A flux-limited sample of z 1 Lyα emitting galaxies in the chandra deep field south

Abstract

We describe a method for obtaining a flux-limited sample of Lyα emitters from Galaxy Evolution Explorer (GALEX) grism data. We show that the multiple GALEX grism images can be converted into a three-dimensional (two spatial axes and one wavelength axis) data cube. The wavelength slices may then be treated as narrowband images and searched for emission-line galaxies. For the GALEX NUV grism data, the method provides a Lyα flux-limited sample over the redshift range z = 0.67-1.16. We test the method on the Chandra Deep Field South field, where we find 28 Lyα emitters with faint continuum magnitudes (NUV > 22) that are not present in the GALEX pipeline sample. We measure the completeness by adding artificial emitters and measuring the fraction recovered. We find that we have an 80% completeness above a Lyα flux of 10-15ergcm-2 s-1. We use the UV spectra and the available X-ray data and optical spectra to estimate the fraction of active galactic nuclei in the selection. We report the first detection of a giant Lyα blob at z < 1, though we find that these objects are much less common at z = 1 than at z = 3. Finally, we compute limits on the z 1 Lyα luminosity function and confirm that there is a dramatic evolution in the luminosity function over the redshift range z = 0-1. © 2012 The American Astronomical Society. All rights reserved.