EDP Sciences
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Volume 402, Number 1, April IV 2003
Page(s) 79 - 85
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20030265

A&A 402, 79-85 (2003)
DOI: 10.1051/0004-6361:20030265

Constraints to the evolution of Ly- $\alpha$ bright galaxies between z = 3 and z = 6

C. Maier1, K. Meisenheimer1, E. Thommes1, 2, H. Hippelein1, H. J. Röser1, J. Fried1, B. von Kuhlmann1, S. Phleps1 and C. Wolf1, 3

1  Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
2  Insitut für Theoretische Physik, Universität Heidelberg, 69111 Heidelberg, Germany
3  Department of Physics, Denys Wilkinson Bldg., University of Oxford, Keble Road, Oxford, OX1 3RH, UK

(Received 6 November 2002 / Accepted 4 February 2003 )

Galaxies at high redshift with a strong Ly- $\alpha$ emission line trace massive star formation in the absence of dust, and can therefore be regarded as a prime signature of the first major starburst in galaxies. We report results of the Ly- $\alpha$ search within the Calar Alto Deep Imaging Survey (CADIS). With the imaging Fabry-Perot interferometer, CADIS can detect emission lines in three waveband windows free of night-sky emission lines at 700 nm, 820 nm, and 920 nm. The typical flux detection limit for Ly- $\alpha$ emission redshifted into these windows, $F_{\rm lim} \ga 3
\times 10^{-20} ~\rm {W}\,\rm {m}^{-2}$ , corresponds to (unobscured) star formation rates of $\ga$ $ 10\, {M}_{\odot}$/yr at z=6. Candidate Ly- $\alpha$-emitting galaxies are selected from the total emission line sample, which contains more than 97% of objects at z<1.2, by the absence of flux below the Lyman limit ( B-band "dropouts"), and the non-detection of secondary emission lines in narrow band filters. We have detected 5 bright Ly- $\alpha$-emitting galaxy candidates at $z \simeq 4.8$, and 11 candidates at $z \simeq 5.7$. For two of four observed Ly- $\alpha$ candidates, one candidate at $z \simeq 4.8$ , and the other at $z \simeq 5.7$, the emission line detected with the Fabry-Perot interferometer has been verified spectroscopically at the VLT.

When compared to Ly- $\alpha$ surveys at $z\leq3.5$, even the upper limits set by our list of candidates show that bright Ly- $\alpha$ galaxies are significantly rarer at $z\ga 5$ than the assumption of a non-evolving population would predict. Therefore we conclude that the Ly- $\alpha$ bright phase of primeval star formation episodes reached its peak at redshifts 3<z<6.

Key words: galaxies: evolution -- galaxies: formation -- galaxies: high-redshift

Offprint request: C. Maier, maier@mpia-hd.mpg.de

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© ESO 2003