- ID:
- ivo://CDS.VizieR/J/MNRAS/406/1583
- Title:
- Quasar from SDSS and UKIDSS
- Short Name:
- J/MNRAS/406/1583
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a sample of 8498 quasars with both Sloan Digital Sky Survey (SDSS) ugriz optical and United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) YJHK near-infrared (near-IR) photometric data. With this sample, we obtain the median colour-z relations based on 7400 quasars with magnitude uncertainties less than 0.1mag in all bands. By analysing the quasar colours, we propose an empirical criterion in the Y-K versus g-z colour-colour diagram to separate stars and quasars with redshift z<4, and two other criteria for selecting high-redshift quasars. Using the SDSS-UKIDSS colour-z relations, we estimate the photometric redshifts of 8498 SDSS-UKIDSS quasars, and find that 85.0 per cent of them are consistent with the spectroscopic redshifts within |{Delta}z|<0.2, which leads to a significant increase of the photometric redshift accuracy from that based on the SDSS colour-z relations only. As two tests, we compare our colour-selection criterion with a small UKIDSS/EDR quasar/star sample and a sample of 4671 variable sources in the SDSS Stripe 82 region with both SDSS and UKIDSS data. We find that they can be clearly divided into two classes (quasars and stars) by our criterion in the Y-K versus g-z plot.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/260/202
- Title:
- Quasar luminosity function
- Short Name:
- J/MNRAS/260/202
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of quasars is selected from a 10-yr sequence of 30 UK Schmidt plates. Luminosity functions are derived in several redshift intervals, which in each case show a featureless power-law rise towards low luminosities. There is no sigh of the 'break' found in the recent UVX sample of Boyle, Shanks & Peterson. It is suggested that reasons for the disagreement are connected with biases in the selection of the UVX sample. The question of the nature of quasar evolution appears to be still unresolved.
- ID:
- ivo://CDS.VizieR/J/MNRAS/266/317
- Title:
- Quasars in ESO/SERC field 927
- Short Name:
- J/MNRAS/266/317
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the spectroscopic observations of 56 quasars that were discovered by AQD (Automated Quasar Detection) in a field of ~25.3deg2, centred at (1950) RA l0h40m00s, Dec. 05deg00'00". These observations, with the CTIO 4-m telescope, led to the discovery by Clowes & Campusano of a large group of quasars with size ~100-200h^-1^Mpc at z~1.3. Quasars of particular interest are noted, including one that is a BAL quasar with z~1.78.
- ID:
- ivo://CDS.VizieR/J/MNRAS/450/3904
- Title:
- Quasars narrow absorption lines from SDSS
- Short Name:
- J/MNRAS/450/3904
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We assemble 3524 quasars from the Sloan Digital Sky Survey (SDSS) with repeated observations to search for variations of the narrow C IV {lambda}{lambda}1548, 1551 and Mg II {lambda}{lambda}2796, 2803 absorption doublets in spectral regions shortward of 7000{AA} in the observed frame, which corresponds to time-scales of about 150-2643d in the quasar rest frame. In these quasar spectra, we detect 3580 CIV absorption systems with z_abs_=1.5188-3.5212 and 1809 MgII absorption systems with z_abs_=0.3948-1.7167. In term of the absorber velocity ({beta}) distribution in the quasar rest frame, we find a substantial number of CIV absorbers with {beta}<0.06, which might be connected to absorption of quasar outflows. The outflow absorption peaks at {upsilon}~2000km/s and drops rapidly below this peak value. Among 3580 CIV absorption systems, 52 systems (~1.5 percent) show obvious variations in equivalent widths in the absorber rest frame (W_r_): 16 enhanced, 16 emerged, 12 weakened and 8 disappeared systems, respectively. We find that changes in W_r_{lambda}1548 are related neither to the time-scales of the two SDSS observations nor to absorber velocities in the quasar rest frame. Variable absorption in low-ionization species is important to constrain the physical conditions of the absorbing gas. There are two variable MgII absorption systems measured from SDSS spectra detected by Hacker et al. (2013, J/MNRAS/434/163). However, in our MgII absorption sample, we find that neither shows variable absorption with confident levels of >4{sigma} for {lambda}2796 lines and >3{sigma} for {lambda}2803 lines.
- ID:
- ivo://CDS.VizieR/J/MNRAS/468/L6
- Title:
- Quasars narrow absorption lines from SDSS
- Short Name:
- J/MNRAS/468/L6
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this Letter, we report the discovery of a strong correlation between the variability of narrow absorption lines (NALs) and the ionizing continuum from a two-epoch spectral sample of 40 quasars containing 52 variable CIV {lambda}{lambda}1548, 1551 absorption doublets. According to the concordance index, this sample is classified into two subsamples. Subsample I shows an anti-correlation between the variations of absorption lines and the continuum, while Subsample II exhibits a positive correlation. These results imply that these variable CIV {lambda}{lambda}1548, 1551 absorption doublets are intrinsic to the corresponding quasars and that their variations are caused primarily by the fluctuations of the ionizing continuum. Based on our analysis, we propose that there might be two kinds of absorption gas: one that is very sensitive to the continuum variations, and another that is not. In addition, we suggest that in many cases the emergence or disappearance of NALs is caused by fluctuations of the ionizing continuum.
