Quasars Research Articles

Quasi-stellar object redshift estimates from optical, near-infrared, and ultraviolet colours

A simple estimate of the photometric redshift would prove invaluable to forthcoming continuum surveys on the next generation of large radio telescopes, as well as mitigating the existing bias towards the most optically bright sources. While there is a well-known correlation between the near-infrared K-band magnitude and redshift for galaxies, we find the K − z relation to break down for samples dominated by quasi-stellar objects. We hypothesise that this is due to the additional contribution to the near-infrared flux by the active galactic nucleus, and, as such, the K-band magnitude can only provide a lower limit to the redshift in the case of active galactic nuclei, which will dominate the radio surveys. From a large optical dataset, we find a tight relationship between the rest-frame (U − K)/(W2 − FUV) colour ratio and spectroscopic redshift over a sample of 17 000 sources, spanning z ≈ 0.1−5. Using the observed-frame ratios of (U − K)/(W2 − FUV) for redshifts of z ≲ 1, (I − W2)/(W3 − U) for 1 ≲ z ≲ 3, and (I − W2.5)/(W4 − R) for z ≳ 3, where W2.5 is the λ = 8.0 μm magnitude and the appropriate redshift ranges are estimated from the W2 (4.5 μm) magnitude, we find this to be a robust photometric redshift estimator for quasars. We suggest that the rest-frame U − K colour traces the excess flux from the AGN over this wide range of redshifts, although the W2 − FUV colour is required to break the degeneracy.

The intrinsic reddening of the Magellanic Clouds as traced by background galaxies – I. The bar and outskirts of the Small Magellanic Cloud

ABSTRACT We present a method to map the total intrinsic reddening of a foreground extinguishing medium via the analysis of spectral energy distributions (SEDs) of background galaxies. In this pilot study, we implement this technique in two distinct regions of the Small Magellanic Cloud (SMC) – the bar and the southern outskirts – using a combination of optical and near-infrared ugrizYJKs broad-band imaging. We adopt the lephare χ2-minimization SED-fitting routine and various samples of galaxies and/or quasi-stellar objects to investigate the intrinsic reddening. We find that only when we construct reddening maps using objects classified as galaxies with low levels of intrinsic reddening (i.e. ellipticals/lenticulars and early-type spirals), the resultant maps are consistent with previous literature determinations, i.e. the intrinsic reddening of the SMC bar is higher than that in the outer environs. We employ two sets of galaxy templates – one theoretical and one empirical – to test for template dependences in the resulting reddening maps and find that the theoretical templates imply systematically higher reddening values by up to 0.20 mag in E(B − V). A comparison with previous reddening maps, based on the stellar components of the SMC, typically shows reasonable agreement. There is, however, significant variation amongst the literature reddening maps as to the level of intrinsic reddening associated with the bar. Thus, it is difficult to unambiguously state that instances of significant discrepancies are the result of appreciable levels of dust not accounted for in some literature reddening maps or whether they reflect issues with our adopted methodology.

Unification of Fanaroff-Riley II Radio Sources with 0.1 < z < 2.0 – 8.4 GHz VLA Observations of 15 Sources – Final Sample

We present high-resolution VLA observations at 8.4 GHz of the last 15 radio sources of a sample of 98 Fanaroff-Riley class II (FR II) sources to study the location and morphology of hot spots (HSs). This final sample consists of 8 radio galaxies (RGs) and 7 quasars (QSRs). We give detailed radio contour maps of each of the 15 sources using the VLA in its A and B configurations. The observed HSs are either edged, i.e., located at the outer edges of the radio lobes or recessed, i.e., well embedded inside the lobes. For the 8 RGs, we were able to identify 5 HSs (4 edged and 1 recessed). For the 7 QSRs, 5 HSs were identified (4 edged and 1 recessed). For these 15 sources, there is no clear distinction between the 8 RGs and 7 QSRs regarding the number of edged and recessed hot spots. We give a detailed morphological analysis of the 15 sources with an emphasis on their HSs.

