Search

We develop a simple method to search for changing-look (CL) active galactic nucleus (AGN) candidates, and conduct a test run. In this method, optical variations of AGNs are monitored and CL-AGNs may appear to have a pattern of being bluer when in brightening flare-like events. Applying this method, previously classified type 2 AGNs that show the bluer-when-brighter (BWB) pattern are selected. Among more than ten thousands type 2 AGNs classified in the Sloan Digital Sky Survey (SDSS), we find 73 candidates with possibly the strongest BWB pattern. We note that 13 of them have previously been reported as CL-AGNs. We have observed nine candidates, and found that five among them showed the CL transition from type 2 to type 1. In addition, we also test extending the selection to previously classified type 1 AGNs in the SDSS by finding sources with a possible redder-when-brighter pattern, but none of the three sources observed by us is found to show the transition from type 1 to type 2. We discuss the variation properties in both the success and failure cases, and plan to observe more candidates selected with the method. From the observational results, a detailed comparison between the CL-AGNs and none CL-AGNs will help quantitatively refine the selection criteria and in turn allow us to configure the general properties of CLAGNs. [ABSTRACT FROM AUTHOR]

S-shaped radio galaxy jets are prime sources for investigating the dynamic interplay between the central active galactic nucleus (AGN), the jets, and the ambient intergalactic medium. These sources are excellent candidates for studying jet precession, as their S-shaped inversion symmetry strongly indicates underlying precession. We present a multiwavelength analysis of the giant inversion-symmetric S-shaped radio galaxy PKS 2300 |$-$| 18, which spans 0.76 Mpc. The host is a quasar at a redshift of 0.128, displaying disturbed optical morphology due to an ongoing merger with a companion galaxy. We conducted a broad-band radio spectral study using multifrequency data ranging from 183 MHz to 6 GHz, incorporating dedicated observations with the upgraded Giant Metrewave Radio Telescope (uGMRT) and Karl G. Jansky Very Large Array (JVLA) alongside archival radio data. A particle injection model was fitted to the spectra of different regions of the source to perform ageing analysis, which was supplemented with a kinematic jet precession model. The ageing analysis revealed a maximum plasma age of |$\sim$| 40 Myr, while the jet precession model indicated a precession period of |$\sim$| 12 Myr. ROentgen SATellite (ROSAT) data revealed an X-ray halo of Mpc size, and from Chandra the AGN X-ray spectrum was modelled using thermal and power-law components. The optical spectrum displaying double-peaked broad emission lines was modelled, indicating complex broad-line region kinematics at the centre with the possibility of a binary SMBH. We present the results of our multiwavelength analysis of the source, spanning scales from a few light-days to a few Mpc, and discuss its potential evolutionary path. [ABSTRACT FROM AUTHOR]

To test the scenario that outflows accelerated by active galactic nuclei (AGN) have a major impact on galaxy-wide scales, we have analysed deep Very Large Telescope/Multi Unit Spectroscopic Explorer (VLT/MUSE) data for the type-2 quasar/ultraluminous infrared galaxy F13451+1232 – an object that represents the major mergers considered in some models of galaxy evolution. After carefully accounting for the effects of atmospheric seeing that had smeared the emission from known compact nuclear outflows across the MUSE field of view, we find that the large-scale kinematics in F13451+1232 are consistent with gravitational motions that are expected in a galaxy merger. Therefore, the fast (⁠|$\mathrm{W_{80}}\gt 500$|  km s |$^{-1}$|⁠) warm-ionized AGN-driven outflows in this object are limited to the central |$\sim$| 100 pc of the galaxy, although we cannot rule out larger scale, lower velocity outflows. Moreover, we directly demonstrate that failure to account for the beam-smearing effects of atmospheric seeing would have led to the mass outflow rates and kinetic powers of spatially extended emission being overestimated by orders of magnitude. We also show that beam-smeared compact-outflow emission can be significant beyond radial distances of 3.5 arcsec (more than 8 times the radius of the seeing disc), and support the argument that some previous claims of large-scale outflows in active galaxies were likely the result of this effect rather than genuine galaxy-wide (⁠|$r\gt 5$|  kpc) outflows. Our study therefore provides further evidence that warm-ionized AGN-driven outflows are limited to the central kiloparsecs of galaxies and highlights the critical importance of accounting for atmospheric seeing in ground-based observational studies of active galaxies. [ABSTRACT FROM AUTHOR]

We study the variability of the thermal (accretion disc) and non-thermal (jet) emission of thirteen flat spectrum radio quasars in the optical and near infrared (OIR) regime using light curves spanning years with an average sampling of three observations per week. We fit a combination of a blackbody and a power-law function to the OIR data, in the blazar rest frame, to extract the corresponding thermal (disc) and non-thermal (jet) components from the total flux. We carry out this analysis for the entire duration of the light curves to obtain the variation of the disc and jet components over years. Reliability of our fits have been affirmed by successfully retrieving accurate parameters by employing our method to simulated data and by comparing our results with published disc luminosity obtained by other methods for a few well-observed blazars. In blazars, the thermal (disc) emission is difficult to extract because the relativistically beamed radiation of the jet dominates at all wavelengths. By employing this method, the disc emission in blazars may be estimated directly from photometric data at OIR bands instead of indirect methods, such as, inferring it from the emission line luminosities. We find that the variability of the disc and jet emission obtained by the above method are strongly correlated in most cases. [ABSTRACT FROM AUTHOR]

The stochastic photometric variability of quasars is known to follow a random-walk phenomenology on emission time-scales of months to years. Some high-cadence rest-frame optical monitoring in the past has hinted at a suppression of variability amplitudes on shorter time-scales of a few days or weeks, opening the question of what drives the suppression and how it might scale with quasar properties. Here, we study a few thousand of the highest luminosity quasars in the sky, mostly in the luminosity range of |$L_{\rm bol}$| |$=[46.4, 47.3]$| and redshift range of |$z=[0.7, 2.4]$|⁠. We use a data set from the NASA/Asteroid Terrestrial-impact Last Alert System facility with nightly cadence, weather permitting, which has been used before to quantify strong regularity in longer term rest-frame-UV variability. As we focus on a careful treatment of short time-scales across the sample, we find that a linear function is sufficient to describe the UV variability structure function. Although the result can not rule out the existence of breaks in some groups completely, a simpler model is usually favoured under this circumstance. In conclusion, the data are consistent with a single-slope random walk across rest-frame time-scales of |$\Delta t=[10, 250]$| d. [ABSTRACT FROM AUTHOR]

Variations in scaling behaviour in the flux and emissions of gravitational lensed quasars can provide valuable information about the dynamics within the sources and their cosmological evolution with time. Here, we study the multifractal behaviour of the light curves (LCs) of 14 lensed quasars with multiple images in the r band, with redshift ranging from 0.657 to 2.730, in the search for potential differences in non-linearity between the signals of the quasar multiple images. Among these lensed systems, nine present two images, two present three images, and three present four images. To this end, we apply the wavelet transform-based multifractal analysis formalism called wavelet transform modulus maxima. We identify strong multifractal signatures in the LCs of the images of all analysed lensed quasar systems, independently of the number of images, with a significant difference between the degree of multifractality of all the images and combinations. We have also searched for a possible connection between the degree of multifractality and the characteristic parameters related to the quasar source and the lensing galaxy. These parameters include the Einstein ring radius and the accretion disc size and the characteristic time-scales related to microlensing variability. The analysis reveals some apparent trends, pointing to a decrease in the degree of multifractality with the increase of the quasar's source size and time-scale. Using a larger sample and following a similar approach, this study confirms a previous finding for the quasar Q0957 + 561. [ABSTRACT FROM AUTHOR]

