J/A+A/673/A100 Candidate fossil groups brightest central galaxies (Chu+, 2023)
A UNIONS view of the brightest central galaxies of candidate fossil groups.
Chu A., Durret F., Ellien A., Sarron F., Adami C., Marquez I., Martinet N.,
de Boer T., Chambers K.C., Cuillandre J.-C., Gwyn S., Magnier E.A.,
McConnachie A.W.
<Astron. Astrophys. 673, A100 (2023)>
=2023A&A...673A.100C 2023A&A...673A.100C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Redshifts ; Photometry, SDSS ;
Magnitudes, absolute
Keywords: galaxies: clusters: general - galaxies: evolution -
galaxies: formation - galaxies: groups: general
Abstract:
The formation process of fossil groups (FGs) is still under debate,
and, due to the relative rarity of FGs, large samples of such objects
are still missing.
The aim of the present paper is to increase the sample of known FGs,
and to analyse the properties of their brightest group galaxies (BGG)
and compare them with a control sample of non-FG BGGs.
Based on the large spectroscopic catalogue of haloes and galaxies
publicly made available by Tinker, we extract a sample of 87 FG and
100 non-FG candidates. For all the objects with data available in
UNIONS (initially the Canada France Imaging Survey, CFIS), in the u
and r bands, and/or in an extra r-band processed to preserve all low
surface brightness features (rLSB hereby), we made a 2D photometric
fit of the BGG with GALFIT with one or two Sersic components. We also
analysed how the subtraction of intracluster light contribution
modifies the BGG properties. From the SDSS spectra available for the
BGGs of 65 FGs and 82 non- FGs, we extracted the properties of their
stellar populations with Firefly. To complement our study, we
investigated the origin of the emission lines in a nearby FG,
dominated by the NGC 4104 galaxy, to illustrate in detail the possible
origin of emission lines in the FG BGGs, involving the presence or
absence of an AGN.
Morphologically, a single Sersic profile can fit most objects in the
u band, while two Sersics are needed in the r and rLSB bands, both
for FGs and non-FGs. Non-FG BGGs cover a larger range of Sersic index
n. FG BGGs follow the Kormendy relation (mean surface brightness
versus effective radius) previously derived for almost one thousand
brightest cluster galaxies (BCGs) by Chu et al. (2022A&A...666A..54C 2022A&A...666A..54C)
while non-FGs BGGs are in majority located below this relation, with
fainter mean surface brightnesses. This suggests that FG BGGs have
evolved similarly to BCGs, and non-FG BGGs have evolved differently
from both FG BGGs and BCGs. All the above properties can be strongly
modified by the subtraction of intracluster light contribution. Based
on spectral fitting, the stellar populations of FG and non-FG BGGs do
not differ significantly.
The morphological properties and the Kormendy relation of FG and
non-FG BGGs differ, suggesting they have had different formation
histories. However, it is not possible to trace differences in their
stellar populations or in their large scale distributions.
Description:
The aim of this paper is to increase the number of known FGs to shed
light on their formation process. Here, we increase the sample by 87
FG candidates confirmed spectroscopically, and with a high probability
of being real FGs in view of their estimated large halo mass, though
the confirmation of the X-ray condition on their X-ray luminosity
(LX>1042erg/s) is still missing. For the FGs with UNIONS data
available (35 in the u band, 25 in the r band and 19 in the rLSB band
(r band treated with the Elixir-LSB software), we analyse the
morphological properties of their brightest group galaxy (BGG), and
compare these properties with those of a control sample of 30 non-FG
BGGs.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 66 87 List of the brightest group galaxies for
the 87 FGs (fossil groups) candidates
tablea2.dat 66 100 List of the brightest group galaxies for the
100 non-FGs (non fossil groups) used as a
comparison sample
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Byte-by-byte Description of file: tablea1.dat tablea2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- Seq Running number
5- 12 F8.4 deg RAdeg Right ascension (J2000)
14- 21 F8.4 deg DEdeg Declination (J2000)
23- 28 F6.4 --- zsp Spectroscopic redshift
30- 35 F6.3 [Msun] logMBGG logarithm of brightest group galaxies (BGG)
mass
37- 43 F7.3 mag gMAG Absolute magnitude in the g band
45- 51 F7.3 mag rMAG Absolute magnitude in the r band
54- 59 F6.4 Mpc rvir Virial radius
61- 66 F6.3 [Msun] logMhalo logarithm of the group halo mass
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Acknowledgements:
Aline Chu, chu(at)iap.fr
(End) Patricia Vannier [CDS] 27-Mar-2023