Possible evolution of the circum-galactic medium around QSOs with QSO age and cosmic time revealed by Ly α haloes

ABSTRACT We first present new Subaru narrow-band observations of the Ly α halo around the quasi-stellar object (QSO) CFHQ J232908−030158 at z = 6.42, which appears the most luminous and extended halo at z &gt; 5 (LLy α = 9.8 × 1043 erg s−1 within 37 pkpc diameter). Then, combining these measurements with available data in the literature, we find two different evolutions of QSOs’ Ly α haloes. First is a possible short-term evolution with QSO age seen in four z &gt; 6 QSOs. We find the anticorrelation between the Ly α halo scales with QSOs’ infrared (IR) luminosity, with J2329−0301’s halo being the brightest and largest. It indicates that ionizing photons escape more easily out to circum-galactic regions when host galaxies are less dusty. We also find a positive correlation between IR luminosity and black hole mass (MBH). Given MBH as an indicator of QSO age, we propose a hypothesis that a large Ly α halo mainly exists around QSOs in the young phase of their activity due to a small amount of dust. The second is an evolution with cosmic time seen over z ∼ 2–5. We find the increase of surface brightness towards lower redshift with a similar growth rate to that of dark matter haloes (DHs) that evolve to MDH = 1012–1013 M⊙ at z = 2. The extent of Ly α haloes is also found to increase at a rate scaling with the virial radius of growing DHs, $r_\text{vir} \propto M_\text{DH}^{1/3}(1+z)^{-1}$. These increases are consistent with a scenario that the circum-galactic medium around QSOs evolves in mass and size keeping pace with hosting DHs.

A Giant Intragroup Nebula Hosting a Damped Absorber at z = 0.313

Abstract This Letter reports the discovery of spatially extended line-emitting nebula, reaching to ≈100 physical kpc (pkpc) from a damped absorber (DLA) at z DLA = 0.313 along the sightline toward quasi-stellar object (QSO) PKS 1127−145 (z QSO = 1.188). This DLA was known to be associated with a galaxy group of dynamical mass M group ∼ 3 × 1012 M ⊙, but its physical origin remained ambiguous. New wide-field integral field observations revealed a giant nebula detected in [O ii], Hβ, [O iii], Hα, and [N ii] emission, with the line-emitting gas following closely the motions of group galaxies. One of the denser streams passes directly in front of the QSO with kinematics that are consistent with the absorption profiles recorded in the QSO echelle spectra. The emission morphology, kinematics, and line ratios of the nebula suggest that shocks and turbulent mixing layers, produced as a result of stripped gaseous streams moving at supersonic speed across the ambient hot medium, contribute significantly to the ionization of the gas. While the DLA may not be associated with any specific detected member of the group, both the kinematic and dust properties are consistent with the DLA originating in streams of gas stripped from sub-L * group members at ≲25 pkpc from the QSO sightline. This study demonstrates that gas stripping in low-mass galaxy groups is effective in releasing metal-enriched gas from star-forming regions, producing absorption systems in QSO spectra, and that combining absorption and emission-line observations provides an exciting new opportunity for studying gas and galaxy co-evolution.

ALMA Resolves the Stellar Birth Explosions in Distant Radio-Loud Quasars

Far-infrared photometry with the Herschel Space Observatory has found many examples of ultra-luminous dust emission at around 40 K in the host galaxies of high-redshift, radio-loud 3C Active Galactic Nuclei (AGN). The dust heating could have its origin in the central black hole activity or extreme circumnuclear starbursts, or both. We have used the Atacama Large Millimeter/submillimeter Array (ALMA) in Cycle 3 to study the dust morphology on the kiloparsec scale in a sample of these AGN, and present the results for three well-known distant quasars: 3C298, 3C318, and 3C454. After correction for the non-thermal radiation at 1 mm, the observations imply a starburst origin for the cool thermal dust emission, and a symbiotic physical relationship with the AGN-driven radio source.

