- ID:
- ivo://CDS.VizieR/J/MNRAS/440/2665
- Title:
- SDSS J021933.13+200830.2 spectroscopy
- Short Name:
- J/MNRAS/440/2665
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first high-resolution spectroscopic observations of one red giant star in the ultra-faint dwarf galaxy Segue 2, which has the lowest total mass (including dark matter) estimated for any known galaxy. These observations were made using the Magellan Inamori Kyocera Echelle (MIKE) spectrograph on the Magellan II Telescope at Las Campanas Observatory. We perform a standard abundance analysis of this star, SDSS J021933.13+200830.2, and present abundances of 21 species of 18 elements as well as upper limits for 25 additional species. We derive [Fe/H]=-2.9, in excellent agreement with previous estimates from medium-resolution spectroscopy. Our main result is that this star bears the chemical signatures commonly found in field stars of similar metallicity. The heavy elements produced by neutron-capture reactions are present, but they are deficient at levels characteristic of stars in other ultra-faint dwarf galaxies and a few luminous dwarf galaxies. The otherwise normal abundance patterns suggest that the gas from which this star formed was enriched by metals from multiple Type II supernovae reflecting a relatively well-sampled IMF. This adds to the growing body of evidence indicating that Segue 2 may have been substantially more massive in the past.
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- ID:
- ivo://CDS.VizieR/J/A+A/618/A184
- Title:
- SDSS J151349.52+035211.28 Xshooter spectra
- Short Name:
- J/A+A/618/A184
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the detection and detailed analysis of a diffuse molecular cloud at z_abs_=2.4636 towards the quasar SDSS J151349.52+035211.28 (hereafter J1513+0352) (zem~=2.68) observed with the X-shooter spectrograph at the Very Large Telescope. We measure very high column densities of atomic and molecular hydrogen, with logN(HI,H_2_)~=21.8,21.3. This is the highest H_2_ column density ever measured in an intervening damped Lyman-{alpha}system but we do not detect CO, implying log N(CO)/N(H_2_)<-7.8, which could be due to a low metallicity of the cloud. From the metal absorption lines, we derive the metallicity to be Z~=0.15Z_{sun}_ and determine the amount of dust by measuring the induced extinction of the background quasar light, AV~=0.4. We simultaneously detect Ly{alpha} emission at the same redshift, with a centroid located at a most probable impact parameter of only {rho}~=1.4kpc. We argue that the line of sight is therefore likely passing through the interstellar medium of a galaxy, as opposed to the circumgalactic medium. The relation between the surface density of gas and that of star formation seems to follow the global empirical relation derived in the nearby Universe although our constraints on the star formation rate and on the galaxy extent remain too loose to be conclusive. We study the transition from atomic to molecular hydrogen using a theoretical description based on the microphysics of molecular hydrogen.We use the derived chemical properties of the cloud and physical conditions (Tk~=90K and n~=250cm^-3^) derived through the excitation of H_2_ rotational levels and neutral carbon fine structure transitions to constrain the fundamental parameters that govern this transition. By comparing the theoretical and observed HI column densities, we are able to bring an independent constraint on the incident UV flux, which we find to be in agreement with that estimated from the observed star formation rate.
- ID:
- ivo://CDS.VizieR/J/ApJ/863/134
- Title:
- SDSS low-metallicity blue compact dwarf galaxies
- Short Name:
- J/ApJ/863/134
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report a method of identifying candidate low-metallicity blue compact dwarf galaxies (BCDs) from the Sloan Digital Sky Survey (SDSS) imaging data, and present 3m Lick Observatory and 10m W.M. Keck Observatory optical spectroscopic observations of 94 new systems that have been discovered with this method. The candidate BCDs are selected from Data Release 12 (DR12) of SDSS on the basis of their photometric colors and morphologies. Using the Kast spectrometer on the 3m telescope, we confirm that the candidate low-metallicity BCDs are emission-line galaxies, and we make metallicity estimates using the empirical R and S calibration methods. Follow-up observations on a subset of the lowest-metallicity systems are made at Keck using the Low Resolution Imaging Spectrometer, which allow for a direct measurement of the oxygen abundance. We determine that 45 of the reported BCDs are low-metallicity candidates with 12+log(O/H)<=7.65, including six systems which are either confirmed or projected to be among the lowest-metallicity galaxies known, at 1/30 of the solar oxygen abundance, or 12+log(O/H)~7.20.
