J/ApJ/470/724 Abell 576 galaxies magnitude and velocities (Mohr+ 1996)
An optical and X-ray study of Abell 576, a galaxy cluster with a cold core.
Mohr J.J., Geller M.J., Fabricant D.G., Wegner G., Thorstensen J.,
Richstone D.O.
<Astrophys. J. 470, 724 (1996)>
=1996ApJ...470..724M 1996ApJ...470..724M (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Magnitudes ; Spectroscopy
Keywords: galaxies: clusters: individual (A576) -
galaxies: distances and redshifts -
galaxies: luminosity function, mass function - galaxies: photometry -
X-rays: galaxies
Abstract:
We analyse the galaxy population and dynamics of the galaxy cluster
A576; the observational constraints include 281 redshifts (230 new),
R-band CCD galaxy photometry over a 2h-1Mpcx2h-1Mpc region
centered on the cluster, an Einstein IPC X-ray image, and an Einstein
MPC X-ray spectrum. We focus on an 86% complete magnitude-limited
sample (R23.5<17) of 169 cluster galaxies. The cluster galaxies with
emission lines in their spectra have a larger velocity dispersion and
are significantly less clustered on this 2h-1Mpc scale than galaxies
without emission lines. We show that excluding the emission-line
galaxies from the cluster sample decreases the velocity dispersion by
18% and the virial mass estimate by a factor of 2. The central cluster
region contains a non-emission galaxy population and an intracluster
medium which is significantly cooler
(σcore=387+250-105km/s and TX=1.6-0.3/+0.4keV at 90%
confidence) than the global populations (σ=977+124-96km/s
for the non-emission population and TX>4keV at 90% confidence).
Because (1) the low-dispersion galaxy population is no more luminous
than the global population and (2) the evidence for a cooling flow is
weak, we suggest that the core of A576 may contain the remnants of a
lower mass subcluster. We examine the cluster mass, baryon fraction,
and luminosity function. The cluster virial mass varies significantly
depending on the galaxy sample used. Consistency between the
hydrostatic and virial estimators can be achieved if (1) the gas
temperature at r∼1h-1Mpc is TX∼8keV (the best-fit value) and
(2) several velocity outliers are excluded from the virial calculation.
Although the best-fit Schechter function parameters and the ratio of
galaxy to gas mass in A576 are typical of other clusters, the baryon
fraction is relatively low. Using the consistent cluster binding mass,
we show that the gas mass fraction is ∼3h-3/2% and the baryon
fraction is ∼4%.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 53 281 Galaxy velocities and photometry
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1 I1 h RAh [7] Right ascension (1950)
3- 4 I2 min RAm Right ascension (1950)
6- 10 F5.2 s RAs Right ascension (1950)
12 A1 --- DE- Declination sign
13- 14 I2 deg DEd [55/56] Declination (1950)
16- 17 I2 arcmin DEm Declination (1950)
19- 22 F4.1 arcsec DEs Declination (1950)
24- 28 F5.2 mag R23.5 Isophotal R=23.5mag/arcsec2 magnitude
29 A1 --- n_R23.5 Note on R23.5 (1)
31- 35 F5.3 mag e_R23.5 rms uncertainty on R23.5
37- 41 I5 km/s Vel Line-of-sight velocity
42 A1 --- n_Vel Note on velocity (1)
44- 46 I3 km/s e_Vel rms uncertainty on Vel
48 A1 --- Type [NE] E: emission; N: non-emission
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Note (1): #: POSS digitized scan photometry
+: Hintzen et al., 1982AJ.....87.1656H 1982AJ.....87.1656H
*: Marzke & Huchra 1996, in prep.
x: Hill et al., 1980ApJ...242L..69H 1980ApJ...242L..69H
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History: Prepared via OCR at CDS.
* 30-Sep-1998: 4 OCR errors detected by H. Andernach and corrected
()
(End) James Marcout, Patricia Bauer [CDS] 30-Sep-1997