Winds are still stirring in the Teacup quasar

Winds are still stirring in the Teacup quasar

Romatolojide Hedef 2019 Sempozyumu Bildiri Özetleri, 17-20 Nisan 2019, Fairmont Quasar İstanbul Hotel, İstanbul

Romatolojide Hedef 2019 Sempozyumu Bildiri Özetleri, 17-20 Nisan 2019, Fairmont Quasar İstanbul Hotel, İstanbul

Dark energy and dark matter unification from dynamical space time: observational constraints and cosmological implications

A recently proposed Dynamical Space-time Cosmology (DSC) that unifies dark energy and dark matter is studied. The general action of this scenario includes a Lagrange multiplier, which is coupled to the energy momentum tensor and a scalar field which is different from quintessence. First for various types of potentials we implement a critical point analysis and we find solutions which lead to cosmic acceleration and under certain conditions to stable late-time attractors. Then the DSC cosmology is confronted with the latest cosmological data from low-redshift probes, namely measurements of the Hubble parameter and standard candles (Pantheon SnIa, Quasi-stellar objects). Performing an overall likelihood analysis and using the appropriate information criteria we find that the explored DSC models are in very good agreement with the data. We also find that one of the DSC models shows a small but non-zero deviation from Λ cosmology, nevertheless the confidence level is close to ∼ 1.5σ.

The COS Absorption Survey of Baryon Harbors (CASBaH): Warm–Hot Circumgalactic Gas Reservoirs Traced by Ne viii Absorption

Abstract We survey the highly ionized circumgalactic media (CGM) of 29 blindly selected galaxies at based on high signal-to-noise ratio ultraviolet spectra of z ≳ 1 quasi-stellar objects and the galaxy database from the COS Absorption Survey of Baryon Harbors (CASBaH). We detect the Ne viii doublet in nine of the galaxies, and for gas with N( ) ( ), we derive a covering fraction ( ) within impact parameters ρ ≤ 200 kpc of M * = 109.5–11.5 M ⊙ galaxies and ( ) within ρ ≤ 1.5 virial radii. We estimate the mass in -traced gas to be , or 6%–20% of the expected baryonic mass if the absorbers have solar metallicity. Ionizing Ne vii to requires 207 eV, and photons with this energy are scarce in the CGM. However, for the median halo mass and redshift of our sample, the virial temperature is close to the peak temperature for the ion, and the -bearing gas is plausibly collisionally ionized near this temperature. Moreover, we find that photoionized requires cool and low-density clouds that would be highly underpressured (by approximately two orders of magnitude) relative to the putative, ambient virialized medium, complicating scenarios where such clouds could survive. Thus, more complex (e.g., nonequilibrium) models may be required; this first statistical sample of absorber/galaxy systems will provide stringent constraints for future CGM studies.

The Discovery of Quasi-stellar Objects behind M31 and M33

Abstract We report the discovery of 11 newly found quasars behind the stellar disks of the spiral galaxies M31 and M33 in the fields covered by the Local Group Galaxy Survey. Their redshifts range from 0.37 to 2.15. Most are X-ray, ultraviolet, and infrared sources. We also report the discovery of five normal background galaxies. Most of these objects were observed owing to their anomalous colors, as part of a program (reported elsewhere) to confirm spectroscopically candidate red supergiant plus B-star binaries; others were discovered as part of our identification of early-type massive stars based upon their optical colors. There are 15 previously known quasars in the same fields, for a grand total of 26, 15 behind M31 and 11 behind M33. Of these, only eight were discovered as part of surveys for quasars; the rest were found accidentally. The quasars are well distributed in the M31 and M33 fields, except for the inner regions, and have the potential for being good probes of the interstellar medium in these stellar disks, as well as serving as zero-point calibrators for Gaia parallaxes.

