- ID:
- ivo://CDS.VizieR/J/ApJ/817/55
- Title:
- NIR spectroscopy of 1.5<z<3.5 broad-band QSOs
- Short Name:
- J/ApJ/817/55
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the rest-frame optical properties of 74 luminous (L_bol_=10^46.2-48.2^erg/s), 1.5<z<3.5 broad-line quasars with near-IR (JHK) slit spectroscopy. Systemic redshifts based on the peak of the [OIII]{lambda}5007 line reveal that redshift estimates from the rest-frame UV broad emission lines (mostly MgII) are intrinsically uncertain by ~200km/s (measurement errors accounted for). The overall full-width-at-half-maximum of the narrow [OIII] line is ~1000km/s on average. A significant fraction of the total [OIII] flux (~40%) is in a blueshifted wing component with a median velocity offset of ~700km/s, indicative of ionized outflows within a few kpc from the nucleus; we do not find evidence of significant [OIII] flux beyond ~10kpc in our slit spectroscopy. The [OIII] line is noticeably more asymmetric and weaker than that in typical less luminous low-z quasars. However, when matched in quasar continuum luminosity, low-z quasars have similar [OIII] profiles and strengths as these high-z systems. Therefore the exceptionally large width and blueshifted wing, and the relatively weak strength of [OIII] in high-z luminous quasars are mostly a luminosity effect rather than redshift evolution. The H{beta}-[OIII] region of these high-z quasars displays a similar spectral diversity and Eigenvector 1 correlations with anti-correlated [OIII] and optical FeII strengths, as seen in low-z quasars; but the average broad H{beta} width is larger by 25% than typical low-z quasars, indicating more massive black holes in these high-z systems. These results highlight the importance of understanding [OIII] in the general context of quasar parameter space in order to understand quasar feedback in the form of [OIII] outflows. The calibrated one-dimensional near-IR spectra are made publicly available, along with a composite spectrum.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/418/863
- Title:
- NLTE corrections for Mg and Ca lines
- Short Name:
- J/MNRAS/418/863
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate NLTE effects for magnesium and calcium in the atmospheres of late-type giant and supergiant stars. The aim of this paper is to provide a grid of NLTE/LTE equivalent width ratios W/W* of Mg and Ca lines for the following range of stellar parameters: Teff in [3500,5250]K, log(g) in [0.5,2.0]dex and [Fe/H] in [-4.0,0.5]dex. We use realistic model atoms with the best physics available and taking into account the fine structure. The Mg and Ca lines of interest are in optical and near IR ranges. A special interest concerns the lines in the Gaia spectrograph (RVS) wavelength domain [847,874]nm. The NLTE corrections are provided as function of stellar parameters in an electronic table as well as in a polynomial form for the Gaia/RVS lines.
- ID:
- ivo://CDS.VizieR/J/ApJ/847/16
- Title:
- NLTE spectroscopy. II. Galactic metal-poor stars
- Short Name:
- J/ApJ/847/16
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From exploratory studies and theoretical expectations it is known that simplifying approximations in spectroscopic analysis (local thermodynamic equilibrium (LTE), 1D) lead to systematic biases of stellar parameters and abundances. These biases depend strongly on surface gravity, temperature and, in particular, for LTE versus non-LTE (NLTE), on metallicity of the stars. Here we analyze the [Mg/Fe] and [Fe/H] plane of a sample of 326 stars, comparing LTE and NLTE results obtained using 1D hydrostatic models and averaged <3D> models. We show that compared to the <3D> NLTE benchmark, the other three methods display increasing biases toward lower metallicities, resulting in false trends of [Mg/Fe] against [Fe/H], which have profound implications for interpretations by chemical evolution models. In our best <3D> NLTE model, the halo and disk stars show a clearer behavior in the [Mg/Fe]-[Fe/H] plane, from the knee in abundance space down to the lowest metallicities. Our sample has a large fraction of thick disk stars and this population extends down to at least [Fe/H]~-1.6dex, further than previously proven. The thick disk stars display a constant [Mg/Fe]~0.3dex, with a small intrinsic dispersion in [Mg/Fe] that suggests that a fast SN Ia channel is not relevant for the disk formation. The halo stars reach higher [Mg/Fe] ratios and display a net trend of [Mg/Fe] at low metallicities, paired with a large dispersion in [Mg/Fe]. These indicate the diverse origin of halo stars from accreted low-mass systems to stochastic/inhomogeneous chemical evolution in the Galactic halo.
