Star formation at high redshift as traced by near-infrared Hα emission surveys
نویسنده
چکیده
Surveys of redshifted emission lines in the near-infrared will provide unique information on the cosmic star formation history. Near-infrared Hα surveys will probe the cosmic star formation density and the evolution of the luminosity function of star forming galaxies out to z ∼ 2.5, including the important z = 1.5 − 2.0 epoch, where according to current knowledge the cosmic star formation density peaks. Hα and other hydrogen recombination lines (except Lyα) and [O ii] are all useful tracers of star formation provided the luminosity function is probed to sufficiently deep levels. However, shallow surveys or surveys of Lyα or [O iii] emission are not suitable for measuring or even constraining the cosmic star formation density. A first estimate of the star formation density at z ≈ 2.25 is derived, based on a new and sensitive large-area ESO near-infrared survey for Hα emission at this redshift. Future observational directions, at near-infrared and longer wavelengths, for reading the cosmic star formation history are outlined.
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