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1661. SDSS-RM project: peak velocities of QSOs
ID:
ivo://CDS.VizieR/J/ApJ/831/7
Title:
SDSS-RM project: peak velocities of QSOs
Short Name:
J/ApJ/831/7
Date:
21 Oct 2021
Publisher:
CDS
Description:
Quasar emission lines are often shifted from the systemic velocity due to various dynamical and radiative processes in the line-emitting region. The level of these velocity shifts depends both on the line species and on quasar properties. We study velocity shifts for the line peaks (not the centroids) of various narrow and broad quasar emission lines relative to systemic using a sample of 849 quasars from the Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project. The coadded (from 32 epochs) spectra of individual quasars have sufficient signal-to-noise ratio (S/N) to measure stellar absorption lines to provide reliable systemic velocity estimates, as well as weak narrow emission lines. The large dynamic range in quasar luminosity (~2dex) of the sample allowed us to explore potential luminosity dependence of the velocity shifts. We derive average line peak velocity shifts as a function of quasar luminosity for different lines, and quantify their intrinsic scatter. We further quantify how well the peak velocity can be measured as a function of continuum S/N, and demonstrate that there is no systematic bias in the velocity measurements when S/N is degraded to as low as ~3 per SDSS pixel (~69kms/s). Based on the observed line shifts, we provide empirical guidelines on redshift estimation from [OII]{lambda}3727, [OIII]{lambda}5007, [NeV]{lambda}3426, MgII, CIII], HeII{lambda}1640, broad H{beta}, CIV, and SiIV, which are calibrated to provide unbiased systemic redshifts in the mean, but with increasing intrinsic uncertainties of 46, 56, 119, 205, 233, 242, 400, 415, and 477kms/s, in addition to the measurement uncertainties. These results demonstrate the infeasibility of measuring quasar redshifts to better than ~200kms/s with only broad lines.
1662. SDSS-RM project: technical overview
ID:
ivo://CDS.VizieR/J/ApJS/216/4
Title:
SDSS-RM project: technical overview
Short Name:
J/ApJS/216/4
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Sloan Digital Sky Survey Reverberation Mapping (SDSS-RM) project is a dedicated multi-object RM experiment that has spectroscopically monitored a sample of 849 broad-line quasars in a single 7deg^2^ field with the SDSS-III Baryon Oscillation Spectroscopic Survey spectrograph. The RM quasar sample is flux-limited to i_psf_=21.7mag, and covers a redshift range of 0.1<z<4.5 without any other cuts on quasar properties. Optical spectroscopy was performed during 2014 January-July dark/gray time, with an average cadence of ~4 days, totaling more than 30 epochs. Supporting photometric monitoring in the g and i bands was conducted at multiple facilities including the Canada-France-Hawaii Telescope (CFHT) and the Steward Observatory Bok telescope in 2014, with a cadence of ~2 days and covering all lunar phases. The RM field (RAJ2000=14:14:49.00, DEJ2000=+53:05:00.0) lies within the CFHT-LS W3 field, and coincides with the Pan-STARRS 1 (PS1) Medium Deep Field MD07, with three prior years of multi-band PS1 light curves. The SDSS-RM six month baseline program aims to detect time lags between the quasar continuum and broad line region (BLR) variability on timescales of up to several months (in the observed frame) for ~10% of the sample, and to anchor the time baseline for continued monitoring in the future to detect lags on longer timescales and at higher redshift. SDSS-RM is the first major program to systematically explore the potential of RM for broad-line quasars at z>0.3, and will investigate the prospects of RM with all major broad lines covered in optical spectroscopy.
