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We studied the ionized gas in the inner region (⁠|$\sim$| |$680\times 470$| pc2) of the galaxy NGC 6868 using Gemini/GMOS (Gemini Multi-Object Spectrograph) integral field unit observations. Channel maps reveal complex kinematics and morphology, indicating multiple processes at work in NGC 6868. Through emission-line fitting, we identified two ubiquitous components in our data: a narrow (⁠|$\sigma \sim 110$| km s |$^{-1}$|⁠) tracing an ionized gas disc and a broad component (⁠|$\sigma \sim 300$| km s |$^{-1}$|⁠) mainly associated with inflowing/outflowing gas. The derived V -band reddening shows a spatial distribution consistent with that obtained from stellar population synthesis, although with generally higher values. For the first time, we measured the electron temperature in NGC 6868, finding values ranging from |$\sim$| 14 000 K in the central region to |$\gtrsim 20000$| K with an outward increasing temperature gradient. The electron density map exhibits an inverse relationship, with central values reaching |$N_e\sim 4000$| cm–3 for the broad component decreasing to |$N_e\sim 100$| cm–3 towards the edges of the field of view. Using BPT diagrams, we found that all spaxels are consistent with both active galactic nucleus (AGN) and shock ionization. However, when this information is combined with our kinematic and temperature findings, and further supported by the WHAN diagram, we argue that an AGN is the dominant ionization mechanism in the central region of NGC 6868, while the extended outer component is ionized by a combination of hot low-mass evolved stars and shocks. According to our findings, shocks play a significant role in the ionization balance of this galaxy. [ABSTRACT FROM AUTHOR]

We present here radiosed , a Bayesian inference framework tailored to modelling and classifying broad-band radio spectral energy distributions (SEDs) using only data from publicly released, large-area surveys. We outline the functionality of radiosed , with its focus on broad-band radio emissions that can trace kiloparsec-scale absorption within both the radio jets and the circumgalactic medium of active galactic nuclei (AGN). In particular, we discuss the capability of radiosed to advance our understanding of AGN physics and composition within youngest and most compact sources, for which high-resolution imaging is often unavailable. These young radio AGN typically manifest as peaked spectrum sources that, before radiosed , were difficult to identify owing to the large, broad-band frequency coverage typically required, and yet they provide an invaluable environment for understanding AGN evolution and feedback. We discuss the implementation details of radiosed , and we validate our approach against both synthetic and observational data. Since the surveys used are drawn from multiple epochs of observation, we also consider the output from radiosed in the context of AGN variability. Finally, we show that radiosed recovers the expected SED shapes for a selection of well-characterized radio sources from the literature, and we discuss avenues for further study of these and other sources using radio SED fitting as a starting point. The scalability and modularity of this framework make it an exciting tool for multiwavelength astronomers as next-generation telescopes begin several all-sky surveys. Accordingly, we make the code for radiosed , which is written in python , available on GitHub. [ABSTRACT FROM AUTHOR]

We derive a mean attenuation curve out to the rest-frame extreme ultraviolet (EUV) for 'BAL dust' – the dust causing the additional extinction of active galactic nuclei (AGNs) with broad absorption lines (BALQSOs). In contrast to the normal, relatively flat, mean AGN attenuation curve, BAL dust is well fit by a steeply rising, SMC-like curve. We confirm the shape of the theoretical Weingartner & Draine SMC curve out to 700 Angstroms but the drop in attenuation at still shorter wavelengths is less than predicted. The similar SMC-like attenuation curve for low-ionization BALQSOs (LoBALs) does not support the idea that they are an early phase in the life of an AGN when it is breaking out of a cocoon of star-forming dust. Although the attenuation is only |$E(B - V) \sim 0.03\!-\!0.05$| in the optical, it rises to one magnitude in the EUV, which is an optimum value for radiative acceleration of dusty gas. Because the spectral energy distribution of AGNs peaks in the EUV, the force on the dust dominates the acceleration of BAL gas. Although the shape of the attenuation curve for LoBALs is similar to the shape for HiBALs, the LoBALs on average show negative attenuation in the optical. This is naturally explained if there is more light scattered into our line of sight in LoBALs compared with non-BALQSOs. We suggest that this and partial covering are causes when attenuation curves appear to be steeper in the UV than an SMC curve. [ABSTRACT FROM AUTHOR]

We investigate the thermodynamics of close encounters between stellar mass black holes (BHs) in the gaseous discs of active galactic nuclei (AGNs), during which binary black holes (BBHs) may form. We consider a suite of 2D viscous hydrodynamical simulations within a shearing box prescription using the Eulerian grid code athena ++. We study formation scenarios where the fluid is either an isothermal gas or an adiabatic mixture of gas and radiation in local thermal equilibrium. We include the effects of viscous and shock heating, as well as optically thick cooling. We co-evolve the embedded BHs with the gas, keeping track of the energetic dissipation and torquing of the BBH by gas and inertial forces. We find that compared to the isothermal case, the minidiscs formed around each BH are significantly hotter and more diffuse, though BBH formation is still efficient. We observe massive blast waves arising from collisions between the radiative minidiscs during both the initial close encounter and subsequent periapsis periods for successfully bound BBHs. These 'disc novae' have a profound effect, depleting the BBH Hill sphere of gas and injecting energy into the surrounding medium. In analysing the thermal emission from these events, we observe periodic peaks in local luminosity associated with close encounters/periapses, with emission peaking in the optical/near-infrared (IR). In the AGN outskirts, these outbursts can reach 4 per cent of the AGN luminosity in the IR band, with flares rising over 0.5–1 yr. Collisions in different disc regions, or when treated in 3D with magnetism, may produce more prominent flares. [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]

For the first time, a calibration between the He  i |$\lambda 5876$| /H  |$\beta$| emission line ratio and the helium abundance y = 12 + log(He/H) for Narrow line regions of Seyfert 2 Active Galactic Nuclei is proposed. In this context, observational data (taken from the SDSS-DR15 and from the literature) and direct abundance estimates (via the |$T_{\rm e}$| -method) for a sample of 65 local (⁠|$z \: \lt \: 0.2$|⁠) Seyfert 2 nuclei are considered. The resulting calibration estimates the y abundance with an average uncertainty of 0.02 dex. Applying our calibration to spectroscopic data containing only strong emission lines, it yields a helium abundance distribution similar to that obtained via the |$T_{\rm e}$| -method. Some cautions must be considered to apply our calibration for Seyfert 2 nuclei with high values of electron temperature (⁠|${\gtrsim} 20\, 000$|  K) or ionization parameter (⁠|$\log U \ \gt\ {-}2.0$|⁠). [ABSTRACT FROM AUTHOR]

