- ID:
- ivo://CDS.VizieR/J/ApJ/857/27
- Title:
- A catalog of post-starburst QSOs from SDSS-DR7Q
- Short Name:
- J/ApJ/857/27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of nearby (z<=0.5) quasars with significant features of post-starburst stellar populations in their optical spectra: so-called post-starburst quasars, or PSQs. After carefully decomposing spectra from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) Quasar Catalog into quasar and host-galaxy components, we derive a sample of 208 PSQs. Their host-galaxy components have strong H{delta} absorption (EW>=6{AA}) indicating a significant contribution of an intermediate-aged stellar population formed in a burst of star formation within the past 1Gyr, which makes them potentially useful for studying the co-evolution of supermassive black holes and their host galaxies.
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- ID:
- ivo://CDS.VizieR/J/ApJ/737/101
- Title:
- AGN pairs from SDSS-DR7. I.
- Short Name:
- J/ApJ/737/101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxy-galaxy mergers and close interactions have long been regarded as a viable mechanism for channeling gas toward the central supermassive black holes (SMBHs) of galaxies which are triggered as active galactic nuclei (AGNs). AGN pairs, in which the central SMBHs of a galaxy merger are both active, are expected to be common from such events. We conduct a systematic study of 1286 AGN pairs at \bar{z}~0.1 with line-of-sight velocity offsets {Delta}v<600km/s and projected separations r_p_<100h^-1^_70_kpc, selected from the Seventh Data Release of the Sloan Digital Sky Survey (SDSS, Cat. II/294). This AGN pair sample was drawn from 138070 AGNs optically identified based on diagnostic emission line ratios and/or line widths. The fraction of AGN pairs with 5h^-1^_70_kpc<~r_p_<100h^-1^_70_kpc among all spectroscopically selected AGNs at 0.02<z<0.16 is 3.6% after correcting for SDSS spectroscopic incompleteness; ~30% of these pairs show morphological tidal features in their SDSS images, and the fraction becomes >~80% for pairs with the brightest nuclei.
- ID:
- ivo://CDS.VizieR/J/AJ/131/84
- Title:
- AGNs and host galaxies information
- Short Name:
- J/AJ/131/84
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using an eigenspectrum decomposition technique, we separate the host galaxy from the broad-line active galactic nucleus (AGN) in a set of 4666 spectra from the Sloan Digital Sky Survey (SDSS), from redshifts near zero up to about 0.75. The decomposition technique uses separate sets of galaxy and quasar eigenspectra to efficiently and reliably separate the AGN and host spectroscopic components. The technique accurately reproduces the host galaxy spectrum, its contributing fraction, and its classification.
- ID:
- ivo://CDS.VizieR/J/ApJ/679/239
- Title:
- Associated MgII absorbers
- Short Name:
- J/ApJ/679/239
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We studied a sample of 415 associated (z_abs_~z_em_; relative velocity with respect to QSO in units of c, {beta}<0.01) MgII absorption systems with 1.0<=z_abs_<=1.86, in the spectra of SDSS DR3 QSOs, to determine the dust content and ionization state in the absorbers. We also compared these properties to those of a similarly selected sample of 809 intervening systems ({beta}>0.01), so as to understand their origin. Normalized, composite spectra were derived for absorption line measurements, for the full sample and for several subsamples, chosen on the basis of the line strengths and other absorber and QSO properties. From these, and from the equivalent widths in individual spectra, we conclude that the associated MgII absorbers have higher ionization (higher ratios of the strengths of CIV and MgII lines), than the intervening absorbers. The ionization decreases with increasing {beta}. Average extinction curves were obtained for the subsamples by comparing their geometric mean QSO spectra with those of matching (in z_em_ and i magnitude) samples of QSOs without absorption lines. There is clear evidence for SMC-like dust attenuation in these systems; the 2175{AA} absorption feature is absent. The extinction is almost twice that observed in intervening systems. We reconfirm that QSOs with nonzero FIRST radio flux are intrinsically redder than the QSOs with no detection in the FIRST survey.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1
- Title:
- Binary quasars in the SDSS
- Short Name:
- J/AJ/131/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 221 new quasar pairs with proper transverse separations R_prop_<1h^1^Mpc over the redshift range 0.5<z<3.0, discovered from an extensive follow-up campaign to find companions around the Sloan Digital Sky Survey (Cat. <VII/243>) and 2dF QSO Redshift Survey (Cat. <VII/241>) quasars. This sample includes 26 new binary quasars with separations R_prop_<50h^-1^kpc ({thetas}<10"), more than doubling the number of such systems known. We define a statistical sample of binaries selected with homogeneous criteria and compute its selection function, taking into account sources of incompleteness. The first measurement of the quasar correlation function on scales 10h^-1^kpc<R_prop_<400h^-1^kpc is presented.
