J/A+A/557/A62 Spectroscopy in Abell 3921 (Pranger+, 2013)
The galaxy population of the complex cluster system Abell 3921.
Pranger F., Boehm A., Ferrari C., Diaferio A., Hunstead R., Maurogordato S.,
Benoist C., Brinchmann J., Schindler S.
<Astron. Astrophys. 557, A62 (2013)>
=2013A&A...557A..62P 2013A&A...557A..62P
ADC_Keywords: Galaxies, spectra ; Clusters, galaxy ; Redshifts
Keywords: galaxies: clusters: general -
galaxies: clusters: individual: Abell 3921 -
galaxies: distances and redshifts - galaxies: evolution -
cosmology: observations
Abstract:
We present a spectrophotometric analysis of the galaxy population in
the area of the merging cluster Abell 3921 at z=0.093.
We investigate the impact of the complex cluster environment on galaxy
properties such as morphology or star formation rate.
We combine multi-object spectroscopy from the Two Degree Field (2dF)
spectrograph with optical imaging taken with the ESO Wide Field
Imager. We carry out a redshift analysis and determine cluster
velocity dispersions using biweight statistics. Applying a
Dressler-Shectman test we seek evidence for cluster substructure.
Cluster and field galaxies are investigated with respect to [OII] and
Hα equivalent width, star formation rate and morphological
descriptors such as concentration index and Gini coefficient. We study
these cluster galaxy properties as a function of clustercentric
distance and investigate the spatial distribution of various galaxy
types.
Applying the Dressler-Shectman test we find a third component
(A3921-C) in addition to the two main subclusters (A3921-A and
A3921-B) already known. The re-determined mass ratio between the main
components A and B is ∼2:1. Similar to previous studies of galaxy
clusters, we find that a large fraction of the disk galaxies close to
the cluster core show no detectable star formation. These are likely
systems that are quenched due to ram pressure stripping.
Interestingly, we also find quenched spirals at rather large distances
of 3-4Mpc from the cluster core.
Description:
Multifibre spectroscopical service observations in the central
2x2deg2 of A3921 were carried out using the Two Degree Field (2dF)
system on the AAT (Anglo-Australian Telescope).
We used the 400 fibre positioner and double spectrograph system of 2dF
to perform two sets of observations both centred at
RA=22:49:45.84, DE=-64:22:16.32.
We used the same 2dF grating (i.e. 300B) in the two available
spectrographs of 2dF and we adopted a central wavelength of 6000Å.
Our observations thus gave 200 spectra per observing run and
spectrograph with a spectral resolution of 8-9Å and covered the
approximate wavelength range 3800-8200Å. Two runs of observations
were carried out in October 2004 and November 2004 with a total
exposure time of 3600 seconds per run.
Table 5 includes observing run, ccd number, target number, coordinates
(J2000), redshifts, redshift errors and a redshift quality flag for
all 523 galaxies observed with the 2dF device at the AAO in September
and November 2004. The combination of observing run, ccd number and
target number is unique for each galaxy and can be used to identify
the associated spectra (spectra FITS-file names are encoded as
"Obs"_ccd"ccd number"."target number".fits, e.g. Nov04_ccd1.001.fits).
The total number of spectra is 658 (including double observations and
stars).
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table5.dat 51 523 Galaxies of Abell 3921 observations
table5.fits 2880 14 FITS version of table5
list.dat 60 658 Summary of fits files (spectra)
fits/* . 658 Individual reduced spectra in FITS format
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See also:
J/MNRAS/366/645 : LARCS. 11 X-ray luminous clusters (Pimbblet+, 2006)
J/A+A/430/19 : VRI photometry of Abell 3921 galaxies (Ferrari+, 2005)
Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Obs Observing run (Sep04 or Nov04)
7 I1 --- CCD [1/2] CCD number
9- 11 I03 --- Targ [1/200] Target number
13- 14 I2 h RAh Hour of right ascension (J2000)
16- 17 I2 min RAm Minute of right ascension (J2000)
19- 23 F5.2 s RAs Second of right ascension (J2000)
25 A1 --- DE- Sign of declination (J2000)
26- 27 I2 deg DEd Degree of declination (J2000)
29- 30 I2 arcmin DEm Arcminute of declination (J2000)
32- 35 F4.1 arcsec DEs Arcsecond of declination (J2000)
37- 42 F6.4 --- zbest [0.01/0.62] Redshift
44- 49 F6.4 --- e_zbest Redsfhit error
51 I1 --- q_zbest [0/2] Reddhift quality, 0=good (1)
--------------------------------------------------------------------------------
Note (1): Flag as follows:
0 = very good redshift determination
1 = uncertain
2 = bad redshift determination
--------------------------------------------------------------------------------
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- Obs Observing run (Sep04 or Nov04)
7 I1 --- CCD [1/2] CCD number
9- 11 I03 --- Targ [1/200] Target number
13- 19 F7.2 0.1nm lam0 [3600/3900] Wavelength lower limit (Å)
21- 27 F7.2 0.1nm lam1 [8000/8300] Wavelength upper limit (Å)
29- 35 F7.5 0.1nm Dlam [4.31/4.32] Wavelength step (Å)
37- 40 I4 --- Nx Number of pixels along X-axis (λ)
42- 60 A19 --- FileName Name of FITS file in subdirectory fits
--------------------------------------------------------------------------------
Acknowledgements:
Florian Pranger <florian.pranger( at )uibk.ac.at>,
Institute of Astro and Particle Physics
(End) Florian Pranger [UIBK], Emmanuelle Perret [CDS] 22-Jul-2013