J/MNRAS/500/310 Properties of brightest cluster galaxies (De Propris+, 2021)
Brightest cluster galaxies: the centre can(not?) hold.
De Propris R., West M.J., Andrade-Santos F., Ragone-Figueroa C., Rasia E.,
Forman W., Jones C., Kipper R., Borgani S., Lambas D.G., Romashkova E.A.,
Patra K.C.
<Mon. Not. R. Astron. Soc., 500, 310-318 (2021)>
=2021MNRAS.500..310D 2021MNRAS.500..310D (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies ; Redshifts ; Velocity dispersion ;
X-ray sources ; Optical
Keywords: galaxies: elliptical and lenticular, cD -
galaxies: kinematics and dynamics
Abstract:
We explore the persistence of the alignment of brightest cluster
galaxies (BCGs) with their local environment. We find that a
significant fraction of BCGs do not coincide with the centroid of the
X-ray gas distribution and/or show peculiar velocities (they are not
at rest with respect to the cluster mean). Despite this, we find that
BCGs are generally aligned with the cluster mass distribution even
when they have significant offsets from the X-ray centre and
significant peculiar velocities. The large offsets are not consistent
with simple theoretical models. To account for these observations BCGs
must undergo mergers preferentially along their major axis, the main
infall direction. Such BCGs may be oscillating within the cluster
potential after having been displaced by mergers or collisions, or the
dark matter halo itself may not yet be relaxed.
Description:
Our first cluster sample is taken from Andrade-Santos et al.
(2017ApJ...843...76A 2017ApJ...843...76A, Cat. J/ApJ/843/76), which consists of 164
clusters in the Planck Early Sunyaev-Zel'dovich sample with z=<0.35
plus a flux-limited X-ray sample of 100 clusters with z=<0.30, with
some overlap. All have Chandra observations obtained as part of the
Chandra-Planck Legacy Program for Massive Clusters of Galaxies
(https://hea-www.harvard.edu/CHANDRA_PLANCK_CLUSTERS), with exposures
that yield at least 10000 source counts. Optical imaging is provided
by data from the Panoramic Survey Telescope and Rapid Response System
(Pan-STARRS) survey (Chambers et al. 2016arXiv161205560C 2016arXiv161205560C) to identify
and measure the properties of BCGs. We choose the BCG as the brightest
galaxy from the Pan-STARRS stacked image over a 3Mpc region centred on
the X-ray peak. In general, BCGs have distinctive appearances,
dominant ellipticals often surrounded by extended haloes of diffuse
starlight, so identification is usually unambiguous. In cases of
merging clusters or subclusters, we opted to use only the primary
component in order to focus on the most massive systems. We refer to
this sample as the X-ray-selected cluster sample.
Because BCGs can be offset from the cluster centre in position and/or
velocity space, we compiled a second cluster sample by selecting all
clusters with 50 or more member galaxies based on available velocities
in NED. The sample is heterogeneous but contains mainly Abell clusters
plus some systems from the HeCS survey (Rines et al.
2016ApJ...819...63R 2016ApJ...819...63R, Cat. J/ApJ/819/63, 2018ApJ...862..172R 2018ApJ...862..172R, Cat.
J/ApJ/862/172) not present in the Abell catalogue. This sample
selection does not depend on X-ray emission, providing an independent
check of BCG alignments when the galaxy is not at rest relative to the
gravitational potential (e.g. see Martel et al. 2014ApJ...786...79M 2014ApJ...786...79M).
As we require 50 or more spectroscopic redshifts per cluster, these
are likely to be comparatively massive systems. We refer to this
sample as the velocity-selected cluster sample.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 66 212 Clusters and properties of BCGs
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See also:
J/ApJ/843/76 : Cool-core clusters with Chandra obs. (Andrade-Santos+, 2017)
J/ApJ/819/63 : Hectospec survey of SZ clusters (HeCS-SZ) (Rines+, 2016)
J/ApJ/862/172 : HeCS-red: Hectospec surveys of redMaPPer clusters
(Rines+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Name Cluster name
18- 34 A17 --- OName Alternative name
36- 40 F5.3 --- z Redshift
42- 52 A11 deg PAc Position angle of the cluster major axis
54- 58 F5.1 deg PAbcg Position angle of the brightest cluster galaxy
(BCG) major axis
60- 63 I4 km/s sigma ? Velocity dispersion
65- 66 A2 --- Sel Sample selection (X for X-rays and V for
velocities)
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 18-Sep-2023