J/A+A/573/A111 Group-dominant elliptical galaxies CO spectra (O'Sullivan+, 2015)
Cold gas in group-dominant elliptical galaxies.
O'Sullivan E., Combes F., Hamer S., Salome P., Babul A., Raychaudhury S.
<Astron. Astrophys. 573, A111 (2015)>
=2015A&A...573A.111O 2015A&A...573A.111O
ADC_Keywords: Galaxies, nearby ; Galaxies, spectra ; Carbon monoxide
Keywords: galaxies: evolution - galaxies: star formation -
galaxies: groups: general - galaxies: kinematics and dynamics -
galaxies: general
Abstract:
We present IRAM 30m telescope observations of the CO(1-0) and (2-1)
lines in a sample of 11 group-dominant elliptical galaxies selected
from the CLoGS nearby groups sample. Our observations confirm the
presence of molecular gas in 4 of the 11 galaxies at >4σ
significance, and combining these with data from the literature we
find a detection rate of 43±14%, significantly higher than for the
wider population of elliptical galaxies, and comparable to the
detection rate for nearby radio galaxies. Those group-dominant
galaxies which are detected typically contain ∼2x108M☉ of
molecular gas, and although most have low star formation rates
(<1M☉/yr) they have short depletion times, indicating that the
gas must be replenished on timescales 108yr. Almost all of the
galaxies contain active nuclei, and we note that while CO detections
are more common in the most radio-loud galaxies, the mass of molecular
gas required to power the active nuclei through accretion is small
compared to the masses observed. We consider the possible origin
mechanisms for the gas, through cooling of stellar ejecta within the
galaxies, group-scale cooling flows, and gas-rich mergers, and find
probable examples of each type within our sample, confirming that a
variety of processes act to drive the build up of molecular gas in
group-dominant ellipticals.
Description:
22 reduced spectra obtained at IRAM-30m are provided in ascii format.
They are presented in Figure 1 and Table 1 of the article.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
spectra.dat 51 22 Source, line and central redshift of spectra
sp/* . 22 Individual spectra
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Byte-by-byte Description of file: spectra.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- N [1/22] Spectrum number
4- 10 A7 --- Source Source name
12- 18 A7 --- Line Line observed: CO(1-0) or CO(2-1)
20- 27 F8.6 --- z [0.005/0.018] Redshift, i.e. spectrum center
(=Vsys/c)
29- 30 I2 h RAh Simbad right ascension (J2000)
32- 33 I2 min RAm Simbad right ascension (J2000)
35- 39 F5.2 s RAs Simbad right ascension (J2000)
41 A1 --- DE- Simbad declination sign (J2000)
42- 43 I2 deg DEd Simbad declination (J2000)
45- 46 I2 arcmin DEm Simbad declination (J2000)
48- 51 F4.1 arcsec DEs Simbad declination (J2000)
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 9 F9.2 km/s Vel Velocity with respect to Vsys (see spectra.dat)
10- 20 F11.6 mK Tmb Main beam temperature
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Acknowledgements:
Francoise Combes, francoise.combes(at)obspm.fr
(End) Francoise Combes [LERMA, France], Patricia Vannier [CDS] 05-Nov-2014