J/A+A/430/19 VRI photometry of Abell 3921 galaxies (Ferrari+, 2005)
Dynamical state and star formation properties of the merging galaxy cluster
Abell 3921.
Ferrari C., Benoist C., Maurogordato S., Cappi A., Slezak E.
<Astron. Astrophys. 430, 19 (2005)>
=2005A&A...430...19F 2005A&A...430...19F
ADC_Keywords: Clusters, galaxy ; Redshifts ; Photometry, VRI ; Equivalent widths
Keywords: galaxies: clusters: general -
galaxies: clusters: individual: Abell 3921 -
galaxies: distances and redshifts - cosmology: observations
Abstract:
We present the analysis and results of a new VRI photometric and
spectroscopic survey of the central ∼1.8x1.2Mpc2 region of the
galaxy cluster A3921 (z=0.094). We detect the presence of two dominant
clumps of galaxies with a mass ratio of ∼5: a main cluster centred on
the Brightest Cluster Galaxy (BCG) (A3921-A), and an NW sub-cluster
(A3921-B) hosting the second brightest cluster galaxy. The distorted
morphology of the two sub-clusters suggests that they are interacting,
while the velocity distribution of 104 confirmed cluster members does
not reveal strong signatures of merging.
Description:
The optical observations of Abell 3921 were carried out using the Wide
Field Imager (WFI) mounted at the Cassegrain focus of the MPG/ESO 2.2m
telescope at La Silla observatory. The data, including photometric
calibration images, were obtained between August 20th and 23rd, 2001.
Positions, V, R, I-band magnitudes (AB magnitude system), radial
velocity measurements, and equivalent widths of [OII]3727Å and
Hδ lines of 239 objects in the central region of the galaxy
cluster Abell 3921 are presented.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea.dat 86 239 Radial velocities and spectral lines for
239 galaxies in A3921
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Byte-by-byte Description of file: tablea.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Identification number
5- 6 I2 h RAh Right ascension (J2000.0)
8- 9 I2 min RAm Right ascension (J2000.0)
11- 15 F5.2 s RAs Right ascension (J2000.0)
17 A1 --- DE- Declination sign (J2000.0)
18- 19 I2 deg DEd Declination (J2000.0)
21- 22 I2 arcmin DEm Declination (J2000.0)
24- 28 F5.2 arcsec DEs Declination (J2000.0)
30- 34 F5.2 --- VmagAB V-band magnitude (AB system)
36- 40 F5.2 --- RmagAB R-band magnitude (AB system)
42- 46 F5.2 --- ImagAB I-band magnitude (AB system)
48- 55 F8.1 km/s cz ?=999999.9 Radial velocity
57- 61 F5.1 km/s e_cz ?=999.9 Error on radial velocity
62 A1 --- n_cz [*f] Note when no redshift value (1)
64- 67 I4 --- Run Year of observation
69 I1 --- q_cz Quality flag for redshift determination (2)
71- 75 F5.1 0.1nm EW([OII]) Equivalent width [OII] (3)
77- 81 F5.1 0.1nm EW(Hdelta) Equivalent width Hdelta (3)
83- 86 A4 --- MType Type of galaxy (4)
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Note (1): When no value of redshift, this column contains:
* = star
f = failed spectrum, no idea of the redshift
Note (2): We have classified the quality of the spectra in the following way:
1 = good determination (R≥3),
2 = uncertain determination,
3 = very poor determination and failed spectra
Note (3): Equivalent-widths have been measured only for spectra with
good redshift determination (quality flag = 1). Positive (negative)
equivalent widths correspond to lines detected in absorption
(emission).
Note (4): Galaxy types are coded as follows:
k = Spectrum resembling a K-star spectrum
k+a = Spectrum presenting an intermediate Hδ line in
absorption, with no detectable [OII] line in emission
k+a? = Candidate k+a galaxy
e(a) = Emission-line galaxy, with strong Hδ absorption and
measurable [OII] emission
e(b) = Starburst galaxy with very strong [OII] emission
e(c) = Spiral forming stars at a constant rate, with weak Balmer
absorption and weak to moderate [OII] emission
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Acknowledgements: Chiara Ferrari, Chiara.Ferrari(at)uibk.ac.at
(End) Patricia Vannier [CDS] 13-Jan-2005