- ID:
- ivo://CDS.VizieR/J/A+A/638/A27
- Title:
- Redshift database towards Shapley Supercluster
- Short Name:
- J/A+A/638/A27
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a database and velocity catalogue towards the region of the Shapley Supercluster based on 18,129 measured velocities for 10,702 galaxies in the approximately 300 square degree area between 12:42:13.219<RA<14:16:59.210 and -38:29:35.70<Dec<-23:28:34.90. The data catalogue contains velocities from the literature found until 2015. It also includes 5,084 velocities, corresponding to 4617 galaxies, observed by us at Las Campanas and CTIO observatories and not reported individually until now. Of these, 2585 correspond to galaxies with no other previously published velocity measurement before 2015. Every galaxy in the velocity database has been identified with a galaxy extracted from the SuperCOSMOS photometric catalogues. We also provide a combined average velocity catalogue for all 10702 galaxies with measured velocities, adopting the SuperCOSMOS positions as a homogeneous base. A general magnitude cut-off at R2=18.0mag was adopted (with exceptions only for some of the new reported velocities). In general terms, we confirm the overall structure of the Shapley Supercluster, as found on earlier papers. However, the more extensive velocity data show finer structure, to be discussed in a future publication.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/130/2439
- Title:
- Redshift estimates in the SDSS DR2
- Short Name:
- J/AJ/130/2439
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have applied ClassX, an oblique decision tree classifier optimized for astronomical analysis, to the homogeneous multicolor imaging database of the Sloan Digital Sky Survey (SDSS), training the software on subsets of SDSS objects whose nature is precisely known via spectroscopy. We find that the software, using photometric data only, correctly classifies a very large fraction of the objects with existing SDSS spectra, both stellar and extragalactic. ClassX also accurately predicts the redshifts of both normal and active galaxies in SDSS. To illustrate ClassX applications in SDSS research, we (1) derive the object content of the SDSS Data Release 2 photometric catalog and (2) provide a sample catalog of resolved SDSS objects that contains a large number of candidate active galactic nucleus (AGN) galaxies (27,000), along with 63,000 candidate normal galaxies at magnitudes substantially fainter than the typical magnitudes of SDSS spectroscopic objects.
- ID:
- ivo://CDS.VizieR/J/A+A/363/517
- Title:
- Redshift from UBRI photometry method
- Short Name:
- J/A+A/363/517
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A new method is developed for estimating photometric redshifts, using realistic template Spectral Energy Distributions (SEDs), extending over four decades in wavelength (i.e. from 0.05{mu}m to 1mm). The template SEDs are constructed for four different spectral types of galaxies (elliptical, spiral, irregular and starburst), satisfying the following characteristics: a) they are normalised to produce the observed colours of galaxies at z~0; b) incorporate the chemo-photometric spectral evolution of galaxies of different types, in agreement with the observations; c) allow treatment of dust contribution and its evolution with redshift, consistent with the spectral evolution models; d) include absorption and re-emission of radiation by dust and hence, realistic estimates of the far-infrared radiation; e) include correction for inter-galactic absorption by Lyman continuum and Lyman forest. Using these template SEDs, the photometric redshifts are estimated to an accuracy of {Delta}z=0.11. The simultaneous and self-consistent modelling of both the photometric and chemical evolution of galaxies and the effect of dust, makes this technique particularly useful for high redshift galaxies. The effects on the estimated photometric redshifts, due to assumptions in the evolutionary population synthesis models, are investigated and discussed. Also, the degeneracy in the predicted photometric redshifts and spectral types are examined, using a simulated galaxy catalogue.
- 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.
- 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/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/AJ/105/1637
- Title:
- Redshifts in equatorial strip
- Short Name:
- J/AJ/105/1637
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 865 redshifts of galaxies located in the equatorial strip -17.5 deg <= Dec. <= -2.5 deg in the right ascension range 20 h <= R.A. <= 5 h. Redshifts have been obtained for the complete sample of all 833 galaxies in the Morphological Catalog of Galaxies with magnitudes brighter than m = 14.5 (corresponding approximately to m(Zwicky) = 15.0). This sample also includes three galaxies from other sources with more reliable magnitudes, satisfying this limit, and 29 fainter galaxies, usually companions of the galaxies in the magnitude limited sample. Our maps of a very large volume of nearby space demonstrate a variety of coherent large scale structures which include large voids, 20-50 h^-1^ Mpc in diameter and large walls at least 70 h^-1^ Mpc across.
3068. Redshifts in LCDCS 0504
- ID:
- ivo://CDS.VizieR/J/A+A/566/A149
- Title:
- Redshifts in LCDCS 0504
- Short Name:
- J/A+A/566/A149
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Constraints on the mass distribution in high-redshift clusters of galaxies are currently not very strong. We aim to constrain the mass profile, M(r), and dynamical status of the z~0.8 LCDCS 0504 cluster of galaxies that is characterized by prominent giant gravitational arcs near its center. Our analysis is based on deep X-ray, optical, and infrared imaging as well as optical spectroscopy, collected with various instruments, which we complemented with archival data. We modeled the mass distribution of the cluster with three different mass density profiles, whose parameters were constrained by the strong lensing features of the inner cluster region, by the X-ray emission from the intracluster medium, and by the kinematics of 71 cluster members.
- ID:
- ivo://CDS.VizieR/J/ApJ/797/106
- Title:
- Redshifts in nine galaxy cluster fields
- Short Name:
- J/ApJ/797/106
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use dense redshift surveys of nine galaxy clusters at z~0.2 to compare the galaxy distribution in each system with the projected matter distribution from weak lensing. By combining 2087 new MMT/Hectospec redshifts and the data in the literature, we construct spectroscopic samples within the region of weak-lensing maps of high (70%-89%) and uniform completeness.
- 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.
