The 3.3 micron PAH Emission as a Star Formation Rate Indicator
  Polycyclic Aromatic Hydrocarbon (PAH) emission features dominate the
mid-infrared spectra of star-forming galaxies and can be useful to calibrate
star formation rates and diagnose ionized states of grains. However, the PAH
3.3 micron feature has not been studied as much as other PAH features since it
is weaker than others and resides outside of Spitzer capability. In order to
detect and calibrate the 3.3 micron PAH emission and investigate its potential
as a star formation rate indicator, we carried out an AKARI mission program,
AKARI mJy Unbiased Survey of Extragalactic Survey (AMUSES) and compare its
sample with various literature samples. We obtained 2 ~5 micron low resolution
spectra of 20 flux-limited galaxies with mixed SED classes, which yields the
detection of the 3.3 micron PAH emission from three out of 20 galaxies. For the
combined sample of AMUSES and literature samples, the 3.3 micron PAH
luminosities correlate with the infrared luminosities of star-forming galaxies,
albeit with a large scatter (1.5 dex). The correlation appears to break down at
the domain of ultra-luminous infrared galaxies (ULIRGs), and the power of the
3.3 micron PAH luminosity as a proxy for the infrared luminosity is hampered at
log[L(PAH3.3)/(erg/sec)] > -42.0. Possible origins for this deviation in the
correlation are discussed, including contribution from AGN and strongly
obscured YSOs, and the destruction of PAH molecules in ULIRGs.
