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521. Narrow MgII absorption lines from SDSS-DR9Q
ID:
ivo://CDS.VizieR/J/ApJS/221/32
Title:
Narrow MgII absorption lines from SDSS-DR9Q
Short Name:
J/ApJS/221/32
Date:
21 Oct 2021
Publisher:
CDS
Description:
Using the Data Release 9 Quasar spectra from the Baryonic Oscillation Spectroscopic Survey, which does not include quasar spectra from the Sloan Digital Sky Survey Data Release 7, we detect narrow MgII{lambda}{lambda}2796,2803 absorption doublets in the spectral data redward of 1250{AA} (quasar rest frame) until the red wing of the MgII{lambda}2800 emission line. Our survey is limited to quasar spectra with a median signal-to-noise ratio <S/N>{>=}4/pixel in the surveyed spectral region, resulting in a sample that contains 43260 quasars. We have detected a total of 18598 MgII absorption doublets with 0.2933<=z_abs_<=2.6529. About 75% of absorbers have an equivalent width at rest frame of W_r_^{lambda}2796^. About 75% of absorbers have doublet ratios (DR=W_r_^{lambda}2796^/W_r_^{lambda}2803^) in the range of 1<=DR<=2, and about 3.2% lie outside the range of 1-{sigma}_DR_<=DR<=2+{sigma}_DR_. We characterize the detection false positives/negatives by the frequency of detected MgII absorption doublets in the limits of the S/N of the spectral data. The S/N=4.5 limit is assigned a completeness fraction of 53% and tends to be complete when the S/N is greater than 4.5. The redshift number densities of all of the detected MgII absorbers moderately increase from z~0.4 to z~1.5, which parallels the evolution of the cosmic star formation rate density. Limiting our investigation to those quasars whose emission redshift can be determined from narrow emission lines, the relative velocities ({beta}) of MgII absorbers have a complex distribution which probably consists of three classes of MgII absorbers: (1) cosmologically intervening absorbers; (2) environmental absorbers that reside within the quasar host galaxies or galaxy clusters; (3) quasar outflow absorbers. After subtracting contributions from cosmologically intervening absorbers and environmental absorbers, the {beta} distribution of the MgII might mainly be contributed by the quasar outflow absorbers and peaks at {upsilon}~1500km/s. This peak velocity is lower than the value of 2000km/s found in statistical analysis of CIV absorbers.
522. NBC Quasar Candidate Catalog
ID:
ivo://CDS.VizieR/J/ApJS/155/257
Title:
NBC Quasar Candidate Catalog
Short Name:
J/ApJS/155/257
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalog of 100563 unresolved, UV-excess (UVX) quasar candidates to g=21 from 2099 deg^2^ of the Sloan Digital Sky Survey (SDSS) Data Release One (DR1) imaging data. Existing spectra of 22737 sources reveals that 22191 (97.6%) are quasars; accounting for the magnitude dependence of this efficiency, we estimate that 95502 (95.0%) of the objects in the catalog are quasars. Such a high efficiency is unprecedented in broadband surveys of quasars. This "proof-of-concept" sample is designed to be maximally efficient, but still has 94.7% completeness to unresolved, g~<19.5, UVX quasars from the DR1 quasar catalog. This efficient and complete selection is the result of our application of a probability density type analysis to training sets that describe the four-dimensional color distribution of stars and spectroscopically confirmed quasars in the SDSS. Specifically, we use a nonparametric Bayesian classification, based on kernel density estimation, to parameterize the color distribution of astronomical sources - allowing for fast and robust classification. We further supplement the catalog by providing photometric redshifts and matches to FIRST/VLA, ROSAT, and USNO-B sources.
523. Nearby Ly{alpha} quasar absorbers
ID:
ivo://CDS.VizieR/J/ApJ/524/536
Title:
Nearby Ly{alpha} quasar absorbers
Short Name:
J/ApJ/524/536
Date:
21 Oct 2021
Publisher:
CDS
Description:
Spectroscopy of 10 quasars obtained with the Goddard High Resolution Spectrograph (GHRS) of the Hubble Space Telescope (HST) is presented. In the 10 sight lines, we detect 357 absorption lines above a significance level of 3{sigma} and 272 lines above a significance level of 4.5{sigma}. Automated software is used to detect and identify the lines, almost all of which are unresolved at the GHRS G140L resolution of 200km/s. After identifying Galactic lines, intervening metal lines, and higher order Lyman lines, we are left with 139 Ly{alpha} absorbers in the redshift range 0<z<0.22 (lines within 900km/s of geocoronal Ly{alpha} are not selected). These diffuse hydrogen absorbers have column densities that are mostly in the range 10^13^-10^15^cm^-2^ for an assumed Doppler parameter of 30km/s. The number density of lines above a rest equivalent width of 0.24{AA}, dN/dz=38.3{+/-}5.3, agrees well with the measurement from the Quasar Absorption-Line Key Project. There is marginal evidence for cosmic variance in the number of absorbers detected among the 10 sight lines.