- ID:
- ivo://CDS.VizieR/J/A+A/562/A135
- Title:
- Northern Galactic OB stars vsini
- Short Name:
- J/A+A/562/A135
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Stellar rotation is an important parameter in the evolution of massive stars. Accurate and reliable measurements of projected rotational velocities in large samples of OB stars are crucial to confront the predictions of stellar evolutionary models with observational constraints. We reassess previous determinations of projected rotational velocities (vsini) in Galactic OB stars using a large, high-quality spectroscopic dataset and a strategy that accounts for other sources of line-broadening in addition to rotation. We present a versatile and user-friendly IDL tool - based on a combined Fourier transform (FT) + goodness-of-fit (GOF) methodology - for the line-broadening characterization in OB-type stars. We used this tool to (a) investigate the impact of macroturbulent and microturbulent broadenings on vsini measurements, and (b) determine vsini and the size of the macroturbulent broadening (v_m_) in a sample of ~200 Galactic OB-type stars.
- ID:
- ivo://CDS.VizieR/J/A+A/576/A89
- Title:
- O abundances from HARPS in F-G stars
- Short Name:
- J/A+A/576/A89
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a detailed and uniform study of oxygen abundance from two different oxygen lines at 6158{AA} and 6300{AA} in a large sample of solar-type stars. The results are used to check the behaviour of these spectral lines as oxygen abundance indicators and to study the evolution of oxygen in thick and thin disk populations of the Galaxy. Equivalent width measurements were carried out for the [OI]6158 and [OI]6300 lines. LTE abundances were obtained from these two lines in 610 and 535 stars, respectively. Careful error analysis has been performed.
- ID:
- ivo://CDS.VizieR/J/A+A/384/473
- Title:
- O, B and Be stars equivalent widths
- Short Name:
- J/A+A/384/473
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an atlas of spectra of O- and B-type stars, obtained with the Short Wavelength Spectrometer (SWS) during the Post-Helium program of the Infrared Space Observatory (ISO). This program is aimed at extending the Morgan & Keenan (1973ARA&A..11...29M) classification scheme into the near-infrared. Later type stars will be discussed in a separate publication. The observations consist of 57 SWS Post-Helium spectra from 2.4 to 4.1{mu}m, supplemented with 10 spectra acquired during the nominal mission with a similar observational setting. For B-type stars, this sample provides ample spectral coverage in terms of subtype and luminosity class. For O-type stars, the ISO sample is coarse and therefore is complemented with 8 UKIRT L'-band observations. In terms of the presence of diagnostic lines, the L'-band is likely the most promising of the near-infrared atmospheric windows for the study of the physical properties of B stars. Specifically, this wavelength interval contains the Br{alpha}, Pf{gamma}, and other Pfund lines which are probes of spectral type, luminosity class and mass loss. Here, we present simple empirical methods based on the lines present in the 2.4 to 4.1{mu}m interval that allow the determination of i) the spectral type of B dwarfs and giants to within two subtypes; ii) the luminosity class of B stars to within two classes; iii) the mass-loss rate of O stars and B supergiants to within 0.25dex.
