- ID:
- ivo://CDS.VizieR/J/AN/329/790
- Title:
- SDSS and Johnson-Cousins photometry of F-K stars
- Short Name:
- J/AN/329/790
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- For an understanding of Galactic stellar populations in the SDSS filter system well defined stellar samples are needed. The nearby stars provide a complete stellar sample representative for the thin disc population. We compare the filter transformations of different authors applied to the main sequence stars from F to K dwarfs to SDSS filter system and discuss the properties of the main sequence. The location of the mean main sequence in colour-magnitude diagrams is very sensitive to systematic differences in the filter transformation. A comparison with fiducial sequences of star clusters observed in g', r', and i' show good agreement. Theoretical isochrones from Padua and from Dartmouth have still some problems, especially in the (r-i) colours.
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- ID:
- ivo://CDS.VizieR/J/ApJ/719/1672
- Title:
- SDSS binary quasars at high redshift. I.
- Short Name:
- J/ApJ/719/1672
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The clustering of quasars on small scales yields fundamental constraints on models of quasar evolution and the buildup of supermassive black holes. This paper describes the first systematic survey to discover high-redshift binary quasars. Using color-selection and photometric redshift techniques, we searched 8142deg^2^ of Sloan Digital Sky Survey imaging data for binary quasar candidates, and confirmed them with follow-up spectroscopy. Our sample of 27 high-redshift binaries (24 of them new discoveries) at redshifts 2.9<z<4.3 with proper transverse separations 10kpc<R_T_<650kpc increases the number of such objects known by an order of magnitude. Eight members of this sample are very close pairs with R_T_<100kpc, and of these close systems four are at z>3.5. The completeness and efficiency of our well-defined selection algorithm are quantified using simulated photometry and we find that our sample is ~50% complete.
- ID:
- ivo://CDS.VizieR/J/ApJS/210/3
- Title:
- SDSS bulge, disk and total stellar mass estimates
- Short Name:
- J/ApJS/210/3
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of bulge, disk, and total stellar mass estimates for ~660000 galaxies in the Legacy area of the Sloan Digital Sky Survey Data (SDSS) Release 7. These masses are based on a homogeneous catalog of g- and r-band photometry described by Simard et al. (2011, Cat. J/ApJS/196/11), which we extend here with bulge+disk and Sersic profile photometric decompositions in the SDSS u, i, and z bands. We discuss the methodology used to derive stellar masses from these data via fitting to broadband spectral energy distributions (SEDs), and show that the typical statistical uncertainty on total, bulge, and disk stellar mass is ~0.15 dex. Despite relatively small formal uncertainties, we argue that SED modeling assumptions, including the choice of synthesis model, extinction law, initial mass function, and details of stellar evolution likely contribute an additional 60% systematic uncertainty in any mass estimate based on broadband SED fitting. We discuss several approaches for identifying genuine bulge+disk systems based on both their statistical likelihood and an analysis of their one-dimensional surface-brightness profiles, and include these metrics in the catalogs. Estimates of the total, bulge and disk stellar masses for both normal and dust-free models and their uncertainties are made publicly available here.
- ID:
- ivo://CDS.VizieR/J/AJ/126/2125
- Title:
- SDSS candidate type II quasars
- Short Name:
- J/AJ/126/2125
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Type II quasars are the long-sought luminous analogs of type 2 (narrow emission line) Seyfert galaxies, suggested by unification models of active galactic nuclei (AGNs) and postulated to account for an appreciable fraction of the cosmic hard X-ray background. We present a sample of 291 type II AGNs at redshifts 0.3<z<0.83 from the spectroscopic data of the Sloan Digital Sky Survey. These objects have narrow (FWHM<2000km/s), high equivalent width emission lines with high-ionization line ratios. We describe the selection procedure and discuss the optical properties of the sample. About 50% of the objects have [O III] {lambda}5008 line luminosities in the range 3x10^8^-10^10^L_{sun}_, comparable to those of luminous (-27<M_B_<-23) quasars; this, along with other evidence, suggests that the objects in the luminous subsample are type II quasars.
- ID:
- ivo://CDS.VizieR/J/ApJS/167/40
- Title:
- SDSS4 confirmed white dwarfs catalog
- Short Name:
- J/ApJS/167/40
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 9316 spectroscopically confirmed white dwarfs from the Sloan Digital Sky Survey Data Release 4. We have selected the stars through photometric cuts and spectroscopic modeling, backed up by a set of visual inspections. About 6000 of the stars are new discoveries, roughly doubling the number of spectroscopically confirmed white dwarfs. We analyze the stars by performing temperature and surface gravity fits to grids of pure hydrogen and helium atmospheres. Among the rare outliers are a set of presumed helium-core DA white dwarfs with estimated masses below 0.3M_{sun}_, including two candidates that may be the lowest-mass yet found. We also present a list of 928 hot subdwarfs.
- ID:
- ivo://CDS.VizieR/J/ApJ/869/122
- Title:
- SDSS-DR14 and LAMOST DR6 spectra in GD-1 stream
- Short Name:
- J/ApJ/869/122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Combining data from Gaia DR2, SDSS DR14, and LAMOST DR6, we update the fit to model of the properties of the stellar stream GD-1 and find that it has an age of ~13Gyr, [Fe/H] of -2.2+/-0.12, and a distance from the Sun of ~8kpc. We tabulate six-dimensional (6D) phase-space fiducial points along the GD-1 stream orbit over a 90{deg} arc. The fitted orbit shows that the stream has an eccentricity e~0.3, perigalacticon of 14.2kpc, apogalacticon of 27.0kpc, and inclination i~40{deg}. There is evidence along the arc for four candidate stellar overdensities, one candidate gap, two candidate stellar underdensities, and that the stream is cut off at {phi}_1_~2{deg} (in the stream-aligned ({phi}_1_, {phi}_2_) coordinate system of Koposov+ 2010ApJ...712..260K). The spur originating at {phi}_1_~-40{deg} implies stars were pulled away from the stream trace by an encounter (potentially a dark matter subhalo). The narrowest place (FWHM~44.6pc) of the GD-1 trace is at ({phi}_1_, {phi}2^c^)~(-14{deg}, 0.15{deg}), which is ~(178.18{deg}, 52.19{deg}) in (RA, DE), where the progenitor is possibly located. We also find six blue horizontal branch and 10 blue stragglers spectroscopic stars in the GD-1 stream.
