J/A+A/693/A61 Radio properties of group galaxies in COSMOS (Vardoulaki+, 2025)
The evolution of the radio luminosity function of group galaxies in COSMOS.
Vardoulaki E., Gozaliasl G., Finoguenov A., Novak M., Khosroshahi H.G.
<Astron. Astrophys. 693, A61 (2025)>
=2025A&A...693A..61V 2025A&A...693A..61V (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, radio ; X-ray sources ; Redshifts
Keywords: galaxies: active - galaxies: evolution - galaxies: groups: general -
radio continuum: galaxies
Abstract:
To understand the role of the galaxy group environment on galaxy
evolution, we present a study of radio luminosity functions (RLFs) of
group galaxies based on the Karl G. Jansky Very Large Array-COSMOS 3
GHz Large Project. The radio-selected sample of 7826 COSMOS galaxies
with robust optical and near-infrared counterparts, excellent
photometric coverage, and the COSMOS X-ray galaxy groups
(M200c>1013.5M☉) enables us to construct the RLFs of group
galaxies (GGs) and their contribution to the total RLF since z∼2.3.
Using the Markov chain Monte Carlo algorithm, we fitted a
redshift-dependent pure luminosity evolution model and a linear and
power-law model to the luminosity functions. We compared it with past
RLF studies from VLA-COSMOS on individual populations of
radio-selected star-forming galaxies (SFGs) and galaxies hosting
active galactic nuclei (AGN). These populations are classified based
on the presence or absence of a radio excess concerning the star
formation rates derived from the infrared emission. We find that the
density of radio galaxies in groups is low compared to the field at
z∼2 down to z∼1.25, followed by a sharp increase at z∼1 by a factor of
six, and then a smooth decline towards low redshifts. This trend is
caused by both a decrease in the volume abundance of massive groups at
high-$z$ and the changes in the halo occupation of radio AGN, which
are found by other studies to reside at smaller halo mass groups. This
indicates that the bulk of high-z log10(M200c/M☉)>13.5
groups must have formed recently, and so the cooling has not been
established yet. The slope of the GG RLF is flatter compared to the
field, with excess at high radio luminosities. The evolution in the GG
RLF is driven mainly by satellite galaxies in groups. At z∼1, the peak
in the RLF, coinciding with a known overdensity in COSMOS, is mainly
driven by AGN, while at z>1 SFGs dominate the RLF of group galaxies. A
drop in the occurrence of AGN in groups at z>1 by a factor of six
results in an important detail for the processes governing galaxy
evolution.
Description:
We presented a study of radio luminosity functions, RLFs, of
group galaxies in the COSMOS field, based on data from the VLA-COSMOS
3 GHz Large Project (Smolcic et al., 2017A&A...602A...1S 2017A&A...602A...1S, Cat.
J/A+A/602/A1) and the X-ray galaxy groups catalogue (Gozaliasl et al.,
2019MNRAS.483.3545G 2019MNRAS.483.3545G, Cat. J/MNRAS/483/3545, and in prep.). The X-ray
galaxy groups cover halo masses in the range
M200c=8x1012-3x1014M☉ and the redshift range 0.07<z<2.3.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tablea1.dat 104 378 Basic radio properties of group galaxies in COSMOS
--------------------------------------------------------------------------------
See also:
J/A+A/602/A1 : VLA-COSMOS 3 GHz Large Project (Smolcic+, 2017)
J/MNRAS/483/3545 : X-ray centres of COSMOS galaxy groups (Gozaliasl+, 2019)
Byte-by-byte Description of file: tablea1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- ID3GHz 3GHz radio ID
7- 9 I3 --- IDXray X-ray galaxy group ID
11- 20 F10.6 deg RAdeg Right Ascension (J2000.0) of radio source
22- 29 F8.6 deg DEdeg Declination (J2000.0) of radio source
31- 40 F10.6 deg RAXdeg Right Ascension (J2000.0) of the
X-ray galaxy group position
42- 48 F7.5 deg DEXdeg Declination (J2000.0) of the
X-ray galaxy group position
50- 54 F5.3 --- zradio Redshift of the radio source
56- 60 F5.3 --- zXray Redshift of the X-ray galaxy group
61 A1 --- n_zXray [sp] s for spectroscopic,
p for photometric zXray
63- 67 F5.2 [W/Hz] logL1.4GHz Radio luminosity at 1.4GHz
69- 72 F4.2 [W/Hz] e_logL1.4GHz Error in Radio luminosity at 1.4GHz
74- 78 F5.2 [10+35W] logLX X-ray galaxy group luminosity
in 1042erg/s
80- 83 F4.2 [10+35W] e_logLX Error in X-ray galaxy group luminosity
in 1042erg/s
85- 89 F5.2 [10+13Msun] logM200c Halo mass M200c
91- 96 F6.4 deg BGG-R200c Virial radius of the group R200c
98-100 I3 --- RadioRank BBG rank (1)
102-104 A3 --- RadioClass Radio classification (2)
--------------------------------------------------------------------------------
Note (1): BBG rank, where 0 denotes if the group galaxy is the brightest of the
X-ray galaxy group and values > 0 are for satellite galaxies
Note (2): Radio classification based on a combination of the radio excess
parameter and objects having radio jets;
'AGN' exhibit radio excess or have radio jets, while 'SFG' do not.
--------------------------------------------------------------------------------
Acknowledgements:
Eleni Vardoulaki, elenivard(at)gmail.com
(End) Patricia Vannier [CDS] 04-Dec-2024