The relation between nuclear star clusters (NSCs) and the growth of the central supermassive black holes (SMBHs), as well as their connection to the properties of the host galaxies, is crucial for understanding the evolution of galaxies. Recent observations have revealed that about 10 per cent of nucleated galaxies host hybrid nuclei, consisting of both NSCs and accreting SMBHs that power active galactic nuclei (AGNs). Motivated by the potential of the recently published multiwavelength data sets from LeMMINGs survey, here we present the most thorough investigation to date of the incidence of hybrid nuclei in a large sample of 100 nearby nucleated galaxies (10 E, 25 S0, 63 S, and 2 Irr), covering a wide range in stellar mass (⁠|$M_{*,\rm gal} \sim 10^{8.7}-10^{12}~\rm M_{\odot }$|⁠). We identify the nuclei and derive their properties by performing detailed 1D and 2D multicomponent decompositions of the optical and near-infrared HST stellar light distributions of the galaxies using Sérsic and core-Sérsic models. Our AGN diagnostics are based on homogeneously derived nuclear 1.5 GHz e -MERLIN radio, Chandra X-ray (0.3–10 keV), and optical emission-line data. We determine the nucleation fraction (⁠|$f_{\rm nuc}$|⁠) as the relative incidence of nuclei across the LeMMINGs HST sample and find |$f_{\rm nuc} =~$| 100/149 (= 67 |$\pm$| 7 per cent), confirming previous work, with a peak value of |$49/56~(= 88 \pm 13$|  per cent) at bulge masses |$M_{*,\rm bulge}\sim 10^{9.4}- 10^{10.8}~ \rm M_{\odot }$|⁠. We identify 30 nucleated LeMMINGs galaxies that are optically active, radio-detected, and X-ray luminous (⁠|$L_\textnormal {X} \gt 10^{39}$| erg s |$^{-1}$|⁠). This indicates that our nucleated sample has a lower limit |$\sim$| 30 per cent occupancy of hybrid nuclei, which is a function of |$M_{*,\rm bulge}$| and |$M_{*,\rm gal}$|⁠. We find that hybrid nuclei have a number density of |$(1.5 \pm 0.4)\times 10^{-5}$|  Mpc |$^{-3}$|⁠ , are more common at |$M_{*,\rm gal}\sim 10^{10.6}- 10^{11.8}~\rm M_{\odot }$| and occur, at least, three times more frequently than previously reported. [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]

Red Geysers are galaxies with low-star formation rates and galactic scale ionized outflows likely driven by low-luminosity active galactic nuclei (AGN). We investigated the impact of AGN winds on the oxygen abundance using integral field spectroscopic data from Mapping Nearby Galaxies for Red Geysers, control galaxies (quiescent galaxies without outflows), and AGN hosts within the inner 1.5 kpc radius. Red Geyser galaxies have higher W |$_{80}$| values compared to those of AGN and controls, with 64 per cent showing W |$_{80}\gt 500$|  km s |$^{-1}$| that is indicative of outflow. Only 40 per cent of controls and 31 per cent of AGNs reach this value. We found a small tendency of the oxygen abundance distribution of controls to be biased towards higher values than those of Red Geysers. However, Red Geysers do not show a correlation between H |$\alpha$| width (parametrized by the W |$_{\rm 80}$|⁠) and oxygen abundance, which indicates that AGN winds are not significantly impacting the chemical abundance of the nuclear region of these galaxies. The oxygen abundance distribution mean value for the tree samples is |$\rm 12+log(O/H)\sim$| 8.7 (⁠|$\mathit{Z}\sim \rm Z_{\odot })$|⁠. On the other hand, AGN hosts show a positive correlation between W |$_{80}$| and O/H which could be due to star formation that outflows from the active nuclei could induce; or to the reservoir of gas that makes the nucleus active, and its is also used in the star formation. [ABSTRACT FROM AUTHOR]

The nature of the interaction between active galactic nuclei (AGNs) and their host galaxies remains an unsolved question. Therefore, conducting an AGN census is valuable for AGN research. Nevertheless, a significant fraction of AGNs are obscured by their environment, which blocks UV and optical emissions due to the dusty torus surrounding the central supermassive black hole (SMBH). To overcome this challenge, mid-infrared (IR) surveys have emerged as a valuable tool for identifying obscured AGNs, as the obscured light is re-emitted in this range. With its high sensitivity, the JWST uncovered more fainter objects than previous telescopes. By applying the SED fitting, this work investigates AGN candidates in JWST Cosmic Evolution Early Release Science (CEERS) fields. We identified 42 candidates; 30 of them are classified as composites (⁠|$0.2\le f_{\text{AGN, IR}} < 0.5$|⁠), and 12 of them are AGNs (⁠|$f_{\text{AGN, IR}}\ge 0.5$|⁠). We report the AGN luminosity contributions and AGN number fractions as a function of redshift and total infrared luminosity, showing that previously reported increasing relations are not apparent in our sample due to the sample size. We also extend the previous results on ultraluminous infrared galaxies (ULIRGs, |$L_{\rm TIR}\ge 10^{12} L_{\odot }$|⁠) to less luminous AGNs, highlighting the power of JWST. [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]

Environmental effects are believed to play an important yet poorly understood role in triggering accretion events onto the supermassive black holes (SMBHs) of galaxies (active galactic nuclei; AGNs). Massive clusters, which represent the densest structures in the Universe, provide an excellent laboratory to isolate environmental effects and study their impact on black hole growth. In this work, we critically review observational evidence for the preferential activation of SMBHs in the outskirts of galaxy clusters. We develop a semi-empirical model under the assumption that the incidence of AGN in galaxies is independent of environment. We demonstrate that the model is broadly consistent with recent observations on the AGN halo occupation at z = 0.2, although it may overpredict satellite AGN in massive haloes at that low redshift. We then use this model to interpret the projected radial distribution of X-ray sources around high redshift (z ≈ 1) massive (⁠|$\gt 5 \times 10^{14} \, M_\odot$|⁠) clusters, which show excess counts outside their virial radius. Such an excess naturally arises in our model as a result of sample variance. Up to 20  per cent of the simulated projected radial distributions show excess counts similar to the observations, which are however, because of background/foreground AGN and hence, not physically associated with the cluster. Our analysis emphasizes the importance of projection effects and shows that current observations of z ≈ 1 clusters remain inconclusive on the activation of SMBHs during infall. [ABSTRACT FROM AUTHOR]

We present Very Long Baseline Array observations of radio continuum and OH line emission toward the OH megamaser (OHM) galaxy IRAS 01298−0744. We recover over 82% of the OH line emission seen in single-dish observations, including multiple strong OH line components and the broad shallow line profile spanning over 1000 km s−1. The OH emission spatially has four compact components, as well as diffuse emission, and the 3σ signals are distributed in a rectangular region with size of ∼40 × 30 mas. The spatial-velocity structure is complex and is consistent with that from HCN and HCO+ lines in the literature, indicating that the nuclear region of this source is likely still in the merging process characterized by intense nuclear activities. The multiple strong OH peaks are blue-shifted compared to dense millimetre-wave molecular gas tracers, but similar to optical Na I absorption. This suggests that the compact masers might be in an outflow driven by an active galactic nucleus or starburst. We have detected compact radio continuum emissions adjacent to the maser positions with a brightness temperature of around 3 × 106 K, similar to other OHM galaxies with very-long-baseline interferometry observations in the literature, which is consistent with a starburst origin. [ABSTRACT FROM AUTHOR]

The detection of blueshifted absorption lines likely associated with ionized iron K-shell transitions in the X-ray spectra of many active galactic nuclei (AGNs) suggests the presence of a highly ionized gas outflowing with mildly relativistic velocities (0.03c–0.6c) named ultra-fast outflow (UFO). Within the SUBWAYS project, we characterized these winds starting from a sample of 22 radio-quiet quasars at an intermediate redshift (0.1 ≤ z ≤ 0.4) and compared the results with similar studies in the literature on samples of local Seyfert galaxies (i.e., 42 radio-quiet AGNs observed with XMM-Newton at z ≤ 0.1) and high redshift radio-quiet quasars (i.e., 14 AGNs observed with XMM-Newton and Chandra at z ≥ 1.4). The scope of our work is a statistical study of UFO parameters and incidence considering the key physical properties of the sources, such as supermassive black hole (SMBH) mass, bolometric luminosity, accretion rates, and spectral energy distribution (SED) with the aim of gaining new insights into the UFO launching mechanisms. We find indications that highly luminous AGNs with a steeper X-ray/UV ratio, αox, are more likely to host UFOs. The presence of UFOs is not significantly related to any other AGN property in our sample. These findings suggest that the UFO phenomenon may be transient. Focusing on AGNs with UFOs, other important findings from this work include: (1) faster UFOs have larger ionization parameters and column densities; (2) X-ray radiation plays a more crucial role in driving highly ionized winds compared to UV; (3) the correlation between outflow velocity and luminosity is significantly flatter than what is expected for radiatively driven winds; (4) more massive black holes experience higher wind mass losses, suppressing the accretion of matter onto the black hole; (5) the UFO launching radius is positively correlated with the Eddington ratio. Furthermore, our analysis suggests the involvement of multiple launching mechanisms, including radiation pressure and magneto-hydrodynamic processes, rather than pointing to a single, universally applicable mechanism. [ABSTRACT FROM AUTHOR]

