- ID:
- ivo://CDS.VizieR/J/ApJ/765/62
- Title:
- SDSS-DR7 optical spectra analysis of radio galaxies
- Short Name:
- J/ApJ/765/62
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study a large sample of narrow-line radio galaxies (NLRGs) with extended radio structures. Using 1.4GHz radio luminosities L_1.4_, narrow optical emission line luminosities L_[OIII]_ and L_Halpha_, as well as black hole masses M_BH_ derived from stellar velocity dispersions measured from the optical spectra obtained with the Sloan Digital Sky Survey, we find that (1) NLRGs cover about four decades of the Eddington ratio, {lambda}{equiv}L_bol_/L_Edd_{prop.to}L_line_/M_BH_; (2) L_1.4_/M_BH_ strongly correlates with {lambda}; and (3) radio loudness, R=L_1.4_/L_Line_, strongly anti-correlates with {lambda}. A very broad range of the Eddington ratio indicates that the parent population of NLRGs includes both radio-loud quasars (RLQs) and broad-line radio galaxies (BLRGs). The correlations they obey and their high jet production efficiencies favor a jet production model which involves the so-called magnetically choked accretion scenario. In this model, production of the jet is dominated by the Blandford-Znajek mechanism, and the magnetic fields in the vicinity of the central black hole are confined by the ram pressure of the accretion flow. Since large net magnetic flux accumulated in central regions of the accretion flow required by the model can take place only via geometrically thick accretion, we speculate that the massive, "cold" accretion events associated with luminous emission-line active galactic nucleus can be accompanied by an efficient jet production only if preceded by a hot, very sub-Eddington accretion phase.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/140/817
- Title:
- SDSS-DR3 OVI QSOs absorbers
- Short Name:
- J/AJ/140/817
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a systematic search for signatures of metal lines in quasar spectra of the Sloan Digital Sky Survey (SDSS) data release 3 (DR3), focusing on finding intervening absorbers via detection of their OVI doublet. Here, we present the search algorithm and criteria for distinguishing candidates from spurious Ly{alpha} forest lines. In addition, we compare our findings with simulations of the Ly{alpha} forest in order to estimate the detectability of OVI doublets over various redshift intervals. We have obtained a sample of 1756 OVI doublet candidates with rest-frame equivalent width (EW)>=0.05{AA} in 855 active galactic nuclei spectra (out of 3702 objects with redshifts in the accessible range for OVI detection).
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/4153
- Title:
- SDSS DR12 QSOs [OIII] doublet
- Short Name:
- J/MNRAS/452/4153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- From the Sloan Digital Sky Survey (SDSS) Data Release 12, which covers the full Baryonic Oscillation Spectroscopic Survey (BOSS) footprint, we investigate the possible variation of the fine-structure constant over cosmological time-scales. We analyse the largest quasar sample considered so far in the literature, which contains 13175 spectra (10363 from SDSS-III/BOSS DR12+2812 from SDSS-II DR7) with redshift z<1. We apply the emission-line method on the [OIII] doublet ({lambda}{lambda}4960, 5008{AA}) and obtain {Delta}{alpha}/{alpha}=(0.9+/-1.8)x10^-5^ for the relative variation of the fine-structure constant. We also investigate the possible sources of systematics: misidentification of the lines, sky OH lines, H{beta} and broad line contamination, Gaussian and Voigt fitting profiles, optimal wavelength range for the Gaussian fits, chosen polynomial order for the continuum spectrum, signal-to-noise ratio and good quality of the fits. The uncertainty of the measurement is dominated by the sky subtraction. The results presented in this work, being systematics limited, have sufficient statistics to constrain robustly the variation of the fine-structure constant in redshift bins ({Delta}z~0.06) over the last 7.9Gyr. In addition, we study the [NeIII] doublet ({lambda}{lambda}3869, 3968{AA}) present in 462 quasar spectra and discuss the systematic effects on using these emission lines to constrain the fine-structure constant variation. Better constraints on {Delta}{alpha}/{alpha}(<10^-6^) using the emission-line method would be possible with high-resolution spectroscopy and large galaxy/qso surveys.