Quasi-stellar objects acting as potential strong gravitational lenses in the SDSS-III BOSS survey

We present a sample of 12 quasi-stellar objects (QSOs) that potentially act as strong gravitational lenses on background emission line galaxies (ELG) or Lyman-α emitters (LAEs) selected through a systematic search of the 297 301 QSOs in the Sloan Digital Sky Survey (SDSS)-III Data Release 12. Candidates were identified by looking for compound spectra, where emission lines at a redshift larger than that of the quasar can be identified in the residuals after a QSO spectral template is subtracted from the observed spectra. The narrow diameter of BOSS fibers (2″) then ensures that the object responsible for the additional emission lines must lie close to the line of sight of the QSO and hence provides a high probability of lensing. Among the 12 candidates identified, nine have definite evidence for the presence of a background ELG identified by at least four higher-redshift nebular emission lines. The remaining three probable candidates present a strong asymmetrical emission line attributed to a background Lyman-α emitter (LAE). The QSO-ELG (QSO-LAE) lens candidates have QSO lens redshifts in the range 0.24 ≲ zQSO ≲ 0.66 (0.75 ≲ zQSO ≲ 1.23 ) and background galaxy redshifts in the range 0.48 ≲ zS, ELG ≲ 0.94 (2.17 ≲ zS, LAE ≲ 4.48). We show that the algorithmic search is complete at &gt; 90% for QSO-ELG systems, whereas it falls at 40−60% for QSO-LAE, depending on the redshift of the source. Upon confirmation of the lensing nature of the systems, this sample may quadruple the number of known QSOs acting as strong lenses. We have determined the completeness of our search, which allows future studies to compute lensing probabilities of galaxies by QSOs and differentiate between different QSO models. Future imaging of the full sample and lens modelling offers a unique approach to study and constrain key properties of QSOs.

Gaia-assisted selection of a quasar reddened by dust in an extremely strong damped Lyman-α absorber at z = 2.226

Damped Lyman-α absorbers (DLAs) as a class of quasi-stellar object (QSO) absorption-line systems are currently our most important source of detailed information on the cosmic chemical evolution of galaxies. However, the degree to which this information is biased by dust remains to be understood. One strategy is to specifically search for QSOs that are reddened by metal-rich and dusty foreground absorbers. In this Letter, we present the discovery of a z = 2.60 QSO that is strongly reddened by dust in an intervening extremely strong DLA at z = 2.226. This QSO was identified through a novel selection that combined the astrometric measurements from ESA’s Gaia satellite with extisting optical and near- to mid-infrared photometry. We infer a total neutral atomic-hydrogen column density of log N(H I) = 21.95 ± 0.15 and a lower limit on the gas-phase metallicity of [Zn/H] &gt; −0.96. This DLA is also remarkable in that it exhibits shielded neutral gas that is visible in C I, and it shows tentative detections of CO molecular bands. The spectral energy distribution of the QSO is well accounted for by a spectral energy distribution that is normal for a QSO and is reddened by dust from a DLA with 10% solar metallicity, a dust extinction of AV = 0.82 ± 0.02 mag, and an extinction curve that resembles that of the Large Magellanic Cloud, including the characteristic 2175 Å extinction feature. Such QSO absorption-line systems have been shown to be very rare in previous surveys, which have mostly revealed sight-lines with low extinction. The present case therefore suggests that previous samples have under-represented the fraction of dusty absorbers. Building a complete sample of such systems is required to assess the significance of this effect.