We investigate close encounters by stellar mass black holes (BHs) in the gaseous discs of active galactic nuclei (AGNs) as a potential formation channel of binary black holes (BBHs). We perform a series of 2D isothermal viscous hydrodynamical simulations within a shearing box prescription using the Eulerian grid code Athena++. We co-evolve the embedded BHs with the gas keeping track of the energetic dissipation and torquing of the BBH by gas gravitation and inertial forces. To probe the dependence of capture on the initial conditions, we discuss a suite of 345 simulations spanning BBH impact parameter (b) and local AGN disc density (ρ0). We identify a clear region in b − ρ0 space where gas assisted BBH capture is efficient. We find that the presence of gas leads to strong energetic dissipation during close encounters between unbound BHs, forming stably bound eccentric BBHs. We find that the gas dissipation during close encounters increases for systems with increased disc density and deeper periapsis passages r p, fitting a power law such that |$\Delta E \propto \rho _0^{\alpha }r_{\mathrm{p}}^{\beta }$|⁠ , where {α, β} = {1.01 ± 0.04, −0.43 ± 0.03}. Alternatively, the gas dissipation is approximately Δ E  = 4.3 M d v H v p, where M d is the mass of a single BH minidisc just prior to the encounter when the binary separation is 2 r H (two binary Hill radii), v H and v p are the relative BH velocities at 2 r H and at the first closest approach, respectively. We derive a prescription for capture which can be used in semi-analytical models of AGN. We do not find the dissipative dynamics observed in these systems to be in agreement with the simple gas dynamical friction models often used in the literature. [ABSTRACT FROM AUTHOR]

Although flux variability is one of the defining properties of accretion flows on to supermassive black holes, its dependence on physical parameters such as the mass of the compact object and the Eddington ratio remains under discussion. In this paper, we address this issue using the structure function statistic to measure the variability at X-ray wavelengths of a sample of optically selected QSOs with available black hole masses and Eddington ratios. We present a new Bayesian methodology for estimating the structure function tailored to the Poisson nature of the X-ray data. This is applied to 15 548 SDSS DRQ16 QSOs with repeat observations in the XMM – Newton archive and/or the SRG/eROSITA All Sky Survey. The X-ray structure function monotonically increases to time intervals of about 10–15 yrs, consistent with scenarios in which instabilities of the accretion disc contribute to the X-ray variability on long time-scales. Additionally, there is evidence that the amplitude of the stochastic X-ray flux variations rises with decreasing black hole mass and Eddington ratio. This finding imposes stringent constraints on empirical models of Active Galactic Nuclei variability derived from local samples, emphasizing the significance of high-redshift population studies for comprehending the stochastic flux variations in active black holes. [ABSTRACT FROM AUTHOR]

In this work we used a sample of 20 variable active galactic nuclei at 0.3 < z < 0.8 from the Ultra-VISTA survey to test whether their emission in the near-infrared (NIR) is consistent with emission from the dusty torus or the accretion disc, and whether the radius–luminosity relation found for local sources, is also seen when we consider sources from our sample. We carried out a spectral energy distribution analysis and conclude that 14 of the 20 sources have a variable component dominated by the dusty torus, and four have a variable component dominated by the accretion disc and two sources give uncertain results. Correcting for the disc contamination in the observed-frame Ks band, however, allowed us to determine dust lags for 13 sources after performing cross-correlation analysis. Special care was taken to consider lags that were not biased by seasonal gaps. Our determined lags are systematically found below the radius–luminosity relationship determined for local sources. Following previous works, we introduce an empirical relation that corrects lags by the rest-frame wavelength of the band that samples the dust emission, as shorter wavelengths arise from hotter regions of the torus. When the correction is introduced, our results are consistent with previous findings. We finally discuss whether other intrinsic parameters might also contribute to this effect and how these corrections will impact future large optical and NIR surveys. [ABSTRACT FROM AUTHOR]

Alongside the recent increase in discoveries of tidal disruption events (TDEs) have come an increasing number of ambiguous nuclear transients (ANTs). These ANTs are characterized by hot blackbody-like UV/optical spectral energy distributions (SEDs) and smooth photometric evolution, often with hard power law-like X-ray emission. ANTs are likely exotic TDEs or smooth flares originating in active galactic nuclei (AGNs). While their emission in the UV/optical and X-ray has been relatively well-explored, their infrared (IR) emission has not been studied in detail. Here, we use the NEOWISE mission and its low-cadence mapping of the entire sky to study mid-IR dust reprocessing echoes of ANTs. We study 19 ANTs, finding significant MIR flares in 18 objects for which we can estimate an IR luminosity and temperature evolution. The dust reprocessing echoes show a wide range in IR luminosities (∼1042–1045 erg s−1) with blackbody temperatures largely consistent with sublimation temperature of graphite grains. Excluding the two sources possibly associated with luminous supernovae (ASASSN-15lh and ASASSN-17jz), the dust covering fractions (f c ) for detected IR flares lie between 0.05 and 0.91, with a mean of f c = 0.29 for all ANTs (including limits) and f c = 0.38 ± 0.04 for detections. These covering fractions are much higher than optically selected TDEs and similar to AGNs. We interpret the high covering fractions in ANT host galaxies as evidence for the presence of a dusty torus. [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]

In this paper, we presented a detailed analysis of the Sloan Digital Sky Survey optical spectrum of a new sub-kpc scale dual AGN candidate SDSS J222428.53+261423.2 (=SDSS J2224). The target is one of the few AGNs with all the optical narrow emission lines characterized by double-peaked profiles and with peak separations in velocity units of about 930 km s−1. If the double-peaked narrow emission lines (DPNELs) are due to a dual AGN in SDSS J2224, the estimated physical separation between the two cores is about 500 pc. Meanwhile, three alternative explanations are also discussed in this paper, however, we can not find solid evidence to completely rule them out. Our results support the presence of a sub-kpc dual AGN with DPNELs in all lines, indicating a key episode of galaxy merging evolution at sub-kpc scale. [ABSTRACT FROM AUTHOR]

We report the discovery of Swift J221951−484240 (hereafter: J221951), a luminous slow-evolving blue transient that was detected by the Neil Gehrels Swift Observatory Ultraviolet/Optical Telescope (Swift /UVOT) during the follow-up of gravitational wave alert S190930t, to which it is unrelated. Swift /UVOT photometry shows the UV spectral energy distribution of the transient to be well modelled by a slowly shrinking blackbody with an approximately constant temperature of T ∼ 2.5 × 104 K. At a redshift z  = 0.5205, J221951 had a peak absolute magnitude of Mu,AB  = −23 mag, peak bolometric luminosity |$L_{max}=1.1\times 10^{45}~{\rm erg\, s}^{-1}$| and a total radiated energy of E > 2.6 × 1052 erg. The archival Wide-field Infrared Survey Explorer IR photometry shows a slow rise prior to a peak near the discovery date. Spectroscopic UV observations display broad absorption lines in N   v and O   vi , pointing towards an outflow at coronal temperatures. The lack of emission in the higher H α lines, N  i and other neutral lines is consistent with a viewing angle close to the plane of the accretion or debris disc. The origin of J221951 cannot be determined with certainty but has properties consistent with a tidal disruption event and the turn-on of an active galactic nucleus. [ABSTRACT FROM AUTHOR]

