- 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.
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- 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/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/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/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.
- ID:
- ivo://CDS.VizieR/J/AJ/131/2788
- Title:
- Redshifts in the SFQS survey
- Short Name:
- J/AJ/131/2788
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we present the first results of a deep spectroscopic survey of faint quasars in the Sloan Digital Sky Survey (SDSS) Southern Survey, a deep survey carried out by repeatedly imaging a 270{deg}^2^ area. Quasar candidates were selected from the deep data with good completeness over 0<z<5 and 2-3mag fainter than the SDSS main survey. Spectroscopic follow-up was carried out on the 6.5m MMT with Hectospec. The preliminary sample of this SDSS faint quasar survey (SFQS) covers ~3.9{deg}^2^, contains 414 quasars, and reaches g=22.5.
- ID:
- ivo://CDS.VizieR/J/ApJ/781/2
- Title:
- Redshifts of 1151 galaxies from SDSS
- Short Name:
- J/ApJ/781/2
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Lines of sight with multiple projected cluster-scale gravitational lenses have high total masses and complex lens plane interactions that can boost the area of magnification, or etendue, making detection of faint background sources more likely than elsewhere. To identify these new "compound" cosmic telescopes, we have found directions in the sky with the highest integrated mass densities, as traced by the projected concentrations of luminous red galaxies (LRGs). We use new galaxy spectroscopy to derive preliminary magnification maps for two such lines of sight with total mass exceeding ~3x10^15^M_{sun}_. From 1151 MMT Hectospec spectra of galaxies down to i_AB_=21.2, we identify two to three group- and cluster-scale halos in each beam. These are well traced by LRGs. The majority of the mass in beam J085007.6+360428 (0850) is contributed by Zwicky 1953, a massive cluster at z=0.3774, whereas beam J130657.5+463219 (1306) is composed of three halos with virial masses of 6x10^14^-2x10^15^M_{sun}_, one of which is A1682. The magnification maps derived from our mass models based on spectroscopy and Sloan Digital Sky Survey photometry alone display substantial etendue: the 68% confidence bands on the lens plane area with magnification exceeding 10 for a source plane of z_s_=10 are [1.2,3.8]arcmin^2^ for 0850 and [2.3,6.7]arcmin^2^ for 1306. In deep Subaru Suprime-Cam imaging of beam 0850, we serendipitously discover a candidate multiply imaged V-dropout source at z_phot_=5.03. The location of the candidate multiply imaged arcs is consistent with the critical curves for a source plane of z=5.03 predicted by our mass model. Incorporating the position of the candidate multiply imaged galaxy as a constraint on the critical curve location in 0850 narrows the 68% confidence band on the lens plane area with {mu}>10 and z_s_=10 to [1.8,4.2]arcmin^2^, an etendue range comparable to that of MACS 0717+3745 and El Gordo, two of the most powerful single cluster lenses known. The significant lensing power of our beams makes them powerful probes of reionization and galaxy formation in the early universe.
- ID:
- ivo://CDS.VizieR/J/MNRAS/283/367
- Title:
- Redshift survey in Per-Psc and Pav-Ind
- Short Name:
- J/MNRAS/283/367
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The list of the measured galaxies is given in Table 3 together with COSMOS coordinates and apparent magnitude. These parameters (plus diameter, axis ratio and position angle) were used to perform cross-identification with the PGC/LEDA objects after reduction to the RC3 system (de Vaucouleurs et al., 1990, see cat. <VII/155>). Both cross correlation results (from `rvsao') and emission line results (from `emsao') are presented. A few galaxies with published redshifts were also observed to derive our external error (see section 3 of the paper).
- ID:
- ivo://CDS.VizieR/J/ApJ/750/168
- Title:
- Redshift survey in the Subaru GTO2deg^2^ field
- Short Name:
- J/ApJ/750/168
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use a dense redshift survey in the foreground of the Subaru GTO2deg^2^ weak-lensing field (centered at 16:04:44+43:11'24 (2000) to assess the completeness and comment on the purity of massive halo identification in the weak-lensing map. The redshift survey (published here) includes 4541 galaxies; 4405 are new redshifts measured with the Hectospec on the MMT. Among the weak-lensing peaks with a signal to noise greater than 4.25, 2/3 correspond to individual massive systems; this result is essentially identical to the Geller et al. (2010ApJ...709..832G) test of the Deep Lens Survey (DLS) field F2. The Subaru map, based on images in substantially better seeing than the DLS, enables detection of less massive halos at fixed redshift as expected. We demonstrate that the procedure adopted by Miyazaki et al. (2002ApJ...580L..97M) for removing some contaminated peaks from the weak-lensing map improves agreement between the lensing map and the redshift survey in the identification of candidate massive systems.
