Blue Quasars Research Articles

Serendipitous Catch of a Giant Jellyfish: An Ionized Nebula around 3C 275.1 with 170 kpc Long Tails

3C 275.1 is a blue quasar at z = 0.55522, hosting powerful outflows and residing in a complex environment. We present a serendipitously detected giant nebula surrounding 3C 275.1, which shows morphological features resembling those of objects known as “jellyfish galaxies,” with extremely long tails of ionized gas extending to 170 kpc in projection. We analyze its optical spectra taken by MUSE on the Very Large Telescope. The brighter part of this giant nebula exceeds 100 kpc, and its rotation curve does not flatten out, making it very different from those of normal spiral galaxies. This system shares some characteristics common to those formed via ram pressure stripping (RPS), yet its long narrow tails and higher ionization are unusual compared to known tails in jellyfish galaxies, not fully consistent with a simple RPS scenario. Our photoionization simulation and the inferred short recombination timescale both suggest that, besides the quasar 3C 275.1, an extra source of ionization is necessary to keep the gas ionized at such a distance from the nucleus, which could be related to RPS, tidal interaction, or active galactic nucleus outflow, providing new evidence of active dynamical interaction of a galaxy with the intracluster medium.

Absence of radio-bright dominance in a near-infrared selected sample of red quasars

Context. The dichotomy between red and blue quasars is still an open question. It is debated whether red quasars are simply blue quasars that are observed at certain inclination angles or if they provide insight into a transitional phase in the evolution of quasars. Aims. We investigate the relation between quasar colors and radio-detected fraction because radio observations of quasars provide a powerful tool in distinguishing between quasar models. Methods. We present the eHAQ+GAIA23 sample, which contains quasars from the High A(V) Quasar (HAQ) Survey, the Extended High A(V) Quasar (eHAQ) Survey, and the Gaia quasar survey. All quasars in this sample have been found using a near-infrared color selection of target candidates that have otherwise been missed by the Sloan Digital Sky Survey (SDSS). We implemented a redshift-dependent color cut in g* − i* to select red quasars in the sample and divided them into redshift bins, while using a nearest-neighbors algorithm to control for luminosity and redshift differences between our red quasar sample and a selected blue sample from the SDSS. Within each bin, we cross-matched the quasars to the Faint Images of the Radio Sky at Twenty centimeters (FIRST) survey and determined the radio-detection fraction. Results. For redshifts 0.8 < z ≤ 1.5, the red and blue quasars have a radio-detection fraction of 0.153−0.032+0.037 and 0.132−0.030+0.034, respectively. The red and blue quasars with redshifts 1.5 < z ≤ 2.4 have radio-detection fractions of 0.059−0.016+0.019 and 0.060−0.016+0.019, respectively, and the red and blue quasars with redshifts z > 2.4 have radio-detection fractions of 0.029−0.012+0.017 and 0.058−0.019+0.024, respectively. For the WISE color-selected red quasars, we find a radio-detection fraction of 0.160−0.034+0.038 for redshifts 0.8 < z ≤ 1.5, 0.063−0.017+0.020 for redshifts 1.5 < z ≤ 2.4, and 0.051−0.022+0.030 for redshifts z > 2.4. In other words, we find similar radio-detection fractions for red and blue quasars within < 1σ uncertainty, independent of redshift. This disagrees with what has been found in the literature for red quasars in SDSS. It should be noted that the fraction of broad absorption line (BAL) quasars in red SDSS quasars is about five times lower. BAL quasars have been observed to be more frequently radio quiet than other quasars, therefore the difference in BAL fractions could explain the difference in radio-detection fraction. Conclusions. The dusty torus of a quasar is transparent to radio emission. When we do not observe a difference between red and blue quasars, it leads us to argue that orientation is the main cause of quasar redness. Moreover, the observed higher proportion of BAL quasars in our dataset relative to the SDSS sample, along with the higher rate of radio detections, indicates an association of the redness of quasars and the inherent BAL fraction within the overall quasar population. This correlation suggests that the redness of quasars is intertwined with the inherent occurrence of BAL quasars within the entire population of quasars. In other words, the question why some quasars appear red or exhibit BAL characteristics might not be isolated; it could be directly related to the overall prevalence of BAL quasars in the quasar population. This finding highlights the need to explore the underlying factors contributing to both the redness and the frequency of BAL quasars, as they appear to be interconnected phenomena.