We use the Hubble Space Telescope to analyse the extended [O  iii ] 5007 Å emission in seven bright radio-quiet type 1 quasars (QSO1s), focusing on the morphology and physical conditions of their extended Narrow-Line Regions (NLRs). We find NLRs extending 3–9 kpc, with four quasars showing roughly symmetrical structures (⁠|$b/a$| =1.2–1.5) and three displaying asymmetric NLRs (⁠|$b/a$| =2.4–5.6). When included with type 1 and type 2 AGNs from previous studies, the sizes of the extended [O  iii ] regions scale with luminosity as |$R_{\rm [O\,{\rm {\small III}}]}\sim L_{\rm [O\,{\rm {\small III}}]}^{0.5}$|⁠ , consistent with photoionization. However, when analysed separately, type 1s exhibit a steeper slope (⁠|$\gamma _{1}$| = 0.57 |$\pm$| 0.05) compared to type 2 AGNs (⁠|$\gamma _{2}$| = 0.48 |$\pm$| 0.02). We use photoionization modelling to estimate the maximum NLRs sizes, assuming a minimum ionization parameter of log |$(U)=-3$|⁠ , an ionizing luminosity based on the |$L_{\rm [O\,{\rm {\small III}}]}$| -derived bolometric luminosity, and a minimum gas number density |$n_{\rm H}\sim 100$|  cm |$^{-3}$|⁠ , assuming that molecular clouds provide a reservoir for the ionized gas. The derived sizes agree well with direct measurements for a sample of type 2 quasars, but are underestimated for the current sample of QSO1s. A better agreement is obtained for the QSO1s using bolometric luminosities derived from the 5100 Å continuum luminosity. Radial mass profiles for the QSO1s show significant extended mass in all cases, but with less [O  iii ]-emitting gas near the central AGN compared to QSO2s. This may suggest that the QSO1s are in a later evolutionary stage than QSO2s, further past the blow-out stage. [ABSTRACT FROM AUTHOR]

We present a comprehensive study of the physical origin of radio emission in optical quasars at redshifts z < 2.5. We focus particularly on the associations between compact radio emission, dust reddening, and outflows identified in our earlier work. Leveraging the deepest low-frequency radio data available to date (LoTSS Deep DR1), we achieve radio detection fractions of up to 94%, demonstrating the virtual ubiquity of radio emission in quasars, and a continuous distribution in radio loudness. Through our analysis of radio properties, combined with spectral energy distribution modelling of deep multiwavelength photometry, we establish that the primary source of radio emission in quasars is the active galactic nucleus (AGN), rather than star formation. Modelling the dust reddening of the accretion disc emission shows a continuous increase in radio detection in quasars as a function of the reddening parameter E(B − V), suggesting a causal link between radio emission and dust reddening. Confirming previous findings, we observe that the radio excess in red quasars is most pronounced for sources with compact radio morphologies and intermediate radio loudness. We find a significant increase in [O III] and C IV outflow velocities for red quasars not seen in our control sample, with particularly powerful [O III] winds in those around the threshold from radio-quiet to radio-loud. Based on the combined characterisation of radio, reddening, and outflow properties in our sample, we favour a model in which the compact radio emission observed in quasars originates in compact radio jets and their interaction with a dusty, circumnuclear environment. In particular, our results align with the theory that jet-induced winds and shocks resulting from this interaction are the origin of the enhanced radio emission in red quasars. Further investigation of this model is crucial for advancing our understanding of quasar feedback mechanisms and their role in galaxy evolution. [ABSTRACT FROM AUTHOR]

We analyzed Multi Unit Spectroscopic Explorer observations of 42 local z ≲ 0.1 type 1 active galactic nucleus (AGN) host galaxies taken from the Palomar-Green quasar sample and the close AGN reference survey. Our goal was to study the relation between the black hole mass (M•) and bulge stellar velocity dispersion (σe) for type 1 active galaxies. The sample spans black hole masses of 106.0 − 109.2 M⊙, bolometric luminosities of 1042.9 − 1046.0 erg s−1, and Eddington ratios of 0.006 − 1.2. We avoided AGN emission by extracting the spectra over annular apertures. We modeled the calcium triplet stellar features and measured stellar velocity dispersions of σ* = 60 − 230 km s−1 for the host galaxies. We find stellar velocity dispersion values in agreement with previous measurements for local (z ≲ 0.1) AGN host galaxies, but slightly lower compared with those reported for nearby X-ray-selected type 2 quasars. Using a novel annular aperture correction recipe to estimate σe from σ* that considers the bulge morphology and observation beam-smearing, we estimate flux-weighted σe = 60 − 250 km s−1. If we consider the bulge type when estimating M•, we find no statistical difference between the distributions of AGN hosts and the inactive galaxies on the M•–σe plane for M• ≲ 108 M⊙. Conversely, if we do not consider the bulge type when computing M•, we find that both distributions disagree. We find no correlation between the degree of offset from the M•–σe relation and Eddington ratio for M• ≲ 108 M⊙. The current statistics preclude firm conclusions from being drawn for the high-mass range. We argue these observations support notions that a significant fraction of the local type 1 AGNs and quasars have undermassive black holes compared with their host galaxy bulge properties. [ABSTRACT FROM AUTHOR]

In this paper we explore the properties of the |$z=6.853$| obscured hyperluminous quasar COS-87259, discovered in the Cosmological Evolution Survey (COSMOS) field, with our recently developed Bayesian spectral energy distribution (SED) fitting code SMART (Spectral energy distributions Markov chain Analysis with Radiative Transfer models). SMART fits SEDs exclusively with multicomponent radiative transfer models that constitute four different types of pre-computed libraries for the active galactic nucleus (AGN) torus, the starburst, and the spheroidal or disc host. We explore two smooth radiative transfer models for the AGN torus and two two-phase models, in order to put constraints on the AGN fraction of the galaxy, the black hole mass, and its star formation rate (SFR). We find that either of the smooth tapered disc or the two-phase flared disc models provide a good fit to the SED of COS-87259. The best-fitting models predict an AGN fraction in the range |$86-92$| per cent, a bolometric AGN luminosity of |$5.8-10.3 \times 10^{13} L_\odot$|⁠ , a black hole mass of |$1.8-3.2 \times 10^{9} M_\odot$| (assuming the quasar is accreting at the Eddington limit), and an SFR in the range |$1985-2001~M_\odot \rm yr^{-1}$|⁠. The predicted space density of such objects in the redshift range |$4-7$| is |$\sim 20$| times more than that of co-eval unobscured quasars. [ABSTRACT FROM AUTHOR]

In this manuscript, strong clues are reported to support the normal broad line AGN SDSS J1617+0638 as the host galaxy harbouring a central tidal disruption event (TDE). Through the optical flare in the CSS 8.5yr-long light curve and the none-variability in the up-to-date ASAS-SN light curves, the theoretical TDE model described by the mosfit code can be applied in SDSS J1617+0638. Meanwhile, considering the assumed central TDE expected continuum emissions not strong enough to describe the continuum emissions in the SDSS spectrum of SDSS J1617+0638, an additional power-law component from pre-existing AGN activity should be necessary in SDSS J1617+0638. Furthermore, considering the short time duration to the observed date for the SDSS spectrum from the starting time of the assumed central TDE in SDSS J1617+0638, TDE model expected accreting mass only about 0.03 |$\mathrm{ M}_\odot$| can lead to few effects of TDEs debris on the observed broad emission lines in the SDSS spectrum of SDSS J1617+0638, indicating the TDE model determined BH mass simply consistent with the virial BH mass by broad emission lines, as determined results in SDSS J1617+0638. Therefore, through both the photometric variability and the spectroscopic results, a central TDE can be preferred in the normal broad line AGN SDSS J1617+0638 with pre-existing central AGN activity and pre-existing broad emission line regions. [ABSTRACT FROM AUTHOR]

We estimated values of spin, mass, and inclination angle for sample of 42 red quasars. Our estimations show that two objects: F2MS J1113+1244 and F2MS J1434+0935 with the highest Eddington ratios may have geometrically thick disk. Six objects: SDSS J0036‐0113, S82X 0040+0058, S82X 0118+0018, S82X 0303‐0115, FBQS J1227+3214, S82X 2328‐0028 may have "retrograde" rotation. Analysis of estimated spin values shows that red quasar population may contain Seyfert galaxies and NLS1. [ABSTRACT FROM AUTHOR]

The unified model of jetted active galactic nuclei (AGNs) based on intrinsic properties presumes that the blazar subtypes of BL Lacertae objects (BLs) and flat-spectrum radio quasars (FSRQs) are aligned equivalents of Fanaroff–Riley type I (FR I) and Fanaroff–Riley type II (FR II) radio galaxies (RGs) from where their parent sources are obtained. Using compiled radio, X-ray and γ -ray data of 397 Fermi Large Area Telescope (Fermi-LAT) blazars and 153 non-Fermi detected RGs, we computed the γ -ray core-dominance parameter (Rγ) and γ -ray emission components (beamed and unbeamed) to study the consequences of relativistic beaming and orientation effects on γ -ray properties of radio RGs, BLs and FSRQs. Data analysis shows that the distributions of RX and Rγ, on average, are consistent with the prediction of the unified scheme in which FSRQs and BLs are strongly beamed and inclined at smaller angles than RGs. Through statistical tests with chance probability, p < 0.05 , we find that the distributions of RX and Rγ for radio galaxies and the blazar subtypes are not significantly different. There is a regular positive trend (r > + 0.60 ) in the variation of radio core-dominance parameter – X-ray luminosity (R − L x ) data from radio galaxies to FSRQs through BLs, which suggests that radio galaxies could be relativistically less beamed population of jetted AGNs. The results are consistent with the unified model for radio galaxies and the conventional blazar subtypes. [ABSTRACT FROM AUTHOR]

