The properties of Lyman break galaxies at z~ 5
Abstract
In a recent paper, Lehnert & Bremer have photometrically selected a sample of Lyman break galaxies at z > 4.8 from a single VLT/FORS2 pointing and spectroscopically confirmed half of them to be at 4.8 < z < 5.8. To study the properties of such galaxies further, we have photometrically selected a similar sample (VAB > 28, iAB < 26.3, iAB-zAB > 0) from the Hubble Space Telescope Advanced Camera for Surveys (HST ACS) images of the Chandra Deep Field-South. This selection results in a sample of 44 sources from ~150 arcmin2. We find that such galaxies are often barely resolved in the ACS images, having half-light radii of 0.1-0.3 arcsec (<2 kpc). They show no difference in spatial clustering from sources selected by iAB < 26.3, iAB-zAB > 0, which are generally galaxies of lower redshift. However, their distribution over the field is not uniform and their surface density varies considerably over areas comparable to a single 8-m or HST pointing. A reliable determination of the surface and volume densities of such galaxies requires a sky area considerably larger than the current ACS imaging of this field. No individual Lyman break candidate was detected to a 3σ limit of 6 × 10-17 erg s-1 cm-2 at 0.5-5 keV by Chandra (a limiting luminosity of below 2 × 1043 erg s-1 at z~ 5.3). By summing over all positions, we find that the mean source must be undetected at a level at least a factor of 4 times fainter than this. This rules out anything other than a weak active galactic nucleus (AGN) contribution to the emission from these objects; we conclude that luminous AGNs made little contribution to the final stages of re-ionization of the Universe.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- January 2004
- DOI:
- 10.1111/j.1365-2966.2004.07352.x
- arXiv:
- arXiv:astro-ph/0306587
- Bibcode:
- 2004MNRAS.347L...7B
- Keywords:
-
- galaxies: distances and redshifts;
- galaxies: evolution;
- galaxies: formation;
- cosmology: observations;
- early Universe;
- Astrophysics
- E-Print:
- Mon.Not.Roy.Astron.Soc.347:L7,2004