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The Calibration of Mid-Infrared Star Formation Rate Indicators
- Publication Year :
- 2007
- Publisher :
- American Astronomical Society, 2007.
-
Abstract
- With the goal of investigating the degree to which the mid-infrared emission traces the star formation rate (SFR), we analyze Spitzer 8 um and 24 um data of star-forming regions in a sample of 33 nearby galaxies with available HST/NICMOS images in the Paschen-alpha (1.8756 um) emission line. The galaxies are drawn from the Spitzer Infrared Nearby Galaxies Survey (SINGS) sample, and cover a range of morphologies and a factor ~10 in oxygen abundance. Published data on local low-metallicity starburst galaxies and Luminous Infrared Galaxies are also included in the analysis. Both the stellar-continuum-subtracted 8 um emission and the 24 um emission correlate with the extinction-corrected Pa-alpha line emission, although neither relationship is linear. Simple models of stellar populations and dust extinction and emission are able to reproduce the observed non-linear trend of the 24 um emission versus number of ionizing photons, including the modest deficiency of 24 um emission in the low metallicity regions, which results from a combination of decreasing dust opacity and dust temperature at low luminosities. Conversely, the trend of the 8 um emission as a function of the number of ionizing photons is not well reproduced by the same models. The 8 um emission is contributed, in larger measure than the 24 um emission, by dust heated by non-ionizing stellar populations, in agreement with previous findings. Two SFR calibrations, one using the 24 um emission and the other using a combination of the 24 um and H-alpha luminosities (Kennicutt et al. 2007), are presented. No calibration is presented for the 8 um emission, because of its significant dependence on both metallicity and environment. The calibrations presented here should be directly applicable to systems dominated by on-going star formation.<br />Comment: 67 pages, 15 figures, accepted for publication on the Astrophysical Journal; replacement contains: correction to equation 8; important tweaks to equation 9; various typos corrected
- Subjects :
- Luminous infrared galaxy
Physics
Opacity
Star formation
Metallicity
Astrophysics::High Energy Astrophysical Phenomena
Extinction (astronomy)
Astrophysics (astro-ph)
FOS: Physical sciences
Astronomy and Astrophysics
Astrophysics
Astrophysics::Cosmology and Extragalactic Astrophysics
Galaxy
Space and Planetary Science
Astrophysics::Solar and Stellar Astrophysics
Emission spectrum
Astrophysics::Earth and Planetary Astrophysics
Astrophysics::Galaxy Astrophysics
Line (formation)
Subjects
Details
- Language :
- English
- Database :
- OpenAIRE
- Accession number :
- edsair.doi.dedup.....880c4ed9e1a8edc7de4e36bd51a0663f