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Title:
Geometrically Derived Timescales for Star Formation in Spiral Galaxies
Authors:
Tamburro, D.; Rix, H.-W.; Walter, F.; Brinks, E.; de Blok, W. J. G.; Kennicutt, R. C.; MacLow, M.-M.
Affiliation:
AA(Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany ), AB(Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany ), AC(Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg, Germany ), AD(Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK ), AE(Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701, South Africa ), AF(Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK ), AG(Department of Astrophysics, American Museum of Natural History, 79th Street and Central Park West, New York, NY 10024-5192, USA ; Also at Max-Planck-Institut für Astronomie, and Institut für Theoretische Astrophysik, Zentrum für Astronomie der Universität Heidelberg, Germany.)
Publication:
The Astronomical Journal, Volume 136, Issue 6, pp. 2872-2885 (2008). (AJ Homepage)
Publication Date:
12/2008
Origin:
IOP
Keywords:
galaxies: evolution, galaxies: ISM, galaxies: kinematics and dynamics, galaxies: spiral, stars: formation
DOI:
10.1088/0004-6256/136/6/2872
Bibliographic Code:
2008AJ....136.2872T

Abstract

We estimate a characteristic timescale for star formation in the spiral arms of disk galaxies, going from atomic hydrogen (H I) to dust-enshrouded massive stars. Drawing on high-resolution H I data from The H I Nearby Galaxy Survey and 24 μm images from the Spitzer Infrared Nearby Galaxies Survey, we measure the average angular offset between the H I and 24 μm emissivity peaks as a function of radius, for a sample of 14 nearby disk galaxies. We model these offsets assuming an instantaneous kinematic pattern speed, Ω p , and a timescale, t H Imap24 μm, for the characteristic time span between the dense H I phase and the formation of massive stars that heat the surrounding dust. Fitting for Ω p and t H Imap24 μm, we find that the radial dependence of the observed angular offset (of the H I and 24 μm emission) is consistent with this simple prescription; the resulting corotation radii of the spiral patterns are typically R cor sime 2.7Rs , consistent with independent estimates. The resulting values of t H Imap24 μm for the sample are in the range 1-4 Myr. We have explored the possible impact of non-circular gas motions on the estimate of t H Imap24 μm and have found it to be substantially less than a factor of 2. This implies a short timescale for the most intense phase of the ensuing star formation in spiral arms, and implies that a considerable fraction of molecular clouds exist only for a few Myr before forming stars. However, our analysis does not preclude that some molecular clouds persist considerably longer. If much of the star formation in spiral arms occurs within this short interval t H Imap24 μm, then star formation must be inefficient, in order to avoid the short-term depletion of the gas reservoir.
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