Broad absorption line (BAL) outflows are commonly detected in active galactic nuclei (AGNs), but their driving mechanism remains poorly constrained. Here, we investigate whether radiation pressure on dust can adequately explain the BAL phenomenon observed in quasars. In the framework of our AGN radiative dusty feedback scenario, we show that dust-driven outflows can reach BAL wind-like velocities (⁠|$v \sim 10^4$| km s |$^{-1}$|⁠) on galactic scales (⁠|$r \lesssim 1$| kpc). This is consistent with recent observations indicating that BAL acceleration typically occurs on scales of |$\sim 10$| pc, and that the majority of BAL outflows are located at galactocentric radii greater than |$\sim 100$| pc. We derive the outflow radial velocity profile and compute the associated outflow momentum rate and kinetic power, which are found to be in agreement with the outflow energetics measured in BAL quasars. Therefore, radiation pressure on dust may account for the observed BAL outflow dynamics and energetics. Furthermore, we consider BAL clouds/clumps (leading to a clumpy BAL flow characterized by a wide range of outflowing velocities), and we analyse how the resulting covering factors affect the shape of the absorption line profiles. We conclude that dust-driven BAL outflows may provide a significant contribution to AGN feedback on galactic scales. [ABSTRACT FROM AUTHOR]

LSST will catalogue the light curves of up to 100 million quasars. Among these there can be |$\sim$| 100 ultra-compact massive black hole (MBH) binaries, whose gravitational waves (GWs) can be detected 5–15 yr later by LISA. Here, we assume such a LISA detection occurred, and assess whether or not its electromagnetic (EM) counterpart can be identified as a periodic quasar in archival LSST data. We use the binary's properties derived from the LISA waveform, including the evolution of its orbital frequency, its total mass, distance, and sky localization, to predict the redshift, magnitude, and historical periodicity of the quasar expected in the LSST data. We then use Monte Carlo simulations to compute the false alarm probability (FAP), i.e. the number of quasars in the LSST catalogue matching these properties by chance, based on the (extrapolated) quasar luminosity function, the cadence of LSST, and intrinsic 'damped random walk' quasar variability. We analyse four fiducial LISA binaries, with masses and redshifts of |$(M_{\rm bin}/{\rm M_{\odot }},z) = (3\times 10^5,0.3)$|⁠ , |$(3\times 10^6,0.3)$|⁠ , |$(10^7,0.3)$|⁠ , and |$(10^7,1)$|⁠. While noise and aliasing due to LSST's cadence produces false periodicities by chance, we find that the frequency chirp of the LISA source during the LSST observations washes out these noise peaks and allows the genuine source to stand out in appropriately scaled Lomb–Scargle periodograms. We find that all four fiducial binaries can be uniquely identified, with |${\rm FAP}\lt 10^{-5}$|⁠ , a week or more before merger. This should enable follow-up EM observations targeting individual EM counterparts during their inspiral stage. [ABSTRACT FROM AUTHOR]

We present a deep X-Shooter rest-frame ultraviolet (UV) to optical spectral analysis of the heavily reddened quasar, ULASJ2315+0143 at |$z=2.566$|⁠ , known to reside in a major-merger host galaxy. The rest-frame optical is best fit by a dust-reddened quasar (E (B – V) |$^{\rm QSO}= 1.55$|⁠) with black-hole mass |$\rm log_{10}(H\beta , M{\small BH} [{\rm M}_{\odot }]) = 10.26 \pm 0.05$|⁠ , bolometric luminosity |$\rm L_{Bol}$|  = |$\rm 10^{48.16}\, erg\,\,s^{-1}$| and Eddington-scaled accretion rate log |$_{10}(\rm \lambda _{Edd}) = -0.19$|⁠. We find remarkable similarities between ULASJ2315+0143 and the high-redshift little red dots (LRDs). The rest-frame UV cannot be explained by a dusty quasar component alone and requires an additional blue component consistent with either a star-forming host galaxy or scattered AGN light. We detect broad high-ionization emission lines in the rest-UV, supporting the scattered light interpretation for the UV excess. The scattering fraction represents just 0.05  per cent of the total luminosity of ULASJ2315+0143 . Analysis of the mid-infrared SED suggests an absence of hot dust on torus-scales similar to what is observed for LRDs. The obscuring medium is therefore likely on galaxy scales. We detect narrow, blueshifted associated absorption-line systems in C  iv , N  v , Si  iv , and Si  iii. There is evidence for significant high-velocity (>1000  |$\rm km\, s^{-1}$|⁠) outflows in both the broad- and narrow-line regions as traced by C  iv and [O  iii ] emission. The kinetic power of the [O  iii ] wind is |$\dot{\epsilon }_{k}^{ion} = 10^{44.61} \rm erg\, s^{-1} \sim 0.001\, L_{Bol}$|⁠. ULASJ2315+0143 is likely in an important transition phase where star formation, black-hole accretion and multiphase gas flows are simultaneously occurring. [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]

Dust-obscured quasars have been suspected of being the intermediate-stage galaxies between merger-driven star-forming galaxies and unobscured quasars. This merger-driven galaxy evolution scenario suggests that dust-obscured quasars exhibit higher Eddington ratios (λEdd) than those of unobscured quasars. However, their high dust obscuration poses challenges to accurately measuring their λEdd using commonly employed bolometric luminosity (Lbol) and black hole mass (MBH) estimators based on the ultraviolet or optical luminosity. Recently, new estimators for Lbol and MBH based on mid-infrared continuum luminosity (LMIR) were established, which are less affected by dust obscuration. These estimators enable the study of a large number of dust-obscured quasars across a wide redshift range. In this study, we measure the λEdd values of 30 dust-obscured quasars at z ≲ 1, the largest sample size to date, using the LMIR-based Lbol and MBH estimators. Our findings reveal that dust-obscured quasars exhibit significantly higher λEdd values compared to unobscured quasars. Moreover, we confirm that the enhanced λEdd values of dust-obscured quasars maintain consistency across the redshift span of 0 to 1. Our results strongly support the picture that dust-obscured quasars are in an earlier stage than unobscured quasars on the merger-driven galaxy evolutionary track. [ABSTRACT FROM AUTHOR]

Context. Giant (> 100 kpc) nebulae associated with active galaxies provide rich information about the circumgalactic medium around galaxies, its link with the interstellar medium of the hosts, and the mechanisms involved in their evolution. Aims. We have studied the giant nebula associated with the Teacup (z = 0.085) quasar based on VLT MUSE integral field spectroscopy to investigate whether the well-known giant (∼10 kpc) active galactic nucleus (AGN) -induced outflow has an impact on the distribution of heavy elements in and outside the host galaxy. Methods. We have mapped the oxygen and nitrogen gas relative abundances (O/H and N/O) in two spatial dimensions across the giant nebula and within the galaxy by means of comparing emission line ratios with photoionisation model predictions. Results. The widely studied AGN-driven outflow responsible for the ∼10 kpc ionised bubble is enhancing the gas metal abundance up to ∼10 kpc from the AGN. O/H is solar or slightly higher at the edges of the bubble, in comparison with the subsolar abundances across the rest of the nebula median (O/H ∼0.63 (O/H)⊙). Conclusions. AGN feedback can produce metal enrichment at large extranuclear distances in galaxies (≥10 kpc). [ABSTRACT FROM AUTHOR]

