J/A+A/590/A27 CO spectra of Virgo cluster galaxies (Grossi,+, 2016)
Star-forming dwarf galaxies in the Virgo cluster: the link between molecular
gas, atomic gas, and dust.
Grossi, M., Corbelli, E., Bizzocchi, L., Giovanardi, C., Bomans D.,
Coelho B., De Looze I., Goncalves T.S., Hunt L.K., Leonardo E., Madden S.,
Menendez-Delmestre K., Pappalardo C., Riguccini L.
<Astron. Astrophys. 590, A27 (2016)>
=2016A&A...590A..27G 2016A&A...590A..27G (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, galaxy ; Galaxies, nearby ; Spectroscopy ;
Carbon monoxide
Keywords: galaxies: dwarf - galaxies: ISM -
galaxies: clusters: individual: Virgo - galaxies: evolution
Abstract:
We present 12CO(1-0) and 12CO(2-1) observations of a sample of 20
star-forming dwarfs selected from the Herschel Virgo Cluster Survey,
with oxygen abundances ranging from 12+log(O/H)∼8.1 to 8.8. CO
emission is observed in ten galaxies and marginally detected in
another one. CO fluxes correlate with the FIR 250um emission, and the
dwarfs follow the same linear relation that holds for more massive
spiral galaxies extended to a wider dynamical range. We compare
different methods to estimate H2 molecular masses, namely a
metallicity-dependent CO-to-H2 conversion factor and one dependent
on H-band luminosity. The molecular-to-stellar mass ratio remains
nearly constant at stellar masses ≤109M☉, contrary to the
atomic hydrogen fraction, MHI/M*, which increases inversely with M*.
The flattening of the MH2/M* ratio at low stellar masses does not
seem to be related to the effects of the cluster environment because
it occurs for both HI-deficient and HI-normal dwarfs. The
molecular-to-atomic ratio is more tightly correlated with stellar
surface density than metallicity, confirming that the interstellar gas
pressure plays a key role in determining the balance between the two
gaseous components of the interstellar medium. Virgo dwarfs follow the
same linear trend between molecular gas mass and star formation rate
as more massive spirals, but gas depletion timescales, tau_dep, are
not constant and range between 100Myr and 6Gyr. The interaction with
the Virgo cluster environment is removing the atomic gas and dust
components of the dwarfs, but the molecular gas appears to be less
affected at the current stage of evolution within the cluster.
However, the correlation between HI deficiency and the molecular gas
depletion time suggests that the lack of gas replenishment from the
outer regions of the disc is lowering the star formation activity.
Description:
Reduced IRAM 30m telescope spectra of 20 star-forming dwarf galaxies
in the Virgo cluster, that are presented in Figure B.1 and Figure B.2
of the paper. The spectra were observed with the EMIR receiver using
the FTS spectrometer.
The nomenclature of the files is: ObjectName_10.dat and
ObjectName_21.dat, for the 12CO(1-0) and 12CO(2-1)
transition, respectively. Multiple pointings for the same target are
indicated with letters (a,b,c,d,e). All spectra have been resampled to
a velocity resolution of 8.1km/s for both lines, with the exception
of VCC0324_10.dat and VCC1686c10.dat which have been resampled to a
velocity resolution of 16.2km/s. The observed sources and the list of
files are given below. The files are created by GILDAS/Class.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 242 20 Main properties of the Virgo SFDs
sp/* . 49 Individual spectra
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See also:
VII/266 : Atlas of Virgo galaxies (McDonald+ 2011)
J/AJ/90/1681 : The Virgo Cluster Catalog (VCC) (Binggeli+, 1985)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Name Name
9- 12 F4.2 [Msun] logM* Stellar mass
14- 17 F4.2 [Msun] e_logM* rms uncertainty on logM*
19- 22 F4.2 [Msun] logMHI HI mass
24- 27 F4.2 [Msun] e_logMHI rms uncertainty on logMHI
29- 32 F4.2 [Msun] logMd Dust mass
34- 38 F5.2 [Msun/yr] logSFR Star formation rate
40- 43 F4.2 [Msun/yr] e_logSFR rms uncertainty on logSFR
45- 48 F4.2 [-] 12+log(O/H) Abundance 12+log(O/H)
50- 53 F4.2 [-] e_12+log(O/H) rms uncertainty on 12+log(O/H)
54 A1 --- n_12+log(O/H) [b] Mote on 12+log(O/H) (1)
56- 60 F5.2 --- DefHI HI deficiency parameter
62- 64 I3 km/s DVHI HI line FWHM
65 A1 --- n_DVHI [a] Note on DVHI (1)
67- 70 F4.1 Mpc Dist Distance
72- 76 F5.1 arcsec a25 Isophotal major diameter at the
25th B-magnitude/arcsec2
78- 82 F5.1 arcsec b25 Isophotal minor diameter at the
25th B-magnitude/arcsec2
84- 98 A15 --- SpCO10a CO(1-0) spectrum filename
in subdirectory sp
100-114 A15 --- SpCO21a CO(2-1) spectrum filename
in subdirectory sp
116-130 A15 --- SpCO10b CO(1-0) spectrum filename
in subdirectory sp
132-146 A15 --- SpCO21b CO(2-1) spectrum filename
in subdirectory sp
148-162 A15 --- SpCO10c CO(1-0) spectrum filename
in subdirectory sp
164-178 A15 --- SpCO21c CO(2-1) spectrum filename
in subdirectory sp
180-194 A15 --- SpCO10d CO(1-0) spectrum filename
in subdirectory sp
196-210 A15 --- SpCO21d CO(2-1) spectrum filename
in subdirectory sp
212-226 A15 --- SpCO10e CO(1-0) spectrum filename
in subdirectory sp
228-242 A15 --- SpCO21e CO(2-1) spectrum filename
in subdirectory sp
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Note (1): Notes as follows:
a = Springob et al. (2005ApJS..160..149S 2005ApJS..160..149S, Cat. VIII/77)
b = Metallicity derived from the mass-metallicity relation of Hughes et al.
(2013, Cat. J/A+A/550/A115)
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Byte-by-byte Description of file: sp/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.1 km/s V Velocity
9- 19 E11.5 K Tmb Main beam temperature
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Acknowledgements:
Marko Grossi, marko.grossi(at)gmail.com
(End) Patricia Vannier [CDS] 12-May-2016