- ID:
- ivo://CDS.VizieR/J/MNRAS/383/581
- Title:
- Broad-line Balmer decrements in blue AGN
- Short Name:
- J/MNRAS/383/581
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have investigated the broad-line Balmer decrements (H{alpha/H{beta}) for a large, homogeneous sample of Seyfert 1 galaxies and quasi-stellar objects (QSOs) using spectroscopic data obtained in the Sloan Digital Sky Survey. The sample, drawn from the Fourth Data Release, comprises 446 low-redshift (z<=0.35) active galactic nuclei (AGN) that have blue optical continua as indicated by the spectral slopes in order to minimize the effect of dust extinction. We find that (i) the distribution of the intrinsic broad-line H{alpha}/H{beta} ratio can be well described by log-Gaussian, with a peak at H{alpha}/H{beta}=3.06 and a standard deviation of about 0.03dex only; (ii) the Balmer decrement does not correlate with AGN properties such as luminosity, accretion rate and continuum slope, etc.; (iii) on average, the Balmer decrements are found to be only slightly larger in radio-loud sources (3.37) and sources having double-peaked emission-line profiles (3.27) compared to the rest of the sample. We therefore suggest that the broad-line H{alpha}/H{beta} ratio can be used as a good indicator for dust extinction in the AGN broad-line region; this is especially true for radio-quiet AGN with regular emission-line profiles, which constitute the vast majority of the AGN population.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/431/2111
- Title:
- BUDHIES I. redshifts and EW[OII]
- Short Name:
- J/MNRAS/431/2111
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the optical spectroscopy for the Blind Ultra Deep HI Environmental Survey (BUDHIES). With the Westerbork Synthesis Radio Telescope, BUDHIES has detected HI in over 150 galaxies in and around two Abell clusters at z=~0.2. With the aim of characterizing the environments of the Hi-detected galaxies, we obtained multifibre spectroscopy with the William Herschel Telescope. In this paper, we describe the spectroscopic observations, report redshifts and EW[OII] measurements for ~600 galaxies, and perform an environmental analysis. In particular, we present cluster velocity dispersion measurements for five clusters and groups in the BUDHIES volume, as well as a detailed substructure analysis.
- ID:
- ivo://CDS.VizieR/J/PAZh/44/383
- Title:
- Byurakan-IRAS galaxies (BIG) with SDSS spectra
- Short Name:
- J/PAZh/44/383
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The sample of Byurakan-IRAS galaxies (BIG) has been created based on optical identifications of IRAS Point Source Catalog (PSC) at high galactic latitudes. As a result, 1178 galaxies have been identified. 172 of them have been observed spectroscopically with Byurakan Astrophysical Observatory (BAO, Armenia) 2.6m, Special Astrophysical Observatory (SAO, Russia) 6m and Observatoire de Haute Provence (OHP, France) 1.93m telescopes. Later on, spectra were obtained for more 83 BIG objects in Sloan Digital Sky Survey (SDSS). We have extracted and studied these spectra, classified them and measured spectral features. Diagnostic diagrams have been built to distinguish starbursts (SB), LINERs and Seyfert galaxies. Cross-correlations were made for these objects with multiwavelength (MW) catalogues and their physical properties were studied. Among these 83 objects, 55 HII, 8 Seyfert galaxies, 2 LINERs, 4 other AGN, 6 composite spectrum objects, and 8 other emission-line galaxies have been revealed. Three of these objects are Ultra-Luminous InfraRed Galaxies (ULIRG).
- ID:
- ivo://CDS.VizieR/J/MNRAS/444/1747
- Title:
- CaII absorbers in SDSS QSOs
- Short Name:
- J/MNRAS/444/1747
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a survey for CaII {lambda}{lambda}3934,3969 absorption-line systems culled from ~95000 Sloan Digital Sky Survey (SDSS) Data Release 7 and Data Release 9 quasar spectra. With 435 doublets identified in the catalogue, this list is the largest CaII catalogue compiled to date, spanning redshifts z<1.34, which corresponds to the most recent ~8.9Gyr of the history of the Universe. We derive statistics on the Caii rest equivalent width distribution and incidence. We find that the {lambda}3934 rest equivalent width (W_0_^{lambda}3934^) distribution cannot be described by a single exponential function. A double exponential function is required to produce a satisfactory description.
