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Star Formation in NGC 5194 (M51a). II. The Spatially Resolved Star Formation Law

Robert C. KennicuttUniversity of CambridgeDaniela CalzettiVisiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science FoundationFabian WalterMax-Planck-Institute für Astronomie, Königstuhl 17, Heidelberg, D-69117, GermanyG. HelouCalifornia Institute of Technology, MS 314-6, Pasadena, CA 91101D. J. HollenbachNASA Ames Research Center, MS 245-3, Moffett Field, CA 94035-1000L. ArmusSpitzer Science Center, Caltech, MS 220-6, Pasadena, CA 91101G. J. BendoAstrophysics Group, Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ, UKDaniel A. DaleDepartment of Physics and Astronomy, University of Wyoming, Laramie, WY 82071B. T. DraineDepartment of Astrophysical Sciences, Princeton University, Princeton, NJ 08544-1001C. W. EngelbrachtVisiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science FoundationKarl D. GordonVisiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science FoundationMoire K. M. PrescottSteward Observatory, University of Arizona, Tucson, AZ 85721Michael W. ReganSpace Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218M. D. ThornleyDepartment of Physics and Astronomy, Bucknell University, Lewisburg, PA 17837Caroline BotSpitzer Science Center, Caltech, MS 220-6, Pasadena, CA 91101E. BrinksSchool of Physics, Astronomy, and Mathematics, University of Hertfordshire, College Lane, Herts AL10 9AB, UKW. J. G. de BlokResearch School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston Creek ACT 2611, AustraliaDulia de MelloCatholic University of AmericaM. MeyerSpace Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218John MoustakasPhysics Department, New York University, 4 Washington Place, New York, NY 10003E. J. MurphyDepartment of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101Kartik ShethSpitzer Science Center, Caltech, MS 220-6, Pasadena, CA 91101J. D. SmithUniversity of Arizona

2007en

ABI

Annotatsiya

We have studied the relationship between the star formation rate (SFR), surface density, and gas surface density in the spiral galaxy M51a (NGC 5194), using multiwavelength data obtained as part of the Spitzer Infrared Nearby Galaxies Survey (SINGS). We introduce a new SFR index based on a linear combination of Halpha emission-line and 24 mum continuum luminosities, which provides reliable extinction-corrected ionizing fluxes and SFR densities over a wide range of dust attenuations. The combination of these extinction-corrected SFR densities with aperture synthesis H I and CO maps has allowed us to probe the form of the spatially resolved star formation law on scales of 0.5-2 kpc. We find that the resolved SFR versus gas surface density relation is well represented by a Schmidt power law, which is similar in form and dispersion to the disk-averaged Schmidt law. We observe a comparably strong correlation of the SFR surface density with the molecular gas surface density, but no significant correlation with the surface density of atomic gas. The best-fitting slope of the Schmidt law varies from N=1.37 to 1.56, with zero point and slope that change systematically with the spatial sampling scale. We tentatively attribute these variations to the effects of areal sampling and averaging of a nonlinear intrinsic star formation law. Our data can also be fitted by an alternative parameterization of the SFR surface density in terms of the ratio of gas surface density to local dynamical time, but with a considerable dispersion.

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DOI: 10.1086/522300

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