- 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.
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Search Results
- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/794/156
- Title:
- MgII/FeII absorption profile for 0.3<z<1.4 galaxies
- Short Name:
- J/ApJ/794/156
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze Mg II {lambda}{lambda}2796, 2803 and Fe II {lambda}{lambda}2586, 2600 absorption profiles in individual spectra of 105 galaxies at 0.3<z<1.4. The galaxies, drawn from redshift surveys of the GOODS fields and the Extended Groth Strip, sample the range in star formation rates (SFRs) occupied by the star-forming sequence with stellar masses log M_*_/M_{sun}_>~9.6 down to SFR>~2 M_{sun}_/yr at 0.3<z<0.7. Using the Doppler shifts of Mg II and Fe II absorption as tracers of cool gas kinematics, we detect large-scale winds in 66+/-5% of the galaxies. Hubble Space Telescope Advanced Camera for Surveys imaging and our spectral analysis indicate that the outflow detection rate depends primarily on galaxy orientation: winds are detected in ~89% of galaxies having inclinations (i) <30{deg} (face-on), while the wind detection rate is ~45% in objects having i>50{deg} (edge-on). Combined with the comparatively weak dependence of wind detection rate on intrinsic galaxy properties, this implies that biconical outflows are ubiquitous in normal, star-forming galaxies at z~0.5. We find that wind velocity is correlated with galaxy M_*_ at 3.4{sigma} significance, while outflow equivalent width is correlated with SFR at 3.5{sigma} significance, suggesting hosts with higher SFR launch more material and/or generate a larger velocity spread for the absorbing clouds. Assuming the gas is driven into halos with isothermal density profiles, the wind velocities (~200-400 km/s) permit escape from the halo potentials only for the lowest-M_*_systems in the sample. However, the gas carries sufficient energy to reach distances >~50 kpc, and may therefore be a viable source of material for the massive, cool circumgalactic medium around bright galaxies at z~0.
- ID:
- ivo://CDS.VizieR/J/ApJ/843/30
- Title:
- MgII line vs 3000{AA} continuum analysis in 68 QSOs
- Short Name:
- J/ApJ/843/30
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the relationship between the MgII{lambda}2798 emission line and the 3000{AA} continuum variations using a sample of 68 intermediate-redshift (z~0.65-1.50) broad-line quasars spanning a bolometric luminosity range of 44.49erg/s<=logL_bol_<=46.31erg/s (Eddington ratio from ~0.026 to 0.862). This sample is constructed from SDSS-DR7Q and BOSS-DR12Q, each with at least two spectroscopic epochs in SDSS-I/II/III surveys. In addition, we adopt the following signal-to-noise ratio (S/N) selection criteria: (a) for MgII and the 3000{AA} continuum, S/N>=10; and (b) for narrow lines, S/N>=5. All our quasar spectra are recalibrated based on the assumption of constant narrow emission- line fluxes. In an analysis of spectrum-to-spectrum variations, we find a fairly close correlation (Spearman {rho}=0.593) between the variations in broad MgII and in the continuum. This is consistent with the idea that MgII is varying in response to the continuum emission variations. Adopting the modified weighted least squares regression method, we statistically constrain the slopes (i.e., the responsivity {alpha} of the broad MgII) between the variations in both components for the sources in different luminosity bins after eliminating intrinsic biases introduced by the rescaling process itself. It is shown that the responsivity is quite small (average {bar}{alpha}~0.464) and anti- correlates with the quasar luminosity. Our results indicate that high signal- to-noise flux measurements are required to robustly detect the intrinsic variability and the time lag of the MgII line.
- ID:
- ivo://CDS.VizieR/J/ApJS/142/79
- Title:
- 1-1.4 micron spectral atlas of stars
- Short Name:
- J/ApJS/142/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of J-band (1.08 to 1.35{mu}m) stellar spectra at low resolution (R~400). The targets consist of 105 stars ranging in spectral type from O9.5 to M7 and luminosity classes I through V. The relatively featureless spectra of hot stars, earlier than A4, can be used to remove the atmospheric features which dominate ground-based J-band spectroscopy. We measure equivalent widths for three absorption lines and nine blended features which we identify in the spectra. Using detailed comparison with higher resolution spectra, we demonstrate that low-resolution data can be used for stellar classification, since several features depend on the effective temperature and gravity. For example, the CN index (1.096-1.104{mu}m) decreases with temperature, but the strength of a blended feature at 1.28{mu}m (consisting of primarily P{beta}) increases. The slope of a star's spectrum can also be used to estimate its effective temperature. The luminosity class of a star correlates with the ratio of the MgI (1.1831{mu}m) line to a blend of several species at 1.16{mu}m. Using these indicators, a star can be classified to within several subclasses. Fifteen stars with particularly high and low metal abundances are included in the catalog, and some spectral dependence on metal abundance is also found.
- ID:
- ivo://CDS.VizieR/J/AJ/127/3075
- Title:
- Mid-infrared population of ELAIS-S1 sample
- Short Name:
- J/AJ/127/3075
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a multiwavelength catalog (15{mu}m, R-band, K-band, and 1.4GHz flux) plus spectroscopic identifications for 406 15{mu}m sources detected in the European Large Area ISO Survey (ELAIS) region S1, over the flux density range 0.5<S15{mu}m<150mJy. Three hundred thirty-two (~82%) sources are optically identified down to R~23.0. Spectra or bona fide stellar identifications are obtained for 290 objects (~88% of the optically identified sources). The areal coverage, mid-infrared (MIR) and optical completeness of the sample are discussed in order to allow statistical and evolutionary analyses.