1663. SDSS-RM project: z<1 QSO host galaxies
ID:
ivo://CDS.VizieR/J/ApJ/811/91
Title:
SDSS-RM project: z<1 QSO host galaxies
Short Name:
J/ApJ/811/91
Date:
21 Oct 2021
Publisher:
CDS
Description:
Quasar host galaxies are key for understanding the relation between galaxies and the supermassive black holes (SMBHs) at their centers. We present a study of 191 broad-line quasars and their host galaxies at z<1 using high signal-to-noise ratio (S/N) spectra produced by the Sloan Digital Sky Survey Reverberation Mapping project. Clear detection of stellar absorption lines allows a reliable decomposition of the observed spectra into nuclear and host components, using spectral models of quasar and stellar radiations as well as emission lines from the interstellar medium. We estimate age, mass M*, and velocity dispersion {sigma}* of the host stars, the star formation rate (SFR), quasar luminosity, and SMBH mass M_{dot}_ for each object. The quasars are preferentially hosted by massive galaxies with M*~10^11^M_{sun}_ characterized by stellar ages around 1 billion yr, which coincides with the transition phase of normal galaxies from the blue cloud to the red sequence. The host galaxies have relatively low SFRs and fall below the main sequence of star-forming galaxies at similar redshifts. These facts suggest that the hosts have experienced an episode of major star formation sometime in the past 1 billion yr, which was subsequently quenched or suppressed. The derived M_{dot}_-{sigma}* and M_{dot}_-M* relations agree with our past measurements and are consistent with no evolution from the local universe. The present analysis demonstrates that reliable measurements of stellar properties of quasar host galaxies are possible with high-S/N fiber spectra, which will be acquired in large numbers with future powerful instruments such as the Subaru Prime Focus Spectrograph.
1664. SDSS-Spitzer AGN properties
ID:
ivo://CDS.VizieR/J/ApJ/758/1
Title:
SDSS-Spitzer AGN properties
Short Name:
J/ApJ/758/1
Date:
21 Oct 2021
Publisher:
CDS
Description:
We study a combined sample of 264 star-forming, 51 composite, and 73 active galaxies using optical spectra from the Sloan Digital Sky Survey (SDSS) and mid-infrared (mid-IR) spectra from the Spitzer Infrared Spectrograph. We examine optical and mid-IR spectroscopic diagnostics that probe the amount of star formation and relative energetic contributions from star formation and an active galactic nucleus (AGN). Overall we find good agreement between optical and mid-IR diagnostics. Misclassifications of galaxies based on the SDSS spectra are rare despite the presence of dust obscuration. The luminosity of the [Ne II] 12.8{mu}m emission line is well correlated with the star formation rate measured from the SDSS spectra, and this holds for the star-forming, composite, and AGN-dominated systems. AGNs show a clear excess of [Ne III] 15.6{mu}m emission relative to star-forming and composite systems. We find good qualitative agreement between various parameters that probe the relative contributions of the AGN and star formation, including the mid-IR spectral slope, the ratio of the [Ne V] 14.3{mu}m to [Ne II] 12.8{mu}m fluxes, the equivalent widths of the 7.7{mu}m, 11.3{mu}m, and 17{mu}m polycyclic aromatic hydrocarbon (PAH) features, and the optical "D" parameter which measures the distance at which a source lies from the locus of star-forming galaxies in the optical BPT emission-line diagnostic diagram. We also consider the behavior of the three individual PAH features by examining how their flux ratios depend upon the degree of AGN dominance. We find that the PAH 11.3{mu}m feature is significantly suppressed in the most AGN-dominated systems.
1665. SDSS-Spitzer type I QSOs IR photometry
ID:
ivo://CDS.VizieR/J/ApJS/166/470
Title:
SDSS-Spitzer type I QSOs IR photometry
Short Name:
J/ApJS/166/470
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of the mid-infrared (MIR) and optical properties of type 1 (broad-line) quasars detected by the Spitzer Space Telescope. The MIR color-redshift relation is characterized to z~3, with predictions to z=7. We demonstrate how combining MIR and optical colors can yield even more efficient selection of active galactic nuclei (AGNs) than MIR or optical colors alone. Composite spectral energy distributions (SEDs) are constructed for 259 quasars with both Sloan Digital Sky Survey and Spitzer photometry, supplemented by near-IR, GALEX, VLA, and ROSAT data, where available.
