Sizes of LYα-emitting Galaxies and Their Rest-frame Ultraviolet Components at z = 3.1

Abstract

We present a rest-frame ultraviolet analysis of ~120 z ~ 3.1 Lyman Alpha Emitters (LAEs) in the Extended Chandra Deep Field South. Using Hubble Space Telescope (HST) images taken as part of the Galaxy Evolution From Morphology and SEDS (GEMS) survey, Great Observatories Origins Deep Survey (GOODS), and Hubble Ultradeep Field surveys, we analyze the sizes of LAEs, as well as the spatial distribution of their components, which are defined as distinct clumps of UV-continuum emission. We set an upper limit of ~1 kpc (~0farcs1) on the rms offset between the centroids of the continuum and Lyα emission. The SFRs of LAE components inferred from the rest-frame ultraviolet continuum range from ~0.1 M _sun yr^-1 to ~5 M _sun yr^-1. A subsample of LAEs with coverage in multiple surveys (at different imaging depths) suggests that one needs a signal-to-noise ratio, S/N gsim30, in order to make a robust estimate of the half-light radius of an LAE system. The majority of LAEs have observed half-light radii lsim2 kpc, and LAE components typically have observed half-light radii lsim1.5 kpc (lsim0farcs20). Although only ~50% of the detected LAE components are resolved at GOODS depth, the brightest (V lsim 26.3) are all resolved in both GOODS and GEMS. Since we find little evidence for a correlation between the rest-UV sizes and magnitudes of LAEs, the majority should be resolved in a deeper survey at the ~0farcs05 angular resolution of the HST. Most of the multi-component LAEs identified in shallow frames become connected in deeper images, suggesting that the majority of the rest-UV "clumps" are individual star-forming regions within a single system.

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).