[en] If broad absorption line (BAL) quasars represent a high-covering-fraction evolutionary state (even if this is not the sole factor governing the presence of BALs), it is expected that they should show an excess of mid-infrared radiation compared to normal quasars. Some previous studies have suggested that this is not the case. We perform the first analysis of the IR properties of radio-loud BAL quasars, using IR data from WISE and optical (rest-frame ultraviolet) data from SDSS, and compare the BAL quasar sample with a well-matched sample of unabsorbed quasars. We find a statistically significant excess in the mid- to near-infrared luminosities of BAL quasars, particularly at rest-frame wavelengths of 1.5 and 4 μm. Our sample was previously used to show that BALs are observed along many lines of sight toward quasars, but with an overabundance of more edge-on sources, suggesting that orientation factors into the appearance of BALs. The evidence here—of a difference in IR luminosities between BAL quasars and unabsorbed quasars—can be ascribed to evolution. This suggests that a merging of the current BAL paradigms is needed to fully describe the class.

[en] Unification by orientation is a ubiquitous concept in the study of active galactic nuclei. A gold standard of the orientation paradigm is the hypothesis that radio galaxies and radio-loud quasars are intrinsically the same, but are observed over different ranges of viewing angles. Historically, strong support for this model was provided by the projected sizes of radio structure in luminous radio galaxies, which were found to be significantly larger than those of quasars, as predicted due to simple geometric projection. Recently, this test of the simplest prediction of orientation-based models has been revisited with larger samples that cover wider ranges of fundamental properties—and no clear difference in projected sizes of radio structure is found. Cast solely in terms of viewing angle effects, these results provide convincing evidence that unification of these objects solely through orientation fails. However, it is possible that conflicting results regarding the role orientation plays in our view of radio sources simply result from insufficient sampling of their intrinsic size distribution. We test this possibility using Monte Carlo simulations constrained by real sample sizes and properties. We develop models for the real intrinsic size distribution of radio sources, simulate observations by randomly sampling intrinsic sizes and viewing angles, and analyze how likely each sample is to support or dispute unification by orientation. We find that, while it is possible to reconcile conflicting results purely within a simple, orientation-based framework, it is very unlikely. We analyze the effects that sample size, relative numbers of radio galaxies and quasars, the critical angle that separates the two subclasses, and the shape of the intrinsic size distribution have on this type of test

[en] We measure the average deflection of cosmic microwave background photons by quasars at $⟨<!--\; ???\; -->z⟩<!--\; ???\; -->=1.7$. Our sample is selected from the Sloan Digital Sky Survey to cover the redshift range 0.9 ≤ z ≤ 2.2 with absolute i-band magnitudes of M _i ≤ –24 (K-corrected to z = 2). A stack of nearly 200,000 targets reveals an 8σ detection of Planck's estimate of the lensing convergence toward the quasars. We fit the signal with a model comprising a Navarro–Frenk–White density profile and a two-halo term accounting for correlated large-scale structure, which dominates the observed signal. The best-fitting model is described by an average halo mass ${\mathrm{l}\mathrm{o}\mathrm{g}}_{10}(M_{\mathrm{h}}/h^{-<!--\; ???\; -->1}{M}_{\odot <!--\; ???\; -->})=12.6\pm <!--\; ??\; -->0.2$ and linear bias b = 2.7 ± 0.3 at $⟨<!--\; ???\; -->z⟩<!--\; ???\; -->=1.7$, in excellent agreement with clustering studies. Here, we also report a hint, at a 90% confidence level, of a correlation between the convergence amplitude and luminosity, indicating that quasars brighter than M _i lesssim –26 reside in halos of typical mass $M_{\mathrm{h}}\approx <!--\; ???\; -->{10}^{13}{h}^{-<!--\; ???\; -->1}{M}_{\odot <!--\; ???\; -->}$, scaling roughly as $M_{\mathrm{h}}\propto <!--\; ???\; -->L_{\mathrm{o}\mathrm{p}\mathrm{t}}^{3/4}$ at $M_i\lesssim <!--\; ???\; -->-<!--\; ???\; -->24$ mag, in good agreement with physically motivated quasar demography models. Although we acknowledge that this luminosity dependence is a marginal result, the observed M _h–L _opt relationship could be interpreted as a reflection of the cutoff in the distribution of black hole accretion rates toward high Eddington ratios: the weak trend of M _h with L _opt observed at low luminosity becomes stronger for the most powerful quasars, which tend to be accreting close to the Eddington limit.