Powerful Radio-loud Quasars Are Triggered by Galaxy Mergers in the Cosmic Bright Ages

While supermassive black holes are ubiquitous features of galactic nuclei, only a small minority are observed during episodes of luminous accretion. The physical mechanism(s) driving the onset of fueling and ignition in these active galactic nuclei (AGN) are still largely unknown for many galaxies and AGN-selection criteria. Attention has focused on AGN triggering by means of major galaxy mergers gravitationally funneling gas toward the galactic center, with evidence both for and against this scenario. However, several recent studies have found that radio-loud AGN overwhelmingly reside in ongoing or recent major galaxy mergers. In this study, we test the hypothesis that major galaxy mergers are important triggers for radio-loud AGN activity in powerful quasars during cosmic noon (1 ≲ z ≲ 2). To this end, we compare Hubble Space Telescope WFC3/IR observations of the z > 1 3CR radio-loud broad-lined quasars to three matched radio-quiet quasar control samples. We find strong evidence for major-merger activity in nearly all radio-loud AGN, in contrast to the much lower merger fraction in the radio-quiet AGN. These results suggest major galaxy mergers are key ingredients in launching powerful radio jets. Given many of our radio-loud quasars are blue, our results present a possible challenge to the “blowout” paradigm of galaxy evolution models in which blue quasars are the quiescent end result following a period of red quasar feedback initiated by a galaxy merger. Finally, we find a tight correlation between black hole mass and host galaxy luminosity for these different high-redshift AGN samples that is inconsistent with those observed for local elliptical galaxies.

Little Red Dots: An Abundant Population of Faint Active Galactic Nuclei at z ∼ 5 Revealed by the EIGER and FRESCO JWST Surveys

Characterizing the prevalence and properties of faint active galactic nuclei (AGNs) in the early Universe is key for understanding the formation of supermassive black holes (SMBHs) and determining their role in cosmic reionization. We perform a spectroscopic search for broad Hα emitters at z ≈ 4–6 using deep JWST/NIRCam imaging and wide field slitless spectroscopy from the EIGER and FRESCO surveys. We identify 20 Hα lines at z = 4.2–5.5 that have broad components with line widths from ∼1200–3700 km s−1, contributing ∼30%–90% of the total line flux. We interpret these broad components as being powered by accretion onto SMBHs with implied masses ∼107–8 M ⊙. In the UV luminosity range M UV,AGN+host = −21 to −18, we measure number densities of ≈10−5 cMpc−3. This is an order of magnitude higher than expected from extrapolating quasar UV luminosity functions (LFs). Yet, such AGN are found in only <1% of star-forming galaxies at z ∼ 5. The number density discrepancy is much lower when compared to the broad Hα LF. The SMBH mass function agrees with large cosmological simulations. In two objects, we detect complex Hα profiles that we tentatively interpret as caused by absorption signatures from dense gas fueling SMBH growth and outflows. We may be witnessing early AGN feedback that will clear dust-free pathways through which more massive blue quasars are seen. We uncover a strong correlation between reddening and the fraction of total galaxy luminosity arising from faint AGN. This implies that early SMBH growth is highly obscured and that faint AGN are only minor contributors to cosmic reionization.