Hierarchical black hole (BH) mergers in active galactic nuclei (AGNs) are unique among formation channels of binary black holes (BBHs) because they are likely associated with electromagnetic counterparts and can efficiently lead to the mass growth of BHs. Here, we explore the impact of gas accretion and migration traps on the evolution of BBHs in AGNs. We have developed a new fast semi-analytic model, that allows us to explore the parameter space while capturing the main physical processes involved. We find that an effective exchange of energy and angular momentum between the BBH and the surrounding gas (i.e., gas hardening) during inspiral greatly enhances the efficiency of hierarchical mergers, leading to the formation of intermediate-mass BHs (up to 104 M⊙) and triggering spin alignment. Moreover, our models with efficient gas hardening show both an anticorrelation between the BBH mass ratio and the effective spin and a correlation between the primary BH mass and the effective spin. In contrast, if gas hardening is inefficient, the hierarchical merger chain is already truncated after the first two or three generations. We compare the BBH population in AGNs with other dynamical channels as well as isolated binary evolution. [ABSTRACT FROM AUTHOR]

Context. The infrared (IR) range is extremely useful in the context of chemical abundance studies of the gas-phase interstellar medium (ISM) due to the large variety of ionic species traced in this regime, the negligible effects from dust attenuation or temperature stratification, and the amount of data that has been and will be released in the coming years. Aims. Taking advantage of available IR emission lines, we analysed the chemical content of the gas-phase ISM in a sample of 131 star-forming galaxies (SFGs) and 73 active galactic nuclei (AGNs). In particular, we derived the chemical content via their total oxygen abundance in combination with nitrogen and sulphur abundances, and with the ionisation parameter. Methods. We used a new version of the code HII-CHI-MISTRY-IR v3.1, which allowed us to estimate log(N/O), 12+log(O/H), log(U) and, for the first time, 12+log(S/H) from IR emission lines, which can be applied to both SFGs and AGNs. We tested whether the estimates from this new version, which only considers sulphur lines for the derivation of sulphur abundances, are compatible with previous studies. Results. While most of the SFGs and AGNs show solar log(N/O) abundances, we find a large spread in the log(S/O) relative abundances. Specifically, we find extremely low log(S/O) values (1/10 solar) in some SFGs and AGNs with solar-like oxygen abundances. This result warns against the use of optical and IR sulphur emission lines to estimate oxygen abundances when no prior estimation of log(S/O) is provided. [ABSTRACT FROM AUTHOR]

In this paper, very blue-shifted broad Hα with a shifted velocity of ∼2200 km s–1 is reported in the low-redshift type-1.9 active galactic nucleus (AGN) SDSS J1052+1036. Blue-shifted broad emission lines may arise owing to the presence of a rotating gas disc around a central black hole (BH), but may also be a signature of rare phenomena such as the gravitational wave recoil of a supermassive BH (rSMBH) or the presence of a binary BH (BBH) system. Here, owing to the higher shifted velocity of the stronger and wider blue-shifted broad Hα, the BBH system is disfavoured. Meanwhile, if this object contains a rSMBH, intrinsic obscuration with E (B – V) ≤ 0.6 should lead to a detectable broad Hβ, indicating that the rSMBH scenario is not preferred. We find that the blue-shifted broad Hα can be well explained by emission from an AGN disc, indicating that SDSS J1052+1036 is likely a disc-emitting AGN. In order to determine which scenario, a rSMBH or a disc-emitter, is preferred, a re-observed spectrum in 2025 could provide robust clues, with a disc-emitter probably leading to clear variations of peak positions, peak separations, and/or peak intensity ratios in broad Hα, but with a rSMBH scenario probably leading to no variations of peak separations in broad Hα. [ABSTRACT FROM AUTHOR]

The active galactic nucleus (AGN) disc has been proposed as a potential channel for the merger of binary black holes. The population of massive stars and black holes in AGN discs captured from the nuclei cluster plays a crucial role in determining the efficiency of binary formation and final merger rate within the AGN discs. In this paper, we investigate the capture process using analytical and numerical approaches. We discover a new constant integral of motion for one object's capture process. Applying this result to the whole population of the nuclei cluster captured by the AGN disc, we find that the population of captured objects depends on the angular density and eccentricity distribution of the nuclei clusters and is effectively independent of the radial density profile of the nuclei cluster and disc models. An isotropic nuclei cluster with thermal eccentricity distribution predicts a captured profile d N /d r  ∝  r −1/4. The captured objects are found to be dynamically crowded within the disc. Direct binary formation right after the capture would be promising, especially for stars. The conventional migration traps that help pile up single objects in AGN discs for black hole mergers might not be required. [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]

The finding of active galactic nuclei (AGNs) in dwarf galaxies has important implications for galaxy evolution and supermassive black hole formation models. Yet, how AGNs in dwarf galaxies form is still debated, in part due to scant demographics. We use the MaNGA survey, comprising ∼10 000 galaxies at z < 0.15, to identify AGN dwarf galaxies using a spaxel-by-spaxel classification in three spatially-resolved emission-line diagnostic diagrams (the [N  ii] -, [S  ii ]-, and [O  i ]-BPT) and the WHAN diagram. This yields a sample of 664 AGN dwarf galaxies, the largest to date, and an AGN fraction of |$\sim 20~{{\ \rm per\ cent}}$| that is significantly larger than that of single-fibre-spectroscopy studies (i.e. |$\sim 1~{{\ \rm per\ cent}}$|⁠). This can be explained by the lower bolometric luminosity (<1042 erg s−1) and accretion rate (sub-Eddington) of the MaNGA AGN dwarf galaxies. We additionally identify 1176 SF-AGNs (classified as star-forming in the [N  ii ]-BPT but as AGNs in the [S  ii ]- and [O  i ]-BPT), 122 Composite, and 173 LINER sources. The offset between the optical centre of the galaxy and the median position of the AGN spaxels is more than 3 arcsec for ∼62% of the AGNs, suggesting that some could be off-nuclear. We also identify seven new broad-line AGNs with log M BH  = 5.0–5.9 M⊙. Our results show how integral-field spectroscopy is a powerful tool for uncovering faint and low-accretion AGNs and better constraining the demographics of AGNs in dwarf galaxies. [ABSTRACT FROM AUTHOR]

Some galaxies show little to no sign of active galactic nucleus (AGN) activity, yet exhibit strong coronal line (CL) emission relative to common narrow emission lines. Many of these CLs have ionization potentials of ≥100 eV, thus requiring strong extreme ultraviolet and/or soft X-ray flux. It has long been thought that such events are powered by tidal disruption events (TDEs), but owing to a lack of detailed multiwavelength follow-up, such a connection has not been firmly made. Here, we compare coronal line emitters (CLEs) and TDEs in terms of their host-galaxy and transient properties. We find that the mid-infrared (MIR) colours of CLE hosts in quiescence are similar to those of TDE hosts. Additionally, many CLEs show evidence of a large dust reprocessing echo in their MIR colours, a sign of significant dust in the nucleus. The stellar masses and star formation rates of the CLE hosts are largely consistent with TDE hosts, with many CLEs residing within the green valley. The blackbody properties of CLEs and TDEs are similar, with some CLEs showing hot (T ≥ 40 000 K) blackbody temperatures. Finally, the location of CLEs on the peak-luminosity/decline-rate parameter space is much closer to TDEs than many other major classes of nuclear transients. Combined, these provide strong evidence to confirm the previous claims that CLEs are indeed TDEs in gas-rich environments. We additionally propose a stricter threshold of CL flux ≥1/3 × [O  iii ] flux to better exclude AGNs from the sample of CLEs. [ABSTRACT FROM AUTHOR]

