J/A+A/522/A3 M33 CO(2-1) and HI integrated intensity maps (Gratier+, 2010)
Molecular and atomic gas in the Local Group galaxy M33.
Gratier P., Braine J., Rodriguez-Fernandez N.J., Schuster K.F., Kramer C.,
Xilouris E.M., Tabatabaei F.S., Henkel C., Corbelli E., Israel F.,
van der Werf P.P., Calzetti D., Garcia-Burillo S., Sievers A., Combes F.,
Wiklind T., Brouillet N., Herpin F., Bontemps S., Aalto S., Koribalski B.,
van der Tak F., Wiedner M.C., Rollig M., Mookerjea B.
<Astron. Astrophys. 522, A3 (2010)>
=2010A&A...522A...3G 2010A&A...522A...3G
ADC_Keywords: Galaxies, nearby ; H I data ; Carbon monoxide
Keywords: galaxies: individual: M 33 - Local Group - galaxies: evolution -
galaxies: ISM - ISM: clouds - stars: formation
Abstract:
We present high-resolution large-scale observations of the molecular
and atomic gas in the Local Group galaxy M 33. The observations were
carried out using the HEterodyne Receiver Array (HERA) at the 30m IRAM
telescope in the CO(2-1) line, achieving a resolution of 12"x2.6km/s,
enabling individual giant molecular clouds (GMCs) to be resolved. The
observed region is 650 square arcminutes mainly along the major axis
and out to a radius of 8.5kpc, and covers entirely the 2'x40' radial
strip observed with the HIFI and PACS Spectrometers as part of the
HERM33ES Herschel key program. The achieved sensitivity in main-beam
temperature is 20-50mK at 2.6km/s velocity resolution. The CO(2-1)
luminosity of the observed region is 1.7±0.1x107K.km/s.pc2 and
is estimated to be 2.8±0.3x107K.km/s.pc2 for the entire galaxy,
corresponding to H2 masses of 1.9x108 and 3.3x108 respectively
(including He), calculated with N(H2)/ICO(1-0) twice the Galactic
value due to the half-solar metallicity of M 33. The HI 21cm VLA
archive observations were reduced, and the mosaic was imaged and
cleaned using the multi-scale task in the CASA software package,
yielding a series of datacube with resolutions ranging from 5" to 25".
The HI mass within a radius of 8.5kpc is estimated to be 1.4x109.
The azimuthally averaged CO surface brightness decreases exponentially
with a scale length of 1.9±0.1kpc whereas the atomicgas surface
density is constant at ΣHI=6±2pc-2 deprojected to face-on.
For an (H2)/ICO(1-0) conversion factor twice that of the Milky
Way, the central kiloparsec H2 surface density is
ΣHI=8.5±0.2pc-2. The star formation rate per unit moecular
gas (SF efficiency, the rate of transformation of molecular gas into
stars), as traced by the ratio of CO to Hα and FIR brightness,
is constant with radus. The SFE, with a N(H2)/ICO(1-0) factor twice
galactic, appears 2-4 times greater than for large spiral galaxies. A
morphological comparison of molecular and atomic gas with tracers of
star formation is presented showing good agreement between these maps
both in terms of peaks and holes. A few exceptions are noted. Several
spectra, including those of a molecular cloud situated more than 8kpc
from the galaxy center, are presented.
Description:
Integrated intensity maps for M33 in the CO(2-1) and HI 21cm lines.
The resolutions are 17arcsec for HI and 12arcsec for CO(2-1)
Objects:
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RA (2000) DE Designation(s)
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01 33 50.9 +30 39 36 M33 = NGC 598
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 50 2 Summary of files
CO12secmom0.fits 2880 1872 HI 21cm integrated intensity map
HI17secmom0.fits 2880 1232 CO(2-1) integrated intensity map (230.538GHz)
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Center of image (J2000)
10- 18 F9.5 deg DEdeg Center of image (J2000)
20- 22 F3.1 arcsec/pix scale Scale of image
24- 26 I3 pix Xsize Size of image along X axis
27 A1 --- --- [x]
28- 31 I4 pix Ysize Size of image along Y axis
33- 50 A18 --- FileName Name of FITS file
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Acknowledgements:
Pierre Gratier, gratier(at)obs.u-bordeaux1.fr
(End) Patricia Vannier [CDS] 26-Oct-2010