J/A+A/575/A48 Alignment of galaxies in galaxy clusters (Sifon+, 2015)
Constraints on the alignment of galaxies in galaxy clusters from
∼14000 spectroscopic members.
Sifon C., Hoekstra H., Cacciato M., Viola M., Koehlinger F.,
Van Der Burg R.F.J., Sand D.J., Graham M.L.
<Astron. Astrophys., 575, A48-48 (2015)>
=2015A&A...575A..48S 2015A&A...575A..48S
ADC_Keywords: Clusters, galaxy ; Velocity dispersion
Keywords: galaxies: clusters: general - galaxies: interactions -
gravitational lensing: weak - cosmology: observations
Abstract:
Torques acting on galaxies lead to physical alignments, but the
resulting ellipticity correlations are difficult to predict. As they
constitute a major contaminant for cosmic shear studies, it is
important to constrain the intrinsic alignment signal observationally.
We measured the alignments of satellite galaxies within 90 massive
galaxy clusters in the redshift range 0.05<z<0.55 and quantified their
impact on the cosmic shear signal. We combined a sample of 38104
galaxies with spectroscopic redshifts with high-quality data from the
Canada-France-Hawaii Telescope. We used phase-space information to
select 14576 cluster members, 14250 of which have shape measurements
and measured three different types of alignment: the radial alignment
of satellite galaxies toward the brightest cluster galaxies (BCGs),
the common orientations of satellite galaxies and BCGs, and the radial
alignments of satellites with each other. Residual systematic effects
are much smaller than the statistical uncertainties. We detect no
galaxy alignment of any kind out to at least 3r200. The signal is
consistent with zero for both blue and red galaxies, bright and faint
ones, and also for subsamples of clusters based on redshift, dynamical
mass, and dynamical state. These conclusions are unchanged if we
expand the sample with bright cluster members from the red sequence.
We augment our constraints with those from the literature to estimate
the importance of the intrinsic alignments of satellites compared to
those of central galaxies, for which the alignments are described by
the linear alignment model. Comparison of the alignment signals to the
expected uncertainties of current surveys such as the Kilo-Degree
Survey suggests that the linear alignment model is an adequate
treatment of intrinsic alignments, but it is not clear whether this
will be the case for larger surveys.
Description:
The cluster sample is drawn from two large, nonoverlapping X-ray
selected cluster surveys carried out with the Canada-France-Hawaii
Telescope (CFHT), namely the Multi-Epoch Nearby Cluster Survey
(MENeaCS; Sand et al., 2012ApJ...746..163S 2012ApJ...746..163S) and the Canadian Cluster
Comparison Project (CCCP; Hoekstra et al., 2012MNRAS.427.1298H 2012MNRAS.427.1298H).
MENeaCS performed multi-epoch observations of 57 clusters in the
redshift range 0.05<z<0.15, aimed at measuring the supernova Ia rate
in these clusters. For this, clusters were observed using the g and r
bands with MegaCam. CCCP was designed to study the scaling relations
between different tracers of mass in galaxy clusters, and includes 50
clusters in the redshift range 0.15<z<0.55. Of these, 20 clusters
had archival B- and R-band data taken with the CFH12k camera, and 30
clusters were observed with the g and r bands with MegaCam (Hoekstra,
2007MNRAS.379..317H 2007MNRAS.379..317H; Hoekstra et al., 2012MNRAS.427.1298H 2012MNRAS.427.1298H).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 95 90 Cluster sample, redshifts, and velocity dispersions
refs.dat 80 33 References
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 17 A17 --- Cluster Cluster name
18 A1 --- n_Cluster [c] c: Spectroscopic members extend out to
less than 0.8*r200
20- 25 F6.4 --- z [0.04/0.55] Redshift
27- 30 I4 --- Nmem Number of members out to arbitrary radius
32- 34 I3 --- N200 Number of members within r200
36- 39 I4 km/s sig200 Velocity dispersion of members within r200
41- 43 I3 km/s e_sig200 rms uncertainty on sig200
45- 48 F4.1 10+14Msun M200 Total mass within r200
50- 52 F3.1 10+14Msun e_M200 rms uncertainty on M200
54- 57 F4.2 Mpc r200 Cluster radius r200
59- 62 F4.2 Mpc e_r200 rms uncertainty on r200
64 A1 --- l_S.DS Limit flag on S.DS
65- 68 F4.2 --- S.DS [0/1] Significance level of the DS test (3)
69 A1 --- --- [+]
70- 73 F4.2 --- E_S.DS [0/0.33]? Error on S.DS (upper value)
74 A1 --- --- [-]
75- 78 F4.2 --- e_S.DS [0/0.26]? Error on S.DS (lower value)
80 A1 --- --- [(]
81 A1 --- Cl [DRI] Cluster classification (1)
82 A1 --- --- [)]
84- 89 A6 --- Ref1 Main sources (2)
91- 95 A5 --- Ref2 Catalogs extracted from NED that contribute
significantly to each cluster, in refs.dat
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Note (1): Cluster classification as follows:
D = disturbed
R = relaxed
I = intermediate
Note (2): Main sources as follows:
1 = WLTV, Crawford et al., 2011, Cat. J/ApJ/741/98
2 = CNOC, Yee et al., 1996ApJS..102..269Y 1996ApJS..102..269Y, 1998, Cat. J/ApJS/116/211;
Ellingson et al., 1997, Cat. J/ApJS/113/1;
Abraham et al., 1998, J/ApJS/116/231
3 = SDSS, DR10, Ahn et al. 2014ApJS..211...17A 2014ApJS..211...17A
4 = HeCS, Rines et al., 2013, Cat. J/ApJ/767/15
5 = MENeaCS-spec, Rines et al., 2013, Cat. J/ApJ/767/15
Note (3): Significance SΔ of tje Dressler-Shectman test
(1988AJ.....95..985D 1988AJ.....95..985D) which gives a measure of substructures.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference number
4- 22 A19 --- BibCode BibCode
24- 49 A26 --- Aut Author's name
50- 80 A31 --- Com Comments
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 21-Apr-2015