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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents



ID: 693875.0, MPI für Astronomie / Publikationen_mpia
The VIRUS-P exploration of nearby galaxies (VENGA): the XCO gradient in NGC 628
Authors:Blanc, G. A.; Schruba, A.; Evans, N. J.; Jogee, S.; Bolatto, A.; Leroy, A. K.; Song, M.; van den Bosch, R. C. E.; Drory, N.; Fabricius, M.; Fisher, D.; Gebhardt, K.; Heiderman, A.; Marinova, I.; Vogel, S.; Weinzirl, T.
Date of Publication (YYYY-MM-DD):2013
Title of Journal:The Astrophysical Journal
Volume:764
Issue / Number:2
Start Page:id. 117 (16 pp)
Audience:Not Specified
Abstract / Description:We measure the radial profile of the 12CO(1-0) to H2 conversion factor (X CO) in NGC 628. The Hα emission from the VENGA integral field spectroscopy is used to map the star formation rate (SFR) surface density (ΣSFR). We estimate the molecular gas surface density (ΣH2) from ΣSFR by inverting the molecular star formation law (SFL), and compare it to the CO intensity to measure X CO. We study the impact of systematic uncertainties by changing the slope of the SFL, using different SFR tracers (Hα versus far-UV plus 24 μm), and CO maps from different telescopes (single-dish and interferometers). The observed X CO profile is robust against these systematics, drops by a factor of two from R ~ 7 kpc to the center of the galaxy, and is well fit by a gradient Δlog(X CO) = 0.06 ± 0.02 dex kpc-1. We study how changes in X CO follow changes in metallicity, gas density, and ionization parameter. Theoretical models show that the gradient in X CO can be explained by a combination of decreasing metallicity, and decreasing ΣH2 with radius. Photoelectric heating from the local
Free Keywords:galaxies: abundances; galaxies: ISM; galaxies: spiral; ISM: clouds; ISM: molecules
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-637X %R 10.1088/0004-637X/764/2/117
URL:http://cdsads.u-strasbg.fr/abs/2013ApJ...764..117B
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