GA-NIFS: The ultra-dense, interacting environment of a dual AGN at z ∼ 3.3 revealed by JWST/NIRSpec IFS (Corrigendum)

LBQS 0302-0019 is a blue quasar (QSO) at z ∼ 3.3, hosting powerful outflows, and residing in a complex environment consisting of an obscured AGN candidate, and multiple companions, all within 30 kpc in projection. We use JWST NIRSpec IFS observations to characterise the ionized gas in this complex system. We develop a procedure to correct for the spurious oscillations (or ‘wiggles’) in NIRSpec single-spaxel spectra, due to the spatial under-sampling of the point spread function. We perform a quasar-host decomposition with the QDeblend3D tools, and use multi-component kinematic decomposition of the optical emission line profiles to infer the physical properties of the emitting gas. The quasar-host decomposition allows us to identify i) a low-velocity component possibly tracing a warm rotating disk, with a dynamical mass Mdyn ∼10^11 Msun and a rotation-to-random motion ratio vrot/σ0 ∼2; ii) a spatially unresolved ionised outflow, with a velocity of ∼ 1000 km/s and an outflow mass rate of ∼10^4 Msun/yr. We also detect eight interacting companion objects close to LBQS 0302-0019. Optical line ratios confirm the presence of a second, obscured AGN at ∼20 kpc of the primary QSO; the dual AGN dominates the ionization state of the gas in the entire NIRSpec field-of-view. This work has unveiled with unprecedented detail the complex environment of this dual AGN, which includes nine interacting companions (five of which were previously unknown), all within 30 kpc of the QSO. Our results support a scenario where mergers can trigger dual AGN, and can be important drivers for rapid early SMBH growth.

Compact and quiescent circumgalactic medium and Ly α haloes around extremely red quasars

ABSTRACT Red quasars may represent a young stage of galaxy evolution that provide important feedback to their host galaxies. We are studying a population of extremely red quasars (ERQs) with exceptionally fast and powerful outflows, at median redshift z = 2.6. We present Keck/Keck Cosmic Web Imager integral field spectra of 11 ERQs, which have median colour i–W3 = 5.9 mag, median 〈 Lbol 〉 ≈ 5 × 1047 erg s−1, Ly α halo luminosity 〈 Lhalo 〉 = 5 × 1043 erg s−1, and maximum linear size &amp;gt;128 kpc. The ERQ haloes are generally similar to blue quasar haloes, following known trends with Lbol in halo properties. ERQs have halo symmetries similar to Type-I blue quasars, suggesting Type-I spatial orientations. ERQ 〈 Lhalo 〉 is ∼2-dex below blue quasars, which is marginal due to scatter, but consistent with obscuration lowering photon escape fractions. ERQ haloes tend to have more compact and circularly symmetric inner regions than blue quasars, with median exponential scale lengths ∼9 kpc, compared with ∼16 kpc for blue quasars. When we include the central regions not available in blue quasar studies (due to point spread function problems), the true median ERQ halo scale length is just ∼6 kpc. ERQ haloes are kinematically quiet, with median velocity dispersion 293 km s−1, consistent with expected virial speeds. Overall, we find no evidence for feedback on circumgalactic scales, and the current episode of quasar activity (perhaps due to long outflow travel times) has not been around long enough to affect the circumgalactic medium. We confirm the narrow Ly α-emission spikes found in ERQ aperture spectra are halo features, and are useful for systemic redshifts and measuring outflow speeds in other features.

Accurate systemic redshifts and outflow speeds for extremely red quasars (ERQs)

