J/A+A/549/A17 IRAM spectra toward M33 Giant Molecular Clouds (Buchbender+, 2013)
Dense Gas in M33 (HerM33es).
Buchbender C., Kramer C., Gonzalez-Garcia M., Israel F.P.,
Garcia-Burillo S., van der Werf P., Braine J., Rosolowsky E., Mookerjea B.,
Aalto S., Boquien M., Gratier P., Henkel C., Quintana-Lacaci G., Verley S.,
der Tak F.van
<Astron. Astrophys. 549, A17 (2013)>
=2013A&A...549A..17B 2013A&A...549A..17B
ADC_Keywords: Galaxies, nearby ; Galaxies, radio ; Interstellar medium
Keywords: galaxies: individual: M33 - galaxies: ISM - ISM: molecules -
ISM: clouds - ISM: photon-dominated region (PDR)
Abstract:
We aim to better understand the emission of molecular tracers of the
diffuse and dense gas in giant molecular clouds and the influence that
metallicity, optical extinction, density, far-UV field, and star
formation rate have on these tracers. Using the IRAM 30m telescope, we
detected HCN, HCO+, 12CO, and 13CO in six GMCs along the major
axis of M33 at a resolution of ∼114pc and out to a radial distance of
3.4kpc. Optical, far-infrared, and submillimeter data from Herschel
and other observatories complement these observations. To interpret
the observed molecular line emission, we created two grids of models
of photon-dominated regions, one for solar and one for M33-type
subsolar metallicity. The observed HCO+/HCN line ratios range
between 1.1 and 2.5. Similarly high ratios have been observed in the
Large Magellanic Cloud. The HCN/CO ratio varies between 0.4% and 2.9%
in the disk of M33. The 12CO/13CO line ratio varies between 9 and
15 similar to variations found in the diffuse gas and the centers of
GMCs of the Milky Way. Stacking of all spectra allowed HNC and C2H
to be detected. The resulting HCO+/HNC and HCN/HNC ratios of ∼8 and
6, respectively, lie at the high end of ratios observed in a large set
of (ultra-)luminous infrared galaxies. HCN abundances are lower in the
subsolar metallicity PDR models, while HCO+ abundances are enhanced.
For HCN this effect is more pronounced at low optical extinctions. The
observed HCO+/HCN and HCN/CO line ratios are naturally explained by
subsolar PDR models of low optical extinctions between 3 and 10mag and
of moderate densities of n=3x103-3x104cm-3, while the FUV field
strength only has a small effect on the modeled line ratios. The line
ratios are almost equally well reproduced by the solar-metallicity
models, indicating that variations in metallicity only play a minor
role in influencing these line ratios.
Description:
The attached FITS spectra contain the reduced IRAM 30m spectra of the
ground state transitions 12CO, 13CO, HCN and HCO+ towards 7 GMC
in M33 that are presented in Figure 3 and Figure A.1 of the paper. The
12CO spectra of GMCs: GMC1, GMC26 and GMC91, that are archived here,
were first presented in Rosolowsky et al. (2011MNRAS.415.1977R 2011MNRAS.415.1977R) and
were observed with the A,B,C,D receiver of the IRAM 30m. All other
spectra were observed with the EMIR receiver. The backends used were:
the FTS spectrometer in case of 12CO and 13CO spectra and the
WILMA autocorrelator in case of HCN and HCO+. All spectra have been
resampled to the intrinsic resolution of the WILMA spectrometer, which
is 2MHz. This frequency resolution corresponds to a velocity
resolution of 5.4km/s for 12CO and 13CO and 6.7km/s for HCN and
HCOp. In addition we provide the 12CO and 13CO spectra at higher
resolution of 333kHz corresponding to ∼1km/s velocity resolution. All
spectra have a bandwidth of 300km/s each. The nomenclature of the
files is: "ObjectName"-"Molecule"-"Resolution"[.fits] The observed
sources and their designations are listed below. The FITS files are
created by GILDAS/Class.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 180 7 List of sources and FITS files
sp/* . 42 Individual FITS spectra
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See also:
J/ApJS/149/343 : Giant molecular clouds in M33 (Engargiola+, 2003)
J/A+A/426/119 : 1.2mm mapping of RCW 106 GMC (Mookerjea+, 2004)
J/MNRAS/353/1025 : JHK photometry of 4 W51 star clusters (Nanda+, 2004)
J/MNRAS/367/1609 : RCW 106 Giant Molecular Cloud 13CO mapping (Bains+, 2006)
J/A+A/471/103 : SIMBA observations of SMC (Bot+, 2007)
J/ApJ/654/240 : Giant molecular clouds in M31 (Rosolowsky+, 2007)
J/ApJ/654/338 : Spitzer photometry in W3 molecular cloud (Ruch+, 2007)
J/ApJ/661/830 : Giant molecular clouds of M33 (Rosolowsky+, 2007)
J/MNRAS/379/663 : W3 giant molecular cloud 850um observations (Moore+, 2007)
J/A+A/489/533 : M83 giant molecular clouds volume densities (Heiner+, 2008)
J/ApJ/686/948 : CO in extragalactic giant molecular clouds (Bolatto+, 2008)
J/ApJS/178/56 : CO observations of LMC Giant Molecular clouds (Fukui+, 2008)
J/ApJ/699/1092 : Giant molecular clouds (SRBY) (Heyer+, 2009)
J/AJ/137/4072 : Infrared photometry of G216-2.5 YSOs (Megeath+, 2009)
J/A+A/534/A131 : Clumps in giant molecular cloud G345.5+1.0 (Lopez+, 2011)
J/A+A/542/A108 : Giant molecular clouds in M33 (Gratier+, 2012)
Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- Name Giant molecular cloud name (in M33)
10- 11 I2 h RAh Right ascension (J2000)
13- 14 I2 min RAm Right ascension (J2000)
16- 20 F5.2 s RAs Right ascension (J2000)
22 A1 --- DE- Declination sign (J2000)
23- 24 I2 deg DEd Declination (J2000)
26- 27 I2 arcmin DEm Declination (J2000)
29- 33 F5.2 arcsec DEs Declination (J2000)
35- 57 A23 --- 12CO-l Name of the FITS file with 12CO 115.271GHz
line (2MHz resolution) in subdirectory sp
59- 83 A25 --- 12CO-h Name of the FITS file with 12CO 115.271GHz
line (333kHz resolution) in subdirectory sp
85-107 A23 --- 13CO-l Name of the FITS file with 13CO 110.201GHz
line (2MHz resolution) in subdirectory sp
109-133 A25 --- 13CO-h Name of the FITS file with 13CO 110.201GHz
line (333kHz resolution) in subdirectory sp
135-157 A23 --- HCN Name of the FITS file with HCN 88.631GHz line
(2MHz resolution) in subdirectory sp
158-180 A23 --- HCOp Name of the FITS file with HCOp 89.188GHz line
(2MHz resolution) in subdirectory sp
--------------------------------------------------------------------------------
Acknowledgements:
Christof Buchbender, christof.buchbender(at)gmail.com
(End) Christof Buchbender [IRAM], Patricia Vannier [CDS] 17-Oct-2012