Starburst galaxies: implications at high-redshift

Abstract

Starbursts are an important component of the present-day universe, being the site of ∼25% of the high-mass star-formation. They also serve as local analogs of the processes that were important in the origin and early evolution of galaxies and in the heating and chemical enrichment of the inter-galactic medium. In this contribution I review starbursts from this cosmological perspective, stressing observations at ultraviolet, infrared, and X-ray wavelengths. These data show that: 1) Local starbursts are quite similar in their UV photometric and structural properties to the UV-selected ‘Lyman-break’ galaxies at high-redshift 2) Dust dramatically affects our view of starbursts 3) More massive galaxies host more metal-rich starbursts, which are in turn more heavily extincted by dust 4) More luminous starbursts are more heavily extincted by dust 5) The strong UV interstellar absorption lines directly trace outflows of metal-rich gas, and 6) X-ray observations show that these ‘superwinds’ are strongly mass-loaded flows that carry out gas at a rate comparable to the rate of star formation at inferred velocities that are close to the escape velocity from a massive galaxy. These results suggest that the Lyman-break galaxies are typically significantly reddened and extincted by dust (average factor of 3 to 10 in the UV), may have moderately high metallicities (0.1 to 1 times solar?), are probably building galaxies with stellar surface-mass-densities similar to present-day bulges and ellipticals, and may be suffering substantial losses of metal-enriched gas that can ‘pollute’ the inter-galactic medium. The sub-mm sources detected at high-z are most likely the high-luminosity tail of the Lyman-break population, and probably represent the most metal-rich (dustiest) starbursts occurring in the most massive halos.