Ultraviolet (UV)/optical variability in quasars is a well-observed phenomenon, yet its primeval origins remain unclear. This study investigates whether the accretion disc turbulence, which is responsible for UV/optical variability, is influenced by the close environment of the accretion by analysing the correlation between variability and infrared emission for two luminous quasar samples from the Sloan Digital Sky Survey (SDSS). The first sample includes light curves from SDSS, Panoramic Survey Telescope and Rapid Response System (Pan-STARRS), and Zwicky Transient Facility g -band photometry, while the second sample utilizes SDSS Stripe 82 g -band light curves. We explore the correlation between the g -band excess variance (⁠|$\sigma _{\mathrm{ rms}}$|⁠) and the wavelength-dependent infrared covering factor (⁠|$L_{\rm IR}(\lambda)/L_{\rm bol}$|⁠), controlling for the effects of redshift, luminosity, and black hole mass. An anticorrelation between two variables is observed in both samples, which is strongest at wavelengths of 2–3  |$\rm{\mu m}$| but gradually weakens towards longer wavelength. This suggests the equatorial dusty torus (which dominates near-infrared emission) plays a significant role in influencing the UV/optical variability, while the cooler polar dust (which contributes significantly to mid-infrared emission) does not. The findings indicate that quasar variability may be connected to the physical conditions within the dusty torus which feeds the accretion, and support the notion that the close environment of the accretion plays an important role in regulating the accretion disc turbulence. [ABSTRACT FROM AUTHOR]

The Fermi -LAT has detected more than 7000 |$\gamma$| -ray sources which show emission above 50 MeV of which more than half are associated with blazars. However, the Fourth Fermi -LAT catalogue (4FGL-DR4) lists 1625 of these as blazar candidates of uncertain type. Increasing the number of classified Fermi -LAT sources is important for improving our understanding of extragalactic |$\gamma$| -ray sources and can be used to search for new classes of very high energy sources. We report on the optical spectroscopy of twelve blazar candidates with hard photon indices included in the Third Catalogue of Hard Fermi -LAT Sources during 2016 and 2017 using the SAAO 1.9-m telescope. We classify all the sources observed as BL Lac objects, and determine the potential spectroscopic redshift for seven of them. [ABSTRACT FROM AUTHOR]

SDSS J083942.11+380526.3 (⁠|$z=2.315$|⁠) is an iron low-ionization broad absorption lines quasar that exhibits visible Balmer absorption lines (H  |$\alpha$|⁠), implying a significant |$n=2$| population. The quasar also shows an array of absorption lines, including O  i , Ni  ii , Fe  ii , Mg  ii , Al  iii  to C  iv , and N v. The high-ionization absorption lines such as C  iv and Si  iv are revealed by slightly blueshifted broad absorption lines troughs. The resonance doublets such as Mg  ii and Al  iii are saturated but did not reached zero intensity which indicates that the broad-line region (BLR) is partially covered. Overall, however, the absorption is predominantly from low-ionization Fe  ii lines, emitted from ground and excited states up to at least 3.814 eV. This implies that the absorbing gas spans the hydrogen ionization front and extends into the partially ionized zone where neutral hydrogen is certainly present. Notably, the hydrogen line spectrum of the quasar shows no signature of expected Ly  |$\alpha$| absorption. Instead, the line spectrum shows an unusual Ly  |$\alpha$| emission characterized by a fully filled emission line spectrum which is a composite of a strong narrow core superposed on a weak broad base. Taking into account the effect of partial covering to BLR, we have extracted a strong Damped Ly α systems (DLA) trough in Ly  |$\alpha$| emission region. To fit the spectrum, we performed photoionized model calculations and compared them to the observations. We found that photoionization modelling using cloudy can successfully reproduce the main characteristics of the quasar spectrum, and the predicted neutral hydrogen column density arising from the clouds responsible for the low-ionization absorption provides a good match to the extracted DLA trough. This indicates that both the DLA and the low-ionization absorption arise from the same medium that is roughly collocated with the dusty torus. [ABSTRACT FROM AUTHOR]

In this work, we explore the connection of three jetted |$\gamma -$| loud AGNs classes: Compact steep-spectrum sources (CSS), Narrow-line Seyfert 1 (NLS1), and flat-spectrum radio quasars, through the modelling of the spectral energy distribution (SED). We selected two sources identified as CSS/NLS1 hybrids, PKS 2004-440 and 3C 286. Additionally, we included the source PKS 0440-00, initially classified as an FSRQ in the first Fermi -LAT catalogue, but recently reclassified as an NLS1. We present the results of their broadband SED modelling using a one-zone leptonic synchrotron-self Compton (SSC) + external Compton (EC) model. By exploring the parameter space and investigating the disc–jet connection in these sources, we analyse their classification in a model-dependent way. Our findings reveal that modeling PKS 2004-447 at relatively large angles, as expected for CSS, results in an SSC-dominated inverse Compton emission. In contrast, at low-observing angles, the inverse Compton emission is dominated by external photon fields. Both scenarios result in a jet with a low-radiative power. For 3C 286, we found that using a one-zone model limits the jet viewing angle to |$\sim 7^{\circ }$|⁠ , mainly due to its impact on the |$\gamma$| -ray emission. Our model results show a magnetically dominated jet, consistent with |$\gamma$| -CSS sources. Our results suggest that PKS 0440-00, can be classified as a powerful |$\gamma -$| NLS1, characterized by high accretion power and a jet dominated by bulk motion, similar to FSRQs. [ABSTRACT FROM AUTHOR]

Broad absorption line (BAL) quasars are characterized by gas clouds that absorb flux at the wavelength of common quasar spectral features, although blueshifted by velocities that can exceed |$0.1c$|⁠. BAL features are interesting as signatures of significant feedback, yet they can also compromise cosmological studies with quasars by distorting the shape of the most prominent quasar emission lines, impacting redshift accuracy and measurements of the matter density distribution traced by the Lyman |$\alpha$| forest. We present a catalogue of BAL quasars discovered in the Dark Energy Spectroscopic Instrument (DESI) survey Early Data Release, which were observed as part of DESI Survey Validation, as well as the first two months of the main survey. We describe our method to automatically identify BAL quasars in DESI data, the quantities we measure for each BAL, and investigate the completeness and purity of this method with mock DESI observations. We mask the wavelengths of the BAL features and re-evaluate each BAL quasar redshift, finding new redshifts which are |$243\, {\rm km}\, {\rm s}^{-1}$| smaller on average for the BAL quasar sample. These new, more accurate redshifts are important to obtain the best measurements of quasar clustering, especially at small scales. Finally, we present some spectra of rarer classes of BALs that illustrate the potential of DESI data to identify such populations for further study. [ABSTRACT FROM AUTHOR]

'Extremely red quasars' (ERQs) are a non-radio-selected, intrinsically luminous population of quasars at cosmic noon selected by their extremely red colour from rest-frame UV to mid-IR. ERQs are uniquely associated with exceptionally broad and blueshifted [O  iii ]  |$\lambda$| 5007 emission reaching speeds |$\gt $| 6000 km s |$^{-1}$|⁠. We obtained adaptive optics integral-field spectroscopic observations using Keck/OSIRIS and Gemini/NIFS of a sample of 10 ERQs with bolometric luminosities (10 |$^{47.0}$| –10 |$^{47.9}$|⁠) erg s |$^{-1}$| at |$z\sim$|  (2.3–3.0). The goal is to measure the sizes and spatially resolved kinematics of the [O  iii ]-emitting regions. We study the surface brightness maps and aperture-extracted spectra and model the point-spread functions. We identify signs of merger activities in the continuum emissions. We identify physically distinct [O  iii ] kinematic components that are bimodal and respectively trace ERQ-driven outflows of velocity dispersion |$\gtrsim$| 250 km s |$^{-1}$| and dynamically quiescent interstellar media. We find that the ERQ-driven ionized outflows are typically at |$\sim$| 1 kpc scales whereas the quiescent ionized gas extend to a few kpc. Compared to normal quasars the extremely fast ERQ-driven [O  iii ] outflows tend to be more compact, supporting the notion that ERQs are in a young stage of quasar/galaxy evolution and represent unique physical conditions beyond orientation differences with normal quasar populations. The kinematically quiescent [O  iii ] emissions in ERQs tend to be spatially resolved but less extended than in normal quasars, which can be explained by global and patchy dust obscuration. The hint of ionization cones suggests some of the obscuration can be partially explained by a patchy torus. [ABSTRACT FROM AUTHOR]

At optical/ultraviolet energies, blazars display an underlying thermal (unpolarized) contribution from the accretion disc, torus, and line-emitting regions, diluting the polarized emission from the jet-component. Optical polarimetry can be used to disentangle the thermal and non-thermal components, and place constraints on the particle populations and acceleration mechanisms responsible for the non-thermal emission. We present the results of a linear optical spectropolarimetric observing campaign of 18 blazars (six BL Lac-type objects and 12 flat-spectrum radio quasars) undertaken with the Southern African Large Telescope between 2016 and 2022. This was done to observe these systems during flaring states, as well as long-term monitoring of PKS1510-089, AP Lib, and PKS 1034-293. The observations traced the frequency dependence of the degree and angle of polarization, as well as changes in the spectral line strengths. We investigated possible correlations between the polarization and other observed characteristics for the sources. While an indication of correlation was found between the frequency dependence and the average level of polarization for some sources, a correlation was not found for the population as a whole. These results highlight that continuous observations and in-depth modelling of polarization and its frequency dependence is required to obtain a more holistic view of TeV blazars. [ABSTRACT FROM AUTHOR]

