AAS 205th Meeting, 9-13 January 2005
Session 128 The Buildup of Galaxy Disks - Star Formation History
Oral, Wednesday, January 12, 2005, 2:00-3:30pm, California
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[128.02] A Comparison of Optical vs. IR SFR Diagnostics of Starforming Galaxies in the SPITZER Extragalactic First Look Survey
P.I. Choi (Spitzer Science Center), Spitzer Extragalactic First Look Survey Team
We investigate the instantaneous star formation rates (SFR)
and extinction properties for a large (N\approx200), NIR
(2.2\micron) + MIR (24\micron) selected sample of normal to
luminous infrared galaxies (LIRGs) with ~.8 in the
First Look Survey (FLS). We combine SPITZER MIPS
24\micron\, observations with high resolution optical Keck
Deimos spectroscopy to compare infrared luminosity and
optical emission-line derived star formation rates
(SFRIR & SFROpt, respectively). The discrepancy
between the optical vs. infrared derived SFRs suggest that
our sample exhibits a wide range of optical extinctions
(1.0v<2.5). Objects with SFRs of a few solar masses per
year have Av values consistent with those of normal
spirals (Av~.0). In contrast, LIRGs at z\gtrsim1,
which make up a large fraction of our sample, have
SFR\approx100 M\odot yr-1 and a mean optical
extinction of Av\approx2.5. For SFRs derived from [OII]
\lambda3727, this translates to as much as 95-98%
attenuation of the [OII] line flux due to dust absorption.
Measuring Av based on a SFRIR/SFROpt diagnostic,
we find that Av is well correlated to the star formation
rate. We derive an IR-luminosity-dependent Av function
that we use to extinction correct our emission line
luminosities. Application of this correction results in a
correlation between SFRIR and SFROpt that has a
mean scatter of 0.3~dex.
The author(s) of this abstract have provided an email address
for comments about the abstract:
pchoi@ipac.caltech.edu
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.