- ID:
- ivo://CDS.VizieR/J/A+A/611/A53
- Title:
- Redshift reliability flags (VVDS data)
- Short Name:
- J/A+A/611/A53
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Future large-scale surveys, as the ESA Euclid mission, will produce a large set of galaxy redshifts (>=10^6) that will require fully automated data-processing pipelines to analyze the data, extract crucial information and ensure that all requirements are met. A fundamental element in these pipelines is to associate to each galaxy redshift measurement a quality, or reliability, estimate. In this work, we introduce a new approach to automate the spectroscopic redshift reliability assessment based on machine learning (ML) and characteristics of the redshift probability density function. We propose to rephrase the spectroscopic redshift estimation into a Bayesian framework, in order to incorporate all sources of information and uncertainties related to the redshift estimation process and produce a redshift posterior probability density function (PDF). To automate the assessment of a reliability flag, we exploit key features in the redshift posterior PDF and machine learning algorithms.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+A/479/1
- Title:
- Redshifts and morphology in A3667
- Short Name:
- J/A+A/479/1
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The galaxy cluster A3667 was observed using the Two-degree Field (2dF) multifibre spectroscopic system on the Anglo-Australian Telescope in a program designed to examine the velocity structure in the region. Specifically, we sought evidence from the optical data for the putative cluster merger believed to be responsible for the observed radio and X-ray emission. We present 184 new redshifts in the region, of which 143 correspond to member galaxies of A3667. We find the cluster velocity distribution to be well modelled by a single Gaussian in agreement with previous results. In addition, new redshift-selected isodensity plots significantly reduce the prominence of the previously reported subgroup to the north-west of the main cluster. Instead, we find the galaxy distribution to be elongated and well mixed, with a high velocity dispersion and no significant evidence for substructure. These results are consistent with the axis of the proposed merger being close to the plane of the sky.
- ID:
- ivo://CDS.VizieR/J/A+A/492/345
- Title:
- Redshifts and SDSS photometry of A1942 galaxies
- Short Name:
- J/A+A/492/345
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a dynamical analysis of the galaxy cluster Abell 1942 based on a set of 128 velocities obtained at the European Southern Observatory. Data on individual galaxies are presented and the accuracy of the determined velocities as some properties of the cluster are discussed. We have also made use of publicly available Chandra X-ray data.
- ID:
- ivo://CDS.VizieR/J/A+A/415/9
- Title:
- Redshifts behind the Southern Milky Way
- Short Name:
- J/A+A/415/9
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- As part of our efforts to unveil extragalactic large-scale structures behind the southern Milky Way, we here present redshifts for 764 galaxies in the Hydra/Antlia, Crux and Great Attractor region (266{deg}<=l<=338{deg}, |b|<=10{deg}), obtained with the Meudon-ESO Fibre Object Spectrograph (MEFOS) at the 3.6-m telescope of ESO. The observations are part of a redshift survey of partially obscured galaxies recorded in the course of a deep optical galaxy search behind the southern Milky Way (Kraan-Korteweg 2000, Cat. <J/A+AS/141/123>; Woudt & Kraan-Korteweg 2001, Cat. <J/A+A/380/441>). A total of 947 galaxies have been observed, a small percentage of the spectra (N=109, 11.5%) were contaminated by foreground stars, and 74 galaxies (7.8%) were too faint to allow a reliable redshift determination. With MEFOS we obtained spectra down to the faintest galaxies of our optical galaxy survey, and hence probe large-scale structures out to larger distances (v<=30000km/s) than our other redshift follow-ups using the 1.9-m telescope at the South African Astronomical Observatory (Kraan-Korteweg et al., 1995, Cat. <J/A+A/297/617>; Fairall et al., 1998, Cat. <J/A+AS/127/463>; Woudt et al., 1999, Cat. <J/A+A/352/39>) and the 64-m Parkes radio telescope (Kraan-Korteweg et al., 2002, Cat. <J/A+A/391/887>). The most distinct large-scale structures revealed in the southern Zone of Avoidance are discussed in context to known structures adjacent to the Milky Way.
- ID:
- ivo://CDS.VizieR/J/A+A/434/475
- Title:
- Redshifts for X-ray selected AGNs
- Short Name:
- J/A+A/434/475
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present photometric redshift estimates for X-ray selected sources detected in the XMM/2dF survey. 5-band photometry for 193 sources has been obtained from the SDSS. We exclude 10 sources associated with Galactic stars. The tabulated data include the optical coordinate of all sources in our sample, their photometric redshift estimate, their r-band magnitude and g-r colour as well as their morphological classification (these optical parameters have been used in the discussion of our results). Spectroscopic redshifts are available only for a sub-sample of our data and are included in Table 1 together with the survey from which they have been obtained.