- ID:
- ivo://CDS.VizieR/J/MNRAS/458/963
- Title:
- CANDELS galaxy structure classification
- Short Name:
- J/MNRAS/458/963
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Important but rare and subtle processes driving galaxy morphology and star formation may be missed by traditional spiral, elliptical, irregular or Sersic bulge/disc classifications. To overcome this limitation, we use a principal component analysis (PCA) of non-parametric morphological indicators (concentration, asymmetry, Gini coefficient, M_20_, multimode, intensity and deviation) measured at rest-frame B band (corresponding to HST/WFC3 F125W at 1.4<z<2) to trace the natural distribution of massive (>10^10^M_{sun}_) galaxy morphologies. PCA quantifies the correlations between these morphological indicators and determines the relative importance of each. The first three principal components (PCs) capture ~75 per cent of the variance inherent to our sample. We interpret the first PC as bulge strength, the second PC as dominated by concentration and the third PC as dominated by asymmetry. Both PC1 and PC2 correlate with the visual appearance of a central bulge and predict galaxy quiescence. PC1 is a better predictor of quenching than stellar mass, as good as other structural indicators (Sersic-n or compactness). We divide the PCA results into groups using an agglomerative hierarchical clustering method. Unlike Sersic, this classification scheme separates compact galaxies from larger, smooth protoelliptical systems, and star-forming disc-dominated clumpy galaxies from star-forming bulge-dominated asymmetric galaxies. Distinguishing between these galaxy structural types in a quantitative manner is an important step towards understanding the connections between morphology, galaxy assembly and star formation.
- ID:
- ivo://CDS.VizieR/J/MNRAS/472/772
- Title:
- Candidate LAEs at z=5.7 and z=6.6
- Short Name:
- J/MNRAS/472/772
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectroscopic follow-up of candidate luminous Ly{alpha} emitters (LAEs) at z=5.7-6.6 in the SA22 field with VLT/X-SHOOTER. We confirm two new luminous LAEs at z=5.676 (SR6) and z=6.532 (VR7), and also present HST follow-up of both sources. These sources have luminosities L_Ly {alpha}_~=3x10^43^erg/s, very high rest-frame equivalent widths of EW_0_>=200{AA} and narrow Ly{alpha} lines (200-340km/s). VR7 is the most UV-luminous LAE at z>6.5, with M_1500_=-22.5, even brighter in the UV than CR7. Besides Ly{alpha}, we do not detect any other rest-frame UV lines in the spectra of SR6 and VR7, and argue that rest-frame UV lines are easier to observe in bright galaxies with low Ly{alpha} equivalent widths. We confirm that Ly{alpha} line widths increase with Ly{alpha} luminosity at z=5.7, while there are indications that Ly{alpha} lines of faint LAEs become broader at z=6.6, potentially due to reionization. We find a large spread of up to 3 dex in UV luminosity for >L* LAEs, but find that the Ly{alpha} luminosity of the brightest LAEs is strongly related to UV luminosity at z=6.6. Under basic assumptions, we find that several LAEs at z~=6-7 have Ly{alpha} escape fractions >=100 per cent, indicating bursty star formation histories, alternative Ly{alpha} production mechanisms, or dust attenuating Ly{alpha} emission differently than UV emission. Finally, we present a method to compute {xi}_ion_, the production efficiency of ionizing photons, and find that LAEs at z~=6-7 have high values of log_10_({xi}_ion_/Hz/erg)~=25.51+/-0.09 that may alleviate the need for high Lyman-Continuum escape fractions required for reionization.