1666. 209276 SDSS star-forming galaxies aperture-free
ID:
ivo://CDS.VizieR/J/A+A/599/A71
Title:
209276 SDSS star-forming galaxies aperture-free
Short Name:
J/A+A/599/A71
Date:
21 Oct 2021
Publisher:
CDS
Description:
Large area surveys with a high number of galaxies observed have undoubtedly marked a milestone in the understanding of several properties of galaxies, such as star-formation history, morphology, and metallicity. However, in many cases, these surveys provide fluxes from fixed small apertures (e.g. fibre), which cover a scant fraction of the galaxy, compelling us to use aperture corrections to study the global properties of galaxies. In this work, we derive the current total star formation rate (SFR) of Sloan Digital Sky Survey (SDSS) star-forming galaxies, using an empirically based aperture correction of the measured H{alpha} flux for the first time, thus minimising the uncertainties associated with reduced apertures. All the H{alpha} fluxes have been extinction-corrected using the H{alpha}/H{beta} ratio free from aperture effects. The total SFR for ~210000 SDSS star-forming galaxies has been derived applying pure empirical H{alpha} and H{alpha}/H{beta} aperture corrections based on the Calar Alto Legacy Integral Field Area (CALIFA) survey. We find that, on average, the aperture-corrected SFR is ~0.65dex higher than the SDSS fibre-based SFR. The relation between the SFR and stellar mass for SDSS star-forming galaxies (SFR-M*) has been obtained, together with its dependence on extinction and H{alpha} equivalent width. We compare our results with those obtained in previous works and examine the behaviour of the derived SFR in six redshift bins, over the redshift range 0.005<=z<=0.22. The SFR-M* sequence derived here is in agreement with selected observational studies based on integral field spectroscopy of individual galaxies as well as with the predictions of recent theoretical models of disc galaxies.
1667. SDSS Stripe 82 star catalogs
ID:
ivo://CDS.VizieR/J/AJ/134/973
Title:
SDSS Stripe 82 star catalogs
Short Name:
J/AJ/134/973
Date:
21 Oct 2021
Publisher:
CDS
Description:
We describe a standard star catalog constructed using multiple SDSS photometric observations (at least four per band, with a median of 10) in the ugriz system. The catalog includes 1.01 million nonvariable unresolved objects from the equatorial stripe 82 (|{delta}_J2000.0_|<1.266{deg}) in the right ascension range 20^h^34^m^-4^h^00^m^ and with the corresponding r-band (approximately Johnson V-band) magnitudes in the range 14-22. The distributions of measurements for individual sources demonstrate that the photometric pipeline correctly estimates random photometric errors, which are below 0.01mag for stars brighter than 19.5, 20.5, 20.5, 20, and 18.5 in ugriz, respectively (about twice as good as for individual SDSS runs). Several independent tests of the internal consistency suggest that the spatial variation of photometric zero points is not larger than ~0.01mag (rms). In addition to being the largest available data set with optical photometry internally consistent at the ~1% level, this catalog provides a practical definition of the SDSS photometric system. Using this catalog, we show that photometric zero points for SDSS observing runs can be calibrated within a nominal uncertainty of 2% even for data obtained through 1mag thick clouds, and we demonstrate the existence of He and H white dwarf sequences using photometric data alone. Based on the properties of this catalog, we conclude that upcoming large-scale optical surveys such as the Large Synoptic Survey Telescope will be capable of delivering robust 1% photometry for billions of sources.