ABSTRACT Extremely Red Quasars (ERQs) are thought to represent a brief episode of young quasar and galactic evolution characterized by rapid outflows and obscured growth due to dusty environments. We use new redshift measurements from CO and narrow Ly α emission-lines to better constrain outflow velocities from previous line measurements. We present sample of 82 ERQs, and the analysis confirms that ERQs have a higher incidence of large C iv blueshifts, accompanied by large Rest Equivalent Width (REW) and narrower line Full Width at Half-Maximum (FWHM) than blue quasars. We find that strong blueshifts (&amp;gt;2000 km s−1) are present in 12/54 (22.2 per cent) of ERQs with the most robust redshift indicators. At least 4 out of 15 ERQs in the sample also have blueshifts in their H β and low-ionization ultraviolet lines ranging from −500 to −1500 km s−1. ERQs with strong C iv blueshifts are substantially offset in C iv REW and FWHM from typical blue quasars in the same velocity range. ERQs have average values of REW = 124 Å and FWHM = 5274 km s−1, while blue quasars have REW = 24 Å and FWHM = 6973 km s−1. The extreme nature of the outflows in ERQs might explain some of their other spectral properties, such as the large C iv REWs and peculiar wingless profiles owing to more extended broad-line regions participating in outflows. The physical reasons for the extreme outflow properties of ERQs are unclear; however, larger Eddington ratios and/or softer ionizing spectra incident on the outflow gas cannot be ruled out.

The most luminous blue quasars at 3.0 &lt; z &lt; 3.3

We present the analysis of the rest frame ultraviolet and optical spectra of 30 bright blue quasars at z ∼ 3, selected to examine the suitability of active galactic nuclei as cosmological probes. In our previous works, based on pointed XMM-Newton observations, we found an unexpectedly high fraction (≈25%) of X-ray weak quasars in the sample. The latter sources also display a flatter UV continuum and a broader and fainter C IV profile in the archival UV data with respect to their X-ray normal counterparts. Here we present new observations with the Large Binocular Telescope in both the zJ (covering the rest frame ≃2300–3100 Å) and the KS (≃4750–5350 Å) bands. We estimated black hole masses (MBH) and Eddington ratios (λEdd) from the available rest frame optical and UV emission lines (Hβ, Mg II), finding that our z ∼ 3 quasars are on average highly accreting (⟨λEdd⟩≃1.2 and ⟨MBH⟩≃109.7 M⊙), with no difference in λEdd or MBH between X-ray weak and X-ray normal quasars. From the zJ spectra, we derived the properties (e.g. flux, equivalent width) of the main emission lines (Mg II, Fe II), finding that X-ray weak quasars display higher Fe II/Mg II ratios with respect to typical quasars. Fe II/Mg II ratios of X-ray normal quasars are instead consistent with other estimates up to z ≃ 6.5, corroborating the idea of already chemically mature broad line regions at early cosmic time. From the KS spectra, we find that all the X-ray weak quasars present generally weaker [O III] emission (EW &lt; 10 Å) than the normal ones. The sample as a whole, however, abides by the known X-ray-[O III] luminosity correlation, hence the different [O III] properties are likely due to an intrinsically weaker [O III] emission in X-ray weak objects, associated to the shape of the spectral energy distribution. We interpret these results in the framework of accretion-disc winds.

SDSS J1058+5443: A Blue Quasar without Optical/NUV Broad Emission Lines

In this paper, the blue quasar SDSS J105816.19+544310.2 (=SDSS J1058+5443) at redshift 0.479 has been reported as the best true type 2 quasar candidate with the disappearance of central broad-line regions. There are no definite conclusions on the very existence of true type 2 active galactic nuclei (AGN), mainly due to detected optical broad emission lines in high-quality spectra of some previously classified true type 2 AGN candidates. Here, unlike previously reported true type 2 AGN candidates among narrow emission-line galaxies with weak AGN activities but strong stellar lights, the definitely blue quasar SDSS J1058+5443 can be well confirmed as a true type 2 quasar due to apparent quasar-shape blue continuum emissions but an apparent loss of both the optical broad Balmer emission lines and the near-UV (NUV) broad Mg ii emission line. Based on different model functions and the F-test statistical technique, after considering blueshifted optical and UV Fe ii emissions, there are no apparent broad optical Balmer emission lines and/or broad NUV Mg ii lines, and the confidence level is smaller than 1σ in support of broad optical and NUV emission lines. Moreover, assuming the virialization assumption to broad-line emission clouds, the reconstructed broad emission lines strongly indicate that the probable intrinsic broad emission lines, if they exist, cannot be hidden or overwhelmed in the noise of the Sloan Digital Sky Survey spectrum of SDSS J1058+5443. Therefore, SDSS J1058+5443 is so far the best and most robust true type 2 quasar candidate, leading to the clear conclusion of the very existence of true type 2 AGN.