- ID:
- ivo://CDS.VizieR/J/other/RAA/19.127
- Title:
- C- and S-shaped radio galaxies
- Short Name:
- J/other/RAA/19.1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We study the environment of radio galaxies with different morphological types using the Proctor sample, which was built from the Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) survey archive. Among the 15 radio galaxy types classified by Proctor, 199 C-shaped (i.e., wide- or narrow-angle tail) and 203 S-shaped (i.e., S- or Z-shaped) sources are selected in this work, which are located in the redshift range of 0.02<z<1, because these two subsamples are relatively larger than the other subsamples in the Proctor sample. By cross-matching these radio galaxies with the optical sources drawn from the Sloan Digital Sky Survey (SDSS) database and counting the SDSS sources with an r-band absolute magnitude brighter than -19 located within a 0.5Mpc distance around each source (i.e., the richness), we find that the fraction of C-shaped sources with a richness above 10 is larger than that of S-shaped sources. We have also correlated the radio galaxies in our sample with the brightest cluster galaxies (BCGs) defined in the NASA/IPAC Extragalactic Database (NED), and infer that the C-shaped sources are more likely to be BCGs than the S-shaped sources. These results support the idea that C-shaped radio galaxies often reside in a richer environment than radio galaxies with other morphological types.
- ID:
- ivo://CDS.VizieR/J/MNRAS/434/1765
- Title:
- Catalog of galaxies around PKS 0405-123
- Short Name:
- J/MNRAS/434/1765
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new absorption-line analysis and new galaxy survey data obtained for the field around PKS 0405-123 at z_QSO_=0.57. Combining previously known OVI absorbers with new identifications in the higher S/N ultraviolet (UV) spectra obtained with the Cosmic Origins Spectrograph, we have established a sample of 7 OVI absorbers and 12 individual components at z=0.0918-0.495 along the sightline towards PKS 0405-123. We complement the available UV absorption spectra with galaxy survey data that reach 100 percent completeness at projected distances {rho}<200kpc of the quasar sightline for galaxies as faint as 0.1L* (0.2L*) out to redshifts of z~0.35 (z~0.5). The high level of completeness achieved at faint magnitudes by our survey reveals that OVI absorbers are closely associated with gas-rich environments containing at least one low-mass, emission-line galaxy. An intriguing exception is a strong OVI system at z~0.183 that does not have a galaxy found at {rho}<4Mpc, and our survey rules out the presence of any galaxies of L>0.04L* at {rho}<250kpc and any galaxies of L>0.3L* at {rho}<1Mpc. We further examine the galactic environments of OVI absorbers and those 'Ly{alpha}-only' absorbers with neutral hydrogen column density log N(HI)<13.6 and no detectable OVI absorption features. The Ly{alpha}-only absorbers serve as a control sample in seeking the discriminating galactic features that result in the observed Ovi absorbing gas at large galactic radii. We find a clear distinction in the radial profiles of mean galaxy surface brightness around different absorbers. Specifically, Ovi absorbers are found to reside in regions of higher mean surface brightness at {rho}<~500kpc ({Delta}{mu}_R_~+5magMpc^-2^ relative to the background at {rho}>500kpc), while only a mild increase in galaxy surface brightness is seen at small {rho} around Ly{alpha}-only absorbers ({Delta}{mu}_R_~+2magMpc^-2^). The additional insights gained from our deep galaxy survey demonstrate the need to probe the galaxy populations to low luminosities in order to better understand the nature of the absorbing systems.
- ID:
- ivo://CDS.VizieR/J/AZh/87/795
- Title:
- Catalog of galaxies in and around A1367
- Short Name:
- J/AZh/87/795
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalog of galaxies in and around the cluster A1367, together with the results of a spectroscopic study of eight faint galaxies projected onto the central part of the cluster. The observations were carried out with the Boller and Chivens spectrograph of the 2m telescope of the Guillermo Haro Observatory (Cananea, Mexico). Redshifts of eight galaxies were derived from both emission and absorption lines; the redshift for one of these, derived from Halpha, SII, OIII, and Hbeta emission lines, is z=0.015. The spectrum of this galaxy displays no absorption lines at z=0.026, testifying that it is located between the observer and A1367.
- ID:
- ivo://CDS.VizieR/VII/255
- Title:
- Catalog of radio galaxies with z>0.3
- Short Name:
- VII/255
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This catalog groups the 2442 galaxies making up the sample of distant galaxies prepared by the authors published as 3 papers in 2009: radio data (paper I, table1), photometric data (paper II, table2), and angular sizes (paper III, table 3). The sample of distant (z>0.3) radio galaxies is aimed at application in cosmological tests. It was created using NED, SDSS, and CATS databases, and is assumed to be cleaned from objects with quasar properties.