In this letter, motivated by double-peaked broad Balmer emission lines probably related to tidal disruption events (TDEs), a potential TDE candidate is reported in Sloan Digital Sky Survey (SDSS) J160536+134838 (=SDSS J1605) at z ∼ 0.44 having quasar-like spectrum but with double-peaked broad H β. The long-term Catalina Sky Survey (CSS) light curve can be naturally described by a main-sequence star of |$2.82_{-0.19}^{+0.20}{\rm M_\odot }$| disrupted by the central black hole (BH) of |$144_{-21}^{+26} \times 10^6{\rm M_\odot }$| in SDSS J1605. Meanwhile, the All-Sky Automated Survey for SuperNovae light curves afterwards show none apparent trend variability, indicating the bright CSS flare in SDSS J1605 unique and different enough from variability of normal active galactic nuclei (AGN). Furthermore, there is a consistency between the TDE model determined sizes of debris with the sizes of emission regions for the double-peaked broad H β described by the accretion disc model, supporting the disc-like broad emission line regions (BLRs) probably related to a central TDE in SDSS J1605. And the virial BH mass ∼7 times higher than the TDE model determined value can be naturally explained by R–L relation determined BLRs sizes very larger than the actual distance of emission regions related to TDEs debris in SDSS J1605. Although no clear conclusion on double-peaked broad lines absolutely related to TDEs, the results here provide clues to detect potential TDEs in AGN with double-peaked broad lines. [ABSTRACT FROM AUTHOR]

Hot dust in the proximity of active galactic nuclei (AGNs) strongly emits in the near-infrared producing a red excess that, in type 2 sources, can be modelled to measure its temperature. In the era of high spatial resolution multiwavelength data, mapping the hot dust around supermassive black holes is important for the efforts to achieve a complete picture of the dust's role and distribution around these compact objects. In this work, we propose a methodology to detect the hot dust emission in the proximity of type 2 AGNs and measure its temperature using K -band spectra (λ c = 2.2 µm). To achieve this, we have developed nirdust , a python package for modelling K -band spectra, estimating the dust temperature, and characterizing the involved uncertainties. We tested synthetic and real spectra in order to check the performance and suitability of the physical model over different types of data. Our tests on synthetic spectra demonstrated that the obtained results are influenced by the signal-to-noise ratio (S/N) of the input spectra. However, we accurately characterized the uncertainties, which remained below ∼150 K for an average S/N per pixel exceeding 20. Applying nirdust to NGC 5128 (Centaurus A), observed with the Gemini South Telescope, we estimated a dust temperature of 662 and 667 K from Flamingos-2 spectra and 697 and 607  K from Gemini Near-Infrared Spectrograph (GNIRS) spectra using two different approaches. [ABSTRACT FROM AUTHOR]

We report the discovery of the 'mm fundamental plane of black hole accretion', which is a tight correlation between the nuclear 1 mm luminosity (L ν, mm), the intrinsic 2–10 keV X-ray luminosity (L X, 2–10) and the supermassive black hole (SMBH) mass (M BH) with an intrinsic scatter (σint) of 0.40 dex. The plane is found for a sample of 48 nearby galaxies, most of which are low-luminosity active galactic nuclei. Combining these sources with a sample of high-luminosity (quasar-like) nearby AGN, we show that the plane still holds. We also find that M BH correlates with L ν, mm at a highly significant level, although such correlation is less tight than the mm fundamental plane (σint = 0.51 dex). Crucially, we show that spectral energy distribution (SED) models for both advection-dominated accretion flows (ADAFs) and compact jets can explain the existence of these relations, which are not reproduced by the standard torus-thin accretion disc models usually associated to quasar-like AGN. The ADAF models reproduces the observed relations somewhat better than those for compact jets, although neither provides a perfect fit. Our findings thus suggest that radiatively inefficient accretion processes such as those in ADAFs or compact (and thus possibly young) jets may play a key role in both low- and high-luminosity AGN. This mm fundamental plane also offers a new, rapid method to (indirectly) estimate SMBH masses. [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]

It is widely accepted that X-ray emission in luminous active galactic nuclei (AGNs) originates from hot corona. To prevent the corona from overcooling by strong X-ray emission, steady heating to the corona is essential, for which the most promising mechanisms is the magnetic reconnection. Detailed studies of the coupled disc and corona, in the frame of magnetic field transferring accretion-released energy from the disc to the corona, reveal that the thermal electrons can only produce X-ray spectrum with |$\Gamma _{\rm 2-10\, keV}\gt 2.1$|⁠ , which is an inevitable consequence of the radiative coupling of the thermal corona and disc. In this work, we develop the magnetic-reconnection-heated corona model by taking into account the potential non-thermal electrons accelerated in the magnetic reconnection process, in addition to the thermal electrons. We show that the features of the structure and spectrum of the coupled disc and corona can be affected by the fraction of magnetic energy allocated to thermal electrons. Furthermore, we investigate the effects of the power-law index and energy range of non-thermal electrons and the magnetic field on the spectrum. It is found that the X-ray spectrum from the Comptonization of the hybrid electrons can be flatter than that from thermal electrons only, in agreement with observations. By comparing with the observed hard X-ray data, we suggest that a large fraction (⁠|$\gt 40~{{\ \rm per\ cent}}$|⁠) of the magnetic energy be allocated to the non-thermal electrons in the luminous and flat X-ray spectrum AGNs. [ABSTRACT FROM AUTHOR]

We analyze JWST NIRSpec+MIRI/MRS observations of the infrared (IR) gas-phase molecular bands of the most enshrouded source (D1) within the interacting system and luminous IR galaxy II Zw 096. We report the detection of rovibrational lines of H2O ν2 = 1 − 0 (∼5.3–7.2 μm) and 12CO ν = 1 − 0 (∼4.45–4.95 μm) in D1. The CO band shows the R- and P-branches in emission and the spectrum of the H2O band shows the P-branch in emission and the R-branch in absorption. The H2O R-branch in absorption unveils an IR-bright embedded compact source in D1 and the CO broad component features a highly turbulent environment. From both bands, we also identified extended intense star-forming (SF) activity associated with circumnuclear photodissociation regions (PDRs), consistent with the strong emission of the ionised 7.7 μm polycyclic aromatic hydrocarbon band in this source. By including the 4.5–7.0 μm continuum information derived from the H2O and CO analysis, we modelled the IR emission of D1 with a dusty torus and SF component. The torus is very compact (diameter of ∼3 pc at 5 μm) and characterised by warm dust (∼370 K), giving an IR surface brightness of ∼3.6 × 108 L⊙ pc−2. This result suggests the presence of a dust-obscured active galactic nucleus (AGN) in D1, which has an exceptionally high covering factor that prevents the direct detection of AGN emission. Our results open a new way to investigate the physical conditions of inner dusty tori via modelling the observed IR molecular bands. [ABSTRACT FROM AUTHOR]

