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The Calibration of Mid-Infrared Star Formation Rate Indicators | | D. Calzetti
; R. C. Kennicutt
; C. W. Engelbracht
; C. Leitherer
; B. T. Draine
; L. Kewley
; J. Moustakas
; M. Sosey
; D.A. Dale
; K. D. Gordon
; G.X. Helou
; D.J. Hollenbach
; L. Armus
; G. Bendo
; C. Bot
; B. Buckalew
; T. Jarrett
; A. Li
; M. Meyer
; E.J. Murphy
; M. Prescott
; M. W. Regan
; G. H. Rieke
; H. Roussel
; K. Sheth
; J. D. T. Smith
; M. D. Thornley
; F. Walter
; | | Date: |
23 May 2007 | | Subject: | Astrophysics (astro-ph) | | 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. | | Source: | arXiv, arxiv.0705.3377 | | Services: | Forum | Review | PDF | Favorites | |
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