The Rest-frame Ultraviolet Light Profile Shapes of Lyα-emitting Galaxies at z = 3.1

Abstract

We present a morphological analysis of the rest-frame ultraviolet emission of 78 resolved, high signal-to-noise z ~ 3.1 Lyα emitters (LAEs) in the Extended Chandra Deep Field-South. Using Hubble Space Telescope/Advanced Camera for Surveys V-band images taken as part of the Galaxy Evolution from Morphology and SEDs, Great Observatories Origins Deep Survey, and Hubble Ultra Deep Field surveys, we investigate both single-component and multi-component LAEs, and derive concentration indices, Sérsic indices, ellipticities, and half-light radii for all resolved components and systems with a signal-to-noise >30. We show that, although the LAE population is heterogeneous in nature, most LAEs are highly concentrated, with a distribution of C values similar to that measured for field stars; this suggests that the diagnostic is a poor discriminator near the resolution limit. The LAEs also display a wide range of Sérsic indices (0 < n < 12), similar to that seen for galaxies in the local neighborhood. However, the majority of LAEs have n < 2, and a visual inspection of the images suggests that the small-n objects have extended or multimodal luminosity profiles, while the LAEs with n > 2 have compact components surrounded by diffuse emission. Moreover, unlike nearby spiral galaxies, whose distribution of ellipticities is flat, the LAE ellipticity distribution peaks near 1 - b/a ~ 0.55. Thus, the population has more in common with z ~ 3 Lyman-break galaxies than local star-forming objects.

Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA), and the Canadian Astronomy Data Centre (CADC/NRC/CSA).