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Abstract We report a detailed analysis of GAMA 376183, a powerful, heavily obscured active galactic nucleus (AGN) hosted by a low-mass galaxy (M_⋆ ≈ 10¹⁰M_⊙) likely experiencing a galaxy merger. The source was initially identified due to its remarkably strong [Nev]λ3426 emission, exhibiting a rest-frame equivalent width of ≈48 Å. We present ∼100 ks Nuclear Spectroscopic Telescope Array (or NuSTAR) follow-up observations, confirming its heavily obscured nature with a column density (in cm⁻²) of $\log N_{\mathrm{H}}=23.3_{-1.2}^{+0.4}$ and an intrinsic 2–10 keV luminosity (in erg s⁻¹) of $\log L_{\mathrm{X},\mathrm{int}}=42.92_{-0.20}^{+0.24}$ . GAMA 376183 thus represents one of the few known heavily obscured AGNs in low-mass galaxies. Its estimated Eddington ratio isλ_Edd ≈ 0.8, indicative of rapid black hole growth. High-resolution optical images reveal a disturbed, likely merging morphology, while its multiwavelength spectral energy distribution indicates a recent starburst in its host galaxy. These pieces of evidence suggest that the ongoing merger has triggered both the heavily obscured, Eddington-limited accretion and the starburst, making GAMA 376183 a rare observed case in low-mass galaxies. Overall, this unique source demonstrates that (i) [Nev] can help identify heavily obscured low-mass AGNs, and (ii) the merger-driven coevolution framework established for massive galaxies may also extend to low-mass galaxies. 

Abstract We report the fastest quasar outflow first detected in the ultraviolet, via variable Civand Siivabsorption at outflow velocities −77,000 km s⁻¹to at least −90,000 km s⁻¹, in the radio-quiet quasar SDSS J231854.31+243954.2 (J2318). J2318 is a weak-lined quasar in the rest-frame ultraviolet, but Gemini GNIRS spectroscopy reveals an Hαredshift ofz = 2.6781 ± 0.0004. A 20 yr photometric time series shows peak-to-peak variability of 0.5 mag in thegband. The Civoutflow strengthened monotonically over three epochs spanning ∼2.2 rest-frame years. The existence of such a high-velocity outflow implies that models of quasar outflows must be able to either accelerate gas to 0.3cwhile still preserving Civand Siivions, or enable the formation of Civand Siivions in gas, which has been accelerated to 0.3c. Virial estimates reveal a black-hole mass of 1.65 × 10⁹M_⊙, which leads to an Eddington luminosity and Eddington ratio of 2.4 × 10⁴⁷erg s⁻¹and 0.45, respectively. Using very conservative assumptions, the UV-absorbing outflow alone has an estimated mass loss of >0.82M_⊙yr⁻¹and a kinetic luminosity ratioL_kin/L_bol≥ 0.75%. The lower limit is just above the threshold usually cited for significant feedback on the host galaxy. Comparison to PDS 456, the only other known quasar with a UV-absorbing outflow at 0.3c, suggests that the true $\dot{M}$ andL_kin/L_bolcould be up to 2 orders of magnitude larger. 

Abstract Changing-look active galactic nuclei (CL-AGNs) exhibit dramatic spectral variability on unexpectedly short timescales, challenging standard accretion flow models. Despite growing samples, the physical drivers of this extreme variability, and the potential link to host-galaxy properties, remain unknown. Regardless of the underlying mechanism, the transition between AGN-dominated and host-dominated spectra offers a unique opportunity to study relations between AGNs and their hosts within the same objects. We present intermediate-resolution spectroscopy of 23 CL-AGNs identified by the Sloan Digital Sky Survey V (SDSS-V), obtained with the Very Large Telescope/X-shooter and Gemini-N/GMOS. An analysis of the Mgiiλ2798 emission line observed in the spectra demonstrates that the majority of these sources cannot be driven by variable obscuration. Our CL-AGNs roughly follow theM_BH–σ_*andM_BH–M_*relations of inactive galaxies, with a median black hole-to-stellar mass ratio of 0.38 %. We find no evidence that the stellar population properties of our CL-AGNs, including stellar mass, age, young stellar fraction, and star formation rate, differ from those of type 2 AGNs in SDSS. These results suggest that CL-AGNs reside in typical AGN host galaxies and that their extreme variability is likely unrelated to host-galaxy environment, supporting the idea that CL-AGNs are not a distinct population, but rather represent a phase of normal AGN activity. This result, in turn, implies that CL-AGNs can serve as useful probes of the AGN-host connection, providing access to both AGN-dominated and host-dominated spectra of the same systems. 