- ID:
- ivo://CDS.VizieR/J/ApJ/718/392
- Title:
- SDSS Lyman limit systems at z~3.5
- Short Name:
- J/ApJ/718/392
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We perform a semi-automated survey for {tau}_912_>=2 Lyman limit systems (LLSs) in quasar spectra from the Sloan Digital Sky Survey, Data Release 7. From a starting sample of 2473 quasars with z_em_=3.6-5.0, we analyze 429 spectra meeting strict selection criteria for a total redshift path {Delta}z=93.8 and identify 190 intervening systems at z_LLS_>=3.3. We also perform a survey for proximate LLSs (PLLSs) and find that {l}_PLLS_(z) is systematically lower (~25%) than intervening systems.
- ID:
- ivo://CDS.VizieR/J/ApJ/871/57
- Title:
- SDSS & MMT obs. of extremely massive QSOs & gal.
- Short Name:
- J/ApJ/871/57
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Black hole mass scaling relations suggest that extremely massive black holes (EMBHs) with M_BH_>~10^9.4^M_{sun}_ are found in the most massive galaxies with M_star_>~10^11.6^M_{sun}_, which are commonly found in dense environments, like galaxy clusters. Therefore, one can expect that there is a close connection between active EMBHs and dense environments. Here, we study the environments of 9461 galaxies and 2943 quasars at 0.24<~z<~0.40, among which 52 are extremely massive quasars with log(M_BH_/M_{sun}_)>=~9.4, using Sloan Digital Sky Survey and MMT Hectospec data. We find that, on average, both massive quasars and massive galaxies reside in environments more than ~2 times as dense as those of their less massive counterparts with log(M_BH_/M_{sun}_)<~9.0. However, massive quasars reside in environments about ~2 times less dense than inactive galaxies with log(M_BH_/M_{sun}_)>=9.4, and only about one third of massive quasars are found in galaxy clusters, while about two thirds of massive galaxies reside in such clusters. This indicates that massive galaxies are a much better signpost for galaxy clusters than massive quasars. The prevalence of massive quasars in moderate to low density environments is puzzling, considering that several simulation results show that these quasars appear to prefer dense environments. Several possible reasons for this discrepancy are discussed, although further investigation is needed to obtain a definite explanation.
- ID:
- ivo://CDS.VizieR/J/ApJS/249/17
- Title:
- SDSS QSO DR14 spectral properties
- Short Name:
- J/ApJS/249/17
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the spectral properties for a total of 526,265 quasars, out of which 63% have a continuum signal-to-noise ratio >3pixel^-1^, selected from the fourteenth data release of the Sloan Digital Sky Survey (SDSS-DR14) quasar catalog. We performed a careful and homogeneous analysis of the SDSS spectra of these sources to estimate the continuum and line properties of several emission lines such as H{alpha}, H{beta}, H{gamma}, MgII, CIII], CIV, and Ly{alpha}. From the derived emission line parameters, we estimated single-epoch virial black hole masses (M_BH_) for the sample using H{beta}, MgII, and CIV emission lines. The sample covers a wide range in bolometric luminosity (logLbol; erg/s) between 44.4 and 47.3 and logM_BH_ between 7.1 and 9.9M_{sin}_. Using the ratio of Lbol to the Eddington luminosity as a measure of the accretion rate, the logarithm of the accretion rate is found to be in the range between -2.06 and 0.43. We performed several correlation analyses between different emission line parameters and found them to match the correlation known earlier using smaller samples. We note that strong FeII sources with a large Balmer line width and highly accreting sources with large M BH are rare in our sample. We make an extended and complete catalog available online that contains various spectral properties of 526,265 quasars derived in this work along with other properties culled from the SDSS-DR14 quasar catalog.
- ID:
- ivo://CDS.VizieR/J/ApJS/221/7
- Title:
- SDSS QSOs at z<0.8. II. New spectroscopic obs.