Context. Evolutionary models suggest that the initial growth phases of active galactic nuclei (AGN) and their central supermassive black holes (SMBHs) are dust-enshrouded and characterised by jet or wind outflows that should gradually clear the interstellar medium (ISM) in the host by heating and/or expelling the surrounding gas. eFEDSJ091157.4+014327 (z ∼ 0.6) was selected from X-ray samples of eROSITA (extended ROentgen Survey with an Imaging Telescope Array) for its characteristics: red colours, X-ray obscuration (NH = 2.7 × 1022 cm−2) and luminous (LX = 6.5 × 1044 erg s−1), similar to those expected in quasars with outflows. It hosts an ionised outflow as revealed by a broad [O III]λ5007 Å emission line in the SDSS integrated spectrum. For a proper characterisation of the outflow properties and their effects, we need spatially resolved information. Aims. We aim to explore the environment around the red quasar, morphology of the [O III] gas and characterise the kinematics, mass outflow rates and energetics within the system. Methods. We used spatially resolved spectroscopic data from Multi Unit Spectroscopic Explorer (MUSE) with an average seeing of 0.6″ to construct flux, velocity and velocity dispersion maps. Thanks to the spatially resolved [O III]λ5007 Å emission detected, we provide insights into the morphology and kinematics of the ionised gas and better estimates of the outflow properties. Results. We find that the quasar is embedded in an interacting and merging system with three other galaxies ∼50 kpc from its nucleus. Spatially resolved kinematics reveal that the quasar has extended ionised outflows of up to 9.2−0.4+1.2 kpc with positive and negative velocities up to 1000 km s−1 and −1200 km s−1, respectively. The velocity dispersion (W80) ranges from 600–1800 km s−1. We associate the presence of high-velocity components with the outflow. The total mass outflow rate is estimated to be ∼10 M⊙ yr−1, a factor of ∼3–7 higher than the previous findings for the same target and kinetic power of 2 × 1042 erg s−1. Considering different AGN bolometric luminosities, the kinetic coupling efficiencies range from 0.01%–0.03% and the momentum boosts are ∼0.2. Conclusions. The kinetic coupling efficiency values are low, which indicates that the ionised outflow is not energetically relevant. These values don't align with the theoretical predictions of both radiation-pressure-driven outflows and energy-conserving mechanisms. However, note that our results are based only on the ionised phase while theoretical predictions are multi-phase. Moreover, the mass loading factor of ∼5 is an indication that these outflows are more likely AGN-driven than star formation-driven. [ABSTRACT FROM AUTHOR]

We present ALMA band-7 observations of J2057−0030, a multi-component merger system at z ∼ 4.68 spanning at least 50 kpc in size, using the [CII] λ157.74 μm line and underlying far-infrared (FIR) continuum. We find two main components, the quasar (or QSO) and a dusty star-forming galaxy (DSFG), both detected in [CII] and continuum emission as well as multiple neighboring clumps detected only in [CII]. Three of these clumps form a (tidal) tail that extends from the QSO in a straight direction to the west, covering a projected distance of ∼10 kpc. This perturbed morphology, added to a spatial distance of ∼20 kpc and a velocity offset of Δv = 68 km s−1 between the QSO and the DSFG, strongly supports a merging scenario. By fitting a spectral energy distribution model to the continuum data, we estimate star formation rates of ≈402 M⊙ yr−1 for the QSO host and ≈244 M⊙ yr−1 for the DSFG, which locate them on or close to the main sequence of star-forming galaxies. The J2057−0030 QSO was selected for being one of the brightest unobscured quasars at its redshift while presenting a rather modest star formation rate. Based on a commonly accepted paradigm regarding the formation of quasars, this result is expected for a quasar that has already passed an obscured phase of rapid star formation during a major merger. However, we see that the merger event in this system is far from being finished, and it is rather likely somewhere between the first pericenter and subsequent close passages. This is presumably another case of a high-z quasar residing in a high-density environment with a companion obscured galaxy. [ABSTRACT FROM AUTHOR]

The realtime program for high-energy neutrino track events detected by the IceCube South Pole Neutrino Observatory releases alerts to the astronomical community with the goal of identifying electromagnetic counterparts to astrophysical neutrinos. Gamma-ray observations from the Fermi-Large Area Telescope (LAT) enabled the identification of the flaring gamma-ray blazar TXS 0506+056 as a likely counterpart to the neutrino event IC-170922A. By continuously monitoring the gamma-ray sky, Fermi-LAT plays a key role in the identification of candidate counterparts to realtime neutrino alerts. In this paper, we present the Fermi-LAT strategy for following up high-energy neutrino alerts applied to seven years of IceCube data. Right after receiving an alert, a search is performed in order to identify gamma-ray activity from known and newly detected sources that are positionally consistent with the neutrino localization. In this work, we study the population of blazars found in coincidence with high-energy neutrinos and compare them to the full population of gamma-ray blazars detected by Fermi-LAT. We also evaluate the relationship between the neutrino and gamma-ray luminosities, finding different trends between the two blazar classes BL Lacs and flat-spectrum radio quasars. [ABSTRACT FROM AUTHOR]

A characteristic feature of quasars is the observed non-linear relationship between their monochromatic luminosities at rest-frame 2500 Å and 2 keV. This relationship is evident across all redshifts and luminosities and, due to its non-linearity, can be implemented to estimate quasar distances and construct a Hubble Diagram for quasars. Historically, a significant challenge in the cosmological application of this relation has been its high observed dispersion. Recent studies have demonstrated that this dispersion can be reduced by excluding biased objects from the sample. Nevertheless, the dispersion remains considerable (δ ∼ 0.20 dex), especially when compared to the Phillips relation for supernovae Ia. Given the absence of a comprehensive physical model for the relation, it remains unclear how much of the remaining dispersion is tied to the physical mechanism behind the relation itself and how much can be attributed to other factors, not addressed by the sample selection and by the choice of X-ray and UV indicators. Potential contributing factors include (i) the scatter produced by using X-ray photometric results instead of spectroscopic ones, (ii) the intrinsic variability of quasars, and (iii) the inclination of the accretion disc relative to our line of sight. In this study, we thoroughly examine these three factors and quantify their individual contributions to the observed dispersion. Based on our findings, we argue that the characteristic dispersion of the X-ray–UV luminosity relationship (which is attributable to the physical mechanism behind it) is likely below 0.06 dex. This result reinforces the validity of using quasars as standard candles and offers valuable insights for developing physical models of the X-ray/UV relation. Achieving such a low dispersion on large observed data sets is hardly feasible, due to the complexity of removing all the empirical contributions to the scatter. Nevertheless, we argue that high-redshift subsamples can show a significantly lower dispersion than the average subsample. This aspect is particularly significant for cosmological applications, indicating that targeted observations of select high-redshift objects can enhance the cosmological power of quasars in constraining the shape of the Hubble Diagram at high redshift. [ABSTRACT FROM AUTHOR]

Context. Blazar flares provide a window onto the extreme physical processes occurring in relativistic outflows. Most numerical codes used for modelling blazar emission during flares use a simplified continuous-loss description of particle cooling due to the inverse Compton (IC) process, neglecting non-continuous (discrete) effects that arise in the Klein–Nishina (KN) regime. The significance of such effects has not yet been explored in detail. Aims. In this study, we investigate the importance of non-continuous Compton cooling losses and their impact on the electron spectrum and spectral energy distribution (SED) of blazars during high flux states (flares), as well as in the low state. Methods. We solve the full transport equation numerically, accounting for large relative jumps in energy by extending our existing blazar flare modelling code EMBLEM. We perform a detailed physical modelling of the brightest γ-ray flare of the archetypal flat-spectrum radio quasar (FSRQ) 3C 279 detected in June 2015. We then compare results obtained using the full cooling term and using the continuous-loss approximation. Results. We show that during flaring states of FSRQs characterised by high Compton dominance, the non-continuous cooling can lead to significant modification of the electron spectrum, introducing a range of distinct features, such as low-energy tails, hardening and/or softening, narrow and extended particle excesses, and shifts in the cooling break position. Such distortion translates to differences in the associated SED of up to ∼50%. This highlights the importance of non-continuous effects and the need to consider them in blazar emission models, particularly applied to extreme γ-ray flares. [ABSTRACT FROM AUTHOR]