ABSTRACT We present an investigation of the rest-frame optical/UV and X-ray properties for a sample of 3027 X-ray selected quasars between $$1.5 \le z \le 3.5$$ detected in the deepest Spectrum Roentgen Gamma/eROSITA data available and observed by the fifth iteration of the Sloan Digital Sky Survey (SDSS-V). We parametrize the C iv $$\lambda 1549$$ emission line to infer the strength of accretion disc winds and perform X-ray spectral fitting. The X-ray spectral properties – namely, the 2 keV monochromatic luminosity ($$L_{2\, \text{keV}}$$) and spectral slope – are not strongly correlated with wind strength. Despite this result, the X-ray selected sample is shifted towards lower C iv blueshifts and higher equivalent widths than the optically selected sample observed in previous SDSS surveys, and matching in optical luminosity, redshift, and Eddington ratio does not reduce these differences. We estimate the far-UV luminosity using the He ii $$\lambda 1640$$ line luminosity and define the slopes between this and the 2500 Å monochromatic luminosity ($$L_{2500}$$) and $$L_{2\, \text{keV}}$$ ($$\alpha _\text{ouv}$$ and $$\alpha _\text{uvx}$$, respectively) in a similar manner to the familiar $$\alpha _\text{ox}$$ parameter, which tracks the spectral slope between $$L_{2500}$$ and $$L_{2\, \text{keV}}$$. The quantity $$\alpha _\text{ouv}$$ is more strongly correlated with wind strength in our sample than $$\alpha _\text{ox}$$. We show that the correlation between $$\alpha _\text{ox}$$ and wind strength is driven by the relationship between the optical luminosity and wind strength. Our results are consistent with a radiation line-driven wind, whereby the ionizing far-UV photons must not over-ionize the gas. The hard X-ray photons are few enough in number to have a negligible effect on the ionization state of the material. 

Abstract Binary supermassive black holes (SMBHs) are consequences of galaxy mergers and dominate the low-frequency gravitational-wave background. Finding binary SMBHs in existing time-domain observations has proven difficult, as their periodic, electromagnetic signals can be confused with the natural variability of single quasars. In this work, we investigate the effects of host-galaxy contamination and survey design (cadence and duration) on the detectability of binary SMBHs with the upcoming Rubin Observatory Legacy Survey of Space and Time (LSST). We simulate millions of LSST light curves of single and binary quasars, with a distribution of quasar and host-galaxy properties motivated by empirical observations and the anticipated LSST detection space. We then apply simple sinusoidal curve fits as a potential computationally inexpensive detection method. We find that host-galaxy contamination will increase false-positive rates and decrease binary parameter recovery rates. Lower-mass, lower-luminosity binary systems are most likely to be negatively affected by host-galaxy contamination. We also find that monitoring duration affects binary detection more than survey effective cadence for this detection method. As the light-curve duration increases, false-positive rates are suppressed and binary parameter recovery rates, especially for binary periods, are improved. Increasing the light-curve duration from 5 to 10 yr shows the most dramatic improvement for successful binary detection and false-positive rejection, with additional improvement from extending the light-curve duration to 20 yr. The observation duration increase is especially critical for recovering binary periods that are longer than a decade. 

Abstract The Legacy Survey of Space and Time (LSST), being conducted by the Vera C. Rubin Observatory, is a wide-field multiband survey that will revolutionize our understanding of extragalactic sources through its unprecedented combination of area and depth. While the LSST survey strategy is still being finalized, the Rubin Observatory team has generated a series of survey simulations using the LSST Operations Simulator to explore the optimal survey strategy that best accommodates the majority of scientific goals. In this study, we utilize the latest simulated data and the Metrics Analysis Framework to predict the number of quasars detectable by LSST in each band and evaluate the impact of different survey strategies. We find that the number of quasars and lower-luminosity active galactic nuclei (AGNs) detected in the baseline strategy (v4.3.1) in the redshift rangez= 0.3–6.7 will be highest in theiband (about 12 million) and lowest in theuband (about 6 million). Over 70% of quasars are expected to be detected within the first year in all bands, as LSST will have already reached the break in the luminosity function at most redshifts. With a limiting magnitude of 25.7 (26.9) mag, we expect to detect 184 (199) million AGNs in thezband (rband) over the 10 yr survey, with quasars constituting only 6% of the total AGNs in each band. This arises because, considering that the luminosities of most low-luminosity AGNs are affected by contamination from their host galaxies, we set a magnitude threshold when predicting the number of quasars. We find that variations in theu-band strategy can impact the number of quasar detections. Specifically, the difference between the baseline strategy and that with the largest total exposure inuis 15%. In contrast, changes in rolling strategies, Deep Drilling Field strategies, weather conditions, and Target of Opportunity observations result in variations below 2%. These results provide valuable insights for optimizing approaches to maximize the scientific output of quasar studies. 