Context. Massive black holes (MBHs) are typically hosted in the centres of massive galaxies but they appear to become rarer in lower mass galaxies, where nuclear star clusters (NSCs) frequently appear instead. The transition region, where both an MBH and NSC can co-exist, has been poorly studied to date and only a few dozen galaxies are known to host them. One avenue for detecting new galaxies with both an MBH and NSC is to look for accretion signatures of MBHs. Aims. Here, we use new SRG/eROSITA all-sky survey eRASS:4 data to search for X-ray signatures of accreting MBHs in NSCs, while also investigating their combined occupation fraction. Methods. We collected more than 200 galaxies containing an NSC, spanning multiple orders in terms of galaxy stellar mass and morphological type, within the footprint of the German eROSITA Consortium survey. We determined the expected X-ray contamination from binary stellar systems using the galaxy stellar mass and star formation rate as estimated from far-ultraviolet and mid-infrared emission. Results. We find significant detections for 18 galaxies (~8.3%), including one ultra-luminous X-ray source; however, only three galaxies (NGC 2903, 4212, and 4639) have X-ray luminosities that are higher than the expected value from X-ray binaries, indicative of the presence of an MBH. In addition, the X-ray luminosity of six galaxies (NGC 2903, 3384, 4321, 4365, 4639, and 4701) differs from previous studies and could indicate the presence of a variable active galactic nucleus. For NGC 4701 specifically, we find a variation of X-ray flux within the eRASS:4 data set. Stacking X-ray non-detected galaxies in the dwarf regime M*gal ≤ 109M⊙) results in luminosity upper limits of a few times 1038 erg s−1. The combined occupation fraction of accreting MBHs and NSCs becomes non-zero for galaxy masses above ~ 107.5M⊙ and this result is slightly elevated as compared to the literature data. Conclusions. Our data extend, for the first time, towards the dwarf elliptical galaxy regime and identify promising MBH candidates for higher resolution follow-up observations. At most galaxy masses (and with the exception of three cases), the X-ray constraints are consistent with the expected emission from binary systems or an Eddington fraction of at most 0.01%, assuming a black holes mass of 106.5M⊙. This work confirms the known complexities in similar-type of studies, while providing the appealing alternative of using X-ray survey data of in-depth observations of individual targets with higher resolution instruments. [ABSTRACT FROM AUTHOR]

Context. The triggering and evolution of active galactic nuclei (AGNs) and the interaction of the AGN with its host galaxy is an important topic in extragalactic astrophysics. Radio sources with peaked spectra (peaked spectrum sources, PSS) and compact symmetric objects (CSO) are powerful, compact, and presumably young AGNs and therefore particularly suitable to study aspects of the AGN-host connection. Aims. We use a statistical approach to investigate properties of a PSS-CSO sample that are related to host galaxies and could potentially shed light on the link between host galaxies and AGNs. The main goal is to compare the PSS-CSO sample with a matching comparison sample of extended sources (ECS) to see if the two have significant differences. Methods. We analysed composite spectra, diagnostic line diagrams, multi-band spectral energy distributions (MBSEDs), star formation (SF) indicators, morphologies, and cluster environments for a sample of 121 PSSs and CSOs for which spectra are available from the Sloan Digital Sky Survey (SDSS). The statistical results were compared with those of the ECS sample, where we generally considered the two subsamples of quasi-stellar objects (QSOs) and radio galaxies separately. The analysis is based on a large set of archival data in the spectral range from the ultraviolet to mid-infrared. Results. We find significant differences between the PSS-CSO and the ECS sample. In particular, we find that the ECS sample has a higher proportion of passive galaxies with a lower star formation activity. This applies to both sub-samples (QSOs or radio galaxies) as well as to the entire sample. The star formation rates of the PSS-CSO host galaxies with available data are typically in the range ∼0 to 5 ℳ⊙ yr−1, and the stellar masses are in the range 3 × 1011 to 1012 ℳ⊙. Secondly, in agreement with previous results, we find a remarkably high proportion of PSS-CSO host galaxies with merger signatures. The merger fraction of the PSS-CSO sample is 0.61 ± 0.07, which is significantly higher than that of the comparison sample (0.15 ± 0.06). We suggest that this difference can be explained by assuming that the majority of the PSSs and CSOs cannot evolve to extended radio sources and are therefore not represented in our comparison sample. [ABSTRACT FROM AUTHOR]

We present an archival Atacama Large Millimeter/submillimeter Array (ALMA) study of the cyanide radical (CN) N  = 1 − 0/carbon monoxide (CO) J  = 1 − 0 intensity ratio in nearby (z < 0.05) ultra-luminous and luminous infrared galaxies (U/LIRGs). We identify 16 U/LIRGs that have been observed in both CN and CO lines at ∼500 pc resolution based on 16 different ALMA projects. We measure the (CN bright)/CO and (CN bright)/(CN faint) intensity ratios at an ensemble of molecular clouds scales (CN bright = CN N  = 1 − 0, J  = 3/2 − 1/2; CN faint = CN N  = 1 − 0, J  = 1/2 − 1/2 hyperfine groupings). Our global measured (CN bright)/CO ratios range 0.02–0.15 in LIRGs and 0.08–0.17 in ULIRGs. We attribute the larger spread in LIRGs to the variety of galaxy environments included in our sample. Overall, we find that the (CN bright)/CO ratio is higher in nuclear regions, where the physical and excitation conditions favour increased CN emission relative to the disc regions. 10 out of 11 galaxies which contain well-documented active galactic nuclei show higher ratios in the nucleus compared with the disc. Finally, we measure the median resolved (CN bright)/(CN faint) ratio and use it to estimate the total integrated CN line optical depth in ULIRGs (τ ∼ 0.96) and LIRGs (τ ∼ 0.23). The optical depth difference is likely due to the higher molecular gas surface densities found in the more compact ULIRG systems. [ABSTRACT FROM AUTHOR]

Studies of spatial distribution, kinematics, and physical structure of dense molecular gas in the centres of galaxies is crucial in understanding the nature of physical processes, especially those related to active galactic nuclei (AGNs) and starbursts, in the vicinity of central massive black holes. However, our current understanding of dense gas in the circumnuclear discs (CND) remains limited, particularly those around AGNs. Here-, we report high-resolution deep observations of the CS (3−2), HC3N (15−14), H2CO (2−1), CH3CCN (8−7), CO (1−0), and (3−2) lines, toward the central region (R  ∼ 0.4 kpc) of the nearest Seyfert-2 galaxy, the Circinus galaxy, using the Atacama Large Millimeter/submillimeter Array. The dense molecular gas traced by CS (3−2) and HC3N (15−14) exhibit an asymmetric and cloud structure, which is in sharp contrast against the symmetric low-density structure traced by CO (1−0). Four molecular cloud structures surrounding the AGN, which have a typical size of ∼ 20 pc, are detected with the optically thin HC3N (15−14) line. HC3N (15−14)/CO (1−0) line ratio in the CND is found to be higher than that in the nuclear region, indicating that the bulk of dense gas accumulates in the CND, instead of the nucleus. HC3N (15−14) line and optically thick tracers in four molecular clouds, provide a good comparison between density layers and show evidence for a density stratification of the CND. [ABSTRACT FROM AUTHOR]

