Spectroscopy of clusters in the ESO distant cluster survey (EDisCS). II. Redshifts, velocity dispersions, and substructure for clusters in the last 15 fields. (2008)
Keywords :
galaxies clusters: general - galaxies: distances and redshifts - galaxies: evolution
Abstract:We present spectroscopic observations of galaxies in 15 survey fields as part of the ESO Distant Cluster Survey (EDisCS). We determine the redshifts and velocity dispersions of the galaxy clusters located in these fields, and we test for possible substructure in the clusters. We obtained multi-object mask spectroscopy using the FORS2 instrument at the VLT. We reduced the data with particular attention to the sky subtraction. We implemented the method of Kelson for performing sky subtraction prior to any rebinning/interpolation of the data. From the measured galaxy redshifts, we determine cluster velocity dispersions using the biweight estimator and test for possible substructure in the
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Spectroscopic observations obtained using VLT/FORS2 are presented for
objects in 14 survey fields of the ESO Distant Cluster Survey
(EDisCS).
The fields contain galaxy clusters at z=0.40-0.96. The objects in the
catalogues are either galaxies (which can be cluster members or fields
galaxies), foreground stars, or objects for which no redshift could be
determined.
For a 15th field (1122.9-1136) which is part of the paper, no data are
published, since very little data was obtained.
We present tables of RA and DE positions for an equinox of 2000
(J2000, epoch 2001), I-band magnitudes for an aperture of radius 1",
spectroscopic redshifts for objects in the 14 fields, and cluster
membership and targeting flags to indicate whether the object is a
cluster member and/or was targeted to be a cluster member
respectively.
The 'main' table contains one entry per unique object, and this is the
table people normally should use. The 'supp' table contains possible
extra redshifts obtained. If an object was observed N times, the best
redshift (decided from a number of rules) is put in 'main' and the
remaining N-1 redshifts are put in 'supp'.
Cl 1238.5-1144 has no data in supp.dat file.
The data tables have been prepared so that they can be read both using
tools that expect data columns separated by white space (e.g. the UNIX
tool awk) and tools that expect things to be at fixed character/byte
locations in the file (e.g. the UNIX tool cut).
The contents of the data tables are fully described in Sect. 4.3 of
the paper (including the sample data in Table 4 in the paper). Some of
the salient features are repeated as Notes.
Finally, note that spectroscopic observations for 5 other EDisCS
fields (1040.7-1155, 1054.4-1146, 1054.7-1245, 1216.8-1201 and
1232.5-1250 ) were presented in a previous paper (Halliday et al.,
2004, Cat. J/A+A/427/397) but note that the format of the published
data tables for that paper is not fully identical to the format used
for this paper.
Bo Milvang-Jensen, milvang(at)astro.ku.dk
