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- ID:
- ivo://CDS.VizieR/J/ApJ/748/131
- Title:
- MgII absorbers in SDSS-DR7 quasar catalog
- Short Name:
- J/ApJ/748/131
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A few percent of quasars show strong associated Mg II absorption, with velocities (v_off_) lying within a few thousand km/s from the quasar systemic redshift. These associated absorption line (AAL) systems are usually interpreted as absorbers that are either intrinsic to the quasar and its host, or arising from external galaxies clustering around the quasar. Using composite spectra of ~1800 Mg II AAL quasars selected from SDSS DR7 at 0.4<~z<~2, we show that quasars with AALs with v_off_<1500km/s have a prominent excess in [OII]{lambda}3727 emission (detected at >7{sigma}) at rest relative to the quasar host, compared to unabsorbed quasars. We interpret this [OII] excess as due to enhanced star formation in the quasar host. Our results suggest that a significant fraction of AALs with v_off_<1500km/s are physically associated with the quasar and its host. AAL quasars also have dust reddening lying between normal quasars and the so-called dust-reddened quasars. We suggest that the unique properties of AAL quasars can be explained if they are the transitional population from heavily dust-reddened quasars to normal quasars in the formation process of quasars and their hosts. This scenario predicts a larger fraction of young bulges, disturbed morphologies, and interactions of AAL quasar hosts compared to normal quasars. The intrinsic link between associated absorbers and quasar hosts opens a new window to probe massive galaxy formation and galactic-scale feedback processes, and provides a crucial test of the evolutionary picture of quasars.
- ID:
- ivo://CDS.VizieR/J/MNRAS/354/L25
- Title:
- MgII absorbers in SDSS QSOs
- Short Name:
- J/MNRAS/354/L25
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the cross-correlation between 212 Mg II quasar absorption systems and ~20000 luminous red galaxies (LRGs) selected from the Sloan Digital Sky Survey Data Release 1 (Cat. <J/AJ/126/2579>) in the redshift range 0.4<=z<=0.8. The Mg II systems were selected to have {lambda}{lambda}2796 and 2803 rest-frame equivalent widths >=1.0{AA} and identifications confirmed by the Fe II {lambda}2600 or Mg I {lambda}2852 lines.
- ID:
- ivo://CDS.VizieR/J/ApJ/779/161
- Title:
- MgII absorbers in 0.4<z<2.3 SDSS QSOs
- Short Name:
- J/ApJ/779/161
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have performed an analysis of over 34000 Mg II doublets at 0.36<z<2.29 in Sloan Digital Sky Survey (SDSS) Data Release 7 quasar spectra; the catalog, advanced data products, and tools for analysis are publicly available. The catalog was divided into 14 small redshift bins with roughly 2500 doublets in each and from Monte Carlo simulations, we estimate 50% completeness at rest equivalent width W_r_{approx}0.8{AA}. The equivalent width frequency distribution is described well by an exponential model at all redshifts, and the distribution becomes flatter with increasing redshift, i.e., there are more strong systems relative to weak ones. Direct comparison with previous SDSS Mg II surveys reveals that we recover at least 70% of the doublets in these other catalogs, in addition to detecting thousands of new systems. We discuss how these surveys came by their different results, which qualitatively agree but because of the very small uncertainties, differ by a statistically significant amount. The estimated physical cross section of Mg II-absorbing galaxy halos increased approximately threefold from z=0.4 to z=2.3, while the W_r_>=1{AA} absorber line density, dN_MgII_/dX, grew by roughly 45%. Finally, we explore the different evolution of various absorber populations --damped Ly{alpha} absorbers, Lyman limit systems, strong C IV absorbers, and strong and weaker MgII systems -- across cosmic time (0<z<6).
- ID:
- ivo://CDS.VizieR/J/ApJ/724/L176
- Title:
- MgII absorbing gas around galaxies
- Short Name:
- J/ApJ/724/L176
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the connections between ongoing star formation, galaxy mass, and extended halo gas, in order to distinguish between starburst-driven outflows and infalling clouds that produce the majority of observed MgII absorbers at large galactic radii (>~10h^-1^kpc) and to gain insights into halo gas contents around galaxies. We present new measurements of total stellar mass (M_star_), H{alpha} emission line strength (EW(H{alpha})), and specific star formation rate (sSFR) for the 94 galaxies described by Chen et al.'s 2010 paper (Cat. J/ApJ/714/1521).
- ID:
- ivo://CDS.VizieR/J/ApJ/754/38
- Title:
- MgII absorption systems for Flat-Spectrum Radio QSOs
- Short Name:
- J/ApJ/754/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The conventional wisdom that the rate of incidence of MgII absorption systems, dN/dz (excluding "associated systems" having a velocity {beta}c relative to the active galactic nucleus (AGN) of less than ~5000km/s), is totally independent of the background AGNs has been challenged by a recent finding that dN/dz for strong MgII absorption systems toward distant blazars is 2.2+/-^0.8^_0.6_ times the value known for normal optically selected quasars (QSOs). This has led to the suggestion that a significant fraction of even the absorption systems with {beta} as high as ~0.1 may have been ejected by the relativistic jets in the blazars, which are expected to be pointed close to our direction. Here, we investigate this scenario using a large sample of 115 flat-spectrum radio-loud quasars (FSRQs) that also possess powerful jets, but are only weakly polarized. We show, for the first time, that dN/dz toward FSRQs is, on the whole, quite similar to that known for QSOs and that the comparative excess of strong MgII absorption systems seen toward blazars is mainly confined to {beta}<0.15. The excess relative to FSRQs probably results from a likely closer alignment of blazar jets with our direction; hence, any gas clouds accelerated by them are more likely to be on the line of sight to the active quasar nucleus.
