Star formation at high redshift as traced by near-infrared Halpha surveys

Abstract

Surveys of redshifted emission lines in the near-infrared will provide unique information on the cosmic star formation history. Near-infrared Halpha surveys will probe the cosmic star formation density and the evolution of the luminosity function of star forming galaxies out to z\sim2.5, including the important z=1.5-2.0 epoch, where according to current knowledge the cosmic star formation density peaks. Halpha and other hydrogen recombination lines (except Lyman alpha) 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 Lyman alpha 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\approx2.25 is derived, based on a new and sensitive large-area ESO near-infrared survey for Halpha emission at this redshift. Future observational directions, at near-infrared and longer wavelengths, for reading the cosmic star formation history are outlined.

Invited review, to appear in "Extragalactic Astronomy in the Infrared", eds. G.A. Mamon, Trinh Xuan Thuan, and J. Tran Thanh Van, Editions Frontieres, Gif-sur-Yvette. LaTeX2e, 10 pages, 3 postscript figures included. See also http://www.strw.leidenuniv.nl/~pvdwerf