A 3.8 yr optical quasi-periodic oscillations in blue quasar SDSS J132144+033055 through combined light curves from CSS and ZTF

ABSTRACT In the manuscript, a 3.8 yr optical quasi-periodic oscillations (QPOs) is reported in blue quasar SDSS J132144+033055 (= SDSS J1321) at z = 0.269, based on 16.3yr-long light curve from both CSS and ZTF directly described by a sinusoidal function. The 3.8 yr QPOs can be confirmed through the Generalized Lomb–Scargle periodogram with confidence level higher than 5σ, through properties of the phase-folded light curve and the WWZ technique. Moreover, the collected Pan-STARRS light curves well follow the sinusoidal function described best fitting results to the Catalina Sky Survey (CSS) and Catalina Sky Survey (ZTF) light curves. The optical QPOs strongly indicate a central binary black hole (BBH) system in SDSS J1321, with expected space separation smaller than 0.018 pc, through the estimated upper limit of total BH mass 3.3 × 109 M⊙ through the correlation between BH mass and continuum luminosity. Meanwhile, we check disc precession applied to explain the optical QPOs. However, under the disc precession assumption, the determined optical emission regions from central BH have sizes about 37RG similar as the sizes 35RG of the expected NUV emission regions through the correlation between disc size and BH mass, indicating the disc precession is not preferred. And due to undetected radio emissions, jet precession can be ruled out. Furthermore, only 0.1 per cent probability can determined as the QPOs mis-detected through CAR process randomly created light curves related to intrinsic AGN activities, re-confirming the optical QPOs with significance level higher than 3σ. Therefore, combining long-term light curves from CSS and ZTF can lead to more QPOs candidates in the near future.

Probing the inner circumgalactic medium and quasar illumination around the reddest ‘extremely red quasar’

ABSTRACT Dusty quasars might be in a young stage of galaxy evolution with prominent quasar feedback. A recently discovered population of luminous, extremely red quasars at z ∼ 2–4 has extreme spectral properties related to exceptionally powerful quasar-driven outflows. We present Keck/KCWI observations of the reddest known ERQ, at z = 2.3184, with extremely fast [O iii] λ5007 outflow at ∼6000 km s−1. The Lyα halo spans ∼100 kpc. The halo is kinematically quiet, with velocity dispersion ∼300 km s−1 and no broadening above the dark matter circular velocity down to the spatial resolution ∼6 kpc from the quasar. We detect spatially resolved He ii λ1640 and C iv λ1549 emissions with kinematics similar to the Lyα halo and a narrow component in the [O iii] λ5007. Quasar reddening acts as a coronagraph, allowing views of the innermost halo. A narrow Lyα spike in the quasar spectrum is inner halo emission, confirming the broad C iv λ1549 in the unresolved quasar is blueshifted by 2240 km s−1 relative to the halo frame. We propose the inner halo is dominated by moderate-speed outflow driven in the past and the outer halo dominated by inflow. The high central concentration of the halo and the symmetric morphology of the inner region are consistent with the ERQ being in earlier evolutionary stage than blue quasars. The He ii λ1640/Lyα ratio of the inner halo and the asymmetry level of the overall halo are dissimilar to Type II quasars, suggesting unique physical conditions for this ERQ that are beyond orientation differences from other quasar populations. We find no evidence of mechanical quasar feedback in the Lyα-emitting halo.

