Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000isass..14..115h&link_type=abstract
The Institute of Space and Astronautical Science Report SP No. 14, p. 115-122.
Astronomy and Astrophysics
Astronomy
Extinction, Galaxy Evolution, H Ii Regions, Infrared Galaxies
Scientific paper
Infrared (IR) dust emission from galaxies is frequently used as an indicator of star formation rate (SFR). However, the effect of dust-to-gas ratio, or amount of dust, on the conversion law from IR luminosity to SFR has not been considered. In this paper, we present a convenient formula including the effect. In order to obtain the dependence of the dust-to-gas ratio, we extend the formula derived in our previous paper, in which a theoretical formula converting IR luminosity to SFR was derived. That formula was expressed as SFR/(Msolar yr -1)= 3.3 × 10-10 (1-η)/(0.4-0.2f+0.6ɛ) (LIR/Lsolar), where f is the fraction of ionizing photons absorbed by hydrogen, ɛ is the efficiency of dust absorption for nonionizing photons, η is the cirrus fraction of observed dust luminosity, and LIR is the observed luminosity of dust emission in the 8-1000-micron range. Throughout the current discussion, we construct an algorithm to relate f and ɛ, both of which depend on the dust-to-gas ratio, to the metallicity, by adopting a galactic relation between dust-to-gas ratio and metallicity. Thus, we estimate the metallicity dependence of our formula. We apply the result to the cosmic star formation history and find that the comoving SFR at z~3 calculated from previous empirical formulae is underestimated by the factor of 4. Finally, we comment on the HII/L2 mission (SPICA).
Hirashita Hiroyuki
Inoue Akio K.
Kamaya Hideyuki
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