- ID:
- ivo://CDS.VizieR/J/MNRAS/464/553
- Title:
- SDSS DR7 QSOs spectral doppelgangers
- Short Name:
- J/MNRAS/464/553
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The spectrum of a quasar contains important information about its properties. Thus, it can be expected that two quasars with similar spectra will have similar properties, but just how similar has not before been quantified. Here we compare the ultraviolet spectra of a sample of 5553 quasars from Data Release 7 of the Sloan Digital Sky Survey, focusing on the 1350{AA}<={lambda}<=2900{AA} rest-frame region which contains prominent emission lines from SiIV, OIV], CIV, CIII], and MgII species. We use principal component analysis to determine the dominant components of spectral variation, as well as to quantitatively measure spectral similarity. As suggested by both the Baldwin effect and modified Baldwin effect, quasars with similar spectra have similar properties: bolometric luminosity, Eddington fraction, and black hole mass. The latter two quantities are calculated from the luminosity in conjunction with spectral features, and the variation between quasars with virtually identical spectra (which we call doppelgangers) is driven by the variance in the luminosity plus measurement uncertainties. In the doppelgangers the luminosity differences show 1{sigma} uncertainties of 57 per cent (or 0.63mag) and ~70 per cent 1{sigma} uncertainties for mass and Eddington fraction. Much of the difference in luminosities may be attributable to time lags between the spectral lines and the continuum. Furthermore, we find that suggestions that the mostly highly accreting quasars should be better standard candles than other quasars are not borne out for doppelgangers. Finally, we discuss the implications for using quasars as cosmological probes and the nature of the first two spectral principal components.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A46
- Title:
- SDSS DR10 radio-loud quasars sample
- Short Name:
- J/A+A/631/A46
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of a sample of 223 radio loud quasars (up to redshift <0.3) in order to investigate their spectral properties. Twenty-six of these radio loud quasars are identified as Flat Spect rum Radio Quasars (FSRQs) and fifty-four are identified as Steep Spectrum Radio Quasars (SSRQs) based on their radio spectral index. We study the [OIII] line properties of these quasars to investigate the origin and properties of blue wings (shift of the profile towards lower wavelengths) and blue outliers (shift of the whole spectroscopic feature). Most of the quasars show blue wings with velocities up to 420km/s. We find that around 17% of the quasars show outliers with velocities spanning 4 19 to -315km/s. Finally, we revisit the M_BH_-{sigma} relation of our sample using [SII]{lambda}6716, 6731 and [OIII] linewidths as surrogates for stellar velocity dispersions, {sigma}, to investigate their location on the M_BH_-{sigma} relation for quiescent galaxies. Due to strong blending of [SII] with H_{alpha}_, we could estimate {sigma}_[SII]_ of only 123 quasars. We find that the radio-loud quasars do not show a relationship between M_BH_ and {sigma}_[SII]/[OIII]_ up to a redshift of 0.3, although they cluster around the local relation. We find an overall offset of 0.12+/-0.05dex of our sample of radio loud quasars from the M_BH_-{sigma} relation of quiescent galaxies. Quasars in our highest redshift bin (z=0.25-0.3) show a deviation of ~0.33+/-0.06dex with respect to the local relation. Implications of the results are discussed.
- ID:
- ivo://CDS.VizieR/J/AJ/149/7
- Title:
- SDSS-III/APOGEE. I. Be stars
- Short Name:
- J/AJ/149/7
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has amassed the largest ever collection of multi-epoch, high-resolution (R~22500), H-band spectra for B-type emission line (Be) stars. These stars were targeted by APOGEE as telluric standard stars and subsequently identified via visual inspection as Be stars based on HI Brackett series emission or shell absorption in addition to otherwise smooth continua and occasionally non-hydrogen emission features. The 128/238 APOGEE Be stars for which emission had never previously been reported serve to increase the total number of known Be stars by ~6%. Because the H band is relatively unexplored compared to other wavelength regimes, we focus here on identification of the H-band lines and analysis of the emission peak velocity separations ({Delta}v_p_) and emission peak intensity ratios (V/R) of the usually double-peaked HI and non-hydrogen emission lines. HI Br11 emission is found to preferentially form in the circumstellar disks at an average distance of ~2.2 stellar radii. Increasing {Delta}v_p_ toward the weaker Br12-Br20 lines suggests these lines are formed interior to Br11. By contrast, the observed IR FeII emission lines present evidence of having significantly larger formation radii; distinctive phase lags between IR FeII and HI Brackett emission lines further supports that these species arise from different radii in Be disks. Several emission lines have been identified for the first time including CI 16895, a prominent feature in the spectra for almost a fifth of the sample and, as inferred from relatively large {Delta}v_p_ compared to the Br11-Br20, a tracer of the inner regions of Be disks. Emission lines at 15760{AA} and 16781{AA} remain unidentified, but usually appear along with and always have similar line profile morphology to FeII 16878. Unlike the typical metallic lines observed for Be stars in the optical, the H-band metallic lines, such as FeII 16878, never exhibit any evidence of shell absorption, even when the HI lines are clearly shell-dominated. The first known example of a quasi-triple-peaked Br11 line profile is reported for HD253659, one of several stars exhibiting intra- and/or extra-species V/R and radial velocity variation within individual spectra. Br11 profiles are presented for all discussed stars, as are full APOGEE spectra for a portion of the sample.