The interband correlations between optical/ultraviolet (UV) and X-ray luminosities of active galactic nuclei (AGNs) are important for understanding the disc–coronal connection, as well as using AGN as standard candles for cosmology. It is conventional to measure the X-ray luminosity at rest-frame 2 keV and compare to the UV luminosity at the rest-frame 2500 Å, but the wavelength dependence was never well explored. In this work, we adopt a well-defined sample of 1169 unobscured quasars in the redshift range 0.13–4.51, and apply the direct-correlation method to explore how the correlation with the 2 keV luminosity changes at different optical/UV wavelengths, from 1280 to 5550 Å where the spectral quality is high. We find that the luminosity at all UV continuum wavelengths correlates with the X-ray luminosity similarly to that at 2500 Å, and that these correlations are better than at the optical wavelengths. Strong self-correlation is also found in the broad-band optical/UV continuum, supporting the scenario that it is dominated by the disc emission. Correlations of various emission lines are also investigated (e.g. C iv , C iii ], Mg ii , Hβ, and [O iii ]λλ4959/5007), including the Baldwin effect and correlations involving linewidths. We find the forms of these line correlations are different, and they are also different from their underlying continua, suggesting various complexities in the line-generation process. We discuss these results in the disc-wind scenario. Our study confirms that the rest-frame 2500 Å is a good wavelength to represent the optical/UV continual properties of quasars, and shows the advantages of the direct-correlation method. [ABSTRACT FROM AUTHOR]

In this letter, we report a potential candidate of recoiling supermassive black hole (rSMBH) in Sloan Digital Sky Survey (SDSS) J1619 based on similar velocity shifts and line widths of the blueshifted broad components in H α and [O  iii ] doublet. The measured line width ratio between blueshifted broad H α and broad [O  iii ] line is 1.06, if compared with common values around 5.12 for normal Type-1 active galactic nuclei, indicating different properties of the blueshifted broad components in SDSS J1619 from those of normal Quasi Stellar Objects (QSOs). The virial BH mass M BHr derived from the broad H α is consistent with the mass expected from the M BH–σ relation. The similar velocity shifts and line widths of the blueshifted broad components in H α and [O  iii ] and the virial BH mass derived from the H α broad line emissions that is consistent with the mass expected from the M BH–σ relation, can be explained by an rSMBH scenario. Besides the rSMBH scenario, either the similar line widths of the blueshifted broad components in H α and in [O  iii ] or the consistency between the virial BH mass and the mass expected from the M BH–σ relation cannot be explained by the other proposed models in SDSS J1619. [ABSTRACT FROM AUTHOR]

Despite powerful X-ray emission, some active galactic nuclei (AGNs) are known to either lack optical emission lines (so-called 'optically dull' AGNs) or have lines that fall on the star-forming branch of the Baldwin–Phillips–Terlevich (BPT) diagram ('misclassified' AGNs). Aperture effects have been proposed to explain such atypical spectra, especially when based on Sloan Digital Sky Survey (SDSS; 3 arcsec) fibres. We use observations from VLT-MUSE with Adaptive Optics to explore the spatially resolved optical emission line properties of four optically dull and one misclassified X-ray AGN candidates. VLT-MUSE IFU spectra allow us to investigate the extent to which the aperture size affects the emission line measurements. The optically dull AGNs become detectable in deeper VLT-MUSE spectroscopic apertures having the same size (3 arcsec) as SDSS fibres, suggesting no AGN is truly lineless. However, in no case does the line become more detectable as the aperture decreases, as would be expected if dilution by strong continuum was responsible for making the lines appear weak. We also show that the misclassified X-ray AGN retains the same position on the BPT diagram in smaller apertures (down to 0.5 arcsec), demonstrating that its misclassification is not the result of the dilution by H  ii regions. Thus, we conclude that continuum swamping or star formation dilution, i.e. aperture effects, are not responsible for atypical lines. Rather, the AGN lines are intrinsically weak. [ABSTRACT FROM AUTHOR]

We present a study of the morphology of star formation and the associated nuclear activity in a sample of eight closely interacting southern galaxies, which are in different stages of interaction, starting with nearly merged nuclei that have one prominent bulge to more widely spaced interacting galaxies. We have used far-ultraviolet (FUV) observations from the Ultraviolet Imaging Telescope (UVIT), near-Infrared observations from the Infrared Survey Facility (IRSF) telescope, and archival optical data from the Very Large Telescope (VLT)/Multi-Unit Spectroscopic Explorer (MUSE) integral field spectrograph. Analysing resolved stellar populations across the disc of the interacting galaxies can provide unique insights into how interactions affect galaxy properties, such as morphology, star formation rates, and chemical composition. We take advantage of the unprecedented capabilities of MUSE and UVIT to carry out a highly detailed spatially and spectrally resolved study of star formation rate, star formation histories, metallicity, and active galactic nucleus activity in the sample of eight interacting galaxies that are in different stages of interaction. Most of our sample galaxies are gas-rich and show evidence of recent, massive star formation in tidal tails, rings, and spiral arms. This is evident from their FUV and Hα emissions, which trace young, massive star-forming regions. We compared the star formation rate in the barred and unbarred galaxies in our sample and found that the barred galaxies do not show significant enhancement in star formation rate or large-scale difference in star formation morphology compared to unbarred galaxies. IC5250 and NGC7733N show extended nuclear outflows of sizes ∼5 and 8 kpc, respectively. [ABSTRACT FROM AUTHOR]

This study uses multifrequency very long baseline interferometry (VLBI) to study the radio emission from 10 radio-quiet quasars (RQQs) and four radio-loud quasars (RLQs). The diverse morphologies, radio spectra, and brightness temperatures observed in the VLBI images of these RQQs, together with the variability in their GHz spectra and VLBI flux densities, shed light on the origins of their nuclear radio emission. The total radio emission of RQQs appears to originate from non-thermal synchrotron radiation due to a combination of active galactic nuclei and star formation activities. However, our data suggest that the VLBI-detected radio emission from these RQQs is primarily associated with compact jets or corona, with extended emissions such as star formation and large-scale jets being resolved by the high resolution of the VLBI images. Wind emission models are not in complete agreement the VLBI observations. Unlike RLQs, where the parsec-scale radio emission is dominated by a relativistically boosted core, the radio cores of RQQs are either not dominant or are mixed with significant jet emission. RQQs with compact cores or core-jet structures typically have more pronounced variability, with flat or inverted spectra, whereas jet-dominated RQQs have steep spectra and unremarkable variability. Future high-resolution observations of more RQQs could help to determine the fraction of different emission sources and their associated physical mechanisms. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the role of active galactic nucleus (AGN) feedback on the late-stage evolution of elliptical galaxies by performing high-resolution hydrodynamical simulation in the MACER framework. By comparing models that take into account different feedback mechanisms, namely AGN and stellar feedback, we find that AGN feedback is crucial in keeping the black hole in a low accretion state and suppressing the star formation. We then compare the energy from AGN radiation and wind deposited in the galaxy and find that only wind can compensate for the radiative cooling of the gas in the galaxy. Further, we investigate which plays the dominant role, the wind from the cold (quasar) or hot (radio) feedback modes, by examining the cumulative energy output and impact area to which the wind can heat the interstellar medium and suppress star formation. Our results indicate that first, although AGN spends most of its time in hot (radio) mode, the cumulative energy output is dominated by the outburst of the cold (quasar) mode. Second, only the impact area of the cold-mode wind is large enough to heat the gas in the halo, while the hot-mode wind is not. Additionally, the cold-mode wind is capable of sweeping up the material from stellar mass-loss. These results indicate the dominant role of cold-mode wind. The limitations of our model, including the absence of jet feedback, are discussed. [ABSTRACT FROM AUTHOR]