524. Near-infrared hydrogen & helium QSO emission lines
ID:
ivo://CDS.VizieR/J/AJ/158/129
Title:
Near-infrared hydrogen & helium QSO emission lines
Short Name:
J/AJ/158/129
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 14 near-infrared (NIR) quasar spectra observed with the Flamingos-2 NIR spectrometer instrument at the Gemini South Observatory. The targets were selected with redshifts of (0.58~<z~<0.63) to ensure the spectral wavelength range included specifically identified hydrogen and helium broad emission lines. We present measurements of their FWHM, equivalent widths, and flux ratios relative to H{alpha}. The quasars are all within the Sloan Digital Sky Survey (SDSS) Stripe 82 region which, then also provides multi-epoch rest-frame UV and optical spectroscopic observations of our targets. In future work, these data and those from Galaxy Evolution Explorer and NUV spectra will be utilized to constrain photoionization models to determine physical conditions within the broad emission line regions, such as the incident ionizing photon flux and gas density.
525. Near-infrared spectra of 27 SDSS quasars
ID:
ivo://CDS.VizieR/J/ApJ/640/579
Title:
Near-infrared spectra of 27 SDSS quasars
Short Name:
J/ApJ/640/579
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a near-infrared quasar composite spectrum spanning the wavelength range 0.58-3.5um. The spectrum has been constructed from observations of 27 quasars obtained at the NASA IRTF telescope and satisfying the criteria Ks<14.5 and M_i_<-23; the redshift range is 0.118<z<0.418. The signal-to-noise ratio is moderate, reaching a maximum of 150 between 1.6 and 1.9um. While a power-law fit to the continuum of the composite spectrum requires two breaks, a single power-law slope of alpha=-0.92 plus a 1260K blackbody provides an excellent description of the spectrum from H{alpha} to 3.5um, strongly suggesting the presence of significant quantities of hot dust in this blue-selected quasar sample. We measure intensities and line widths for 10 lines, finding that the Paschen line ratios rule out case B recombination. We compute K-corrections for the J, H, K, and Spitzer 3.6um bands, which will be useful in analyzing observations of quasars up to z=10.
526. Near-IR astrometry of Southern ICRF quasars
ID:
ivo://CDS.VizieR/J/A+A/437/1135
Title:
Near-IR astrometry of Southern ICRF quasars
Short Name:
J/A+A/437/1135
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present high quality astrometry, along with J, H, and Ks photometry, for 30 southern International Celestial Reference Frame (ICRF) quasars observed with the ESO NTT/SOFI at La Silla. Our main purpose is to document the optical counterpart of ICRF quasars, by reporting their position in a stellar reference frame and their near-infrared photometry. Our investigation lies within the scope of extending the (radio) extragalactic reference frame into the optical range. An internal precision generally better than 10mas was obtained in positioning the near-infrared counterpart of these quasars within their stellar surroundings. The actual astrometric accuracy is estimated from the departure between the observed and the radio (VLBI) positions of quasars, and is about 35mas, mainly due to the statistical uncertainties of the stellar reference catalogue (UCAC2, Cat. <I/289>). The positional accuracy was improved to 25mas for a subset of 14 quasars observed with extended fields of view, as obtained from mosaics of overlapping images. The 3-band photometry was achieved with a precision most often better than 0.04mag, based on calibration with the 2MASS magnitudes.
527. Near-IR spectroscopy follow-up of 60 SDSS-DR7 QSOs
ID:
ivo://CDS.VizieR/J/ApJ/753/125
Title:
Near-IR spectroscopy follow-up of 60 SDSS-DR7 QSOs
Short Name:
J/ApJ/753/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
Single-epoch virial black hole (BH) mass estimators utilizing broad emission lines have been routinely applied to high-redshift quasars to estimate their BH masses. Depending on the redshift, different line estimators (H{alpha}, H{beta}, MgII{lambda}2798, CIV{lambda}1549) are often used with optical/near-infrared spectroscopy. Here, we use a homogeneous sample of 60 intermediate-redshift (z~1.5-2.2) Sloan Digital Sky Survey quasars with optical and near-infrared spectra covering CIV through H{alpha} to investigate the consistency between different single-epoch virial BH mass estimators.
