J/AJ/123/1807 SDSS galaxy clusters redshifts (Goto+, 2002)
The cut-and-enhance method: selecting clusters of galaxies from the
Sloan Digital Sky Survey commissioning data.
Goto T., Sekiguchi M., Nichol R.C., Bahcall N.A., Kim R.S.J., Annis J.,
Ivezic Z., Brinkmann J., Hennessy G.S., Szokoly G.P., Tucker D.L.
<Astron. J. 123, 1807 (2002)>
=2002AJ....123.1807G 2002AJ....123.1807G
ADC_Keywords: Clusters, galaxy ; Redshifts
Keywords: galaxies: clusters: general - methods: analytical
Abstract:
We describe an automated method, the cut-and-enhance (CE) method, for
detecting clusters of galaxies in multicolor optical imaging surveys.
This method uses simple color cuts, combined with a density
enhancement algorithm, to up-weight pairs of galaxies that are close
in both angular separation and color. The method is semiparametric,
since it uses minimal assumptions about cluster properties in order to
minimize possible biases. No assumptions are made about the shape of
clusters, their radial profile, or their luminosity function. The
method is successful in finding systems ranging from poor to rich
clusters of galaxies, of both regular and irregular shape. We
determine the selection function of the CE method via extensive Monte
Carlo simulations that use both the real, observed background of
galaxies and a randomized background of galaxies. We use
position-shuffled and color-shuffled data to perform false-positive
tests. We have also visually checked all the clusters detected by the
CE method. We apply the CE method to the 350°2 of the Sloan
Digital Sky Survey (SDSS) commissioning data, taken in 1998 September
and 1999 March, and construct an SDSS CE galaxy cluster catalog with
an estimated redshift and richness for each cluster. The CE method is
compared with other cluster selection methods used on SDSS data such
as the matched filter, "maxBCG," and Voronoi tessellation techniques.
The CE method can be adopted for cluster selection in any multicolor
imaging survey.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
v4-7526.dat 54 2770 SDSS Cut & Enhance Galaxy cluster catalog,
145.1°< RA<236°, |b|<1.25°
v4-94125.dat 54 1868 SDSS Cut & Enhance Galaxy cluster catalog,
350.5°<RA<56.51°, |b|<1.25°
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See also:
http://www.sdss.org : Sloan Digital Sky Survey Home Page
Byte-by-byte Description of file: v4-7526.dat v4-94125.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- 20 F9.6 deg DEdeg Declination, in decimal degrees (J2000)
22- 29 F8.6 deg Rad Radius
31- 33 I3 --- Rich Richness of the cluster (1)
35- 44 F10.6 --- Ngal Number of galaxies fed (2)
46- 54 F9.6 --- z Estimated redshift using maxBCG strategy
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Note (1): the richness is defined here as the number of galaxies inside
the detected cluster radius that lie in the 2 mag range (r* band)
from m3 (the third brightest galaxy) to m3 + 2 (CE richness).
Note (2): Ngal the number of galaxies (within 2.1 Abell radius) input
to a cluster, whose magnitudes are r*<21.5 at the redshift of A1577.
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History:
Copied at http://astrophysics.phys.cmu.edu/~tomo
(End) James Marcout, Patricia Bauer [CDS] 27-May-2002