DUST-INDUCED SYSTEMATIC ERRORS IN ULTRAVIOLET-DERIVED STAR FORMATION RATES

摘要

Rest-frame far-ultraviolet (FUV) luminosities form the 'backbone' of our understanding of star formation at all cosmic epochs. FUV luminosities are typically corrected for dust by assuming that extinction indicators which have been calibrated for local starbursting galaxies apply to all star-forming galaxies. I present evidence that 'normal' star-forming galaxies have systematically redder UV/optical colors than starbursting galaxies at a given PUV extinction. This is attributed to differences in star/dust geometry, coupled with a small contribution from older stellar populations. Folding in data for starbursts and ultra-luminous infrared galaxies, I conclude that SF rates from rest-frame UV and optical data alone are subject to large (factors of at least a few) systematic uncertainties because of dust, which cannot be reliably corrected for using only UV/optical diagnostics.