A Quasar Shedding Its Dust Cocoon at Redshift 2

We present the first near-IR spectroscopy and joint analyses of multiwavelength observations for SDSS J082747.14+425241.1, a dust-reddened, weak broad emission-line quasar (WLQ) undergoing a remarkable broad-absorption line (BAL) transformation. The systemic redshift is more precisely measured to be z = 2.070 ± 0.001 using Hβ compared to z = 2.040 ± 0.003 using Mg ii from the literature, signifying an extreme Mg ii blueshift of 2140 ± 530 km s−1 relative to Hβ. Using the Hβ-based single-epoch scaling relation with a systematic uncertainty of 0.3 dex, its black hole (BH) mass and Eddington ratio are estimated to be M BH ∼ 6.1 × 108 M ⊙ and λ Edd ∼ 0.71, indicative of being in a rapidly accreting phase. Our investigations confirm the WLQ nature and the LoBAL → HiBAL transformation, along with a factor of 2 increase in the Mg ii+Fe ii emission strength and a decrease of 0.1 in E(B − V) over two decades. The kinetic power of this LoBAL wind at R ∼ 15 pc from its BH is estimated to be ∼43% of the Eddington luminosity, sufficient for quasar feedback upon its host galaxy albeit with an order-of-magnitude uncertainty. This quasar provides a clear example of the long-sought scenario where LoBAL quasars are surrounded by dust cocoons, and wide-angle nuclear winds play a key role in the transition of red quasars evolving into the commonly seen blue quasars.

Fundamental differences in the properties of red and blue quasars: measuring the reddening and accretion properties with X-shooter

ABSTRACT We have recently found fundamental differences in the radio properties of red quasars when compared to typical blue quasars. In this paper, we use data from the X-shooter spectrograph on the Very Large Telescope, providing spectral coverage from ∼3000–$25\,000\,$ Å, of a sample of 40 red and blue luminous quasars at 1.45 &amp;lt; z &amp;lt; 1.65 to explore the connections between the radio, emission-line, and accretion-disc properties. We fit various dust-extinction curves to the data and find that dust reddening can fully explain the observed colours for the majority of the red quasars in our sample, with moderate extinctions ranging from AV ∼ 0.06–0.7 mag. We confront our spectra with a simple thin accretion-disc model and find this can describe the continua of both the blue and red quasars, once corrected for dust extinction; we also find no significant differences in the accretion properties. We detect ionized outflows in a number of red and blue quasars, but do not find any significant evidence that they are more prevalent in the red quasar population. Overall our findings imply that the radio emission is more closely connected to circumnuclear/ISM opacity rather than accretion disc or outflow differences.

Host Dark Matter Halos of SDSS Red and Blue Quasars: No Significant Difference in Large-scale Environment

Abstract The observed optical colors of quasars are generally interpreted in one of two frameworks: unified models that attribute the color to the random orientation of the accretion disk along the line of sight, and evolutionary models that invoke connections between quasar systems and their environments. We test these schemas by probing the dark matter halo environments of optically selected quasars as a function of g − i optical color by measuring the two-point correlation functions of ∼0.34 million eBOSS quasars as well as the gravitational deflection of cosmic microwave background photons around ∼0.66 million XDQSO photometric quasar candidates. We do not detect a trend of halo bias with optical color through either analysis, finding that optically selected quasars at 0.8 &lt; z &lt; 2.2 occupy halos of characteristic mass M h ∼ 3 × 1012 h −1 M ⊙ regardless of their color. This result implies that a quasar’s large-scale halo environment is not strongly connected to its observed optical color. We also confirm the findings of fundamental differences in the radio properties of red and blue quasars by stacking 1.4 GHz FIRST images at their positions, suggesting the observed differences cannot be attributed to orientation. Instead, the differences between red and blue quasars likely arise on nuclear-galactic scales, perhaps owing to reddening by a nuclear dusty wind. Finally, we show that optically selected quasars’ halo environments are also independent of their r − W2 optical–infrared colors, while previous work has suggested that mid-infrared-selected obscured quasars occupy more massive halos. We discuss the implications of this result for models of quasar and galaxy coevolution.