Lensed quasars are powerful cosmic laboratories; they are used to simultaneously probe various astrophysical phenomena. Microlensing by stars within distant galaxies acts as strong gravitational lenses of multiply imaged quasars, and provides a unique and direct measurement of the lensed quasar internal structure. Microlensing of the continuum emitting region as well as the broad-line region (BLR) is well characterized by four observable indices, μcont, μBLR, WCI (wing-core), and RBI (red-blue), measured directly from the spectra. During the 2004−2007 monitoring period, image A of the quadruply lensed system Q2237+0305 underwent a strong microlensing amplification, while image D remained unaffected. We used 35 epochs of archival spectrophotometric data of Q2237+0305 obtained with the Very Large Telescope of the European Southern Observatory to develop an independent microlensing method for estimating the geometry and size of the BLR. We measured the index time series for the C IV line and the continuum emission at 1450 Å. We built a library of the simulated microlensing index time series that reproduce the observed times series based on three representative BLR models: Keplerian disk (KD), polar wind (PW), and equatorial wind (EW). After sampling the model parameter space, we find that KD is the predominant model, while PW and EW are less likely. We infer that the system is viewed at an intermediate viewing angle i ∼ 35°, and we estimate the most likely C IV BLR half-light radius r1/2 = 51 ± 23 light days. Our results are in good agreement with previous findings in the literature and extend the validity of the index-based approach to a temporal domain. [ABSTRACT FROM AUTHOR]

Context. A sub-population of AGNs where the central engine is obscured are known as type II quasars (QSO2s). These luminous AGNs have a thick and dusty torus that obscures the accretion disc from our line of sight. Thus, their special orientation allows for detailed studies of the AGN-host co-evolution. Increasing the sample size of QSO2 sources in critical redshift ranges is crucial for understanding the interplay of AGN feedback, the AGN-host relationship, and the evolution of active galaxies. Aims. We aim to identify QSO2 candidates in the 'redshift desert' using optical and infrared photometry. At this intermediate redshift range (i.e. 1 ≤ ɀ ≤ 2), most of the prominent optical emission lines in QSO2 sources (e.g. CIVλl549; [OIII]λλ4959, 5008) fall either outside the wavelength range of the SDSS optical spectra or in particularly noisy wavelength ranges, making QSO2 identification challenging. Therefore, we adopted a semi-supervised machine learning approach to select candidates in the SDSS galaxy sample. Methods. Recent applications of machine learning in astronomy focus on problems involving large data sets, with small data sets often being overlooked. We developed a 'few-shot' learning approach for the identification and classification of rare-object classes using limited training data (200 sources). The new AMELIA pipeline uses a transfer-learning based approach with decision trees, distance-based, and deep learning methods to build a classifier capable of identifying rare objects on the basis of an observational training data set. Results. We validated the performance of AMELIA by addressing the problem of identifying QSO2s at 1 ≤ ɀ ≤ 2 using SDSS and WISE photometry, obtaining an F1-score above 0.8 in a supervised approach. We then used AMELIA to select new QSO2 candidates in the 'redshift desert' and examined the nature of the candidates using SDSS spectra, when available. In particular, we identified a sub-population of [NeV]λ3426 emitters at ɀ ~ 1.1, which are highly likely to contain obscured AGNs. We used X-ray and radio crossmatching to validate our classification and investigated the performance of photometric criteria from the literature showing that our candidates have an inherent dusty nature. Finally, we derived physical properties for our QSO2 sample using photoionisation models and verified the AGN classification using an SED fitting. Conclusions. Our results demonstrate the potential of few-shot learning applied to small data sets of rare objects, in particular QSO2s, and confirms that optical-IR information can be further explored to search for obscured AGNs. We present a new sample of candidates to be further studied and validated using multi-wavelength observations. [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]

We investigate the black hole mass function at z ∼ 5 using XQz5, our recent sample of the most luminous quasars between the redshifts 4.5 < z < 5.3. We include 72 quasars with black hole masses estimated from velocity-broadened emission-line measurements and single-epoch virial prescriptions in the footprint of a highly complete parent survey. The sample mean Eddington ratio and standard deviation is log λ ≈ −0.20 ± 0.24. The completeness-corrected mass function is modelled as a double power law, and we constrain its evolution across redshift assuming accretion-dominated mass growth. We estimate the evolution of the mass function from z  = 5–4, presenting joint constraints on accretion properties through a measured dimensionless e-folding parameter, k ef ≡ 〈λ〉 U (1 − ϵ)/ϵ = 1.79 ± 0.06, where 〈λ〉 is the mean Eddington ratio, U is the duty cycle, and ϵ is the radiative efficiency. If these supermassive black holes were to form from seeds smaller than |$10^8\, {\rm M}_{\odot }$|⁠ , the growth rate must have been considerably faster at z ≫ 5 than observed from z  = 5–4. A growth rate exceeding 3 × the observed rate would reduce the initial heavy seed mass to |$10^{5-6}\, {\rm M}_{\odot }$|⁠ , aligning with supermassive star and/or direct collapse seed masses. Stellar mass (⁠|$10^2\, {\rm M}_{\odot }$|⁠) black hole seeds would require ≳4.5 × the observed growth rate at z ≫ 5 to reproduce the measured active black hole mass function. A possible pathway to produce the most extreme quasars is radiatively inefficient accretion flow, suggesting black holes with low angular momentum or photon trapping in supercritically accreting thick discs. [ABSTRACT FROM AUTHOR]

Observations of high-redshift quasars frequently promote suggestions of large black hole masses, whose presence so early in cosmic time is not easily explicable. I consider the parallel with ultraluminous X-ray sources (ULXs) – now known to be stellar-mass black hole (and neutron star) binaries apparently radiating far above their Eddington luminosities L Edd. The true luminosity in ULXs is actually only of order L Edd, for stellar-mass accretors, but has a very anisotropic ('beamed') component, plus a near-isotropic component of similar luminosity but much lower specific intensity. Observers viewing ULXs from within the beam but assuming spherical symmetry deduce a luminosity ≫ L Edd. These features appear because the accretors are fed mass at highly super-Eddington rates, most of it expelled in high-speed (v > 0.2 c) outflows from the accretion disc. I show that in similarly beamed AGN, emission-line properties would be essentially the same as in unbeamed sources, but standard virial mass indicators unusable because velocity widths are dominated by the outflows, not bound motions about the black holes. In an ensemble of this kind the apparently most luminous systems are always the most distant, but have the lowest black hole masses. Interpreting observations of this ensemble without knowing that they are beamed leads instead to very high black hole mass estimates. The analogy with ULXs therefore suggests that high-redshift quasars might actually have central black hole masses which could have grown from stellar values within the lookback time. I consider how one might test these ideas observationally. [ABSTRACT FROM AUTHOR]

Active galactic nuclei (AGNs) are known to exhibit optical/ultraviolet variability and most of them can be well modelled by the damped random walks. Physical processes that are not related to the accretion disc, such as tidal disruption events (TDEs) or moving foreground dusty clouds, can cause flare-like and eclipse-like features in the optical light curve. Both long-term and high-cadence monitoring are needed to identify such features. By combining the Sloan Digital Sky Survey (SDSS), Panoramic Survey Telescope and Rapid Response System, and the Zwicky Transient Facility (ZTF) survey, we are able to identify a rare sample (11) out of the SDSS quasar catalogue (⁠|$\sim\!\! 83\, 000$|⁠). These quasars exhibit more or less constant brightness but show rapid optical variation in the epochs of ZTF Public Data Release 2. To investigate the possible origins of these flare/eclipse-like variabilities, we propose the second-epoch spectroscopic observations with the Gran Telescopio CANARIAS. We find that the change in accretion rate plays a significant role in these quasar variabilities. Among them, we identify two changing-look AGN candidates: SDSS J1427+2930 and SDSS J1420+3757. The luminosity change of the former may be caused by the enhanced supermassive black hole's accretion or the TDE, while the latter is more related to the change in the accretion rate. [ABSTRACT FROM AUTHOR]

