- ID:
- ivo://CDS.VizieR/J/MNRAS/455/1043
- Title:
- SDSS DLA and absorber quasar samples
- Short Name:
- J/MNRAS/455/1043
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The dust content of damped Lyman {alpha} systems (DLAs) is an important observable for understanding their origin and the neutral gas reservoirs of galaxies. While the average colour excess of DLAs, E(B-V), is known to be <~15-millimagnitude (mmag), both detections and non-detections with ~2mmag precision have been reported. Here we find 3.2{sigma} statistical evidence for DLA dust-reddening of 774 Sloan Digital Sky Survey (SDSS) quasars by comparing their fitted spectral slopes to those of ~7000 control quasars. The corresponding E(B-V) is 3.0+/-1.0mmag, assuming a Small Magellanic Cloud (SMC) dust extinction law, and it correlates strongly (3.5{sigma}) with the metal content, characterized by the SiII {lambda}1526 absorption-line equivalent width, providing additional confidence that the detection is due to dust in the DLAs. Evolution of E(B-V) over the redshift range 2.1<z<4.0 is limited to <2.5mmag per unit redshift (1{sigma}), consistent with the known, mild DLA metallicity evolution. There is also no apparent relationship with neutral hydrogen column density, N_HI_, though the data are consistent with a mean E(B-V)/N_HI_=(3.5+/-1.0)*10^-24^mag*cm^2^, approximately the ratio expected from the SMC scaled to the lower metallicities typical of DLAs. We implement the SDSS selection algorithm in a portable code to assess the potential for systematic, redshift-dependent biases stemming from its magnitude and colour-selection criteria. The effect on the mean E(B-V) is negligible (<5 per cent) over the entire redshift range of interest. Given the broad potential usefulness of this implementation, we make it publicly available.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/804/L15
- Title:
- SDSS-DR7 broad-line QSOs
- Short Name:
- J/ApJ/804/L15
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The diverse properties of broad-line quasars appear to follow a well-defined main sequence along which the optical FeII strength increases. It has been suggested that this sequence is mainly driven by the Eddington ratio (L/L_Edd_) of the black hole (BH) accretion. Shen & Ho (2014Natur.513..210S) demonstrated with quasar clustering analysis that the average BH mass decreases with increasing FeII strength when quasar luminosity is fixed, consistent with this suggestion. Here we perform an independent test by measuring the stellar velocity dispersion {sigma}_*_ (hence, the BH mass via the M-{sigma}_*_ relation) from decomposed host spectra in low-redshift Sloan Digital Sky Survey quasars. We found that at fixed quasar luminosity, {sigma}_*_ systematically decreases with increasing FeII strength, confirming that the Eddington ratio increases with FeII strength. We also found that at fixed luminosity and FeII strength, there is little dependence of {sigma}_*_ on the broad H{beta} FWHM. These new results reinforce the framework that the Eddington ratio and orientation govern most of the diversity seen in broad-line quasar properties.
- ID:
- ivo://CDS.VizieR/J/MNRAS/477/5625
- Title:
- SDSSDR12 eclipsing damped Lyalpha systems
- Short Name:
- J/MNRAS/477/5625
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of our automatic search for proximate damped Ly{alpha} absorption (PDLA) systems in the quasar spectra from the Sloan Digital Sky Survey Data Release 12. We constrain our search to those PDLAs lying within 1500km/s from the quasar to make sure that the broad DLA absorption trough masks most of the strong Ly{alpha} emission from the broad-line region (BLR) of the quasar. When the Ly{alpha} emission from the BLR is blocked by these so-called eclipsing DLAs, narrow Ly{alpha} emission from the host galaxy could be revealed as a narrow emission line (NEL) in the DLA trough. We define a statistical sample of 399 eclipsing DLAs with logN(HI)>=21.10. We divide our statistical sample into three subsamples based on the strength of the NEL detected in the DLA trough. By studying the stacked spectra of these subsamples, we found that absorptions from high ionization species are stronger in DLAs with stronger NEL in their absorption core. Moreover, absorption from the excited states of species like SIII are also stronger in DLAs with stronger NEL. We also found no correlation between the luminosity of the Ly{alpha} NEL and the quasar luminosity. These observations are consistent with a scenario in which the DLAs with stronger NEL are denser and physically closer to the quasar. We propose that these eclipsing DLAs could be the product of the interaction between infalling and outflowing gas. High-resolution spectroscopic observation would be needed to shed some light on the nature of these eclipsing DLAs.
- ID:
- ivo://CDS.VizieR/J/ApJS/220/3
- Title:
- SDSS-DR7 isolated galaxy morphologies
- Short Name:
- J/ApJS/220/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Isolated galaxies in low-density regions are significant in the sense that they are least affected by the hierarchical pattern of galaxy growth and interactions with perturbers, at least for the last few gigayears. To form a comprehensive picture of the star-formation history of isolated galaxies, we constructed a catalog of isolated galaxies and their comparison sample in relatively denser environments. The galaxies are drawn from the Sloan Digital Sky Survey Data Release 7 in the redshift range of 0.025<z<0.044. We performed a visual inspection and classified their morphology following the Hubble classification scheme. For the spectroscopic study, we make use of the catalog provided by Oh et al. (2011ApJS..195...13O). We confirm most of the earlier understanding on isolated galaxies. The most remarkable additional results are as follows. Isolated galaxies are dominantly late type with the morphology distribution (E:S0:S:Irr)=(9.9:11.3:77.6:1.2)%. The frequency of elliptical galaxies among isolated galaxies is only a third of that of the comparison sample. Most of the photometric and spectroscopic properties are surprisingly similar between the isolated and comparison samples. However, early-type isolated galaxies are less massive by 50% and younger (by H{beta}) by 20% than their counterparts in the comparison sample. This can be explained as a result of different merger and star-formation histories for differing environments in the hierarchical merger paradigm.
