- ID:
- ivo://CDS.VizieR/J/A+A/435/781
- Title:
- Redshifts of galaxies in 21 EIS cluster fields
- Short Name:
- J/A+A/435/781
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out an investigation of the properties of low redshift EIS clusters using both spectroscopy and imaging data. We present new redshifts for 738 galaxies in 21 ESO Imaging Survey (EIS) Cluster fields. We use the "gap"-technique to search for significant overdensities in redshift space and to identify groups/clusters of galaxies corresponding to the original EIS matched filter cluster candidates. In this way we spectroscopically confirm 20 of the 21 cluster candidates with a matched-filter estimated redshift z_MF_=0.2. We have now obtained spectroscopic redshifts for 34 EIS cluster candidates with z_MF_=0.2 (see also Hansen et al., 2002, Cat. <J/A+A/388/1>; Olsen et al., 2003, Cat. <J/A+A/409/439>. Of those we spectroscopically confirm 32 with redshifts ranging from z=0.064 to 0.283. We find that: 1) the velocity dispersions of the systems range from sigma_v_<=130km/s to sigma_v_=1200km/s, typical of galaxy groups to rich clusters; 2) richnesses corresponding to Abell classes R<=1; and 3) concentration indices ranging from C=0.2 to C=1.2. From the analysis of the colours of the galaxy populations we find that 53% of the spectroscopically confirmed systems have a "significant" red sequence. These systems are on average richer and have higher velocity dispersions. We find that the colour of the red sequence galaxies matches passive stellar evolution predictions.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/658/865
- Title:
- Redshifts of galaxies in X-ray-luminous groups
- Short Name:
- J/ApJ/658/865
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the galaxy populations in seven X-ray-selected, intermediate-redshift groups (0.2<z<0.6). Overall, the galaxy populations in these systems are similar to those in clusters at the same redshift; they have large fractions of early-type galaxies (fe~70%) and small fractions of galaxies with significant star formation (f~30%).
- ID:
- ivo://CDS.VizieR/J/AJ/131/1280
- Title:
- Redshifts of HRS galaxies
- Short Name:
- J/AJ/131/1280
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 118 new optical redshifts for galaxies in 12 clusters in the Horologium-Reticulum supercluster (HRS) of galaxies. For 76 galaxies, the data were obtained with the Dual Beam Spectrograph on the 2.3m telescope of the Australian National University at Siding Spring Observatory. After combining 42 previously unpublished redshifts with our new sample, we determine mean redshifts and velocity dispersions for 13 clusters in which previous observational data were sparse.
- ID:
- ivo://CDS.VizieR/J/ApJ/888/35
- Title:
- Redshifts of lensed systems toward RXCJ2248.7-4431
- Short Name:
- J/ApJ/888/35
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an iterative method to construct a freeform lens model that self-consistently reproduces the sky positions, geometrically inferred redshifts, and relative brightnesses of all multiply lensed images toward a galaxy cluster. This method is applied to the cluster RXCJ2248.7-4431 (z=0.348) from the Hubble Frontier Fields program, toward which 10 multiply lensed sources with accurate spectroscopic redshifts and 6 others with inexact photometric redshifts have been identified. Using the spectroscopically secure systems to define an initial lens model, we compute the geometric redshifts of the photometric systems. We then iterate the lens model by incorporating the photometric systems at redshifts shifted by incremental amounts toward their geometric redshifts inferred from the previous step; on convergence, we find geometric redshifts in good agreement with the spectroscopically determined redshifts, but they can depart significantly from the photometrically determined redshifts. In the final lens model, all 16 lensed sources tightly follow the cosmological form of the angular diameter distance relation. Furthermore, although they are not used as model constraints, our lens model predicts relative brightnesses between image pairs for a given set of multiply lensed images in reasonable agreement with observations, thus providing independent validation of this model.