1668. SDSS Stripe 82 VLA 1-2GHz survey
ID:
ivo://CDS.VizieR/J/MNRAS/460/4433
Title:
SDSS Stripe 82 VLA 1-2GHz survey
Short Name:
J/MNRAS/460/4433
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have used the Karl G. Jansky Very Large Array to image ~100deg^2^ of SDSS Stripe 82 at 1-2GHz. The survey consists of 1026 snapshot observations of 2.5-min duration, using the hybrid CnB configuration. The survey has good sensitivity to diffuse, low surface brightness structures and extended radio emission, making it highly synergistic with existing 1.4GHz radio observations of the region. The principal data products are continuum images, with 16x10 arcsec resolution, and a catalogue containing 11782 point and Gaussian components resulting from fits to the thresholded Stokes-I brightness distribution, forming approximately 8948 unique radio sources. The typical effective 1{sigma} noise level is 88{mu}Jy/beam. Spectral index estimates are included, as derived from the 1GHz of instantaneous bandwidth. Astrometric and photometric accuracy are in excellent agreement with existing narrowband observations. A large-scale simulation is used to investigate clean bias, which we extend into the spectral domain. Clean bias remains an issue for snapshot surveys with the VLA, affecting our total intensity measurements at the ~1{sigma} level. Statistical spectral index measurements are in good agreement with existing measurements derived from matching separate surveys at two frequencies. At flux densities below ~35{sigma} the median in-band spectral index measurements begin to exhibit a bias towards flatness that is dependent on both flux density and the intrinsic spectral index. In-band spectral curvature measurements are likely to be unreliable for all but the very brightest components. Image products and catalogues are publicly available via an FTP server (ftp://ftp.atnf.csiro.au/pub/people/hey036/Stripe82).
1669. Search for peculiar objects
ID:
ivo://CDS.VizieR/J/ApJ/509/309
Title:
Search for peculiar objects
Short Name:
J/ApJ/509/309
Date:
21 Oct 2021
Publisher:
CDS
Description:
The NASA Orbital Debris Observatory (NODO) astronomical survey uses a transit 3m liquid mirror telescope to observe a strip of sky in 20 narrowband filters. In this article, we analyze a subset of data from the 1996 observing season. The catalog consists of 18,000 objects with 10<V<19 observed in 10 narrowband filters ranging from 500 to 950nm. We first demonstrate the reliability of the data by fitting the Bahcall-Soneira model of the Galaxy to the NODO magnitude counts and color counts at various Galactic latitudes. We then perform a hierarchical clustering analysis on the sample to extract 206 objects, out of a total of 18,000, showing peculiar spectral energy distributions. It is a measure of the reliability of the instrument that we extract so few peculiar objects. Although the data and results, per se, may not seem otherwise particularly remarkable, this work constitutes a milestone in optical astronomy, since this is the first article that demonstrates astronomical research with a radically new type of mirror.
1670. Second AGILE catalogue of gamma-ray sources
ID:
ivo://CDS.VizieR/J/A+A/627/A13
Title:
Second AGILE catalogue of gamma-ray sources
Short Name:
J/A+A/627/A13
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the second AGILE-GRID catalogue (2AGL) of gamma-ray sources in the energy range 100MeV-10GeV. With respect to previous AGILE-GRID catalogues, the current 2AGL catalogue is based on the first 2.3 years of science data from the AGILE mission (the so-called pointing mode) and incorporates more data and several analysis improvements, including better calibrations at the event reconstruction level, an updated model for the Galactic diffuse gamma-ray emission, a refined procedure for point-like source detection, and the inclusion of a search for extended gamma-ray sources. The 2AGL catalogue includes 175 high-confidence sources (above 4{sigma} significance) with their location regions and spectral properties and a variability analysis with four-day light curves for the most significant. Relying on the error region of each source position, including systematic uncertainties, 122 sources are considered as positionally associated with known counterparts at different wavelengths or detected by other gamma-ray instruments. Among the identified or associated sources, 62 are active galactic nuclei (AGNs) of the blazar class. Pulsars represent the largest Galactic source class, with 41 associated pulsars, 7 of which have detected pulsation; 8 supernova remnants and 4 high-mass X-ray binaries have also been identified. A substantial number of 2AGL sources are unidentified: for 53 sources no known counterpart is found at different wavelengths. Among these sources, we discuss a subclass of 29 AGILE-GRID-only gamma-ray sources that are not present in 1FGL, 2FGL, or 3FGL catalogues; the remaining sources are unidentified in both 2AGL and 3FGL catalogues. We also present an extension of the analysis of 2AGL sources detected in the energy range 50-100MeV.

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