528. Neutral gas in the Milky Way halo
ID:
ivo://CDS.VizieR/J/A+A/542/A110
Title:
Neutral gas in the Milky Way halo
Short Name:
J/A+A/542/A110
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an absorption-selected survey of CaII and NaI features located in the halo of the Milky Way using QSO absorption spectroscopy. We made use of the ESO data archive and retrieved all publically available absorption-line data for low- and high-redshift QSOs observed with the Ultraviolet and Visual Echelle Spectrograph (UVES) on the VLT. This enormous data archive (Spectral Quasar Absorption Database, SQUAD; PI: M.T. Murphy) provides high-quality spectral data for ~400 quasars and active galactic nuclei (AGN). Most of these spectra were taken in the UVES standard configuration using the 1" slit, providing a spectral resolution of R~45000 (corresponding to a velocity resolution of ~6.6km/sFWHM). The spectral coverage as well as the signal-to-noise ratio (S/N) varies substantially among the spectra, reflecting the various scientific goals of the original proposals. For several of the sight lines we performed deep (brightness temperature limit, Tb_lim_~30mK, angular resolution: 9' FWHM, spectral resolution: 0.5km/s FWHM) follow-up radio observations using the Effelsberg 100-m telescope to search for HI emission. Furthermore for a large fraction of the sight lines we obtained HI data from the new Galactic All-Sky survey (GASS, Tb_lim_~60mK, angular resolution: 15.6' FWHM, spectral resolution: 0.8km/s FWHM) and the Effelsberg-Bonn HI survey (EBHIS, Tb_lim_~90mK, angular resolution: 10.5' FWHM, spectral resolution: 1.2km/s FWHM). All HI data were corrected for stray radiation using software by P. Kalberla.
529. [NeV] or [NeIII] double peaked SDSS quasars
ID:
ivo://CDS.VizieR/J/ApJ/769/95
Title:
[NeV] or [NeIII] double peaked SDSS quasars
Short Name:
J/ApJ/769/95
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a sample of 131 quasars from the Sloan Digital Sky Survey at redshifts 0.8<z<1.6 with double peaks in either of the high-ionization narrow emission lines [NeV]{lambda}3426 or [NeIII]{lambda}3869. These sources were selected with the intention of identifying high-redshift analogs of the z<0.8 active galactic nuclei (AGNs) with double-peaked [OIII]{lambda}5007 lines, which might represent AGN outflows or dual AGNs. Lines of high ionization potential are believed to originate in the inner, highly photoionized portion of the narrow line region, and we exploit this assumption to investigate the possible kinematic origins of the double-peaked lines. For comparison, we measure the [NeV]{lambda}3426 and [NeIII]{lambda}3869 double peaks in low-redshift (z<0.8) [OIII]-selected sources. We find that [NeV]{lambda}3426 and [NeIII]{lambda}3869 show a correlation between line splitting and line width similar to that of [OIII]{lambda}5007 in other studies, and the velocity splittings are correlated with the quasar Eddington ratio. These results suggest an outflow origin for at least a subset of the double peaks, allowing us to study the high-ionization gas kinematics around quasars. However, we find that a non-negligible fraction of our sample show no evidence for an ionization stratification. For these sources, the outflow scenario is less compelling, leaving the dual AGN scenario as a viable possibility. Finally, we find that our sample shows an anti-correlation between the velocity-offset ratio and luminosity ratio of the components, which is a potential dynamical argument for the presence of dual AGNs. Therefore, this study serves as a first attempt at extending the selection of candidate dual AGNs to higher redshifts.
530. New damped Ly{alpha} absorbers
ID:
ivo://CDS.VizieR/J/MNRAS/449/1536
Title:
New damped Ly{alpha} absorbers
Short Name:
J/MNRAS/449/1536
Date:
21 Oct 2021
Publisher:
CDS
Description:
Quasar damped Ly{alpha} (DLA) absorption-line systems with redshifts z<1.65 are used to trace neutral gas over approximately 70 percent of the most recent history of the Universe. However, such systems fall in the UV and are rarely found in blind UV spectroscopic surveys. Therefore, it has been difficult to compile a moderate-sized sample of UV DLAs in any narrow cosmic time interval. However, DLAs are easy to identify in low-resolution spectra because they have large absorption rest equivalent widths. We have performed an efficient strong-Mg ii-selected survey for UV DLAs at redshifts z=[0.42,0.70] using Hubble Space Telescope's low-resolution ACS-HRC-PR200L prism. This redshift interval covers ~1.8Gyr in cosmic time, i.e. t~[7.2,9.0]Gyr after the big bang. A total of 96 strong MgII absorption-line systems identified in Sloan Digital Sky Survey spectra were successfully observed with the prism at the predicted UV wavelengths of Ly{alpha} absorption. We found that 35 of the 96 systems had a significant probability of being DLAs. One additional observed system could be a very high N_HI_ DLA (N_HI_~2x10^22^atoms/cm^2^ or possibly higher), but since very high N_HI_ systems are extremely rare, it would be unusual for this system to be a DLA given the size of our sample. Here we present information on our prism sample, including our best estimates of N_HI_ and errors for the 36 systems fitted with DLA profiles. This list is valuable for future follow-up studies of low-redshift DLAs in a small redshift interval, although such work would clearly benefit from improved UV spectroscopy to more accurately determine their neutral hydrogen column densities.