J/A+A/654/A135 12 strong galactic bars CO spectra (Diaz-Garcia+, 2021)
Molecular gas and star formation within 12 strong galactic bars observed with
IRAM-30m.
Diaz-Garcia S., Lisenfeld U., Perez I., Zurita A., Verley S., Combes F.,
Espada D., Leon S., Martinez-Badenes V., Sabater J., Verdes-Montenegro L.
<Astron. Astrophys. 654, A135 (2021)>
=2021A&A...654A.135D 2021A&A...654A.135D (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Galaxies, photometry ; Galaxies, radio ;
Photometry, infrared ; Photometry, millimetric/submm ;
Photometry, ultraviolet
Keywords: galaxies: star formation - galaxies: ISM - galaxies: structure -
galaxies: evolution - galaxies: statistics
Abstract:
While some galactic bars show recent massive star formation (SF) along
them, some others present a lack of it. Whether bars with low level of
SF are a consequence of low star formation efficiency, low gas inflow
rate, or dynamical effects, remains a matter of debate.
In order to study the physical conditions that enable or prevent SF,
we perform a multi-wavelength analysis of 12 strongly barred galaxies
with total stellar masses log10(M*/M☉)∈[10.2,11], chosen to
host different degrees of SF along the bar major axis without any
prior condition on gas content. We observe the CO(1-0) and CO(2-1)
emission within bars with the IRAM-30m telescope (beam sizes of
1.7-3.9kpc and 0.9-2.0kpc, respectively; 7-8 pointings per galaxy on
average).
We estimate molecular gas masses (Mmol) from the CO(1-0) and CO(2-1)
emissions. SF rates (SFR) are calculated from GALEX near-ultraviolet
(UV) and WISE 12um images within the beam-pointings, covering the
full bar extent (SFRs are also derived from far-UV and 22um).
Results. We detect molecular gas along the bars of all probed
galaxies. Molecular gas and SFR surface densities span the ranges
log10(Σmol/[M☉/pc2])∈[0.4,2.4] and
log10(ΣSFR/[M☉/pc/kpc2])∈[-3.25,-0.75],
respectively. The star formation efficiency (SFE=SFR/Mmol) in bars
varies between galaxies by up to an order of magnitude
(SFE∈[0.1,1.8]Gyr-1). On average, SFEs are roughly constant along
bars. SFEs are not significantly different from the mean value in
spiral galaxies reported in the literature (∼0.43Gyr-1), regardless
of whether we estimate Mmol from CO(1-0) or CO(2-1). Interestingly,
the higher the total stellar mass of the host galaxy, the lower the
SFE within their bars. In particular, the two galaxies in our sample
with lowest SFE and ΣSFR (NGC 4548 and NGC 5850,
SFE≤0.25Gyr-1, ΣSFR≤10-2.25M☉/yr/kpc2,
M*≤1010.7M☉) are also the ones hosting massive bulges and
signs of past interactions with nearby companions.
We present a statistical analysis of the SFE in bars for a sample of
12 galaxies. The SFE in strong bars is not systematically inhibited
(either in the central, mid- or end-parts of the bar). Both
environmental and internal quenching are likely responsible for the
lowest SFEs reported in this work.
Description:
Here we provide the CO(1-0) and CO(2-1) spectra gathered with the
IRAM-30m telescope along the bars of 12 nearby galaxies (see Sect.
2.2).
For each galaxy, we tabulate the J2000 equatorial coordinates of the
central pointing (in degrees).
For each pointing, we list the observed frequency (in MHz) and
intensity of the spectra (in the main beam temperature scale, in units
of mK, baseline subtracted).
The file names with the spectra indicate the offset of the pointings
with respect to the central one (in RA and DEC, respectively, in units
of arcsec). For instance, NGC4548CO10-40_-20.dat tabulates
NGC4548's CO(1-0) spectra for a pointing with an offset of -40arcsec
in RA and -20arcsec in DEC with respect to the central pointing.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
galaxies.dat 27 12 Equatorial coordinates (J2000) of central
pointing for each galaxy
listsp.dat 48 186 List of individual spectra
sp/* . 186 Individual CO(1-0) and CO(2-1) spectra within
pointings along the bar major axis
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Byte-by-byte Description of file: galaxies.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Galaxy Galaxy identification
9- 17 F9.5 deg RAdeg Right ascension of centre of the
IRAM-30m central pointing (J2000)
19- 27 F9.5 deg DEdeg Declination of centre of the
IRAM-30m central pointing (J2000)
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Byte-by-byte Description of file: listsp.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 A7 --- Galaxy Galaxy name
9- 11 I3 arcsec oRA Offset in Right ascension (1)
13- 15 I3 arcsec oDE Offset in DEclination (1)
17- 23 A7 --- Line Line (CO(1-0) or CO(2-1))
25- 48 A24 --- FileName Name of the spectrum file in subdirectory sp
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Note (1): Offsets from positions in galaxies.dat table.
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Byte-by-byte Description of file: sp/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.1 MHz Freq Observed frequency
10- 17 F8.5 mK T Intensity
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Acknowledgements:
Simon Diaz Garcia, simondiazgar(at)gmail.com,
Instituto de Astrofisica de Canarias, Spain - Queen's University, Canada
(End) S. Diaz Garcia [IAC & Queen's Univ., Canada], P. Vannier [CDS] 23-Sep-2021