ISO Observations of Star-forming Galaxies

The Infrared Space Observatory (ISO) is used to carry out mid-IR (7 and 15 µm) and far-IR (90 µm) observations of a sample of star-forming sub-mJy radio sources. By selecting the sample at radio wavelengths, one avoids biases due to dust obscuration. It is found that the mid-IR luminosities, covering the PAH features, measure the star formation rate for galaxies with P1.4GHz < 10 23 W Hz −1 . This is further confirmed using the Hluminosities. The far-IR emission is also found to trace the SFR over the whole range of radio and Hluminosities. The implication of the mid-IR measurements in estimating the SFRs from the future infrared space missions (SIRTF and ASTRO-F) is discussed.