnetic spectrum. For example, these sources have allowed us to explore the innermost regions of the central engine of AGN using X-ray observations and have also provided clues about the origin of relativistic jets considering radio and gamma-ray bands. Keeping in mind the ongoing and upcoming wide-field, multifrequency sky surveys, we present a new catalogue of NLSy1 galaxies. This was done by carrying out a detailed decomposition of >2 million optical spectra of quasars and galaxies from the Sloan Digital Sky Survey Data Release 17 (SDSS-DR17) using the publicly available software 'Bayesian AGN Decomposition Analysis for SDSS Spectra'. The catalogue contains 22656 NLSy1 galaxies which is more than twice the size of the previously identified NLSy1s based on SDSS-DR12. As a corollary, we also release a new catalogue of 52273 broad-line Seyfert 1 (BLSy1) galaxies. The estimated optical spectral parameters and derived quantities confirm the previously known finding of NLSy1 galaxies being AGN powered by highly accreting, low-mass black holes. We conclude that this enlarged sample of NLSy1 and BLSy1 galaxies will enable us to explore the low-luminosity end of the AGN population by effectively utilizing the sensitive, high-quality observations delivered by ongoing/upcoming wide-field sky surveys. The catalogue has been made public at https://www.ucm.es/blazars/seyfert. [ABSTRACT FROM AUTHOR]

We present the first results of a high-cadence Swift monitoring campaign (3–4 visits per day for 75 d) of the type 1.5 Seyfert galaxy NGC 6814 characterizing its variability throughout the X-ray and ultraviolet (UV)/optical wavebands. Structure function analysis reveals an X-ray power law (⁠|$\alpha =0.5^{+0.2}_{-0.1}$|⁠) that is significantly flatter than the one measured in the UV/optical bands (〈α〉 ≈ 1.5), suggesting different physical mechanisms driving the observed variability in each emission region. The structure function break-time is consistent across the UV/optical bands (〈τ〉 ≈ 2.3 d), suggesting a very compact emission region in the disc. Correlated short time-scale variability measured through cross-correlation analysis finds a lag–wavelength spectrum that is inconsistent with a standard disc reprocessing scenario (τ ∝ λ4/3) due to significant flattening in the optical wavebands. Flux–flux analysis finds an extremely blue active galactic nucleus (AGN) spectral component (F ν ∝ λ−0.85) that does not follow a standard accretion disc profile (F ν ∝ λ−1/3). While extreme outer disc truncation (R out = 202 ± 5 rg) at a standard accretion rate (⁠|$\dot{m}_{\mathrm{Edd}}=0.0255\pm 0.0006$|⁠) may explain the shape of the AGN spectral component, the lag–wavelength spectrum requires more modest truncation (⁠|$R_{\mathrm{out}}=1382^{+398}_{-404}\,r_g$|⁠) at an extreme accretion rate (⁠|$\dot{m}_{\mathrm{Edd}}=1.3^{+2.1}_{-0.9}$|⁠). No combination of parameters can simultaneously explain both results in a self-consistent way. Our results point towards the possibility of a non-standard disc geometry in NGC 6814. [ABSTRACT FROM AUTHOR]

We study the connection between the variations in the far-ultraviolet (FUV), near-ultraviolet (NUV), and X-ray band emission from NGC 4051 using 4 d long AstroSat observations performed during 5–9 June 2016. NGC 4051 showed rapid variability in all three bands with the strongest variability amplitude in the X-ray band (⁠|$F_{\mathrm{ var}} \sim 37~{{\ \rm per\ cent}}$|⁠) and much weaker variability in the UV bands (⁠|$F_{\mathrm{ var}} \sim 3{\!-\!}5~{{\ \rm per\ cent}}$|⁠). Cross-correlation analysis performed using interpolated cross-correlation functions and discrete cross-correlation functions revealed a robust correlation (∼0.75) between the UV and X-ray light curves. The variations in the X-ray band are found to lead those in the FUV and NUV bands by ∼7.4 ks and ∼24.2 ks, respectively. The UV lags favour the thermal disc reprocessing model. The FUV and NUV bands are strongly correlated (∼0.9) and the variations in the FUV band lead those in the NUV band by ∼13 ks. Comparison of the UV lags found using the AstroSat observations with those reported earlier and the theoretical model for thermal reverberation timelag suggests a possible change in either the geometry of the accretion disc/corona or the height of the corona. [ABSTRACT FROM AUTHOR]