- ID:
- ivo://CDS.VizieR/J/ApJ/738/79
- Title:
- SDSS-DR8 BHB stars in the Milky Way's halo
- Short Name:
- J/ApJ/738/79
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present and analyze the positions, distances, and radial velocities for over 4000 blue horizontal-branch (BHB) stars in the Milky Way's halo, drawn from SDSS DR8. We search for position-velocity substructure in these data, a signature of the hierarchical assembly of the stellar halo. Using a cumulative "close pair distribution" as a statistic in the four-dimensional space of sky position, distance, and velocity, we quantify the presence of position-velocity substructure at high statistical significance among the BHB stars: pairs of BHB stars that are close in position on the sky tend to have more similar distances and radial velocities compared to a random sampling of these overall distributions. We make analogous mock observations of 11 numerical halo formation simulations, in which the stellar halo is entirely composed of disrupted satellite debris, and find a level of substructure comparable to that seen in the actually observed BHB star sample. This result quantitatively confirms the hierarchical build-up of the stellar halo through a signature in phase (position-velocity) space. In detail, the structure present in the BHB stars is somewhat less prominent than that seen in most simulated halos, quite possibly because BHB stars represent an older sub-population. BHB stars located beyond 20kpc from the Galactic center exhibit stronger substructure than at r_gc_<20kpc.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/3893
- Title:
- SDSS DR10 catalogue of candidate quasars
- Short Name:
- J/MNRAS/450/3893
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We discuss whether modern machine learning methods can be used to characterize the physical nature of the large number of objects sampled by the modern multi-band digital surveys. In particular, we applied the MLPQNA (Multi Layer Perceptron with Quasi Newton Algorithm) method to the optical data of the Sloan Digital Sky Survey - Data Release 10, investigating whether photometric data alone suffice to disentangle different classes of objects as they are defined in the SDSS spectroscopic classification. We discuss three groups of classification problems: (i) the simultaneous classification of galaxies, quasars and stars; (ii) the separation of stars from quasars; (iii) the separation of galaxies with normal spectral energy distribution from those with peculiar spectra, such as starburst or starforming galaxies and AGN. While confirming the difficulty of disentangling AGN from normal galaxies on a photometric basis only, MLPQNA proved to be quite effective in the three-class separation. In disentangling quasars from stars and galaxies, our method achieved an overall efficiency of 91.31% and a QSO class purity of ~95%. The resulting catalogue of candidate quasars/AGNs consists of ~3.6 million objects, of which about half a million are also flagged as robust candidates.
- ID:
- ivo://CDS.VizieR/J/other/NewA/58.61
- Title:
- SDSS DR9 galaxy clusters optical catalog
- Short Name:
- J/other/NewA/58.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new galaxy cluster catalog constructed from the Sloan Digital Sky Survey Data Release 9 (SDSS DR9) using an Adaptive Matched Filter (AMF) technique. Our catalog has 46479 galaxy clusters with richness {Lambda}_200_>20 in the redshift range 0.045<=z<0.641 in ~11500 deg^2^ of the sky. Angular position, richness, core and virial radii and redshift estimates for these clusters, as well as their error analysis, are provided as part of this catalog. In addition to the main version of the catalog, we also provide an extended version with a lower richness cut, containing 79368 clusters. This version, in addition to the clusters in the main catalog, also contains those clusters (with richness 10<{Lambda}_200_<20) which have a one-to-one match in the DR8 catalog developed by Wen et al (WHL). We obtain probabilities for cluster membership for each galaxy and implement several procedures for the identification and removal of false cluster detections. We cross-correlate the main AMF DR9 catalog with a number of cluster catalogs in different wavebands (Optical, X-ray). We compare our catalog with other SDSS-based ones such as the redMaPPer (Rykoff et al., 2014, Cat. J/ApJ/785/104, 26350 clusters) and the Wen et al. (WHL, 2012, Cat. J/ApJS/199/34) (132684 clusters) in the same area of the sky and in the overlapping redshift range. We match 97% of the richest Abell clusters (Richness group 3), the same as WHL, while redMaPPer matches ~90% of these clusters. Considering AMF DR9 richness bins, redMaPPer does not have one-to-one matches for 70% of our lowest richness clusters (20<{Lambda}_200_<40), while WHL matches 54% of these missed clusters (not present in redMaPPer). redMaPPer consistently does not possess one-to-one matches for ~20% AMF DR9 clusters with {Lambda}_200_>40, while WHL matches >=70% of these missed clusters on average. For comparisons with X-ray clusters, we match the AMF catalog with BAX, MCXC and a combined catalog from NORAS and REFLEX. We consistently obtain a greater number of one-to-one matches for X--ray clusters across higher luminosity bins (L_x_>6x10^44^erg/s) than redMaPPer while WHL matches the most clusters overall. For the most luminous clusters (L_x_>8), our catalog performs equivalently to WHL. This new catalog provides a wider sample than redMaPPer while retaining many fewer objects than WHL.
- 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.