- ID:
- ivo://CDS.VizieR/J/A+A/618/A66
- Title:
- Redshifts of obscured AGN
- Short Name:
- J/A+A/618/A66
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Redshifts are fundamental for our understanding of extragalactic X-ray sources. Ambiguous counterpart associations, expensive optical spectroscopy and/or multimission multiwavelength coverage to resolve degeneracies make estimation often difficult in practice. We attempt to constrain redshifts of obscured Active Galactic Nuclei (AGN) using only low-resolution X-ray spectra. Our XZ method fits AGN X-ray spectra with a moderately complex spectral model incorporating a corona, torus obscurer and warm mirror. Using the Bayesian X-ray Astronomy (BXA) package, we constrain redshift, column density, photon index and luminosity simultaneously. The redshift information primarily comes from absorption edges in Compton-thin AGN, and from the Fe K{alpha} fluorescent line in heavily obscured AGN. A new generic background fitting method allows us to extract more information from limited numbers of source counts. We derive redshift constraints for 74/321 hard-band detected sources in the Chandra deep field South. Comparing with spectroscopic redshifts, we find an outlier fraction of 8%, indicating that our model assumptions are valid. For three Chandra deep fields, we release our XZ redshift estimates. The independent XZ estimate is easy to apply and effective for a large fraction of obscured AGN in todays deep surveys without the need for any additional data. Comparing to different redshift estimation methods, XZ can resolve degeneracies in photometric redshifts, help to detect potential association problems and confirm uncertain single-line spectroscopic redshifts. With high spectral resolution and large collecting area, this technique will be highly effective for Athena/WFI observations.
- ID:
- ivo://CDS.VizieR/J/ApJS/150/181
- Title:
- Redshifts of 110 radio-loud AGNs
- Short Name:
- J/ApJS/150/181
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report accurate redshifts of 110 active galaxies (mostly radio-loud objects at z<0.4) observed in the course of a survey to find broad, double-peaked emission lines. These redshifts are measured from the narrow emission lines of these objects and are accurate to at least one part in 10^4^. For each object we determine a redshift from high- and low-ionization lines separately, as well as an average redshift from all the available lines. We find that in about 15% of cases, the low-ionization lines yield a slightly higher redshift than the high-ionization lines; the average redshift difference amounts to a velocity difference of approximately 80km/s. In addition to the redshift measurements we also report revised redshifts for two objects as well as new classifications for three narrow-line objects.
- ID:
- ivo://CDS.VizieR/J/AJ/123/3018
- Title:
- Redshifts of radio-selected poor clusters
- Short Name:
- J/AJ/123/3018
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multifiber optical spectroscopy has been performed on galaxies in the vicinity of strong, nearby radio galaxies. These radio galaxies were selected from the 3CR and B2 catalogs based on their exclusion from the Abell catalog, which is puzzling given the hypothesis that an external medium is required to confine the radio plasma of such galaxies. Velocities derived from the spectra were used to confirm the existence of groups and poor clusters in the fields of most of the radio galaxies. We find that all radio galaxies with classical Fanaroff-Riley type I morphologies prove to reside in clusters, whereas the other radio galaxies often appear to be recent galaxy-galaxy mergers in regions of low galaxy density. These findings confirm the earlier result that the existence of extended X-ray emission combined with a statistical excess of neighboring galaxies can be used to identify poor clusters associated with radio galaxies.
- ID:
- ivo://CDS.VizieR/J/ApJS/96/343
- Title:
- Redshifts of rich clusters of galaxies
- Short Name:
- J/ApJS/96/343
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectroscopic observations and accurate positions for 286 galaxies in clusters taken over several observing sessions, mostly with the DuPont telescope at Las Campanas Observatorv. We derive 165 redshifts of rich clusters of which 130 are apparently new values. Redshifts encompass a wide range out to z=0.27
- ID:
- ivo://CDS.VizieR/J/AJ/134/169
- Title:
- Redshifts of UDF emission-line objects
- Short Name:
- J/AJ/134/169
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present redshifts for 115 emission-line objects in the Hubble Ultra Deep Field identified through the Grism ACS Program for Extragalactic Science (GRAPES) project using the slitless grism spectroscopy mode of the Advanced Camera for Surveys on the Hubble Space Telescope (HST). The sample was selected by an emission-line search on all extracted one-dimensional GRAPES spectra. We identify the emission lines using line wavelength ratios where multiple lines are detected in the grism wavelength range (5800{AA}<~lambda<~9600{AA}), and using photometric redshift information where multiple lines are unavailable. We then derive redshifts using the identified lines.
- ID:
- ivo://CDS.VizieR/J/AJ/124/1266
- Title:
- Redshift survey around Abell 2199
- Short Name:
- J/AJ/124/1266
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Using a redshift survey of 1323 galaxies (1092 new or remeasured) in a region of 95deg^2^ centered on the nearby galaxy cluster Abell 2199, we analyze the supercluster containing A2199, A2197, and an X-ray group.