A substantial fraction of quasars display broad absorption lines (BALs) in their rest-frame ultraviolet spectra. While the origin of BALs is thought to be related to the accretion disc wind, it remains unclear whether the observed ratio of BAL to non-BAL quasars is a result of orientation. We conducted observations of 48 BAL quasars and the same number of non-BAL quasars at 322 MHz using the Giant Metrewave Radio Telescope. Combined with previous flux measurements ranging from MHz to GHz frequencies, we compared continuum radio spectra between the two quasar groups. These data offer insights into low-frequency radio properties that have been difficult to investigate with previous observations only at GHz frequencies. Our results show that 73 ± 13 per cent of the BAL quasars exhibit steep or peaked spectra, a higher proportion than the 44 ± 14 per cent observed in the non-BAL quasars. In contrast, there are no discernible differences between the two quasar groups in the radio luminosity, peak frequency, and spectral index distributions of sources with steep or peaked spectra and sources with flat or inverted spectra. Generally, as the jet axis and line of sight become closer to parallel, quasars exhibit flat or inverted spectra rather than steep or peaked spectra. Therefore, these results suggest that BAL quasars are more frequently observed farther from the jet axis than non-BAL quasars. However, given that a certain proportion of BAL quasars exhibit flat or inverted spectra, more than the simple orientation scenario is required to elucidate the radio properties of BAL quasars. [ABSTRACT FROM AUTHOR]

In this work, we study the co-evolution of central black holes (BHs) and host galaxies by utilizing an advanced iteration of the DELPHI semi-analytical model of galaxy formation and evolution. Based on dark matter halo merger trees spanning the redshift range from z  = 20 to z  = 4, it now incorporates essential components such as gas heating and cooling, cold and hot BH accretion, jet and radiative AGN feedback. We show how different BH growth models impact quasar and galaxy observables at z ≥ 5, providing predictions that will help discriminate between super-Eddington and Eddington-limited accretion models: despite being both consistent with observed properties of SMBHs and their host galaxies at z ∼ 5–7, they become very clearly distinguishable at higher redshift and in the intermediate mass regime. We find that the super-Eddington model, unlike the Eddington-limited scenario, predicts a gap in the BH mass function corresponding to the intermediate-mass range 104 M⊙ < M bh < 106 M⊙. Additionally, it predicts black holes up to two orders of magnitude more massive for the same stellar mass at z  = 9. The resulting velocity dispersion–BH mass relation at z ≥ 5 is consistent with local measurements, suggesting that its slope and normalization are independent of redshift. Depending on the Eddington ratio, we also model the emergence of AGN jets, predicting their duty cycle across as a function of BH mass and their potential impact on the observed number density distribution of high-redshift AGN in the hard X-ray band. [ABSTRACT FROM AUTHOR]

We report the identification of 64 new candidates of compact galaxies, potentially hosting faint quasars with bolometric luminosities of Lbol = 1043–1046 erg s−1, residing in the reionization epoch within the redshift range of 6 ≲ z ≲ 8. These candidates were selected by harnessing the rich multiband datasets provided by the emerging JWST-driven extragalactic surveys, focusing on COSMOS-Web, as well as JADES, UNCOVER, CEERS, and PRIMER. Our search strategy includes two stages: applying stringent photometric cuts to catalog-level data and detailed spectral energy distribution fitting. These techniques effectively isolate the quasar candidates while mitigating contamination from low-redshift interlopers, such as brown dwarfs and nearby galaxies. The selected candidates indicate physical traits compatible with low-luminosity active galactic nuclei, likely hosting ≈105–107M⊙ supermassive black holes (SMBHs) living in galaxies with stellar masses of ≈108–1010M⊙. The SMBHs selected in this study, on average, exhibit an elevated mass compared to their hosts, with the mass ratio distribution slightly higher than those of galaxies in the local Universe. As with other high-z studies, this is at least in part due to the selection method for these quasars. An extensive Monte Carlo analysis provides compelling evidence that heavy black hole seeds from the direct collapse scenario appear to be the preferred pathway to mature this specific subset of SMBHs by z ≈ 7. Notably, most of the selected candidates might have emerged from seeds with masses of ∼105M⊙, assuming a thin disk accretion with an average Eddington ratio of fEdd = 0.6 ± 0.3 and a radiative efficiency of ϵ = 0.2 ± 0.1. This work underscores the significance of further spectroscopic observations, as the quasar candidates presented here offer exceptional opportunities to delve into the nature of the earliest galaxies and SMBHs that formed during cosmic infancy. [ABSTRACT FROM AUTHOR]

We identify a fading AGN SDSS J220141.64+115124.3 from the internal Product Launch-11 (MPL-11) in Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. The central region with a projected radius of |$\sim$| 2.4 kpc is characterized as LINER-like line ratios while the outskirts extended to |$\sim$| 15 kpc show Seyfert-like line ratios. The |${\rm{[O {\small III}]}}$| |$\lambda$| 5007 luminosity of the Seyfert regions is a factor of 37 (2) higher than the LINER regions without (with) dust attenuation correction, suggesting that the AGN activity decreases at least |$\sim$| 8 |$\times$| 10 |$^3$| yr (⁠|$\sim$| 2.4 kpc/light-speed) ago. We model the emission line spectra in the central region with double Gaussian components (a narrow core and a broad wing) and analyse the properties of each component. The narrow core component mostly co-rotates with the stellar disc, whereas the broad wing component with a median of the velocity dispersion |$\sim$| 300 km s |$^{-1}$| is related to a wind outflow. The kinematic position angle (PA) of the ionized gas shows an |$\sim 20^{\circ }$| twist from the galaxy centre to 1.5 effective radius. The median of the PA difference between the gas and stellar components is as large as |$\sim 50^{\circ }$| within 0.4 effective radius. The tidal feature in DESI image and star–gas misalignment suggest this galaxy is a merger remnant. Combining all these observational results as well as public available X-ray and MIR luminosities, we confirm this is a fading AGN, the merger process kick-started the central engine to quasar phase which ionized gas composed of tidal debris, and now the activity of the central black hole decreases. The discontinuity in |${\rm{[O {\small III}]}}$| |$\lambda$| 5007 flux and EQW maps is due to multiple AGN outbursts triggered by merger remnant gas inflows. [ABSTRACT FROM AUTHOR]

Studies show that both radio jets from the active galactic nuclei (AGNs) and the star formation (SF) activity in quasar host galaxies contribute to the quasar radio emission; yet their relative contributions across the population remain unclear. Here, we present an improved parametric model that allows us to statistically separate the SF and AGN components in observed quasar radio flux density distributions, and investigate how their relative contributions evolve with AGN bolometric luminosity (⁠|$L_\mathrm{bol}$|⁠) and redshift (z) using a fully Bayesian method. Based on the newest data from LOw-Frequency ARray Two-metre Sky Survey data release 2, our model gives robust fitting results out to |$z\sim 4$|⁠ , showing a quasar host galaxy SF rate (SFR) evolution that increases with bolometric luminosity and with redshift out to |$z\sim 4$|⁠. This differs from the global cosmic SFR density, perhaps due to the importance of galaxy mergers. The prevalence of radio AGN emissions increases with quasar luminosity, but has little dependence on redshift. Furthermore, our new methodology and large sample size allow us to subdivide our data set to investigate the role of other parameters. Specifically, in this paper, we explore quasar colour and demonstrate that the radio excess in red quasars is due to an enhancement in AGN-related emission, since the host galaxy SF contribution to the total radio emission is independent of quasar colour. We also find evidence that this radio enhancement occurs mostly in quasars with weak or intermediate radio power. [ABSTRACT FROM AUTHOR]

We have identified a broad absorption line (BAL) outflow in the HST /STIS spectrum of the quasar QSO B0254-3327B at velocity v  = −3200 km s−1. The outflow has absorption troughs from ions such as Ne  viii , Na  ix , Si  xii , and Ne  v. We also report the first detection of S  xiv absorption troughs, implying very high ionization. Via measurement of the ionic column densities, photoionization analysis, and determination of the electron number density of the outflow, we found the kinetic luminosity of the outflow system to be up to ∼1 per cent of the quasar's Eddington luminosity, or ∼5 per cent of the bolometric luminosity, making it a potential contributor to AGN feedback. A solution with two ionization phases was needed, as a single phase was not sufficient to satisfy the constraints from the measured ionic column densities. We find that the ionization parameter of the very high-ionization phase of the outflow is within the expected range of an X-ray warm absorber. We also examined the physical properties of the outflow of Q0254-334 along with previously studied extreme UV outflows, with a total sample of 24 outflow systems, finding a weak negative correlation between outflow velocity and distance from the central source, with larger distances corresponding to slower velocities. The very high-ionization phase of the Q0254-334 outflow has one of the highest ionization parameters of UV absorption outflows to date, which we attribute to the presence of S  xiv. [ABSTRACT FROM AUTHOR]