- ID:
- ivo://CDS.VizieR/J/A+A/428/1043
- Title:
- Redshifts from VIMOS VLT Deep Survey
- Short Name:
- J/A+A/428/1043
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the VIMOS VLT Deep Survey around the Chandra Deep Field South (CDFS). We have measured 1599 new redshifts with VIMOS on the European Observatory Very Large Telescope - UT3, in an area 21x21.6arcmin^2^, including 784 redshifts in the Hubble Space Telescope - Advanced Camera for Surveys GOODS area. 30% of all objects with I_AB_=24 have been observed independently of magnitude, indicating that the sample is purely magnitude limited. We have reached an unprecedented completeness level of 84% in terms of the ratio of secure measurements vs. observed objects, while 95% of all objects have a redshift measurement. A total of 1452 galaxies, 139 stars, 8 QSOs have a redshift identification, 141 of these being unsecure measurements. The redshift distribution down to IAB=24 is peaked at a median redshift z=0.73, with a significant high redshift tail extending up to ~4. Several high density peaks in the distribution of galaxies are identified. In particular, the strong peak at z=0.735 contains more than 130 galaxies in a velocity range +/-2000km/s distributed all across the transverse ~20h^-1^Mpc of the survey. We are releasing all redshifts to the community, along with the cross identification with HST-ACS GOODS sources on the CENCOS database environment http://cencosw.oamp.fr .
1037. Redshifts in A2125
- ID:
- ivo://CDS.VizieR/J/ApJ/613/841
- Title:
- Redshifts in A2125
- Short Name:
- J/ApJ/613/841
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 371 galaxy velocities in the field of the very rich cluster A2125 (z~0.25). These were determined using optical spectroscopy collected over several years from both the WIYN 3.5m telescope and NOAO Mayall 4m telescope. Prior studies at a variety of wavelengths (radio, optical, and X-ray) have indicated that A2125 is a likely cluster-cluster merger, a scenario that we are able to test using our large velocity database. We identified 224 cluster galaxies, which were subjected to a broad range of statistical tests using both positional and velocity information to evaluate the cluster dynamics and substructure. The tests confirmed the presence of substructures within the A2125 system at high significance, demonstrating that A2125 is a complex dynamical system. Comparison of the test results with existing simulations strengthens the merger hypothesis and provides clues about the merger geometry and stage. The merger model for the system can reconcile A2125's low X-ray temperature and luminosity with its apparently high richness and might also explain A2125's high fraction of active galaxies identified in prior radio and optical studies.
1038. Redshifts in A3128/A3125
- ID:
- ivo://CDS.VizieR/J/AJ/123/1216
- Title:
- Redshifts in A3128/A3125
- Short Name:
- J/AJ/123/1216
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multifiber spectroscopy has been obtained for 335 galaxies in the field of the double cluster A3128/A3125, using the 2dF multifiber positioner on the Anglo-Australian Telescope. When combined with previously published results, a total of 532 objects in the double cluster now have known redshifts. We have also obtained a 20ks Chandra ACIS-I image of the central 16'x16' of A3128 and radio imaging of the cluster with the Molonglo Observatory Synthesis Telescope and the Australia Telescope Compact Array. The spatial/kinematic distribution of redshifts in the field of A3128/A3125, when combined with the Chandra ACIS-I image of A3128, reveals a variety of substructures present in the galaxy distribution and in the hot intracluster medium (ICM).
- ID:
- ivo://CDS.VizieR/J/A+A/548/A18
- Title:
- Redshifts in A1413 cluster center
- Short Name:
- J/A+A/548/A18
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the morphology and dynamics of the massive nearby galaxy cluster Abell 1413. Using wide field imaging and spectroscopic data obtained from observations at the Canada-France-Hawaii Telescope and archival SDSS data, we build a sample of more than 250 galaxies covering a region centered on the cluster and extending to its outskirts on large scales.
- ID:
- ivo://CDS.VizieR/J/AJ/119/44
- Title:
- Redshifts in AWM 7 galaxy cluster
- Short Name:
- J/AJ/119/44
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have measured 492 redshifts (311 new) in the direction of the poor cluster AWM 7 and have identified 179 cluster members (73 new).