J/A+A/583/A124 Ophiuchus r'g'z' photometry and redshifts (Durret+, 2015)
Ophiuchus: an optical view of a very massive cluster of galaxies hidden
behind the Milky Way.
Durret F., Wakamatsu K.-I., Nagayama T., Adami C., Biviano A.
<Astron. Astrophys. 583, A124 (2015)>
=2015A&A...583A.124D 2015A&A...583A.124D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, photometry ; Redshifts
Keywords: galaxies: clusters: individual: Ophiuchus -
galaxies: photometry
Abstract:
The Ophiuchus cluster, at a redshift z=0.0296, is known from X-rays to
be one of the most massive nearby clusters, but due to its very low
Galactic latitude its optical properties have not been investigated in
detail. Aims. We discuss the optical properties of the galaxies in the
Ophiuchus cluster, in particular with the aim of understanding better
its dynamical properties.
We have obtained deep optical imaging in several bands with various
telescopes, and applied a sophisticated method to model and subtract
the contributions of stars in order to measure galaxy magnitudes as
accurately as possible. The colour-magnitude relations obtained show
that there are hardly any blue galaxies in Ophiuchus (at least
brighter than r'≤19.5), and this is confirmed by the fact that we
only detect two galaxies in Hα. We also obtained a number of
spectra with ESO-FORS2, that we combined with previously available
redshifts. Altogether, we have 152 galaxies with spectroscopic
redshifts in the 0.02≤z≤0.04 range, and 89 galaxies with both a
redshift within the cluster redshift range and a measured r' band
magnitude (limited to the Megacam 1x1deg2 field).
Description:
We obtained optical images in various bands with several telescopes,
CFHT/Megacam, VLT/FORS2 and SOAR/SOI.
Good quality measurements were achieved for 162 galaxies in the g',
r', and z' bands respectively. In the region covered by Megacam but
not by FORS2, only r' band magnitudes were measured for the galaxies
with spectroscopic redshifts.
Redshifts of bright galaxies were obtained covering a very large area
on the sky with the AAO 6dF, CTIO 1.5m and Lick 3m telescopes
(Wakamatsu et al., 2005, ASP Conf. Ser., 329, 189), and are listed in
Table A.3. We also obtained spectroscopic data with the ESO VLT/UT1
telescope using FORS2 in two adjacent fields covering the very central
region of the cluster, for a total exposure time of 1500s. Spectra
were obtained for 55 objects, out of which 54 gave reliable redshifts.
We built a spectroscopic redshift catalogue by combining the Wakamatsu
et al. (2005, ASP Conf. Ser., 329, 189) measurements and our FORS2
measurements, and adding redshifts available in NED for galaxies
which were not in the two previous catalogues.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 103 162 Photometric catalogue in the r', g' and z' bands
in the central region covered by the
FORS2 z' band image
tablea2.dat 75 65 r band photometric catalogue for the objects
with a measured spectroscopic redshift but
outside the VLT/FORS2 area
tablea3.dat 59 152 Spectroscopic redshift catalogue
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Running number
4 A1 --- n_Seq [*] *: have a spectroscopic redshift given
in tablea3.dat
6- 8 A3 --- --- [OPH]
10- 26 A17 --- OPH Object OPH name (JHHMMSS.ss+DDMMSS)
29- 37 F9.5 deg RAdeg Right ascension (J2000.0)
39- 47 F9.5 deg DEdeg Declination (J2000.0)
49- 54 F6.3 mag r'mag r' band magnitude
55- 56 A2 --- u_r'mag [: ] Uncertainty flag on r'mag (1)
58- 63 F6.3 mag g'mag ? g' band magnitude
64- 65 A2 --- u_g'mag [: ] Uncertainty flag on g'mag (1)
67- 72 F6.3 mag z'mag ? z' band magnitude
73- 74 A2 --- u_z'mag [: ] Uncertainty flag on z'mag
76 I1 --- Qual [1/3]? Quality of the galaxy classification (2)
78 A1 --- Code [1/3]? poor photometric condition code (3)
80-105 A26 --- Notes Other identifications and comments
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Note (1): Uncertainty flag as follows:
: = a relatively large uncertainty
:: = a large uncertainty
Note (2): Quality flag as follows:
1 = almost definitely a galaxy
2 = probably a galaxy
3 = possibly a galaxy
when the object is certainly a galaxy, there is no indication in this column
Note (3): Poor photometric condition around object, e.g., bright stars or
diffraction on the spider, are expressed as 1, 2, and 3.
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Seq Running number
4- 6 A3 --- --- [OPH]
8- 24 A17 --- OPH Object OPH name (JHHMMSS.ss+DDMMSS)
26- 34 F9.5 deg RAdeg Right ascension (J2000.0)
36- 44 F9.5 deg DEdeg Declination (J2000.0)
46- 51 F6.3 mag r'mag r' band magnitude
53- 75 A23 --- OName Other identification
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Running number
4 A1 --- n_Seq [*] *: photometric data are given in
tablea1.dat (VLT/FORS2 area) and
tablea2.dat (outside the VLT/FORS2 area)
6- 28 A23 --- Name Object name
30- 35 F6.4 --- zsp Spectroscopic redshift
37 I1 --- r_zsp [1/3] Reference to the origin of the redshift (1)
39- 41 A3 --- --- [OPH]
43- 59 A17 --- OPH Object OPH name (JHHMMSS.ss+DDMMSS)
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Note (1): Redshift reference as follows:
1 = our FORS2 data
2 = our 6df, CTIO 1.5m, and Lick 3m data
(Wakamatsu et al., 2005, ASP Conf. Ser., 329, 189)
3 = NED
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Acknowledgements:
Florence Durret, durret(at)iap.fr
(End) Patricia Vannier [CDS] 07-Sep-2015