Title:

Star Formation Rate Discrepancies & the Madau Plot


Lisa Kewley
Institute for Astronomy


Abstract:

Observing the star formation rate since the earliest times in
the universe is crucial to understanding galaxy formation and
evolution.  I present results from our investigation into the
use of H-alpha and [OII] as star formation rate (SFR) indicators
for local and high-z samples.  Comparisons between the Kennicutt
[OII] and H-alpha SFR calibrations show that there are two
significant effects which produce strong disagreement between
SFR([OII]) and SFR(H-alpha): reddening and metallicity.  Such a
disagreement can appear as a function of redshift, contaminating
cosmic star formation history studies (Madau plot).  I present a
new SFR([OII]) calibration which does not contain a reddening
assumption, and includes an optional correction for
metallicity.  This new SFR([OII]) removes the previously
observed discrepancy between the star formation history based on
[OII] and the star formation history based on H-alpha.