Abstract It is well established that cosmic supermassive black hole (SMBH) growth peaks atz ≈ 1.5–2, followed by a strong decline of ≈1–1.5 dex toward the present day, with the comoving number density of higher-luminosity active galactic nuclei (AGNs) peaking at higher redshift (referred to as “AGN downsizing”). We leverage the best current measurements of the SMBH accretion distribution, based upon data from nine well-characterized extragalactic fields with a “wedding-cake” design, to investigate and quantify the drivers of the drastic decline in cosmic SMBH growth. The decline in the typical Eddington ratio (λ_Edd) of AGNs (decreasing by ≈1.35 dex fromz ≈ 1.5–2 toz ≈ 0.2) is the dominant driver for the broad decline in SMBH growth, rather than a shift of accretion activity to less-massive SMBHs. Asλ_Edddecreases toward lower redshift, the primary contributor to the cosmic SMBH accretion density (ρ_BHAR) has shifted from high-λ_EddAGNs to low-λ_EddAGNs, even though the latter always dominate the comoving AGN number density atz < 4. We also find that the decline in SMBH growth toward lower SMBH mass in less-massive galaxies is primarily due to the decreasing outburst luminosity rather than the duty cycle. 

Abstract SDSS J1539+3954 (z ≈ 1.935), a radio-quiet weak-line quasar (WLQ), exhibited exceptional X-ray variability in 2019–2020, with its X-ray flux increasing by over 20 times from 2013 to 2019 and subsequently dropping by at least a factor of 9 in 2020. Motivated by the empirical correlations between X-ray and radio emission in the cores of active galactic nuclei (AGNs), we carried out a follow-up radio study in the 0.3–10 GHz range using the Giant Metrewave Radio Telescope (GMRT; 2020, 2022, 2024) and Very Large Array (VLA; 2022), and analyzed archival Very Large Array Sky Survey (VLASS) 3 GHz data (2017–2023) to investigate the source’s radio properties and potential connection with the X-ray behavior. Our observations reveal a compact radio source with a spectral index of −0.65 ± 0.15 in the frequency range 0.3–1.4 GHz and −1.09 ± 0.16 in 3–10 GHz. While the source was undetected in VLA-FIRST (1994) and VLASS epochs, the GMRT and VLA observations show no statistically significant variability over the monitored period. The absence of detectable changes in the radio flux, despite strong X-ray variability, suggests no direct connection between the X-ray variability and the radio emission, consistent with the thick-disk-plus-outflow (TDO) model for WLQs. However, the sensitivity limit of the surveys prevents us from drawing definitive conclusions regarding variability on longer timescales between the VLA-FIRST and GMRT epochs. We further explore possible mechanisms driving the radio emission from this source. Our analysis rules out small-scale jets and coronal emission as the primary drivers of the radio emission, suggesting that extended emission from AGN winds and star formation is the more plausible mechanism. 

Abstract Ultrafast outflows (UFOs) are powerful, highly ionized winds launched from the innermost regions of active galactic nuclei (AGNs), reaching velocities of 0.03–0.3cand playing a key role in AGN feedback. We present a photoionization analysis of an 18 ks XMM-Newton snapshot of the Seyfert 1 AGN Mrk 877, revealing three distinct UFO components with line-of-sight velocities of $0.10_{-0.005}^{+0.005}c$ , $0.04_{-0.004}^{+0.005}c$ , and $0.05_{-0.004}^{+0.005}c$ . These components span a broad range of ionization parameters and column densities, producing absorption features across both soft and hard X-ray bands. Even under the most conservative assumption for the volume filling factor, the fastest component exceeds 5% of the Eddington luminosity, making it capable of driving strong galaxy-scale feedback. The soft X-ray UFO component, despite its lower ionization, shares a similar velocity as a higher-ionization component, hinting at a two-phase medium likely shaped by clumpiness or interactions with ambient material. The density profile inferred from the absorption measurement distributions and the positive trend between outflow momentum rate and radiation momentum flux suggest that wind is powered by a combination of radiative and magnetic driving. 

Abstract Dust-obscured galaxies (DOGs) with extremely red optical-to-infrared colors are often associated with intense starburst and active galactic nucleus (AGN) activity. Studying DOGs can provide insights into the processes that drive the growth of galaxies and their central supermassive black holes. However, the general DOG population is heterogeneous, spanning a wide range of evolutionary stages, and has X-ray obscuring column densities (N_H) covering low to high levels. In this work, we focus on seven high Eddington ratio DOGs ( $\log {\lambda }_{\mathrm{Edd}}\gtrsim -0.5$ ) to examine their X-ray obscuration properties using new and archival X-ray observations. We confirm that these systems are generally heavily obscured, with six out of seven havingN_H ≳ 10²³cm⁻²and three out of seven havingN_H ≳ 10²⁴cm⁻². Based on the observed similarity with the rare Hot DOG population, we argue that both high-λ_EddDOGs and Hot DOGs likely trace the postmerger phase, during which AGNs are enshrouded by large columns of dust-rich material.