276. Quasar variability
- ID:
- ivo://CDS.VizieR/J/A+AS/143/465
- Title:
- Quasar variability
- Short Name:
- J/A+AS/143/465
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The relation between quasar variability and parameters such as luminosity and redshift has been a matter of hot debate over the last few years with many papers on the subject. Any correlations which can be established will have a profound effect on models of quasar structure and evolution. The sample of quasars with redshifts in ESO/SERC field 287 contains over 600 quasars in the range 0<z<3.5 and is now large enough to bin in luminosity and redshift, and give definitive measures of the correlations. We find no significant correlation between amplitude and redshift, except perhaps at very low redshift, but an inverse correlation between amplitude and luminosity. This is examined in the context of various models for quasar variability.
277. Quasar variability
- ID:
- ivo://CDS.VizieR/J/MNRAS/375/989
- Title:
- Quasar variability
- Short Name:
- J/MNRAS/375/989
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In order to investigate the dependence of quasar variability on fundamental physical parameters like black hole mass, we have matched quasars from the Quasar Equatorial Survey Team, Phase 1 (QUEST1) variability survey with broad-lined objects from the Sloan Digital Sky Survey. The matched sample contains 104 quasars, and the Sloan spectra are used to estimate black hole masses and bolometric luminosities. Variability amplitudes are measured from the QUEST1 light curves. We find that black hole mass correlates with several measures of the variability amplitude at the 99 per cent significance level or better. The correlation does not appear to be caused by obvious selection effects inherent to flux-limited quasar samples, host galaxy contamination or other well-known correlations between quasar variability and luminosity/redshift. We evaluate variability as a function of rest-frame time lag using structure functions and find further support for the variability-black hole mass correlation.
- ID:
- ivo://CDS.VizieR/J/A+AS/114/565
- Title:
- Radial velocities in clusters of galaxies.
- Short Name:
- J/A+AS/114/565
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained 65 new redshifts in 4 Abell galaxy as well as 15 velocities of galaxies observed through the galactic plane, at ESO and OHP. Data on individual galaxies are presented, and the accuracy of the determined velocities are discussed as well as some properties of the clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/445/955
- Title:
- Radio-AGN feedback for 0.5<z<1
- Short Name:
- J/MNRAS/445/955
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the first measurement of the radio luminosity function of 'jet-mode' (radiatively inefficient) radio-AGN out to z=1, in order to investigate the cosmic evolution of radio-AGN feedback. Eight radio source samples are combined to produce a catalogue of 211 radio-loud AGN with 0.5<z<1.0, which are spectroscopically classified into jet-mode and radiative-mode (radiatively efficient) AGN classes. Comparing with large samples of local radio-AGN from the Sloan Digital Sky Survey, the cosmic evolution of the radio luminosity function of each radio-AGN class is independently derived. Radiative-mode radio-AGN show an order of magnitude increase in space density out to z~1 at all luminosities, consistent with these AGN being fuelled by cold gas. In contrast, the space density of jet-mode radio-AGN decreases with increasing redshift at low radio luminosities (L_1.4GHz_<~10^24^W/Hz) but increases at higher radio luminosities. Simple models are developed to explain the observed evolution. In the best-fitting models, the characteristic space density of jet-mode AGN declines with redshift in accordance with the declining space density of massive quiescent galaxies, which fuel them via cooling of gas in their hot haloes. A time delay of 1.5-2Gyr may be present between the quenching of star formation and the onset of jet-mode radio-AGN activity. The behaviour at higher radio luminosities can be explained either by an increasing characteristic luminosity of jet-mode radio-AGN activity with redshift (roughly as (1+z)^3^) or if the jet-mode radio-AGN population also includes some contribution of cold-gas-fuelled sources seen at a time when their accretion rate was low. Higher redshifts measurements would distinguish between these possibilities.
- ID:
- ivo://CDS.VizieR/J/MNRAS/347/837
- Title:
- Radio and K-band obs. of Ultra-Steep sources
- Short Name:
- J/MNRAS/347/837
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of 76 ultra-steep spectrum (USS) radio sources is defined from the 843-MHz Sydney University Molonglo Sky Survey (SUMSS) and 1.4-GHz NRAO VLA Sky Survey (NVSS) radio surveys with spectral index {alpha}<-1.3 and S(1.4GHz)>15mJy; 71 of these sources without bright optical or near-infrared counterparts at 1.385GHz were observed with the Australia Telescope Compact Array (ATCA), providing 5arcsec resolution images and subarcsec positional accuracy. To identify their host galaxies, near-infrared K-band images were obtained with IRIS2 at the AAT and SofI at the NTT; 92% of the USS sources could be identified down to K~20.5. 142 FITS files containing the radio maps and the K-band images are included in the fits subdirectory.