[en] Representing simultaneous black hole accretion during a merger, binary active galactic nuclei (AGNs) could provide valuable observational constraints to models of galaxy mergers and AGN triggering. High-resolution radio interferometer imaging offers a promising method for identifying a large and uniform sample of binary AGNs because it probes a generic feature of nuclear activity and is free from dust obscuration. Our previous search yielded 52 strong candidates of kiloparsec-scale binaries over the 92 deg² of the Sloan Digital Sky Survey Stripe 82 area with 2″-resolution Very Large Array (VLA) images. Here we present 0.″3-resolution VLA 6 GHz observations for six candidates that have complete optical spectroscopy. The new data confirm the binary nature of four candidates and identify the other two as line of sight projections of radio structures from single AGNs. The four binary AGNs at z ∼ 0.1 reside in major mergers with projected separations of 4.2–12 kpc. Optical spectral modeling shows that their hosts have stellar masses between $10.3<<!--\; <\; -->\mathrm{l}\mathrm{o}\mathrm{g}(M_{\star <!--\; ???\; -->}/M_{\odot <!--\; ???\; -->})<<!--\; <\; -->11.5$ and velocity dispersions between $120<<!--\; <\; -->{\mathrm{\sigma <!--\; ??\; -->}}_{\star <!--\; ???\; -->}<<!--\; <\; -->320$ km s⁻¹. The radio emission is compact (≲0.″4) and shows a steep spectrum ($-<!--\; ???\; -->1.8<<!--\; <\; -->\mathrm{\alpha <!--\; ??\; -->}<<!--\; <\; -->-<!--\; ???\; -->0.5$) at 6 GHz. The host galaxy properties and the Eddington-scaled accretion rates broadly correlate with the excitation state, similar to the general radio-AGN population at low redshifts. Our estimated binary AGN fraction indicates that simultaneous accretion occurs $⩾<!--\; ???\; -->{23}_{-<!--\; ???\; -->8}^{+15}$% of the time when a kiloparsec-scale galaxy pair is detectable as a radio-AGN. The high duty cycle of the binary phase strongly suggests that major mergers can trigger and synchronize black hole accretion.

[en] Quasar luminosity functions are a fundamental probe of the growth and evolution of supermassive black holes. Measuring the intrinsic luminosity function is difficult in practice, due to a multitude of observational and systematic effects. As sample sizes increase and measurement errors drop, characterizing the systematic effects is becoming more important. It is well known that the continuum emission from the accretion disk of quasars is anisotropic—in part due to its disk-like structure—but current luminosity function calculations effectively assume isotropy over the range of unobscured lines of sight. Here, we provide the first steps in characterizing the effect of random quasar orientations and simple models of anisotropy on observed luminosity functions. We find that the effect of orientation is not insignificant and exceeds other potential corrections such as those from gravitational lensing of foreground structures. We argue that current observational constraints may overestimate the intrinsic luminosity function by as much as a factor of ∼2 on the bright end. This has implications for models of quasars and their role in the universe, such as quasars' contribution to cosmological backgrounds.

[en] Galaxy mergers play an important role in the growth of galaxies and their supermassive black holes. Simulations suggest that tidal interactions could enhance black hole accretion, which can be tested by the fraction of binary active galactic nuclei (AGNs) among galaxy mergers. However, determining the fraction requires a statistical sample of binaries. We have identified kiloparsec-scale binary AGNs directly from high-resolution radio imaging. Inside the 92 deg² covered by the high-resolution Very Large Array survey of the Sloan Digital Sky Survey (SDSS) Stripe 82 field, we identified 22 grade A and 30 grade B candidates of binary radio AGNs with angular separations less than 5'' (10 kpc at z = 0.1). Eight of the candidates have optical spectra for both components from the SDSS spectroscopic surveys and our Keck program. Two grade B candidates are projected pairs, but the remaining six candidates are all compelling cases of binary AGNs based on either emission line ratios or the excess in radio power compared to the Hα-traced star formation rate. Only two of the six binaries were previously discovered by an optical spectroscopic search. Based on these results, we estimate that ∼60% of our binary candidates would be confirmed once we obtain complete spectroscopic information. We conclude that wide-area high-resolution radio surveys offer an efficient method to identify large samples of binary AGNs. These radio-selected binary AGNs complement binaries identified at other wavelengths and are useful for understanding the triggering mechanisms of black hole accretion