- ID:
- ivo://CDS.VizieR/J/A+A/547/L1
- Title:
- SDSS-III DR9 DLA catalogue
- Short Name:
- J/A+A/547/L1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the column density distribution and cosmological mass density of neutral gas from a survey of Damped Lyman-alpha systems in the Sloan Digital Sky Survey III Data Release 9.
- ID:
- ivo://CDS.VizieR/J/AJ/135/348
- Title:
- SDSS-II SNe survey: search and follow-up
- Short Name:
- J/AJ/135/348
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sloan Digital Sky Survey-II Supernova Survey has identified a large number of new transient sources in a 300deg^2^ region along the celestial equator during its first two seasons of a three-season campaign. Multi-band (ugriz) light curves were measured for most of the sources, which include solar system objects, galactic variable stars, active galactic nuclei, supernovae (SNe), and other astronomical transients. The imaging survey is augmented by an extensive spectroscopic follow-up program to identify SNe, measure their redshifts, and study the physical conditions of the explosions and their environment through spectroscopic diagnostics. During the survey, light curves are rapidly evaluated to provide an initial photometric type of the SNe, and a selected sample of sources are targeted for spectroscopic observations. In the first two seasons, 476 sources were selected for spectroscopic observations, of which 403 were identified as SNe. For the type Ia SNe, the main driver for the survey, our photometric typing and targeting efficiency is 90%. Only 6% of the photometric SN Ia candidates were spectroscopically classified as non-SN Ia instead, and the remaining 4% resulted in low signal-to-noise, unclassified spectra.
- ID:
- ivo://CDS.VizieR/J/ApJ/821/115
- Title:
- SDSS-II SN Survey: host-galaxy spectral data
- Short Name:
- J/ApJ/821/115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using the largest single-survey sample of Type Ia supernovae (SNe Ia) to date, we study the relationship between properties of SNe Ia and those of their host galaxies, focusing primarily on correlations with Hubble residuals (HRs). Our sample consists of 345 photometrically classified or spectroscopically confirmed SNe Ia discovered as part of the SDSS-II Supernova Survey (SDSS-SNS). This analysis utilizes host-galaxy spectroscopy obtained during the SDSS-I/II spectroscopic survey and from an ancillary program on the SDSS-III Baryon Oscillation Spectroscopic Survey that obtained spectra for nearly all host galaxies of SDSS-II SN candidates. In addition, we use photometric host-galaxy properties from the SDSS-SNS data release such as host stellar mass and star formation rate. We confirm the well-known relation between HR and host-galaxy mass and find a 3.6{sigma} significance of a nonzero linear slope. We also recover correlations between HR and host-galaxy gas-phase metallicity and specific star formation rate as they are reported in the literature. With our large data set, we examine correlations between HR and multiple host-galaxy properties simultaneously and find no evidence of a significant correlation. We also independently analyze our spectroscopically confirmed and photometrically classified SNe Ia and comment on the significance of similar combined data sets for future surveys.
- ID:
- ivo://CDS.VizieR/J/ApJ/708/661
- Title:
- SDSS-II SN Survey: SNe II-P standardization
- Short Name:
- J/ApJ/708/661
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We apply the Standardized Candle Method (SCM) for Type II Plateau supernovae (SNe II-P), which relates the velocity of the ejecta of a SN to its luminosity during the plateau, to 15 SNe II-P discovered over the three season run of the Sloan Digital Sky Survey-II Supernova Survey. The redshifts of these SNe - 0.027<z<0.144 - cover a range hitherto sparsely sampled in the literature; in particular, our SNe II-P sample contains nearly as many SNe in the Hubble flow (z>0.01) as all of the current literature on the SCM combined. We find that the SDSS SNe have a very small intrinsic I-band dispersion (0.22mag), which can be attributed to selection effects. When the SCM is applied to the combined SDSS-plus-literature set of SNe II-P, the dispersion increases to 0.29mag, larger than the scatter for either set of SNe separately. We show that the standardization cannot be further improved by eliminating SNe with positive plateau decline rates, as proposed in Poznanski et al. (2009ApJ...694.1067P). We thoroughly examine all potential systematic effects and conclude that for the SCM to be useful for cosmology, the methods currently used to determine the FeII velocity at day 50 must be improved, and spectral templates able to encompass the intrinsic variations of Type II-P SNe will be needed.
