EDP Sciences
Free access
Issue
A&A
Volume 467, Number 1, May III 2007
Page(s) 63 - 72
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20065825


A&A 467, 63-72 (2007)
DOI: 10.1051/0004-6361:20065825

Ly$\alpha$ emission in high-redshift galaxies

C. Tapken1, 2, I. Appenzeller1, S. Noll3, S. Richling4, J. Heidt1, E. Meinköhn5, and D. Mehlert2

1  Landessternwarte Heidelberg-Königstuhl, 69117 Heidelberg, Germany
2  Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany
    e-mail: tapken@mpia.de
3  Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße, 85741 Garching, Germany
4  Institut d' astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
5  Institut für Theoretische Astrophysik, Albert-Ueberle-Straße 2, 69120 Heidelberg, Germany

(Received 14 June 2006 / Accepted 5 February 2007)

Abstract
Context. A significant fraction of the high-redshift galaxies show strong ${\rm Ly}{\alpha}$ emission lines. For redshifts z > 5, most known galaxies belong to this class. However, so far not much is known about the physical structure and nature of these objects.
Aims.Our aim is to analyse the ${\rm Ly}{\alpha}$ emission in a sample of high-redshift UV-continuum selected galaxies and to derive the physical conditions that determine the ${\rm Ly}{\alpha}$ profile and the line strength.
Methods. VLT/FORS spectra with a resolution of R $\approx$ 2000 of 16 galaxies in the redshift range of z = 2.7 to 5 are presented. The observed ${\rm Ly}{\alpha}$ profiles are compared with theoretical models.
Results.The ${\rm Ly}{\alpha}$ lines range from pure absorption (EW = -17 Å) to strong emission (EW = 153 Å). Most ${\rm Ly}{\alpha}$ emission lines show an asymmetric profile, and three galaxies have a double-peaked profile. Both types of profiles can be explained by a uniform model consisting of an expanding shell of neutral and ionised hydrogen around a compact starburst region. The broad, blueshifted, low-ionisation interstellar absorption lines indicate a galaxy-scale outflow of the ISM. The strengths of these lines are found to be determined in part by the velocity dispersion of the outflowing medium. We find star-formation rates of these galaxies ranging from $SFR_{\rm {UV}}$ = 1.2 to 63.2 $M_{\odot}$yr-1 uncorrected for dust absorption.
Conclusions.The ${\rm Ly}{\alpha}$ emission strength of our target galaxies is found to be determined by the amount of dust and the kinematics of the outflowing material.


Key words: galaxies: high-redshift -- galaxies: ISM -- galaxies: emission lines



© ESO 2007

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access.

An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.

  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account.
    In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.