- ID:
- ivo://CDS.VizieR/J/ApJ/773/14
- Title:
- BOSS: quasar luminosity function
- Short Name:
- J/ApJ/773/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new measurement of the optical quasar luminosity function (QLF), using data from the Sloan Digital Sky Survey-III: Baryon Oscillation Spectroscopic Survey (SDSS-III: BOSS). From the SDSS-III Data Release Nine, a uniform sample of 22301 i<~21.8 quasars are selected over an area of 2236deg^2^, with confirmed spectroscopic redshifts between 2.2<z<3.5, filling in a key part of the luminosity-redshift plane for optical quasar studies. The completeness of the survey is derived through simulated quasar photometry, and this completeness estimate is checked using a sample of quasars selected by their photometric variability within the BOSS footprint. We investigate the level of systematics associated with our quasar sample using the simulations, in the process generating color-redshift relations and a new quasar K-correction. We probe the faint end of the QLF to M_i_(z=2.2){approx}-24.5 and see a clear break in the QLF at all redshifts up to z=3.5. A log-linear relation (in log{Phi}*-M*) for a luminosity evolution and density evolution model is found to adequately describe our data within the range 2.2<z<3.5; across this interval the break luminosity increases by a factor of ~2.6 while {Phi}* declines by a factor of ~8. At z<~2.2 our data are reasonably well fit by a pure luminosity evolution model, and only a weak signature of "AGN downsizing" is seen, in line with recent studies of the hard X-ray luminosity function. We compare our measured QLF to a number of theoretical models and find that models making a variety of assumptions about quasar triggering and halo occupation can fit our data over a wide range of redshifts and luminosities.
- ID:
- ivo://CDS.VizieR/J/AJ/125/1711
- Title:
- Broad Absorption Line Quasars from SDSS
- Short Name:
- J/AJ/125/1711
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of 224 broad absorption line quasars (BALQSOs) from the Sloan Digital Sky Survey's Early Data Release Quasar Catalog, (Schneider et al., 2002, Cat. <J/AJ/123/567>) including a relatively complete and homogeneous subsample of 131 BALQSOs. Since the identification of BALQSOs is subject to considerable systematic uncertainties, we attempt to create a complete sample of SDSS BALQSOs by combining the results of two automated selection algorithms and a by-eye classification scheme. One of these automated algorithms finds broad absorption line troughs by comparing with a composite quasar spectrum. We present the details of this algorithm and compare this method with one that uses a power-law fit to the continuum. The BALQSOs in our sample are further classified as high-ionization BALQSOs (HiBALs), low-ionization BALQSOs (LoBALs), and BALQSOs with excited iron absorption features (FeLoBALs); composite spectra of each type are presented. We further present a study of the properties of the BALQSOs in terms of the balnicity distribution, which rises with decreasing balnicity. This distribution of balnicities suggests that the fraction of quasars with intrinsic outflows may be significantly underestimated. The balnicity index defined by Weymann et al. (1991ApJ...373...23W) amounts to a sort of equivalent width: a quasar is declared to be a BAL when its balnicity index is >=0.