- Short Name:
- J/ApJS/221/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new spectroscopic observations that are part of our continuing monitoring campaign of 88 quasars at z<0.7 whose broad H{beta} lines are offset from their systemic redshifts by a few thousand km/s. These quasars have been considered as candidates for hosting supermassive black hole binaries (SBHBs) by analogy with single-lined spectroscopic binary stars. We present the data and describe our improved analysis techniques, which include an extensive evaluation of uncertainties. We also present a variety of measurements from the spectra that are of general interest and will be useful in later stages of our analysis. Additionally, we take this opportunity to study the variability of the optical continuum and integrated flux of the broad H{beta} line. We compare the variability properties of the SBHB candidates to those of a sample of typical quasars with similar redshifts and luminosities observed multiple times during the Sloan Digital Sky Survey. We find that the variability properties of the two samples are similar (variability amplitudes of 10%-30% on timescales of approximately 1-7 years) and that their structure functions can be described by a common model with parameters characteristic of typical quasars. These results suggest that the broad-line regions of SBHB candidates have a similar extent as those of typical quasars. We discuss the implications of this result for the SBHB scenario and the ensuing constraints on the orbital parameters.
- ID:
- ivo://CDS.VizieR/J/ApJ/648/L97
- Title:
- 2 SDSS QSOs supersolar super-Lyman limit systems
- Short Name:
- J/ApJ/648/L97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present abundance measurements for two super-Lyman limit systems (SLLSs; quasar absorption-line systems with 10^19^cm^-2^<N_HI_<10^20.3^cm^-2^) selected from a set of metal-strong absorbers in the SDSS quasar database.
- ID:
- ivo://CDS.VizieR/VII/269
- Title:
- SDSS Quasar Catalog, DR9Q
- Short Name:
- VII/269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Data Release 9 Quasar (DR9Q) catalog from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. The catalog includes all BOSS objects that were targeted as quasar candidates during the survey, are spectroscopically confirmed as quasars via visual inspection. This catalog contains 87,822 quasars (78,086 are new discoveries) detected over 3,275{deg}^2^ with robust identification and redshift measured by a combination of principal component eigenspectra newly derived from a training set of 8,632 spectra from SDSS-DR7. The number of quasars with z>2.15 (61,931) is 2.8 times larger than the number of z>2.15 quasars previously known. Redshifts and FWHMs are provided for the strongest emission lines (CIV, CIII], MgII). The catalog identifies 7,533 broad absorption line quasars and gives their characteristics. For each object the catalog presents five-band (u,g,r,i,z) CCD-based photometry with typical accuracy of 0.03mag, and information on the morphology and selection method. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. We also provide a supplemental list of an additional 949 quasars that have been identified, among galaxy targets of the BOSS or among quasar targets after DR9 was frozen.
- ID:
- ivo://CDS.VizieR/J/A+A/548/A66
- Title:
- SDSS Quasar Catalog, DR9Q
- Short Name:
- VII/269
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the Data Release 9 Quasar (DR9Q) catalog from the Baryon Oscillation Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey III. The catalog includes all BOSS objects that were targeted as quasar candidates during the survey, are spectroscopically confirmed as quasars via visual inspection. This catalog contains 87,822 quasars (78,086 are new discoveries) detected over 3,275°<SUP>2</SUP> with robust identification and redshift measured by a combination of principal component eigenspectra newly derived from a training set of 8,632 spectra from SDSS-DR7. The number of quasars with z>2.15 (61,931) is 2.8 times larger than the number of z>2.15 quasars previously known. Redshifts and FWHMs are provided for the strongest emission lines (CIV, CIII], MgII). The catalog identifies 7,533 broad absorption line quasars and gives their characteristics. For each object the catalog presents five-band (u,g,r,i,z) CCD-based photometry with typical accuracy of 0.03mag, and information on the morphology and selection method. The catalog also contains X-ray, ultraviolet, near-infrared, and radio emission properties of the quasars, when available, from other large-area surveys. We also provide a supplemental list of an additional 949 quasars that have been identified, among galaxy targets of the BOSS or among quasar targets after DR9 was frozen.