Improved selection of extremely red quasars with boxy C iv lines in BOSS

ABSTRACT Extremely red quasars (ERQs) are an interesting sample of quasars in the Baryon Oscillation Spectroscopic Sample (BOSS) in the redshift range of 2.0–3.4 and have extreme red colours of i − W3 ≥ 4.6. Core ERQs have strong C iv emission lines with rest equivalent width of ≥100 Å. Many core ERQs also have C iv line profiles with peculiar boxy shapes which distinguish them from normal blue quasars. We show, using a combination of kernel density estimation and local outlier factor analyses on a space of the i − W3 colour, C iv rest equivalent width and line kurtosis, that core ERQs likely represent a separate population rather than a smooth transition between normal blue quasars and the quasars in the tail of the colour-REW distribution. We apply our analyses to find new criteria for selecting ERQs in this 3D parameter space. Our final selection produces 133 quasars, which are three times more likely to have a visually verified C iv broad absorption line feature than the previous core ERQ sample. We further show that our newly selected sample are extreme objects in the intersection of the WISE AGN catalogue with the MILLIQUAS quasar catalogue in the colour–colour space of (W1 − W2, W2 − W3). This paper validates an improved selection method for red quasars which can be applied to future data sets such as the quasar catalogue from the Dark Energy Spectroscopic Instrument.

SDSS J1451 + 2709 a normal blue quasar but mis-classified as a H ii galaxy in the BPT diagram by flux ratios of narrow emission lines

ABSTRACT In the manuscript, we discuss properties of SDSS J1451 + 2709, a normal blue quasar but mis-classified as a H ii galaxy in the BPT diagram (called as a mis-classified quasar). The emission lines around H α and around H β are well measured by different model functions with broad Balmer lines described by Gaussian or Lorentz functions, in the SDSS spectrum in 2007 and in the KPNO spectrum in 1990. After considering variations of broad emission lines, different model functions lead to different determined fluxes of narrow emission lines, but the different narrow emission line flux ratios lead the SDSS J1451 + 2709 as a H ii galaxy in the BPT diagram. In order to explain the unique properties of the mis-classified quasar SDSS J1451+2709 in the BPT diagram, two methods are proposed, the starforming contributions and compressed NLRs with high electron densities near to critical densities of forbidden emission lines. Unfortunately, the two methods cannot be preferred in the SDSS J1451+2709, further efforts are necessary to find the physical origin of the unique properties of the mis-classified quasar SDSS J1451+2709 in the BPT diagram. Meanwhile, there are not quite different long-term variabilities of SDSS J1451+2709 from the normal quasars. The mis-classified quasar SDSS J1451 + 2709, an extremely unique case or a special case among the normal quasars, could provide further clues on the applications of BPT diagrams to the normal broad line AGN and to narrow emission line objects, indicating part of narrow emission line H ii galaxies actually harbouring central AGN activities.

How Are Red and Blue Quasars Different? The Radio Properties

A non-negligible fraction of quasars are red at optical wavelengths, indicating (in the majority of cases) that the accretion disc is obscured by a column of dust which extinguishes the shorter-wavelength blue emission. In this paper, we summarize recent work by our group, where we find fundamental differences in the radio properties of SDSS optically-selected red quasars. We also present new analyses, using a consistent color-selected quasar parent sample matched to four radio surveys (FIRST, VLA Stripe 82, VLA COSMOS 3 GHz, and LoTSS DR1) across a frequency range 144 MHz–3 GHz and four orders of magnitude in radio flux. We show that red quasars have enhanced small-scale radio emission (∼kpc) that peaks around the radio-quiet threshold (defined as the ratio of 1.4 GHz luminosity to 6 μm luminosity) across the four radio samples. Exploring the potential mechanisms behind this enhancement, we rule out star-formation and propose either small-scale synchrotron jets, frustrated jets, or dusty winds interacting with the interstellar medium; the latter two scenarios would provide a more direct connection between opacity (dust; gas) and the production of the radio emission. In our future study, using new multi-band uGMRT data, we aim to robustly distinguish between these scenarios.