Context. Quasar outflows are often analyzed to determine their ability to contribute to active galactic nucleus (AGN) feedback. We identified a broad absorption line (BAL) outflow in the VLT/UVES spectrum of the quasar SDSS J1321−0041. The outflow shows troughs from Fe II, and is thus categorized as an FeLoBAL. This outfow is unusual among the population of FeLoBAL outflows, as it displays C II and Si II BALs. Aims. Outflow systems require a kinetic luminosity above ∼0.5% of the quasar's luminosity to contribute to AGN feedback. For this reason, we analyzed the spectrum of J1321−0041 to determine the outflow's kinetic luminosity, as well as the quasar's bolometric luminosity. Methods. We measured the ionic column densities from the absorption troughs in the spectrum and determined the hydrogen column density and ionization parameter using those column densities as our constraints. We also determined the electron number density, ne, based on the ratios between the excited-state and resonance-state column densities of Fe II and Si II. This allowed us to find the distance of the outflow from its central source, as well as its kinetic luminosity. Results. We determined the kinetic luminosity of the outflow to be 8.4−5.4+13.7 × 1045 erg s−1 8. 4 − 5.4 + 13.7 × 10 45 erg s − 1 $ 8.4^{+13.7}_{-5.4}\times 10^{45}\,\mathrm{erg\,s}^{-1} $ and the quasar's bolometric luminosity to be 1.72 ± 0.13 × 1047 erg s−1, resulting in a ratio of Ėk/LBol = 4.8−3.1+8.0% E ˙ k / L Bol = 4. 8 − 3.1 + 8.0 % $ \dot{E}_{\mathrm{k}}/L_{\mathrm{Bol}}=4.8^{+8.0}_{-3.1}\% $. We conclude that this outflow has a sufficiently high kinetic luminosity to contribute to AGN feedback. [ABSTRACT FROM AUTHOR]

We investigate possible factors that drive fast quasar outflows using a sample of 39 249 quasars at median redshift 〈 z 〉 ≈ 2.17. Unique to this study, the quasar redshifts are re-measured based on the Mg  ii emission line, and explore unprecedented outflow velocities (>6000 km s−1), while maintaining statistical significance. We measure reliable C  iv blueshifts for 1178 quasars with velocities >2500 km s−1. From those, 255(13) quasars have blueshifts above 4000(6000) km s−1, with the highest C  iv velocity ≈7000 km s−1. Several correlations are observed, where higher C  iv blueshifts in general are in quasars with broader, weaker C  iv emission profiles, weak He  ii emission, larger Eddington ratios, and bluer ultraviolet (UV) continuum slope across the rest-frame UV to near-infrared. Analysis reveals two primary factors contributing to faster outflows: higher Eddington ratios, and softer far-UV continuum (hν >24.6 eV). We find supporting evidence that radiative line driving may generate extreme outflow velocities, influenced by multiple factors as suggested by the aforementioned correlations. This evidence highlights the importance of considering a multidimensional parameter space in future studies when analyzing large C  iv blueshifts to determine the fundamental causes of outflows. [ABSTRACT FROM AUTHOR]

Cold quasars are a rare population of luminous, unobscured quasars associated with host galaxies that have a high star formation rate. We aimed to study the host galaxies of 64 of these cold quasars in order to probe how the supermassive black holes and host galaxies were co-evolving. We compiled data from the XMM-XXL survey and cross-matched with the VHS, WISE, and HerMES surveys to obtain multiwavelength photometry spanning the X-ray to the infrared and including optical spectroscopy. From the data, we calculated the supermassive black hole's mass using broad emission from the Mg  ii and Hbeta lines. We compared this with the stellar mass of the entire galaxy and found that the black holes are significantly more massive than would be predicted by local relations, indicating that the majority of black hole growth precedes the bulk of the the stellar mass formation. In addition to this, we created a spectral energy distribution for each galaxy to calculate the star formation rate. We compared the star formation rate with the black hole accretion rate and find that the stellar mass is rapidly increasing at a relative rate faster than the black hole growth, supporting the picture where the black hole grows first. [ABSTRACT FROM AUTHOR]

Quasar winds can shock and sweep up ambient interstellar medium (ISM) gas, contributing to galactic quenching. We combine and extend past models of energy-conserving shock bubbles around quasars, investigate model implications from an observational standpoint, and test model predictions using new high-resolution spectroscopic observations of the broad absorption-line quasar SDSS J030000.56+004828.0 (J0300). Even with constant energy input from the wind, a bubble's expansion decelerates over time as more ISM gas is swept up. Our new observations enable a direct search for this deceleration. We obtain the tightest reported 3σ limit on the average rest-frame deceleration (or acceleration) of a quasar outflow: | a | < 0.1 km s−1 yr−1 (<3 × 10−4 cm s−2) in the relatively low-velocity Ca  ii outflow of J0300 over 9.65 rest-frame years. We can satisfy these limits with certain parameter choices in our model, but the large velocity range of the Ca  ii absorption in J0300 rules out the hypothesis that such gas shares the velocity of the swept-up ISM gas in a self-similar shock bubble. We investigate the possibility of ram-pressure acceleration of preexisting ISM clouds and conclude that the velocity range seen in Ca  ii in J0300 is potentially consistent with such an explanation. The Ca  ii -absorbing gas clouds in J0300 have been inferred to have high densities by Choi et al. in which case they can only have been accelerated to their current speeds if they were originally at least an order of magnitude less dense than they are today. [ABSTRACT FROM AUTHOR]

We examine the long-term (rest-frame time-scales from a few months to ∼20 yr) X-ray variability of a sample of 2344 X-ray bright quasars from the Sloan Digital Sky Survey (SDSS) data release 14 quasar (DR14Q) catalogue, based on the data of the Spectrum-Roentgen-Gamma (SRG)/ eROSITA All-Sky Survey complemented for ∼7 per cent of the sample by archival data from the XMM–Newton Serendipitous Source Catalogue. We characterize variability by a structure function, SF2(Δ t). We confirm the previously known anticorrelation of the X-ray variability amplitude with luminosity. We also study the dependence of X-ray variability on black hole mass, M BH, and on an X-ray-based proxy of the Eddington ratio, λX. Less massive black holes prove to be more variable for given Eddington ratio and time-scale. X-ray variability also grows with decreasing Eddington ratio and becomes particularly strong at λX of less than a few per cent. We confirm that the X-ray variability amplitude increases with increasing time-scale. The SF2(Δ t) dependence can be satisfactorily described by a power law, with the slope ranging from ∼0 to ∼0.4 for different (M BH, λX) subsamples (except for the subsample with the lowest black hole mass and Eddington ratio, where it is equal to 1.1 ± 0.4). [ABSTRACT FROM AUTHOR]

We use new 144 MHz observations over 5634 deg2 from the LOFAR (Low Frequency Array) Two-metre Sky Survey (LoTSS) to compile the largest sample of uniformly selected, spectroscopically confirmed quasars from the 14th data release of the Sloan Digital Sky Survey (SDSS-DR14). Using the classical definition of radio loudness, R = log (L 1.4GHz/ Li), we identify 3697 radio-loud (RL) and 111 132 radio-quiet (RQ) sources at 0.6 < z < 3.4. To study their properties, we develop a new rest-frame spectral stacking algorithm, designed with forthcoming massively multiplexed spectroscopic surveys in mind, and use it to create high signal-to-noise composite spectra of each class, matched in redshift and absolute i -band magnitude. We show that RL quasars have redder continuum and enhanced [O  ii ] emission than their RQ counterparts. These results persist when additionally matching in black hole mass, suggesting that this parameter is not the defining factor in making a quasi-stellar object (QSO) RL. We find that these features are not gradually varying as a function of radio loudness, but are maintained even when probing deeper into the RQ population, indicating that a clear-cut division in radio loudness is not apparent. Upon examining the star formation rates (SFRs) inferred from the [O  ii ] emission line, with the contribution from active galactic nucleus removed using the [Ne  v ] line, we find that RL quasars have a significant excess of star formation relative to RQ quasars out to z = 1.9 at least. Given our findings, we suggest that RL sources either preferably reside in gas-rich systems with rapidly spinning black holes, or represent an earlier obscured phase of QSO evolution. [ABSTRACT FROM AUTHOR]