J/A+A/490/945 Redshifts of galaxies in 23 EIS fields (Grove+, 2008)
Multi-object spectroscopy of low redshift EIS clusters.
IV. Reliability of matched-filter results at z∼0.3-0.4
Grove L.F., da Costa L., Benoist C.
<Astron. Astrophys. 490, 945 (2008)>
=2008A&A...490..945G 2008A&A...490..945G
ADC_Keywords: Clusters, galaxy ; Galaxies, photometry ; Redshifts
Keywords: galaxies: clusters: general - cosmology: observations -
galaxies: distances and redshifts - galaxies: photometry
Abstract:
We have carried out a spectroscopic survey of low-redshift galaxy
systems identified by the matched-filter technique in a moderately
deep I-band survey. We present new redshifts for 747 galaxies in 23
ESO Imaging Survey (EIS) cluster fields. We use the "gap"-technique
to search for significant overdensities in redshift space for
identifying groups/clusters of galaxies corresponding to the original
EIS matched-filter cluster candidates.
In this way we spectroscopically confirm systems in 10 of the 23
cluster candidate fields with a matched-filter estimated redshift
zMF=0.3-0.4 and with spectroscopic redshifts in the range from
z=0.158 to z=0.534, with the observations favouring the confirmation
of systems at the lower redshift end. After careful analysis of the
redshift distribution, one system was split into two very close clumps
in redshift space. We find that the systems identified in the present
paper span a broad range of velocity dispersion and richness. The
measured one-dimensional velocity dispersion range from 175km/s to
497km/s, consistent with the values obtained in previous papers using
much larger samples for systems over the same redshift range. Both
undersampling and contamination by substructures contribute to the
uncertainty of these measurements. The richness range corresponds to
clusters with an estimated total luminosity in the range
12L*-65L*, but these estimates are very uncertain as are their
relation to the velocity dispersion (mass) of the systems. From the
analysis of the colours of the galaxy populations we find that ∼60% of
the spectroscopically confirmed systems have a "significant" red
sequence. We find that the colour of the red sequence galaxies matches
passive stellar evolution predictions. With this paper we complete our
spectroscopic survey of the fields of 58 EIS cluster candidates with
estimated redshifts z≤0.4 (see also Hansen et al., 2002, Cat.
J/A+A/388/1; Olsen et al., 2003, Cat. J/A+A/409/439, Olsen et al.,
2005, Cat. J/A+A/435/781). We have measured a total of 1954 galaxy
redshifts in the range z=0.0065 to z=0.6706. Of the 58 systems we
confirm 42 (∼75%) with redshifts between z=0.095 and z=0.534.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 42 747 List of galaxy redshifts
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See also:
J/A+A/388/1 : Redshifts of five EIS clusters (Hansen+, 2002)
J/A+A/409/439 : Redshifts of 11 EIS clusters (Olsen+, 2003)
J/A+A/435/781 : Redshifts of galaxies in 21 EIS cluster fields (Olsen+, 2005)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq [1/747] Sequential number
5- 14 F10.6 deg RAdeg Right ascension in decimal degrees (J2000)
17- 26 F10.6 deg DEdeg Declination in decimal degrees (J2000)
29- 33 F5.2 mag Imag EIS I magnitude
36- 41 F6.4 --- z Measured spectroscopic redshift
42 A1 --- n_z [e:] emission lines, or uncertain measurement (1)
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Note (1):
e = emission line(s) identified
: = uncertain measurement, where no features could be identified
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Acknowledgements:
Lisbeth Fogh Grove, lisbeth(at)dark-cosmology.dk
(End) L. Fogh Grove [Dark Cosmology Centre], P. Vannier [CDS] 30-Sep-2008