J/MNRAS/427/2047 Formation of cD Galaxies and their Clusters (Tovmassian+ 2012)
On the Formation of cD Galaxies and their Parent Clusters
Tovmassian H.M., Andernach H.
<Mon. Not. R. Astron. Soc. 427, 2047 (2012)>
=2012MNRAS.427.2047T 2012MNRAS.427.2047T
ADC_Keywords: Clusters, galaxy
Keywords: galaxies: clusters -- clusters: general -- galaxies: formation --
galaxies: cD galaxies
Abstract:
In order to study the mechanism of formation of cD galaxies we search
for possible dependencies between the K-band luminosity of cDs and the
parameters of their host clusters which we select to have a dominant
cD galaxy, corresponding to a cluster morphology of Bautz-Morgan
(BM) type I. As a comparison sample we use cD galaxies in clusters
where they are not dominant, which we define here as non-BM I (NBMI)
type clusters. We find that for 71 BM I clusters the absolute K-band
luminosity of cDs depends on the cluster richness, but less strongly on
the cluster velocity dispersion. Meanwhile, for 35 NBMI clusters the
correlation between cD luminosity and cluster richness is weaker, and
is absent between cD luminosity and velocity dispersion. In addition,
we find that the luminosity of the cD galaxy hosted in BM I clusters
tends to increase with the cD's peculiar velocity with respect to the
cluster mean velocity. In contrast, for NBMI clusters the cD luminosity
decreases with increasing peculiar velocity. Also, the X-ray luminosity of
BM I clusters depends on the cluster velocity dispersion, while in NBMI
clusters such a correlation is absent. These findings favour the cannibalism
scenario for the formation of cD galaxies. We suggest that cDs in clusters
of BM I type were formed and evolved preferentially in one and the same
cluster. In contrast, cDs in NBMI type clusters were either originally
formed in clusters that later merged with groups or clusters to form
the current cluster, or are now in the process of merging.
Description:
For 128 Abell clusters selected as hosting a cD galaxy as well as having
a minimum number of members with measured redshifts, we extracted the
Ks(tot) magnitude from 2MASS for the cD galaxy and the 2nd-brightest
member of the cluster. Depending on the magnitude difference between
these two galaxies we subdivide the sample into 71 clusters with a
dominant cD (BM I), 22 clusters of intermediate type, and 35 clusters
with a non-dominant cD (NBMI). The table contains cluster name, mean
redshift, number of members with redshift, difference in Ks(tot)
magnitude between the cD galaxy and the 2nd-brightest cluster member,
the absolute Ks(tot) magnitude of the cD galaxy, the Abell count, the
cluster velocity dispersion, the peculiar velocity of the cD galaxy,
and the names in NED of the cD galaxy and the 2nd-brightest galaxy.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 174 128 Data on the 71 clusters of type BM I, 22 of
intermediate type, and 35 of type NBMI
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See also:
J/AJ/137/4795 : Dynamical state of brightest cluster galaxies (Coziol+, 2009)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1 A1 --- Smpl [abc] Subsample the cluster belongs to (1)
3- 8 A6 --- cluID Cluster identification (2)
10- 15 F6.4 --- z Mean galactocentric redshift of the cluster
17- 19 I3 --- Nz Number of galaxies used to determine redshift
21- 25 F5.2 mag DK Difference in Ks,tot mag between cD and
2nd-brightest galaxy ΔK
27- 32 F6.2 mag KMAG Absolute Ks,tot magnitude of cD galaxy (H_0=72)
34- 36 I3 --- NA Abell richness count
37 A1 --- f_NA [* ] Corrected Abell richness count (3)
40- 43 I4 km/s sigV ? Cluster velocity dispersion (4)
45- 49 I5 km/s Vpec ? Peculiar velocity of cD galaxy wrt to the
cluster mean velocity (5)
51- 73 A23 --- Name1 NED name of cD galaxy
75- 76 I2 h RAB.h Right ascension (B1950) of cD galaxy
77- 78 I2 min RAB.m Right ascension (B1950) of cD galaxy
79- 82 F4.1 s RAB.s Right ascension (B1950) of cD galaxy
83 A1 --- DEB.- Declination sign (B1950) of cD galaxy