- ID:
- ivo://CDS.VizieR/J/ApJ/719/1191
- Title:
- Mid-IR indicators of SF and AGN in galaxies
- Short Name:
- J/ApJ/719/1191
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the use of mid-infrared (MIR) polycyclic aromatic hydrocarbon (PAH) bands, the continuum, and emission lines as probes of star formation (SF) and active galactic nucleus (AGN) activity in a sample of 100 "normal" and local (z~0.1) emission-line galaxies. The MIR spectra were obtained with the Spitzer Space Telescope Infrared Spectrograph as part of the Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS), which includes multi-wavelength photometry from the ultraviolet to the far-infrared and optical spectroscopy. The continuum and features were extracted using PAHFIT, a decomposition code which we find to yield PAH equivalent widths (EWs) up to ~30 times larger than the commonly used spline methods. Despite the lack of extreme objects in our sample (such as strong AGNs, low-metallicity galaxies, or ULIRGs), we find significant variations in PAH, continuum, and emission-line properties, and systematic trends between these MIR properties and optically derived physical properties, such as age, metallicity, and radiation field hardness. We revisit the diagnostic diagram relating PAH EWs and [NeII]12.8um/[OIV]25.9um line ratios and find it to be in much better agreement with the standard optical SF/AGN classification than when spline decompositions are used, while also potentially revealing obscured AGNs.
- ID:
- ivo://CDS.VizieR/J/ApJS/206/1
- Title:
- Mid-IR properties of GOALS nearby LIRGs
- Short Name:
- J/ApJS/206/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Great Observatories All-Sky LIRG Survey (GOALS, Armus et al. 2009PASP..121..559A) is a comprehensive, multiwavelength study of luminous infrared galaxies (LIRGs) in the local universe. Here we present low resolution Spitzer Infrared Spectrograph spectra covering 5-38um and provide a basic analysis of the mid-IR spectral properties observed for nearby LIRGs. In a companion paper, we discuss detailed fits to the spectra and compare the LIRGs to other classes of galaxies. The GOALS sample of 244 nuclei in 180 luminous (10^11^<=L_IR_/L_{sun}_<10^12^) and 22 ultraluminous (L_IR_/L_{sun}_>=10^12^) IR galaxies represents a complete subset of the IRAS Revised Bright Galaxy Sample (Sanders, 2003, Cat. J/AJ/126/1607) and covers a range of merger stages, morphologies, and spectral types. The majority (>60%) of the GOALS LIRGs have high 6.2um polycyclic aromatic hydrocarbon (PAH) equivalent widths (EQW_6.2um_>0.4um) and low levels of silicate absorption (s_9.7um_>-1.0).
- ID:
- ivo://CDS.VizieR/J/ApJ/883/84
- Title:
- MIKE obs. of 2 metal-poor stars in Sylgr stream
- Short Name:
- J/ApJ/883/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We observe two metal-poor main-sequence stars that are members of the recently discovered Sylgr stellar stream. We present radial velocities, stellar parameters, and abundances for 13 elements derived from high-resolution optical spectra collected using the Magellan Inamori Kyocera Echelle spectrograph. The two stars have identical compositions (within 0.13 dex or 1.2{sigma}) among all elements detected. Both stars are very metal-poor ([Fe/H]=-2.92+/-0.06). Neither star is highly enhanced in C ([C/Fe]<+1.0). Both stars are enhanced in the {alpha} elements Mg, Si, and Ca ([{alpha}/Fe]=+0.32+/-0.06), and the ratios among Na, Al, and all Fe-group elements are typical for other stars in the halo and ultra-faint and dwarf spheroidal galaxies at this metallicity. Sr is mildly enhanced ([Sr/Fe]=+0.22+/-0.11), but Ba is not enhanced ([Ba/Fe]{<}-0.4), indicating that these stars do not contain high levels of neutron-capture elements. The Li abundances match those found in metal-poor unevolved field stars and globular clusters (GCs) (log{epsilon}(Li)=2.05+/-0.07), which implies that environment is not a dominant factor in determining the Li content of metal-poor stars. The chemical compositions of these two stars cannot distinguish whether the progenitor of the Sylgr stream was a dwarf galaxy or a GC. If the progenitor was a dwarf galaxy, the stream may originate from a dense region such as a nuclear star cluster. If the progenitor was a GC, it would be the most metal-poor GC known.
- ID:
- ivo://CDS.VizieR/J/ApJ/704/385
- Title:
- M31 integrated light abundances
- Short Name:
- J/ApJ/704/385
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the first detailed chemical abundances for five globular clusters (GCs) in M31 from high-resolution (R~25000) spectroscopy of their integrated light (IL). These GCs are the first in a larger set of clusters observed as part of an ongoing project to study the formation history of M31 and its GC population. The data presented here were obtained with the HIRES echelle spectrograph on the Keck I telescope and are analyzed using a new IL spectra analysis method that we have developed. In these clusters, we measure abundances for Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, and Ba, ages >=10Gyr, and a range in [Fe/H] of -0.9 to -2.2. As is typical of Milky Way GCs, we find these M31 GCs to be enhanced in the {alpha}-elements Ca, Si, and Ti relative to Fe.