- ID:
- ivo://CDS.VizieR/J/MNRAS/354/L31
- Title:
- SDSS DR2 QSO and DLA properties
- Short Name:
- J/MNRAS/354/L31
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use Sloan Digital Sky Survey (SDSS) Data Release 2 quasi-stellar object (QSO) spectra to constrain the dust-reddening caused by intervening damped Lyman {alpha} systems (DLAs). Comparing the spectral index distribution of a 70 sight-line DLA sample with that of a large control sample reveals no evidence for dust-reddening at z~3.
- ID:
- ivo://CDS.VizieR/J/ApJ/639/766
- Title:
- SDSS-DR3 strong MgII absorbers
- Short Name:
- J/ApJ/639/766
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of two complementary investigations into the nature of strong (rest equivalent width, Wr>1.0{AA}) MgII absorption systems at high redshift. The first line of questioning examines the complete Sloan Digital Sky Survey Data Release 3 set of quasar spectra to determine the evolution of the incidence of strong MgII absorption. This search resulted in 7421 confirmed MgII systems of Wr>1.0{AA}, yielding a >95% complete statistical sample of 4835 absorbers (systems detected in S/N>7 spectral regions) spanning a redshift range 0.35<z<2.3.
- ID:
- ivo://CDS.VizieR/J/A+A/546/A122
- Title:
- SDSS extremely metal-poor emission-line galaxies
- Short Name:
- J/A+A/546/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 6.5-m MMT and 3.5m APO spectrophotometry of 69 HII regions in 42 low-metallicity emission-line galaxies, selected from the data release 7 of the Sloan Digital Sky Survey to have mostly [OIII]{lambda}4959/H{beta}<~1 and [NII]{lambda}6583/H{beta}<~0.1. The electron temperature-sensitive emission line [OIII]{lambda}4363 is detected in 53 HII regions allowing a direct abundance determination. The oxygen abundance in the remaining 16 HII regions is derived using a semi-empirical method. The oxygen abundance of the galaxies in our sample ranges from 12+logO/H~7.1 to ~7.9, with 14 HII regions in 7 galaxies with 12+logO/H<=7.35. In 5 of the latter galaxies, the oxygen abundance is derived here for the first time. Including other known extremely metal-deficient emission-line galaxies from the literature, e.g. SBS 0335-052W, SBS 0335-052E and I Zw 18, we have compiled a sample of the 17 most metal-deficient (with 12+logO/H<=7.35) emission-line galaxies known in the local universe. There appears to be a metallicity floor at 12+log O/H~6.9, suggesting that the matter from which dwarf emission-line galaxies formed was pre-enriched to that level by e.g. Population III stars.
- ID:
- ivo://CDS.VizieR/J/ApJS/221/24
- Title:
- SDSS-III APOGEE H-band spectral line lists
- Short Name:
- J/ApJS/221/24
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the H-band spectral line lists adopted by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). The APOGEE line lists comprise astrophysical, theoretical, and laboratory sources from the literature, as well as newly evaluated astrophysical oscillator strengths and damping parameters. We discuss the construction of the APOGEE line list, which is one of the critical inputs for the APOGEE Stellar Parameters and Chemical Abundances Pipeline, and present three different versions that have been used at various stages of the project. The methodology for the newly calculated astrophysical line lists is reviewed. The largest of these three line lists contains 134457 molecular and atomic transitions. In addition to the format adopted to store the data, the line lists are available in MOOG, Synspec, and Turbospectrum formats. The limitations of the line lists along with guidance for its use on different spectral types are discussed. We also present a list of H-band spectral features that are either poorly represented or completely missing in our line list. This list is based on the average of a large number of spectral fit residuals for APOGEE observations spanning a wide range of stellar parameters.
- ID:
- ivo://CDS.VizieR/J/AJ/153/174
- Title:
- SDSS-III/APOGEE. II. The multi-epoch ABE sample
- Short Name:
- J/AJ/153/174
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report on the H-band spectral variability of classical Be stars observed over the course of the Apache Point Galactic Evolution Experiment (APOGEE), one of four subsurveys comprising SDSS-III. As described in the first paper of this series, the APOGEE B-type emission-line (ABE) star sample was culled from the large number of blue stars observed as telluric standards during APOGEE observations. In this paper, we explore the multi-epoch ABE sample, consisting of 1100 spectra for 213 stars. These "snapshots" of the circumstellar disk activity have revealed a wealth of temporal variability including, but not limited to, gradual disappearance of the line emission and vice versa over both short and long timescales. Other forms of variability include variation in emission strength, emission peak intensity ratios, and emission peak separations. We also analyze radial velocities (RVs) of the emission lines for a subsample of 162 stars with sufficiently strong features, and we discuss on a case-by-case basis whether the RV variability exhibited by some stars is caused by binary motion versus dynamical processes in the circumstellar disks. Ten systems are identified as convincing candidates for binary Be stars with as of yet undetected companions.
- ID:
- ivo://CDS.VizieR/J/A+A/547/L1
- Title:
- SDSS-III DR9 DLA catalogue
- Short Name:
- J/A+A/547/L1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the column density distribution and cosmological mass density of neutral gas from a survey of Damped Lyman-alpha systems in the Sloan Digital Sky Survey III Data Release 9.
