J/MNRAS/380/1608 LRG catalog (Lopes+, 2007)
Empirical photometric redshifts of luminous red galaxies and clusters in the
Sloan Digital Sky Survey.
Lopes P.A.A.
<Mon. Not. R. Astron. Soc., 380, 1608-1620 (2007)>
=2007MNRAS.380.1608L 2007MNRAS.380.1608L (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxy catalogs ; Redshifts ; Photometry, SDSS
Keywords: surveys - galaxies: clusters: general -
galaxies: distances and redshifts
Abstract:
In this work I discuss the necessary steps for deriving photometric
redshifts for luminous red galaxies (LRGs) and galaxy clusters through
simple empirical methods. The data used are from the Sloan Digital Sky
Survey (SDSS). I show that with three bands only (gri) it is possible
to achieve results as accurate as the ones obtained by other
techniques, generally based on more filters. In particular, the use of
the (g-i) colour helps improving the final redshifts (especially for
clusters), as this colour monotonically increases up to z∼0.8. For
the LRGs I generate a catalogue of ∼1.5 million objects at z<0.70.
The accuracy of this catalogue is sigma=0.027 for z≤0.55 and
sigma=0.049 for 0.55<z≤0.70. The photometric redshift technique
employed for clusters is independent of a cluster selection algorithm.
Thus, it can be applied to systems selected by any method or
wavelength, as long as the proper optical photometry is available.
When comparing the redshift listed in literature to the photometric
estimate, the accuracy achieved for clusters is sigma=0.024 for
z≤0.30 and sigma=0.037 for 0.30<z≤0.55. However, when considering the
spectroscopic redshift as the mean value of SDSS galaxies on each
cluster region, the accuracy is at the same level as found by other
authors: sigma=0.011 for z≤0.30 and sigma=0.016 for 0.30<z≤0.55. The
photometric redshift relation derived here is applied to thousands of
cluster candidates selected elsewhere. I have also used galaxy
photometric redshifts available in SDSS to identify groups in redshift
space and then compare the redshift peak of the nearest group to each
cluster redshift. This procedure provides an alternative approach for
cluster selection, especially at high redshifts, as the cluster red
sequence may be poorly defined.
Description:
The photometric and spectroscopic data for this paper were taken from
the fifth release of the SDSS.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 140 1459536 The LRG catalog
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See also:
II/276 : The SDSS Photometric Catalog, Release 5 (Adelman-McCarthy+, 2007)
http://www.sdss.org : SDSS Home Page
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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1- 10 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
12- 21 F10.6 deg DEdeg Declination in decimal degrees (J2000)
24- 29 F6.3 mag umag SDSS u magnitude
32- 37 F6.3 mag gmag SDSS g magnitude
40- 45 F6.3 mag rmag SDSS r magnitude
48- 53 F6.3 mag imag SDSS i magnitude
56- 61 F6.3 mag zmag SDSS z magnitude
63- 69 F7.3 mag e_umag ?=-99.000 rms uncertainty on umag
72- 77 F6.3 mag e_gmag rms uncertainty on gmag
81- 85 F5.3 mag e_rmag rms uncertainty on rmag
89- 93 F5.3 mag e_imag rms uncertainty on imag
95-101 F7.3 mag e_zmag ?=-99.000 rms uncertainty on zmag
104-111 F8.5 --- zphot Photometric redshift
113-120 F8.5 --- e_zphot ?=-9.99000 rms uncertainty on zphot
122-139 A18 --- objID SDSS identification number
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 18-Jan-2008