- ID:
- ivo://CDS.VizieR/J/AN/341/703
- Title:
- Radio spectral indices of active galaxies
- Short Name:
- J/AN/341/703
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper, we investigate radio properties of active galaxies taken from the reference Veron-Cetty & Veron (2010, Cat. VII/258) catalog. The galaxies are limited to magnitudes in the range of 12^m^-19^m^. We have cross-correlated the list with radio catalogs and selected those galaxies that have data on six or more radio fluxes at different wavelengths. As a result, we have 198 galaxies that satisfy these conditions. Using SDSS DR15, we have obtained 96 spectroscopic identifications of the 198 objects. After the classification, 85% of the 96 objects have changed their types. Available data on the classification of these objects and our classification showed that 56.7% of them are Seyfert galaxies. For all the objects, we have built radio spectra and estimated radio spectral indices. As a result, we obtain {alpha}>=-0.6089+/-0.056> ({alpha}_Seyfert_=-0.6013+/-0.027, {alpha}_LINER_=-0.5955+/-0.025, {alpha}_HII_=-0.6672+/-0.039, {alpha}_Comp._=-0.7128+/-0.043). We discuss the radio properties of active galaxies based on their radio spectral indices.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/VIII/43
- Title:
- Radio survey of clusters of galaxies
- Short Name:
- VIII/43
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observations of Abell clusters at 11.1, 6.2, 6.3 and 2.8cm with the 100m Effelsberg telescope. The data were compiled by H.J. Andernach.
293. RASS AGN sample
- ID:
- ivo://CDS.VizieR/J/A+AS/139/575
- Title:
- RASS AGN sample
- Short Name:
- J/A+AS/139/575
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the first results of a program to identify the unknown bright active galactic nuclei (AGN) in the ROSAT All Sky Survey Bright Source Catalog (RASS-BSC). We have used logC+0.4R as an alternative expression for log(f_X_/f_opt_), where C is X-ray count rate and R stands for R magnitude. Then a high X-ray-to-optical flux ratio criterion has been used to select an AGN sample with 165 unidentified X-ray sources for optical spectroscopy. Those 165 X-ray sources have been identified in the following classes: 115 emission line AGN (QSOs and Seyferts), 2 BL Lac objects and 4 BL Lac candidates, 22 clusters of galaxies, 12 Galactic stars and 10 objects remain unidentified. This represent a success rate of about 73% for detecting AGN using our selection criteria. Plausibility is based upon the optical classification and X-ray characteristics of the sources.
294. RASS-6dFGS catalogue
- ID:
- ivo://CDS.VizieR/J/MNRAS/401/1151
- Title:
- RASS-6dFGS catalogue
- Short Name:
- J/MNRAS/401/1151
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a catalogue of 3405 X-ray sources from the ROSAT All Sky Survey (RASS) Bright Source Catalogue which fall within the area covered by the 6dF Galaxy Survey (6dFGS). The catalogue is count-rate limited at 0.05cts/s in the X-ray and covers the area of sky with {delta}<0{deg} and |b|>10{deg}. The RASS-6dFGS sample was one of the additional target catalogues of the 6dFGS and as a result we obtained optical spectra for 2224 (65 per cent) RASS sources. Of these, 1715 (77 per cent) have reliable redshifts with a median redshift of z=0.16 (excluding the Galactic sources). For the optically bright sources (b_J_<=17.5) in the observed sample, over 90 per cent have reliable redshifts. The catalogue mainly comprises quasi-stellar objects (QSOs) and active galaxies but also includes 238 Galactic sources. Of the sources with reliable redshifts the majority are type 1 active galactic nuclei (AGN, 69 per cent), while 12 per cent are type 2 AGN, 6 per cent absorption-line galaxies and 13 per cent are stars. We also identify a small number of optically faint, very low redshift, compact objects which fall outside the general trend in the b_J_-z plane. The RASS-6dFGS catalogue complements a number of Northern hemisphere samples, particularly the ROSAT Bright Source Catalogue-NRAO VLA Sky Survey (RBSC-NVSS) sample (Bauer et al., 2000, Cat. J/ApJS/129/547/), and furthermore, in the same region of sky (-40{deg}<{delta}<0{deg}) reveals an additional 561 sources that were not identified as part of that sample. We detect 918 sources (27 per cent) of the RASS-6dFGS sample in the radio using either the 1.4GHz NVSS or the 843MHz Sydney University Molonglo Sky Survey (SUMSS) catalogues and find that the detection rate changes with redshift. At redshifts larger than 1 virtually all of these sources have radio counterparts and with a median flux density of 1.15Jy, they are much stronger than the median flux density of 28.6mJy for the full sample. We attribute this to the fact that the X-ray flux of these objects is being boosted by a jet component, possibly Doppler boosted, that is only present in radio-loud AGN. The RASS-6dFGS sample provides a large set of homogeneous optical spectra ideal for future studies of X-ray emitting AGN.