84- 85 I2 deg DEB.d Declination (B1950) of cD galaxy
86- 87 I2 arcmin DEB.m Declination (B1950) of cD galaxy
88- 89 I2 arcsec DEB.s Declination (B1950) of cD galaxy
91- 92 I2 h RAh Right ascension (J2000) of cD galaxy
93- 94 I2 min RAm Right ascension (J2000) of cD galaxy
95- 98 F4.1 s RAs Right ascension (J2000) of cD galaxy
99 A1 --- DE- Declination sign (J2000) of cD galaxy
100-101 I2 deg DEd Declination (J2000) of cD galaxy
102-103 I2 arcmin DEm Declination (J2000) of cD galaxy
104-105 I2 arcsec DEs Declination (J2000) of cD galaxy
107-111 F5.4 --- z1 Heliocentric redshift of cD galaxy
112 A1 --- r_z1 [*] Origin of z1: * from our own unpublished
measurement, blank for NED
113-135 A23 --- Name2 NED name of 2nd-brightest cluster member
137-138 I2 h RA2B.h Right ascension (B1950) of 2nd-brightest galaxy
139-140 I2 min RA2B.m Right ascension (B1950) of 2nd-brightest galaxy
141-144 F4.1 s RA2B.s Right ascension (B1950) of 2nd-brightest galaxy
145 A1 --- DE2B.- Declination sign (B1950) of 2nd-brightest galaxy
146-147 I2 deg DE2B.d Declination (B1950) of 2nd-brightest galaxy
148-149 I2 arcmin DE2B.m Declination (B1950) of 2nd-brightest galaxy
150-151 I2 arcsec DE2B.s Declination (B1950) of 2nd-brightest galaxy
153-154 I2 h RA2h Right ascension (J2000) of 2nd-brightest galaxy
155-156 I2 min RA2m Right ascension (J2000) of 2nd-brightest galaxy
157-160 F4.1 s RA2s Right ascension (J2000) of 2nd-brightest galaxy
161 A1 --- DE2- Declination sign (J2000) of 2nd-brightest galaxy
162-163 I2 deg DE2d Declination (J2000) of 2nd-brightest galaxy
164-165 I2 arcmin DE2m Declination (J2000) of 2nd-brightest galaxy
166-167 I2 arcsec DE2s Declination (J2000) of 2nd-brightest galaxy
169-173 F5.4 --- z2 ? heliocentric redshift of 2nd-brightest galaxy
(NED)
174 A1 --- f_z2 ? redshift flag from NED (6)
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Note (1): subsamples are as follows:
a = Clusters of BM I type (ΔK ≥ 1.00 mag);
b = Clusters of intermediate type (0.70 mag < ΔK < 1.00 mag);
c = Clusters of NBMI type (ΔK ≤ 0.70 mag).
Note (2): The first 5 bytes are the Abell cluster name, followed by the
redshift component of the cluster (A,B,C,...), according to Andernach's
Abell cluster redshift compilation (cf. 2005ASPC..329..283A 2005ASPC..329..283A). The
last byte may be blank.
Note (3): taken from 1989ApJS...70....1A 1989ApJS...70....1A; * indicates a downward correction
for an overlap of two or more redshift components of a cluster (see text).
Note (4): value taken from Andernach's Abell cluster redshift compilation
(cf. 2005ASPC..329..283A 2005ASPC..329..283A) or from the literature.
Note (5): calculated according to Vpec = (c * z1 - Vcl)/[1 + (Vcl/c)] where
Vcl is the mean heliocentric velocity of the cluster; note also that
we used weighted averages for z1, not directly the NED value; most
peculiar velocities are taken from 2009AJ....137.4795C 2009AJ....137.4795C
Note (6): an F means a Friends-of-Friends (FoF) type of redshift
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History:
* 26-Nov-2012: The positions and redshifts of the cD and 2nd-brightest
galaxies were not included in the printed version, but appear only
in the electronic version.
* 29-Nov-2012: The electronic version published by MNRAS on 20-Nov-2012
had an error in the name of the 2nd-brightest galaxy for A0690A, which
was corrected here and also in the electronic journal version on
29-Nov-2012, as well as in the printed version.
* 02-Dec-2012: the 2nd-brightest galaxy in A1149 (record#99) was corrected
to 2MASX J11032040+0730463 at z=0.0714, implying ΔK=0.15.
This does not change the cluster's category as NBMI.
* 01-Apr-2014: the brightest galaxy of A0193 (record#6) was incorrectly
given identical to the 2nd-brightest one. The name, coordinates and
redshift of the brightest one were replaced with those of IC 1695.
(found by Marion Schmitz of NED)
Acknowledgements:
Heinz Andernach heinz(at)astro.ugto.mx
(End) Heinz Andernach [Univ. Guanajuato, Mexico] 26-Nov-2012