- ID:
- ivo://CDS.VizieR/J/MNRAS/492/719
- Title:
- Chandra observations of 2106 radio-quiet QSOs
- Short Name:
- J/MNRAS/492/719
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present Chandra observations of 2106 radio-quiet quasars in the redshift range 1.7<=z<=2.7 from the Sloan Digital Sky Survey (SDSS), through data release fourteen (DR14, 2018ApJS..235...42A), that do not contain broad absorption lines (BAL) in their rest-frame UV spectra. This sample adds over a decade worth of SDSS and Chandra observations to our previously published sample of 139 quasars from SDSS DR5 which is still used to correlate X-ray and optical/UV emission in typical quasars. We fit the SDSS spectra for 753 of the quasars in our sample that have high-quality (large exposure time and small off-axis observation angle) X-ray observations, and analyze their X-ray properties (aox and daox) with respect to the measured CIV and MgII emission-line rest-frame equivalent width (EW) and the CIV emission-line blueshift. We find significant correlations (at the >=99.99% level) between aox and these emission-line parameters, as well as between daox and CIV EW. Slight correlations are found between daox and CIV blueshift, MgII EW, and the ratio of CIV EW to MgII EW. The best-fit trend in each parameter space is used to compare the X-ray weakness (daox) and optical/UV emission properties of typical quasars and weak-line quasars (WLQs). The WLQs clearly deviate from the expectation for every relationship, typically exhibiting much weaker X-ray emission than predicted by the typical quasar relationships. The best-fit relationships for our typical quasars are consistent with predictions from the disk-wind quasar model. The behavior of the WLQs with respect to our typical quasars can be explained by an X-ray shielding model.
- ID:
- ivo://CDS.VizieR/J/other/RAA/19.29
- Title:
- Compilation of known QSOs for the Gaia mission
- Short Name:
- J/other/RAA/19.2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Quasars are essential for astrometric in the sense that they are spatial stationary because of their large distance from the Sun. The European Space Agency (ESA) space astrometric satellite Gaia is scanning the whole sky with unprecedented accuracy up to a few uas level. However, Gaia's two fields of view observations strategy may introduce a parallax bias in the Gaia catalog. Since it presents no significant parallax, quasar is perfect nature object to detect such bias. More importantly, quasars can be used to construct a Celestial Reference Frame in the optical wavelengths in Gaia mission. In this paper, we compile the most reliable quasars existing in literatures.The final compilation (designated as Known Quasars Catalog for Gaia mission, KQCG) contains 1842076 objects, among of them, 797632 objects are found in Gaia DR1 after cross-identifications. This catalog will be very useful in Gaia mission.
- ID:
- ivo://CDS.VizieR/J/AJ/155/110
- Title:
- Deep CFHT imaging of VVDS-F22 field. II. Quasars
- Short Name:
- J/AJ/155/110
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the results of a faint quasar survey in a one-square-degree field. The aim is to test the Y-K/g-z and J-K/i-Y color selection criteria for quasars at faint magnitudes to obtain a complete sample of quasars based on deep optical and near-infrared color-color selection and to measure the faint end of the quasar luminosity function (QLF) over a wide redshift range. We carried out a quasar survey based on the Y-K/g-z and J-K/i-Y quasar selection criteria, using the deep Y-band data obtained from our CFHT/WIRCam Y-band images in a two-degree field within the F22 field of the VIMOS VLT deep survey, optical co-added data from Sloan Digital Sky Survey Stripe 82 and deep near-infrared data from the UKIDSS Deep Extragalactic Survey in the same field. We discovered 25 new quasars at 0.5<z<4.5 and i<22.5 mag within one-square-degree field. The survey significantly increases the number of faint quasars in this field, especially at z~2-3. It confirms that our color selections are highly complete in a wide redshift range (z<4.5), especially over the quasar number density peak at z~2-3, even for faint quasars. Combining all previous known quasars and new discoveries, we construct a sample with 109 quasars and measure the binned QLF and parametric QLF. Although the sample is small, our results agree with a pure luminosity evolution at lower redshift and luminosity evolution and density evolution model at redshift z>2.5.