J/ApJ/728/27 Chandra and AAOmega observations of Abell 2744 (Owers+, 2011)
The dissection of Abell 2744: a rich cluster growing through major and
minor mergers.
Owers M.S., Randall S.W., Nulsen P.E.J., Couch W.J., David L.P.,
Kempner J.C.
<Astrophys. J., 728, 27 (2011)>
=2011ApJ...728...27O 2011ApJ...728...27O
ADC_Keywords: Clusters, galaxy ; Redshifts ; Spectroscopy ; Galaxies, optical
Keywords: galaxies: clusters: individual (Abell 2744) -
X-rays: galaxies: clusters
Abstract:
New Chandra X-ray data and extensive optical spectroscopy, obtained
with AAOmega on the 3.9m Anglo-Australian Telescope, are used to study
the complex merger taking place in the galaxy cluster Abell 2744.
Combining our spectra with data from the literature provides a catalog
of 1237 redshifts for extragalactic objects lying within 15' of the
cluster center. From these, we confirm 343 cluster members projected
within 3Mpc of the cluster center. Combining positions and velocities,
we identify two major substructures, corresponding to the remnants of
two major subclusters. The new data are consistent with a
post-core-passage, major merger taking place along an axis that is
tilted well out of the plane of the sky, together with an interloping
minor merger. Supporting this interpretation, the new X-ray data
reveal enriched, low entropy gas from the core of the approaching,
major subcluster, lying ∼2' north of the cluster center, and a shock
front to the southeast of the previously known bright, compact core
associated with the receding subcluster. The X-ray morphology of the
compact core is consistent with a Bullet-like cluster viewed from
within ∼45° of the merger axis. An X-ray peak ∼3' northwest of the
cluster center, with an associated cold front to the northeast and a
trail of low entropy gas to the south, is interpreted as the remnant
of an interloping minor merger taking place roughly in the plane of
the sky. We infer approximate paths for the three merging components.
Description:
Abell 2744 has been observed with Chandra using both the ACIS-I and
ACIS-S chip arrays in 2001 Sep 3 (obsID 2212), 2007 Sep 10 (obsID
7712), 2006 Nov 8 (obsID 7915), 2007 Jun 10 (obsID 8477) and 2007 Jun
14 (obsID 8557).
The primary photometric catalog used for selection of the galaxies
targeted for spectroscopic observations was drawn from the Supercosmos
Sky Survey (SSS) server. Observations were taken during the nights of
2006 September 12-18 using the AAOmega MOS on the Anglo-Australian
Telescope (AAT). During our observations, we used the
medium-resolution (R∼1300) 580V (blue arm) and 385R (red arm) gratings
which provide a wavelength coverage of 3700-8800Å and spectral
resolutions of 3.5Å and 5.3Å at 4800Å and 7250Å, respectively.
343 bona fide cluster members remain from which we determine a cluster
redshift of zclus=0.3064±0.0004 and a velocity dispersion of
σclus=1497±57km/s. See section 3.1.6 for further details.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table5.dat 70 1509 Combined redshift catalog
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2012)
J/A+A/500/947 : Spectroscopy and photometry in A2744 & A2537 (Braglia+, 2009)
J/A+A/449/461 : Radial velocities in A2744 (Boschin+, 2006)
J/ApJS/142/153 : Distant galaxy clusters photometry (Stanford+, 2002)
J/ApJ/497/188 : A103, A118 and A114 morphological studies (Couch+ 1998)
http://www-wfau.roe.ac.uk/sss/ : SuperCOSMOS Sky Surveys home page
Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 8 F8.6 deg RAdeg Right Ascention in decimal degrees (J2000)
10- 19 F10.6 deg DEdeg Declination in decimal degrees (J2000)
21- 25 F5.2 mag rmag [16.51/22.99] The rF band magnitude
27- 36 F10.2 km/s cz Redshift
38- 44 F7.2 km/s e_cz Uncertainty in cz
46 I1 --- q_cz [3/6] Quality of cz (1)
48- 70 A23 --- r_cz Source of cz (2)
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Note (1): The quality of the assigned redshift was determined by visual
inspection and an integer value classification, Q, was assigned, where
Q ranges from 1 to 6, using the same scheme adopted for the 2dFGRS, as
described in Owers et al. (2009ApJ...693..901O 2009ApJ...693..901O, 2009ApJ...692..702O 2009ApJ...692..702O).
Briefly, objects with Q≤2 are assigned no redshift or an unreliable
redshift, objects with Q=3, 4, or 5 have reliable redshifts (with Q=5
having a template-like quality spectrum) and objects with Q=6 are
stars or non-extragalactic objects. Redshifts obtained from the
literature are assigned a redshift quality of 3.
Note (2): Source of cz as follows:
AAT/AAOmega = this paper (Anglo-Australian Telescope)
Archival AAT/2dF = archives
Boschin et al. (2006) = Cat. J/A+A/449/461
Braglia et al. (2009) = Cat. J/A+A/500/947
Couch & Sharples (1987) = 1987MNRAS.229..423C 1987MNRAS.229..423C
Couch et al. (1998) = Cat. J/ApJ/497/188
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Nomenclature note:
Objects are <[ORN2011] DDD.dddddd+DD.dddddd> in Simbad.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 03-Sep-2012