- ID:
- ivo://CDS.VizieR/J/ApJ/890/132
- Title:
- MgII abs. toward SDSS QSOs with rotation measures
- Short Name:
- J/ApJ/890/132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We probed the magnetic fields in high-redshift galaxies using excess extragalactic contribution to residual rotation measure (RRM) for quasar sightlines with intervening MgII absorbers. Based on a large sample of 1132 quasars, we have computed RRM distributions broadening using median absolute deviation from the mean ({sigma}_rrm_^md^), and found it to be 17.1+/-0.7rad/m^2^ for 352 sightlines having MgII intervening absorbers in comparison to its value of 15.1+/-0.6rad/m^2^ for 780 sightlines without such absorbers, resulting in an excess broadening ({sigma}_rrm_^ex^) of 8.0+/-1.9rad:m^2^ among these two subsamples. This value of {sigma}_rrm_^ex^, has allowed us to constrain the average strength of magnetic field (rest frame) in high-redshift galaxies responsible for these Mg II absorbers, to be ~1.3+/-0.3{mu}G at a median redshift of 0.92. This estimate of magnetic field is consistent with the reported estimate in earlier studies based on radio-infrared correlation and energy equipartition for galaxies in the local universe. A similar analysis on subsample split based on the radio spectral index, {alpha} (with F_{nu}_{propto}{nu}^{alpha}^), for flat ({alpha}>=-0.3; 315 sources) and steep ({alpha}<=-0.7; 476 sources) spectrum sources shows a significant {sigma}_rrm_^ex^ (at 3.5{sigma} level) for the former and absent in the latter. An anticorrelation found between the {sigma}_rrm_^md^ and percentage polarization (p) with a similar Pearson correlation of -0.62 and -0.87 for subsamples with and without MgII, respectively, suggests the main contribution for decrements in the p value to be intrinsic to the local environment of quasars.
- ID:
- ivo://CDS.VizieR/J/ApJ/698/819
- Title:
- MgII and LRGs cross-correlation analysis
- Short Name:
- J/ApJ/698/819
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the cross-correlation of MgII({lambda}2796, 2803) quasar absorption systems with luminous red galaxies (LRGs) from the Fifth Data Release (DR5) of the Sloan Digital Sky Survey. The absorption line sample consists of 2705 unambiguously intervening MgII absorption systems, detected at a 4{sigma} level, covering a redshift range (0.36<=z_abs_<=0.8) and a rest equivalent-width range of 0.8{AA}<=W^{lambda}2796^_r_<=5.0{AA}. We cross-correlate these absorbers with 1495604 LRGs with accurate photometric redshifts in the same redshift range and examine the relationship of MgII equivalent width and clustering amplitude.
- ID:
- ivo://CDS.VizieR/J/ApJS/242/28
- Title:
- MgII-BAL quasar variability in SDSS spectra
- Short Name:
- J/ApJS/242/28
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present absorption variability results for 134 bona fide MgII broad absorption-line (BAL) quasars at 0.46<=z<=2.3 covering days to ~10yr in the rest frame. We use multiple-epoch spectra from the Sloan Digital Sky Survey, which has delivered the largest such BAL variability sample ever studied. MgII-BAL identifications and related measurements are compiled and presented in a catalog. We find a remarkable time-dependent asymmetry in the equivalent width (EW) variation from the sample, such that weakening troughs outnumber strengthening troughs, the first report of such a phenomenon in BAL variability. Our investigations of the sample further reveal that (i) the frequency of BAL variability is significantly lower (typically by a factor of 2) than that in high-ionization BALQSO samples, (ii) MgII-BAL absorbers tend to have relatively high optical depths and small covering factors along our line of sight, (iii) there is no significant EW-variability correlation between MgII troughs at different velocities in the same quasar, and (iv) the EW-variability correlation between MgII and AlIII BALs is significantly stronger than that between MgII and CIV BALs at the same velocities. These observational results can be explained by a combined transverse-motion/ionization-change scenario, where transverse motions likely dominate the strengthening BALs while ionization changes and/or other mechanisms dominate the weakening BALs.
- ID:
- ivo://CDS.VizieR/J/A+A/410/33
- Title:
- MgII/FeII absorbers in 2dF-quasar survey
- Short Name:
- J/A+A/410/33
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use the first data release of the 2-degree Field quasar survey (Cat. <VII/223>) to investigate the effect of gravitational magnification by foreground absorbing systems on background quasars. We select two populations of quasars from this sample: one with strong MgII/FeII absorbers and one without. The selection is done in such a way that the two populations have the same redshift distribution and the absorber detection procedure discards possible biases with quasar magnitude.
