AAS 207th Meeting, 8-12 January 2006
Session 179 Evolution of Galaxies, and Galaxies Surveys at Low Redshift
Poster, Thursday, 9:20am-4:00pm, January 12, 2006, Exhibit Hall

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[179.07] Spitzer IRAC Observations of Nearby Star-Forming Galaxies and Implications for Star Formation Rates

J.E. Young, C. Gronwall (Penn State), J.L. Rosenberg (CfA), J.J. Salzer (Wesleyan)

Tracing the star formation history of the universe is key to understanding galaxy formation and evolution and has been the subject of intense research. Studies of star formation in high redshift galaxies depend critically on star formation rate indicators calibrated with nearby samples of star-forming galaxies. The calibration of these indicators at various wavelengths is inconsistent, and different indicators tend to be used at different wavelengths. While nearby samples rely on H-alpha flux, higher redshift studies often rely on rest-frame UV flux. Systematic uncertainties in the calibration of these indicators lead to differences of up to a factor of five in SFR estimates. Improved SFR calibrations are crucial to our understanding of the star formation history of the universe.

Since most of the UV flux from young stars in absorbed by dust and then reemitted in the IR continuum, mid-IR flux may be a useful SFR indicator. In this poster, we address this issue with a multi- wavelength analysis of a volume limited set of 131 H-alpha selected emission-line galaxies from the Kitt Peak International Spectroscopic Survey (KISS) which overlaps with the NOAO Deep Wide-Field Survey (NDWFS) in Bootes. These galaxies are a representative star-forming sample of low redshift galaxies (z < 0.1). Using H-alpha flux and mid-IR photometry from the Spitzer IRAC Shallow Survery, we compare these galaxies at the relevant wavelengths to characterize the relationship between mid-IR flux and SFR. This will aid in proper calibration of mid-IR flux as a SFR indicator.

J.Y. and C.G. acknowledge support from NSF-AST 01-37927 for this work. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.

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