Astronomy Tea Talks at Caltech

"The Spitzer View of Lyman Break Galaxies: Testing Star Formation Rate Diagnostics at High Redshift"

The star formation rates (SFRs) of Lyman Break Galaxies (LBGs) are typically estimated based on
their UV properties alone, as their infrared SEDs and nebular emission lines are often too faint to be
observed. Recently, several lensed LBGs have been discovered, allowing detailed infrared studies of these
otherwise unobservable objects. I'll present the Spitzer mid-IR spectra and mid- to far-IR photometry of
two lensed LBGs, cB58 and the "Cosmic Eye." The spectra show strong PAH emission with little to no hot
dust continuum, similar to low-z starbursts with no AGN activity. The far-IR photometry of both objects
suggests infrared luminosities and star formation rates far lower than predictions based on their UV
properties alone (assuming a Calzetti reddening law). I'll discuss possible explanations for these
discrepancies, and implications for determinations of the star formation rate history of the universe.