Context. Markarian (Mrk) galaxies, revealed due to their ultraviolet excess are very famous; they play a significant role in many astro-physical problems and come in a variety of types: Seyferts (Sys), low-ionization narrow emission-line regions (LINERs), starbursts (SBs), blue compact dwarf galaxies (BCDGs), as well as some quasars (QSOs) and blazars. They also appear as sources of non-optical radiation, such as gamma-ray, X-ray, ultraviolet (UV), infrared (IR), and radio, including some extremely high-energy gamma-ray sources (Mrk 421, Mrk 501) and very high-luminosity IR galaxies (Mrk 231). Aims. The classifications of Mrk galaxies for activity types have been carried out based on old mostly poor-quality and inhomoge-neous spectra (relatively low-resolution photographic spectra and low S/N spectra). The Sloan Digital Sky Surveys (SDSS) provides ~90% of the existing medium-resolution spectra, and is a relevant homogeneous database for classification of galaxies. Our aim was to obtain homogeneous classifications of Mrk galaxies by means of the SDSS spectra. Methods. Based on our work on the classification of newly revealed objects from various recent catalogs, we developed a fine classification scheme for activity types based on the homogeneous database of the SDSS spectroscopy. This scheme was applied to Mrk galaxies having spectra in the SDSS (779 out of 1544, 50.45%). Results. As a result, 779 Mrk galaxies now have homogeneous optical spectral classification that can be used for further studies and statistics of their physical and spatial properties. We revealed 2 QSOs, 49 classical Seyferts (broad-line Seyferts 1, BLS1s), 17 narrow-line Seyferts 1 (NLS1s), 4 Sy2s, 12 LINERs, 11 active galactic nuclei (AGN) without a definite type, 31 Composite spectrum objects, and 533 HII/Starbursts. Due to low-quality spectra, some objects were left without definite activity types and were classified as emission or absorption galaxies. [ABSTRACT FROM AUTHOR]

The prototypical powerful FR II radio galaxy Cygnus A fits extremely well into the quasar/radio galaxy unified model: high polarization with an angle almost perpendicular to the radio jet and polarized flux showing broad permitted lines. It has been claimed that ionized gas in the torus reveals a very clear torus shape via Bremmstrahlung emission. We rule out the later with an energetic argument, and we constrain the molecular and atomic gas properties with existing observations. The atomic absorption against the core has been shown to match the X-ray column only if the spin temperature is an implausible T s = 1 × 106 K. This points to a molecular medium for the X-ray column |$\log (N_{\rm H} ~[\rm {cm^{-2}}]) \sim 23.5$|⁠. Yet not low-J CO absorption is detected to sensitive limits. The non-detection is surprising given that this powerful radio galaxy hosts a luminous, dust-obscured active nucleus and copious warm molecular hydrogen. These conditions suggest a detectable level of emission. Furthermore, the torus X-ray column density suggests detectable absorption. We explore various possibilities to explain the lack of a signature from warm CO (200–250 K). Specifically, that the radiative excitation by the radio core renders low-J CO absorption below current sensitivities, and that high-J levels are well populated and conducive to producing absorption. We test this hypothesis using archival Hershel /SPIRE FTS observations of Cygnus A of high-J CO lines (14 ≥ J ≥ 4 transitions). Still high-J CO lines are not detected. We suggest that ALMA observations near its high frequency limit can be critical to obtain the signature of molecular line of the torus of Cygnus A. [ABSTRACT FROM AUTHOR]