Searching for the 380 GHz H2O emission from the high-z lensed quasi-stellar object MG J0414+0534

Abstract We report the results of our search for the 380 GHz H2O line emissions from the quadruply lensed quasi-stellar object (QSO) MG J0104+0534 at z = 2.639 with the Atacama Large Millimeter/submillimeter Array. Our observation shows a tentative detection of the 380 GHz line from the lensed QSO, and the line spectrum shows a broad spectral distribution that has a velocity width of ∼290 km s−1 and a peak flux of ∼0.8 mJy. The integrated intensity map of the H2O line shows lensed emissions at the A1 and A2 component of the QSO, with the A2 component slightly resolved. The integrated line flux ratio between the A1 and A2 components shows an unexpected difference from the continuum flux ratio. Based on our gravitational lens modeling, assuming our tentative detection is real, this flux ratio anomaly would suggest that the 380 GHz line emissions come from two or three spatially displaced locations in the QSO, with the dominant one located at the position of the continuum emission from the QSO, and the other one(s) displaced from the continuum by ∼1.5 kpc on the source plane.

The Blueshift of the C iv Broad Emission Line in QSOs

Abstract For the sample from Ge et al. of 87 low-z Palomar–Green quasi-stellar objects (QSOs) and 130 high-z QSOs (0 &lt; z &lt; 5) with -based single-epoch supermassive black hole masses, we perform a uniform decomposition of the C iv λ1549 broad-line profile. Based on the rest frame defined by the [O iii] λ5007 narrow emission line, a medium-strong positive correlation is found between the C iv blueshift and the luminosity at 5100 Å or the Eddington ratio . A medium-strong negative relationship is found between the C iv blueshift and C iv equivalent width. These results support the postulation where the radiation pressure may be the driver of C iv blueshift. There is a medium-strong correlation between the mass ratio of C iv-based to -based and the C iv blueshift, which indicates that the bias for C iv-based is affected by the C iv profile.

A New Einstein Cross Gravitational Lens of a Lyman-break Galaxy

Abstract We report the study of an “Einstein Cross” configuration first identified in a set of HST images by Cerny et al. Deep spectroscopic observations obtained at the Spanish 10.4 m Gran Telescopio Canarias telescope, allowed us to demonstrate the lens nature of the system, that consists of a Lyman-break galaxy (LBG), not a quasi-stellar object as is usually the case, at z = 3.03 lensed by a galaxy at z = 0.556. Combining the new spectroscopy with the archival HST data, it turns out that the lens is an elliptical galaxy with M V = −21.0, effective radius 2.8 kpc, and stellar velocity dispersion σ = 208 ± 39 km s−1. The source is an LBG with Lyα luminosity ∼L* at that redshift. From the modeling of the system, performed by assuming a singular isothermal ellipsoid (SIE) with external shear, we estimate that the flux source is magnified about 4.5 times, and the velocity dispersion of the lens is km s−1, in good agreement with the value derived spectroscopically. This is the second case known of an Einstein cross of an LBG.

The relation between the environment and nuclear activity in nearby QSOs: Defining a control sample

AbstractIn this study, we aim to investigate the relation between nuclear activity and the environment for luminous (L[O III] &gt;7.63 × 1041 erg s–1) Active Galactic Nuclei (AGN) - that, at these luminosities are classified as quasi-stellar objects (QSOs) - using a sample of 436 type 2 QSOs. Recent studies suggest that there is an excess of interacting hosts in luminous AGN, indicating that interactions trigger the nuclear activity. In order to examine this, it is necessary to select a control sample of non-active galaxies, matched to the active ones by the properties of the host galaxies, such as distance and stellar mass. We present here the results of the search for such a control sample.

Large Ly α opacity fluctuations and low CMB τ in models of late reionization with large islands of neutral hydrogen extending to z &amp;lt; 5.5

