J/A+A/667/A52 3 KiDS cluster galaxies at z∼0.4 CO spectra (Castignani+, 2022)
Star forming and gas rich brightest cluster galaxies at z∼0.4 in the
Kilo-Degree Survey.
Castignani G., Radovich M., Combes F., Salome P., Maturi M., Moscardini L.,
Bardelli S., Giocoli C., Lesci G., Marulli F., Puddu E., Sereno M.
<Astron. Astrophys. 667, A52 (2022)>
=2022A&A...667A..52C 2022A&A...667A..52C (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Carbon monoxide ; Spectra, radio
Keywords: galaxies: clusters: general - galaxies: star formation -
galaxies: evolution - galaxies: active - molecular data
Abstract:
Brightest Cluster Galaxies (BCGs) are typically massive ellipticals at
the centers of clusters. They are believed to experience strong
environmental processing, and their mass assembly and star formation
history are still debated. We have selected three star forming BCGs in
the equatorial field of the Kilo-Degree Survey (KiDS). They are KiDS
0920 (z=0.3216), KiDS 1220 (z=0.3886), and KiDS 1444 (z=0.4417). We
have observed them with the IRAM-30m telescope in the first three CO
transitions. We remarkably detected all BCGs at high signal-to-noise
ratio S/N≃(3.8-10.2), for a total of 7 detected lines out of 8,
corresponding to a success rate of 88%. This allows us to double the
number of distant BCGs with clear detections in at least two CO lines.
We have then combined our observations with available stellar, star
formation, and dust properties of the BCGs, and we have compared them
with a sample of 100 distant cluster galaxies with observations in CO.
Our analysis yields large molecular gas reservoirs
MH2≃(0.5-1.4)*1011M☉, excitation ratios
r31=L'CO(3->2)/L'CO(1->0)_≃(0.1-0.3), as well as long depletion
times τdep≃(2-4)Gyr and high MH2/Mdust≃(170-300) for the
three targeted BCGs. The excitation ratio r31 of intermediate-z BCGs,
including RX1532 and M1932 from previous studies, appears to be well
correlated with the star formation rate and efficiency, which suggests
that excited gas is found only in highly star forming and cool-core
BCGs. By performing color-magnitude plots and a red sequence modeling
we find that recent bursts of star formation are needed to explain the
fact that the BCGs are measurably bluer than photometrically selected
cluster members. To explain the global observed phenomenology we
suggest that a substantial amount of the molecular gas has been
accreted by the KiDS BCGs, but still not efficiently converted into
stars. KiDS 1220 also shows a double-horn emission in CO(3->2) which
implies a low gas concentration. The modeling of the spectrum yields
an extended molecular gas reservoir of 9kpc, which is reminiscent of a
mature extended-disk phase observed in some local BCGs.
Description:
IRAM 30m spectra reported in Fig. 3
Each files contains one spectrum. The filename contains both source
and file names. For example, in "0920co10.dat" there is the CO(1-0)
spectrum for the source K0920.
Objects:
-----------------------------------------------------
RA (2000) DE Designation(s) (z)
-----------------------------------------------------
09 20 17.28 -00 46 58.51 KiDS 0920 (0.3216)
12 20 02.30 -02 25 31.15 KiDS 1220 (0.3886)
14 44 10.87 +02 34 18.23 KiDS 1444 (0.4417)
-----------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
0920co10.dat 20 58 K0920 IRAM 30m spectrum, CO(1-0)
0920co32.dat 19 56 K0920 IRAM 30m spectrum, CO(3-2)
1220co10.dat 20 92 K1220 IRAM 30m spectrum, CO(1-0)
1220co21.dat 20 85 K1220 IRAM 30m spectrum, CO(2-1)
1220co32.dat 19 81 K1220 IRAM 30m spectrum, CO(3-2)
1444co10.dat 20 53 K1444 IRAM 30m spectrum, CO(1-0)
1444co21.dat 19 54 K1444 IRAM 30m spectrum, CO(2-1)
1444co32.dat 20 53 K1444 IRAM 30m spectrum, CO(3-2)
--------------------------------------------------------------------------------
See also:
II/347 : KiDS-ESO-DR3 multi-band source catalog (de Jong+, 2017)
Byte-by-byte Description of file: *.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
2- 10 F9.3 km/s RVel Relative velocity, with respect to the BCG
redshift
12- 20 F9.5 mJy Flux Observed flux
--------------------------------------------------------------------------------
Acknowledgements:
Gianluca Castignani, gianluca.castignani(at)unibo.it
(End) Patricia Vannier [CDS] 28-Jul-2022