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Astron. Astrophys. 325, 961-971 (1997)

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The star formation law in disk galaxies: a Bayesian view

J. , Köppen 1, 3, 4, H.-E. and Fröhlich 2

1 Institut für Astronomie und Astrophysik der Universität, D-24098 Kiel, Germany
2 Astrophysikalisches Institut Potsdam, An der Sternwarte 16, D-14482 Potsdam, Germany
3 Observatoire Astronomique, 11 Rue de l'Université, F-67 000 Strasbourg, France
4 International Space University, Parc d'Innovation, F-67400 Illkirch, France

Received 30 October 1996 / Accepted 8 April 1997


The dependence of the star formation rate [FORMULA] on gas surface density g and galactocentric radius r are studied in disk galaxies. The sample includes the Milky Way galaxy and 11 nearby Sb and Sc galaxies with known radial gas surface densities and H [FORMULA] surface brightnesses, used as a measure of the SFR. The Bayesian approach permits to compute genuine probabilities for the validity of several different functional forms. We do not find any significant explicit dependence of the SFR on radius. A linear dependence on gas density [FORMULA] is found to be an order of magnitude more probable than any universal non-linear law. If each galaxy has its own exponent x, the non-linear law [FORMULA] would also be highly probable. These findings are fairly independent of the CO-H2 conversion recipe used.

Key words: methods: data analysis – methods: statistical – stars: formation – Galaxy: structure – galaxies: ISM – galaxies: spiral

Send offprint requests to: J. Köppen1

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© European Southern Observatory (ESO) 1997

Online publication: April 28, 1998