- ID:
- ivo://CDS.VizieR/J/MNRAS/470/4838
- Title:
- Redshift catalog of HE 0435-1223 field-of-view
- Short Name:
- J/MNRAS/470/4838
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Galaxies located in the environment or along the line of sight towards gravitational lenses can significantly affect lensing observables, and can lead to systematic errors on the measurement of H_0_ from the time-delay technique. We present the results of a systematic spectroscopic identification of the galaxies in the field of view of the lensed quasar HE 0435-1223 using the W.M. Keck, Gemini and ESO-Very Large telescopes. Our new catalogue triples the number of known galaxy redshifts in the direct vicinity of the lens, expanding to 102 the number of measured redshifts for galaxies separated by less than 3 arcmin from the lens. We complement our catalogue with literature data to gather redshifts up to 15 arcmin from the lens, and search for galaxy groups or clusters projected towards HE 0435-1223. We confirm that the lens is a member of a small group that includes at least 12 galaxies, and find 8 other group candidates near the line of sight of the lens. The flexion shift, namely the shift of lensed images produced by high-order perturbation of the lens potential, is calculated for each galaxy/group and used to identify which objects produce the largest perturbation of the lens potential. This analysis demonstrates that (i) at most three of the five brightest galaxies projected within 12 arcsec of the lens need to be explicitly used in the lens models, and (ii) the groups can be treated in the lens model as an external tidal field (shear) contribution.
- ID:
- ivo://CDS.VizieR/VII/177
- Title:
- Redshifts and Velocity Dispersions for Abell Clusters
- Short Name:
- VII/177
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog presents a list of redshifts for 758 Abell clusters, and velocity dispersions for 121, published as of 1991 March. We present another list of 33 Abell clusters with published redshifts, most of which are probably redshifts of foreground or background galaxies superposed on, or near, the Abell clusters. Over the past 4 years, the published number of redshifts of member galaxies in clusters increased by a factor of 2.0, but the number of cluster redshifts increased by only a factor of 1.3, while the number of cluster velocity dispersions derived from 50 or more redshifts of member galaxies increased by a factor of 3.8 (from 6 to 23).
- ID:
- ivo://CDS.VizieR/VII/56
- Title:
- Redshifts for Abell Clusters
- Short Name:
- VII/56
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The catalog gives redshifts for 329 Abell clusters, all those known to the authors in published or preprint form at the time of the compilation (through 1982). The data table has been compiled critically, based partially on a number of photometric distance estimators derived from the redshift data. These were used to evaluate probable accuracies of the redshifts and to resolve discrepancies among different values for the same clusters. The catalog includes Abell (1958) cluster numbers, redshifts, and the number of redshifts of different galaxies averaged to determine the cluster value. The machine version was prepared at the Astronomical Data Center, NASA/GSFC. Note that Struble and Rood published further compilations in 1987 (1987ApJS...63..543S) and 1991 (1991ApJS...77..363S). Other redshift compilations are also available in electronic form (see "See also" section below).
- ID:
- ivo://CDS.VizieR/J/MNRAS/381/1369
- Title:
- Redshifts in Subaru/XMM Deep Field
- Short Name:
- J/MNRAS/381/1369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present multiobject spectroscopy of galaxies in the immediate (Mpc-scale) environments of four low-power (L_1.4GHz_~<10^25^W/Hz) radio galaxies at z~0.5, selected from the Subaru/XMM-Newton Deep Field. We use the spectra to calculate velocity dispersions and central redshifts of the groups the radio galaxies inhabit, and combined with XMM-Newton (0.3-10keV) X-ray observations investigate the L_X_-{sigma}_v_ and T_X_-{sigma}_v_ scaling relationships. All the radio galaxies reside in moderately rich groups - intermediate environments between poor groups and rich clusters, with remarkably similar X-ray properties.
- ID:
- ivo://CDS.VizieR/J/MNRAS/346/1103
- Title:
- Redshifts of damped Lyman{alpha} absorbers
- Short Name:
- J/MNRAS/346/1103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the evolution of the column density distribution, f(N,z), and total neutral hydrogen mass in high column density quasar absorbers using candidates from a recent high-redshift survey for damped Lyman{alpha} (DLA) and Lyman-limit system (LLS) absorbers.
- ID:
- ivo://CDS.VizieR/J/MNRAS/316/326
- Title:
- Redshifts of Ophiuchus region galaxies
- Short Name:
- J/MNRAS/316/326
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The large-scale structure around the Ophiuchus cluster of galaxies in the vicinity of the Galactic Centre (l=0.5{deg}, b=9.5{deg}, cz=8500km/s) is investigated on the basis of a galaxy survey and spectroscopic observations made for a 120{deg}x170{deg} area. The galaxy survey was performed using six ESO/SERC Sky Survey Atlas films, and 4021 galaxies were detected in total. Recession velocities were newly obtained for 179 galaxies to make the total number of galaxies in the survey area with known velocities 219. In the distribution of bright galaxies, we identified seven new clumps of galaxies. Comparing the surface number density of bright galaxies with the Galactic extinction, which is estimated from the 100-{mu}m flux density in the IRAS Sky Survey Atlas, we demonstrate that the seven clumps are not spurious as a result of the inhomogeneity of the Galactic extinction. Among the seven clumps, two are found to be clusters and four to be groups on the basis of the histogram of recession velocities and the number of member galaxies. The Ophiuchus cluster, two newly identified clusters, and four groups are all concentrated at 9000km/s. Field galaxies are also distributed centred at 8500km/s. Hence field galaxies occupy a common three-dimensional region with galaxies in the clusters and groups, and altogether they form a large-scale structure of supercluster size. As opposed to the overdensity in the supercluster region, the mean number density of galaxies in the velocity range 0-5000km/s is only 25 per cent of the mean number density of the Universe, comparable with the density of the well-known Bootes void. Hence this nearby three-dimensional region in Ophiuchus is a void of galaxies also.