Abstract High-redshift quasi-stellar object (QSO) spectra show large spatial fluctuations in the Ly α opacity of the intergalactic medium on surprisingly large scales at $z$ ≳ 5.5. We present a radiative transfer simulation of cosmic reionization driven by galaxies that reproduces this large scatter and the rapid evolution of the Ly α opacity distribution at 5 &amp;lt; $z$ &amp;lt; 6. The simulation also reproduces the low Thomson scattering optical depth reported by the latest cosmic microwave background (CMB) measurement and is consistent with the observed short near-zones and strong red damping wings in the highest redshift QSOs. It also matches the rapid disappearance of observed Ly α emission by galaxies at $z$ ≳ 6. Reionization is complete at $z$ = 5.3 in our model, and 50 per cent of the volume of the Universe is ionized at $z$ = 7. Agreement with the Ly α forest data in such a late reionization model requires a rapid evolution of the ionizing emissivity of galaxies that peaks at $z$ ∼ 6.8. The late end of reionization results in a large scatter in the photoionization rate and the neutral hydrogen fraction at redshifts as low as $z$ ≲ 5.5 with large residual neutral ‘islands’ that can produce very long Gunn–Peterson troughs resembling those seen in the data.

Black versus Dark: Rapid Growth of Supermassive Black Holes in Dark Matter Halos at z ∼ 6

Abstract We report on the relation between the mass of supermassive black holes (SMBHs; ) and that of hosting dark matter halos ( ) for 49 z ∼ 6 quasi-stellar objects (QSOs) with [C ii]158 μm velocity-width measurements. Here, we estimate assuming that the rotation velocity from is equal to the circular velocity of the halo; we have tested this procedure using z ∼ 3 QSOs that also have clustering-based estimates. We find that a vast majority of the z ∼ 6 SMBHs are more massive than expected from the local – relation, with one-third of the sample by factors ≳102. The median mass ratio of the sample, , means that 0.4% of the baryons in halos are locked up in SMBHs. The mass growth rates of our SMBHs amount to ∼10% of the star formation rates (SFRs), or ∼1% of the mean baryon accretion rates, of the hosting galaxies. A large fraction of the hosting galaxies are consistent with average galaxies in terms of SFR and perhaps of stellar mass and size. Our study indicates that the growth of SMBHs ( ) in luminous z ∼ 6 QSOs greatly precedes that of hosting halos owing to efficient gas accretion even under normal star formation activities, although we cannot rule out the possibility that undetected SMBHs have local ratios. This preceding growth is in contrast to much milder evolution of the stellar-to-halo mass ratio.

A Sub-damped Lyα Absorber with Unusual Abundances: Evidence of Gas Recycling in a Low-redshift Galaxy Group

Abstract Using Hubble Space Telescope/Space Telescope Imaging Spectrograph G140M spectroscopy, we investigate an absorption-line system at z = 0.07489 in the spectrum of the quasi-stellar object PG 1543+489 (z QSO = 0.401). The sightline passes within ρ = 66 kpc of an edge-on disk galaxy at a similar redshift, but the galaxy belongs to a group with four other galaxies within ρ = 160 kpc. We detect H i [log N(H i/cm−2) = 19.12 ± 0.04] as well as N i, Mg ii, Si ii, and Si iii, from which we measure a gas-phase abundance of [N/H] = −1.0 ± 0.1. Photoionization models indicate that the nitrogen-to-silicon relative abundance is solar, yet magnesium is underabundant by a factor of ≈2. We also report spatially resolved emission-line spectroscopy of the nearby galaxy, and we extract its rotation curve. The galaxy’s metallicity is ≈8× higher than [N/H] in the absorber, and interestingly, the absorber velocities suggest that the gas at ρ = 66 kpc is corotating with the galaxy’s stellar disk, possibly with an inflow component. These characteristics could indicate that this sub-damped Lyα absorber system arises in a “cold-accretion” flow. However, the absorber abundance patterns are peculiar. We hypothesize that the gas was ejected from its galaxy of origin (or perhaps is a result of tidal debris from interactions between the group galaxies) with a solar nitrogen abundance, but that subsequently mixed with (and was diluted by) gas in the circumgalactic medium or group. If the gas is bound to the nearby galaxy, this system may be an example of the gas “recycling” predicted by theoretical galaxy simulations. Our hypothesis is testable with future observations.