We present a selection technique to detect Compton-thick (CT) active galactic nuclei (AGNs) in the 3XMM/SDSS-DR7 cross-correlation. A subsample of 3481 X-ray sources that are detected in the hard band (2–8 keV) and have photometric redshifts constitute our parent sample. We first applied an automated spectral-fitting procedure to select highly absorbed sources (N H > 1023 cm−2). We found 184 highly absorbed candidates. Then, we performed the Bayesian Monte Carlo Markov chains (MCMCs) selection technique to find CT AGNs. We also tested the MCMC selection technique by applying Monte Carlo simulations. We found that the method is accurate at 90 per cent independently of the nature of the underlying source. Our sample contains 52 bona fide CT AGNs. The CT AGNs were selected to have a range >0.75 of probability of being CT when either fitting with the two models Torus and MYTorus. About 75 per cent of CT AGNs in our sample had probabilities >90 per cent. From the spectral analysis, we significantly found an anticorrelation between the equivalent width of the neutral Fe K α line and the X-ray luminosity at 2–10 keV, the so-called X-ray Baldwin effect. [ABSTRACT FROM AUTHOR]

The multiwavelength data of nuclear transient AT2018dyk, initially discovered as a changing-look low-ionization nuclear emission-line region (LINER) galaxy, has been revisited by us and found being in agreement with a tidal disruption event (TDE) scenario. The optical light curve of AT2018dyk declines as a power-law form approximately with index –5/3 yet its X-ray emission lags behind the optical peak by ∼140 d, both of which are typical characteristics for TDEs. The X-ray spectra are softer than normal active galactic nuclei (AGNs) although they show a slight trend of hardening. Interestingly, its rising time-scale belongs to the longest among TDEs while it is nicely consistent with the theoretical prediction from its relatively large supermassive black hole (SMBH) mass (∼107.38M⊙). Moreover, a prominent infrared echo with peak luminosity ∼7.4 × 1042 erg s−1 has been also detected in AT2018dyk, implying an unusually dusty subparsec nuclear environment in contrast with other TDEs. In our sample, LINERs share similar covering factors with AGNs, which indicates the existence of the dusty torus in these objects. Our work suggests that the nature of nuclear transients in LINERs needs to be carefully identified and their infrared echoes offer us a unique opportunity for exploring the environment of SMBHs at low accretion rate, which has been so far poorly explored but is crucial for understanding the SMBH activity. [ABSTRACT FROM AUTHOR]

Measurements of the luminosity function of active galactic nuclei (AGN) at high redshift (z ≳ 6) are expected to suffer from field-to-field variance, including cosmic and Poisson variances. Future surveys, such as those from the Euclid telescope and JWST, will also be affected by field variance. We use the Uchuu simulation, a state-of-the-art cosmological N -body simulation with 2.1 trillion particles in a volume of 25.7 Gpc3, combined with a semi-analytic galaxy and AGN formation model, to generate the Uchuu–ν2GC catalogue, publicly available, that allows us to investigate the field-to-field variance of the luminosity function of AGN. With this Uchuu–ν2GC model, we quantify the cosmic variance as a function of survey area, AGN luminosity, and redshift. In general, cosmic variance decreases with increasing survey area and decreasing redshift. We find that at z ∼ 6 − 7, the cosmic variance depends weakly on AGN luminosity. This is because the typical mass of dark matter haloes in which AGN reside does not significantly depend on luminosity. Due to the rarity of AGN, Poisson variance dominates the total field-to-field variance, especially for bright AGN. We also examine the effect of parameters related to galaxy formation physics on the field variance. We discuss uncertainties present in the estimation of the faint-end of the AGN luminosity function from recent observations, and extend this to make predictions for the expected number of AGN and their variance for upcoming observations with Euclid , JWST, and the Legacy Survey of Space and Time (LSST). [ABSTRACT FROM AUTHOR]

We analyse the integral field spectroscopy data for the ≈10 000 galaxies in final data release of the MaNGA survey. We identify 188 galaxies for which the emission lines cannot be described by single Gaussian components. These galaxies can be classified into (1) 38 galaxies with broad |$\rm H\alpha$| and [O  iii ]  |$\rm \lambda$| 5007 lines, (2) 101 galaxies with broad |$\rm H\alpha$| lines but no broad [O  iii ]  |$\rm \lambda$| 5007 lines, and (3) 49 galaxies with double-peaked narrow emission lines. Most of the broad-line galaxies are classified as active galactic nuclei (AGNs) from their line ratios. The catalogue helps us further understand the AGN-galaxy coevolution through the stellar population of broad-line region host galaxies and the relation between broad lines' properties and the host galaxies' dynamical properties. The stellar population properties (including mass, age, and metallicity) of broad-line host galaxies suggest there is no significant difference between narrow-line Seyfert-2 galaxies and Type-1 AGNs with broad |$\rm H\alpha$| lines. We use the broad- |$\rm H\alpha$| line width and luminosity to estimate masses of black hole in these galaxies, and test the M BH–σe relation in Type-1 AGN host galaxies. Furthermore, we find three dual AGN candidates supported by radio images from the VLA FIRST survey. This sample may be useful for further studies on AGN activities and feedback processes. [ABSTRACT FROM AUTHOR]

The cosmological inflow of a galaxy is speculated to be able to enter the galaxy and enhance the star formation rate (SFR) and black hole accretion rate (BHAR). In this paper, by performing high-resolution hydrodynamic simulations in the framework of macer , we investigate the fate of the inflow and its impacts on the evolution of a massive elliptical galaxy. The inflow properties are adopted from the cosmological simulation IllustrisTNG. We find that the inflow gas hardly enters but is blocked beyond ∼20 kpc from the central galaxy and becomes part of the circumgalactic medium (CGM). The gas pressure gradient, mainly contributed by the thermalized stellar wind and subdominant contributed by the energy input from the active galactic nuclei (AGNs), balances gravity and prevents the inflow from entering the galaxy. The SFR and BHAR are almost not affected by the normal inflow. However, if the rate of cosmological inflow were increased by a factor of 3, a small fraction of the inflow would enter the galaxy and contribute about 10 per cent of the gas in the galaxy. In this case, the gas density in the galaxy would increase by a factor of |$\gtrsim$| 20. This increase is not because of the additional gas supply by the inflow but due to the increase of gas density and pressure in the CGM caused by the inflow. Consequently, the SFR and BHAR would increase by a factor of ∼5 and ∼1000, respectively. Finally, AGN feedback can perturb the motion of the inflow and heat the CGM through its intermittent outbursts. [ABSTRACT FROM AUTHOR]

We present a novel algorithm to detect double nuclei galaxies (DNG) called Gothic (G raph-b O os T ed iterated HI ll C limbing) – that detects whether a given image of a galaxy has two or more closely separated nuclei. Our aim is to test for the presence of dual/multiple active galactic nuclei (AGN) in galaxies that visually represent a DNG. Although galaxy mergers are common, the detection of dual AGN is rare. Their detection is very important as they help us understand the formation of supermassive black hole (SMBH) binaries, SMBH growth and AGN feedback effects in multiple nuclei systems. There is thus a need for an algorithm to do a systematic survey of existing imaging data for the discovery of DNGs and dual AGNs. We have tested Gothic on an established sample of DNGs with a 100 per cent detection rate and subsequently conducted a blind search of 1 million SDSS DR16 galaxies (with spectroscopic data available) lying in the redshift range of z  = 0 to 0.75. From the list of candidate DNGs found, we have detected 159 dual AGNs, of which 2 are triple AGN systems. Our results show that dual AGNs are not common, and triple AGN even rarer. The colour (u–r) magnitude plots of the DNGs indicate that star formation is quenched as the nuclei come closer and as the AGN fraction increases. The quenching is especially prominent for dual/triple AGN galaxies that lie at the extreme end of the red sequence. [ABSTRACT FROM AUTHOR]