[en] We combine the most precise small-scale (< 100 h^-1kpc) quasar clustering constraints to date with recent measurements at large scales (> 1 h^-1Mpc) from the extended Baryon Oscillation Spectroscopic Survey (eBOSS) to better constrain the satellite fraction of quasars at z ~1.5 in the halo occupation formalism. We build our Halo Occupation Distribution (HOD) framework based on commonly used analytic forms for the one and two-halo terms with two free parameters: the minimum halo mass that hosts a central quasar and the fraction of satellite quasars that are within one halo. Inspired by recent studies that propose a steeper density profile for the dark matter haloes that host quasars, we explore HOD models at kiloparsec scales and best-fit parameters for models with 10x higher concentration parameter. We find that an HOD model with a satellite fraction of f_sat = 0.071$\genfrac{}{}{0ex}{}{+0.009}{-<!--\; ???\; -->0.004}$ and minimum mass of M_m = 2.31$\genfrac{}{}{0ex}{}{+0.41}{-<!--\; ???\; -->0.38}$ × 10¹² h^-1 M_⊙ for the host dark matter haloes best describes quasar clustering (on all scales) at z~1.5. Our results are marginally inconsistent with earlier work that studied brighter quasars, hinting at a luminosity-dependence to the one-halo term.

[en] Blazars are classically divided into the BL Lacertae (BLL) and flat-spectrum radio quasar (FSRQ) subclasses, corresponding to radiatively inefficient and efficient accretion regimes, respectively, largely based on the equivalent width (EW) of their optical broad emission lines (BELs). However, EW-based classification criteria are not physically motivated, and a few blazars have previously transitioned' from one subclass to the other. We present the first systematic search for these transition blazars in a sample of 602 unique pairs of repeat spectra of 354 blazars in the Sloan Digital Sky Survey, finding six clear cases. These transition blazars have bolometric Eddington ratios of ∼0.3 and low-frequency synchrotron peaks, and are thus FSRQ-like. We show that the strong EW variability (up to an unprecedented factor of >60) is due to swamping of the BELs from variability in jet continuum emission, which is stronger in amplitude and shorter in timescale than typical blazars. Although these transition blazars appear to switch between FSRQ and BLL according to the phenomenologically based EW scheme, we show that they are most likely rare cases of FSRQs with radiatively efficient accretion flows and especially strongly beamed jets. These results have implications for the decrease of the apparent BLL population at high redshifts, and may lend credence to claims of a negative BLL redshift evolution.

[en] We perform a semi-automated search for strong gravitational lensing systems in the 9000 deg² Dark Energy Camera Legacy Survey (DECaLS), part of the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys. The combination of the depth and breadth of these surveys are unparalleled at this time, making them particularly suitable for discovering new strong gravitational lensing systems. We adopt the deep residual neural network architecture developed by Lanusse et al. for the purpose of finding strong lenses in photometric surveys. We compile a training sample that consists of known lensing systems in the Legacy Surveys and the Dark Energy Survey as well as non-lenses in the footprint of DECaLS. In this paper we show the results of applying our trained neural network to the cutout images centered on galaxies typed as ellipticals in DECaLS. The images that receive the highest scores (probabilities) are visually inspected and ranked. Here we present 335 candidate strong lensing systems, identified for the first time.

[en] We have conducted a search for new strong gravitational lensing systems in the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys’ Data Release 8. We use deep residual neural networks, building on previous work presented by Huang et al. These surveys together cover approximately one-third of the sky visible from the Northern Hemisphere, reaching a z-band AB magnitude of ∼22.5. We compile a training sample that consists of known lensing systems as well as non-lenses in the Legacy Surveys and the Dark Energy Survey. After applying our trained neural networks to the survey data, we visually inspect and rank images with probabilities above a threshold. Here we present 1210 new strong lens candidates.