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One of the outstanding problems in galaxy evolution studies is to link the evolution of the star formation rate of galaxies to their molecular gas content. Observationally, the last decade of studies have led to a clear picture of the cosmic star formation history, which peaked at z~2 and has declined since then. However, it is unclear whether the declining star formation rates are simply the result of lower molecular gas masses, or whether the star formation efficiency has also evolved. In this talk I will discuss how the molecular gas contents of galaxies are measured and highlight the difficulties of doing so at high redshift. I will describe one of the most popular approaches, which relies upon the dust continuum emission, and will present our recent work where we test the validity of the this dust continuum calibration via a unique sample of z~2 galaxies with observations of both dust continuum and CO(1-0) line emission. |
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