Universität zu Köln

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., Roellig, M. and Mookerjea, B. (2010). Molecular and atomic gas in the Local Group galaxy M 33. Astron. Astrophys., 522. LES ULIS CEDEX A: EDP SCIENCES S A. ISSN 0004-6361

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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 30 m IRAM telescope in the CO(2-1) line, achieving a resolution of 12 '' x 2.6 km s(-1), 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 8.5 kpc, and covers entirely the 2' x 40' 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 20-50 mK at 2.6 km s(-1) velocity resolution. The CO(2-1) luminosity of the observed region is 1.7 +/- 0.1 x 10(7) K km s(-1) pc(2) and is estimated to be 2.8 +/- 0.3 x 10(7) K km s(-1) pc(2) for the entire galaxy, corresponding to H(2) masses of 1.9 x 10(8) M(circle dot) and 3.3 x 10(8) M(circle dot) respectively (including He), calculated with N(H(2))/I(CO(1-0)) twice the Galactic value due to the half-solar metallicity of M 33. The HI 21 cm 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 datacubes with resolutions ranging from 5 '' to 25 ''. The HI mass within a radius of 8.5 kpc is estimated to be 1.4 x 10(9) M(circle dot). The azimuthally averaged CO surface brightness decreases exponentially with a scale length of 1.9 +/- 0.1 kpc whereas the atomic gas surface density is constant at Sigma(HI) = 6 +/- 2 M(circle dot) pc(-2) deprojected to face-on. For an N(H(2))/I(CO(1-0)) conversion factor twice that of the Milky Way, the central kiloparsec H(2) surface density is Sigma(H2) = 8.5 +/- 0.2 M(circle dot) pc(-2). The star formation rate per unit molecular gas (SF efficiency, the rate of transformation of molecular gas into stars), as traced by the ratio of CO to H(alpha) and FIR brightness, is constant with radius. The SFE, with a N(H(2))/I(CO(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 8 kpc from the galaxy center, are presented.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Gratier, P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Braine, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Rodriguez-Fernandez, N. J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Schuster, K. F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kramer, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Xilouris, E. M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Tabatabaei, F. S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Henkel, C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Corbelli, E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Israel, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED van der Werf, P. P. UNSPECIFIED UNSPECIFIED UNSPECIFIED Calzetti, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Garcia-Burillo, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Sievers, A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Combes, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wiklind, T. UNSPECIFIED UNSPECIFIED UNSPECIFIED Brouillet, N. UNSPECIFIED UNSPECIFIED UNSPECIFIED Herpin, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Bontemps, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Aalto, S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Koribalski, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED van der Tak, F. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wiedner, M. C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Roellig, M. UNSPECIFIED UNSPECIFIED UNSPECIFIED Mookerjea, B. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-492982
DOI:	10.1051/0004-6361/201014441
Journal or Publication Title:	Astron. Astrophys.
Volume:	522
Date:	2010
Publisher:	EDP SCIENCES S A
Place of Publication:	LES ULIS CEDEX A
ISSN:	0004-6361
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language STAR-FORMATION EFFICIENCY; RADIO-CONTINUUM SURVEY; STELLAR POPULATION; FORMATION HISTORY; FORMING GALAXIES; FAR-ULTRAVIOLET; SPIRAL GALAXIES; SCHMIDT LAW; CO EMISSION; M33 Multiple languages Astronomy & Astrophysics Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/49298