Multiepoch Spectroscopy of Mg ii Broad Absorption Line Transitions

Abstract Built upon a sample of 134 quasars that was dedicated to a systematic study of Mg ii–BAL variability from Yi et al., we investigate these quasars, showing Mg ii–BAL disappearance or emergence with the aid of at least three epoch optical spectra sampled more than 15 yr in the observed frame. We identified 3/3 quasars undergoing pristine/tentative BAL transformations. The incidence of pristine BAL transformations in the sample is therefore derived to be 2.2 − 1.2 + 2.2 %, consistent with that of high-ionization BAL transformations from the literature. Adopting an average Mg ii–BAL disappearance timescale of rest frame 6.89 yr among the six quasars, the average characteristic lifetime of Mg ii BALs in the sample is constrained to be &gt;160 yr along our line of sight. There is a diversity of BAL profile variability observed in the six quasars, probably reflecting a variety of mechanisms at work. Our investigations of Mg ii–BAL transitions, combined with observational studies of BAL transitions from the literature, imply an overall FeLoBAL/LoBAL → HiBAL/non-BAL transformation sequence, along with a decrease in reddening. This sequence is consistent with the evacuation models for the origin of commonly seen blue quasars, in which LoBAL quasars are in a short-lived blowout phase.

Fundamental differences in the radio properties of red and blue quasars: kiloparsec-scale structures revealed by e-MERLIN

ABSTRACT Red quasi-stellar objects (QSOs) are a subset of the quasar population with colours consistent with reddening due to intervening dust. Recent work has demonstrated that red QSOs show special radio properties that fundamentally distinguish them from normal blue QSOs, specifically a higher incidence of low-power radio emission (1.4 GHz luminosities L1.4 ≈ 1025–1027 W Hz−1) that is physically compact when imaged by arcsecond-resolution radio surveys such as FIRST. In this work, we present e-MERLIN imaging of a set of intermediate-redshift (1.0 &amp;lt; z &amp;lt; 1.55), luminous (bolometric luminosities Lbol ≈ 1046–1047 erg s−1) red and normal QSOs carefully selected to have radio properties that span the range over which red QSOs show the most divergence from the general population. With an angular resolution 25× better than FIRST, we resolve structures within the host galaxies of these QSOs (&amp;gt;2 kpc). We report a statistically significant difference in the incidence of extended kpc-scale emission in red QSOs. From an analysis of the radio size distributions of the sample, we find that the excess radio emission in red QSOs can be attributed to structures that are confined to galaxy scales (&amp;lt;10 kpc), while we confirm previous results that red and normal QSOs have similar incidences of radio jets and lobes on circumgalactic or larger scales (&amp;gt;10 kpc). Our results indicate that the primary mechanism that generates the enhanced radio emission in red QSOs is not directly connected with the nuclear engine or accretion disc, but is likely to arise from extended components such as AGN-driven jets or winds.

Evidence for Radio Loud to Radio Quiet Evolution from Red and Blue Quasars

Recent work on red and blue quasi-stellar objects (QSOs) has identified peculiar number distributions as a function of radio-loudness that we explore and attempt to explain from the perspective of a picture in which a subset of the population of active galaxies evolves from the radio-loud to the radio-quiet state. Because the time evolution is slowed down by an order of magnitude or more for the radio-quiet phase, the numbers of red and blue QSOs approach each other at the extreme end of the radio-quiet range of radio-loudness with larger numbers. The rapid time evolution of most radio-loud phases, instead, makes the numbers similar but lower at the far radio-loud end. At the midpoint of radio-loudness, instead, the differences between red and blue QSOs experience their largest values which results from accretion rapidly spinning black holes down but subsequently spinning them up more slowly. Recovering these basic features of the observations is evidence for rapid evolution away from radio-loudness and slow evolution in radio-quiet states.