- ID:
- ivo://CDS.VizieR/J/AJ/154/29
- Title:
- Observation of 148 young stars toward NGC 1980
- Short Name:
- J/AJ/154/29
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- NGC1980 is a young cluster that is located about 0.5{deg} south of the Orion Nebula Cluster (ONC). Recent studies by Bouy et al. and Pillitteri et al. have suggested that NGC1980 contains an older population of stars compared to a much younger ONC, and that it belongs to a foreground population that may be located in front of the Orion A molecular gas by as much as 40pc. In this work, we present low-resolution spectra toward 148 young stars found toward the NGC1980 region. We determine the spectral types of these stars, examine accretion signatures and measure the extinction toward them. We determine that based on these observations, the age of the population of NGC1980 is indistinguishable from L1641, estimated to be ~3Myr, comparable with the study by Fang et al.
- ID:
- ivo://CDS.VizieR/J/ApJ/822/L5
- Title:
- Observed red supergiants in the inner Galaxy
- Short Name:
- J/ApJ/822/L5
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this Letter, we present a search for Galactic red supergiant stars (RSGs) in the direction of the inner Galaxy. A total of 94 targets selected from the 2MASS (Cat. VII/233) and GLIMPSE I North (Benjamin et al. 2003, Cat. II/293; Churchwell et al. 2009PASP..121..213C) catalogs - via their blue extinction-free Q1 and Q2 colors - were spectroscopically observed at infrared wavelengths (in the H- and K-bands at R~1000), and an extraordinary high detection rate of RSGs (>61%) was found. We identified spectroscopically 58 RSGs, based on their flat continua and large equivalent widths of the CO-band at 2.293 {mu}m (EW>45 {AA}). This increase corresponds to about 25% of previously known RSGs in the Galactic region 10{deg}<l<60{deg}, -1.1{deg}<b<1.1{deg}. In order to confirm the location of the new RSGs in the inner Galaxy, distances were estimated for a subsample of 47 stars with the clump method and found to range from 3.6+/-0.4 to 8.6+/-0.7 kpc. The large new sample will allow us to investigate Galactic metallicity gradients as a function of galactocentric distances and azimuthal angles. Such information is currently an highly disputed issue to constrain models of Galaxy formation and evolution.
- ID:
- ivo://CDS.VizieR/J/ApJ/883/163
- Title:
- OI abs. search in Keck and VLT spectra of 199 QSOs
- Short Name:
- J/ApJ/883/163
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a survey for metal absorption systems traced by neutral oxygen over 3.2<z<6.5. Our survey uses Keck/ESI and VLT/X-Shooter spectra of 199 QSOs with redshifts up to 6.6. In total, we detect 74 OI absorbers, of which 57 are separated from the background QSO by more than 5000km/s. We use a maximum likelihood approach to fit the distribution of OI{lambda}1302 equivalent widths in bins of redshift and from this determine the evolution in number density of absorbers with W_1302_>0.05{AA}, of which there are 49 nonproximate systems in our sample. We find that the number density does not monotonically increase with decreasing redshift, as would naively be expected from the buildup of metal-enriched circumgalactic gas with time. The number density over 4.9<z<5.7 is a factor of 1.7-4.1 lower (68% confidence) than that over 5.7<z<6.5, with a lower value at z<5.7 favored with 99% confidence. This decrease suggests that the fraction of metals in a low-ionization phase is larger at z~6 than at lower redshifts. Absorption from highly ionized metals traced by CIV is also weaker in higher-redshift OI systems, supporting this picture. The evolution of OI absorbers implies that metal-enriched circumgalactic gas at z~6 is undergoing an ionization transition driven by a strengthening ultraviolet background. This in turn suggests that the reionization of the diffuse intergalactic medium may still be ongoing at or only recently ended by this epoch.
- ID:
- ivo://CDS.VizieR/J/A+A/390/235
- Title:
- OI and FeII equivalent widths in metal-poor stars
- Short Name:
- J/A+A/390/235
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The table gives equivalent widths (in m{AA}) of OI and FeII lines for 35 metal-poor main sequence and subgiant stars as measured from high resolution, high S/N spectra observed with the ESO VLT/UVES spectrograph, during three observing runs: April 8-12, 2000, July 22-24, 2000, and April 10-12, 2001.
