We describe the results of a new, wide-field survey for z=3.1 Ly-alpha emission-line galaxies (LAEs) in the Extended Chandra Deep Field South (ECDF-S). By using a nearly top-hat 5010 Angstrom filter and complementary broadband photometry from the MUS
YC survey, we identify a complete sample of 141 objects with monochromatic fluxes brighter than 2.4E-17 ergs/cm^2/s and observers-frame equivalent widths greater than ~ 80 Angstroms (i.e., 20 Angstroms in the rest-frame of Ly-alpha). The bright-end of this dataset is dominated by x-ray sources and foreground objects with GALEX detections, but when these interlopers are removed, we are still left with a sample of 130 LAE candidates, 39 of which have spectroscopic confirmations. This sample overlaps the set of objects found in an earlier ECDF-S survey, but due to our filters redder bandpass, it also includes 68 previously uncataloged sources. We confirm earlier measurements of the z=3.1 LAE emission-line luminosity function, and show that an apparent anti-correlation between equivalent width and continuum brightness is likely due to the effect of correlated errors in our heteroskedastic dataset. Finally, we compare the properties of z=3.1 LAEs to LAEs found at z=2.1. We show that in the ~1 Gyr after z~3, the LAE luminosity function evolved significantly, with L* fading by ~0.4 mag, the number density of sources with L > 1.5E42 ergs/s declining by ~50%, and the equivalent width scale-length contracting from 70^{+7}_{-5} Angstroms to 50^{+9}_{-6} Angstroms. When combined with literature results, our observations demonstrate that over the redshift range z~0 to z~4, LAEs contain less than ~10% of the star-formation rate density of the universe.
We present a rest-frame ultraviolet morphological analysis of 78 resolved, high S/N z ~ 3.1 Lyman Alpha Emitters (LAEs) in the Extended Chandra Deep Field South (ECDF-S). Using HST/ACS V -band images taken as part of the GEMS, GOODS, and HUDF surveys
. For each LAE system identified via our ground-based narrow-band imaging, we have identified those LAE systems with multiple components. We measure the concentration index and present the results of our GALFIT fits for ellipticity, Sersic index, and sizes for each resolved component with S/N > 30 as well as for each LAE system with S/N > 30. The LAEs show a heterogeneous distribution of morphologies while the ma jority tend to be highly concentrated and compact in size. We only measure the morphological properties of resolved LAEs. For systems showing multiple components we also measured the morphology of the individual components. The resolved LAEs are highly concentrated (2 < C < 4) and show a similar distribution to that measured for stars, suggesting that this diagnostic is a poor discriminator near the resolution limit. The measured ellipticities for components show a distribution peaked at {epsilon} ~ 0.55 which is significantly different from the flat distribution of ellipticities observed for local spiral galaxies and is similar to the distribution found for Lyman-break galaxies at the same redshift. There is a wide range of best-fit Sersic indices (1 < n < 10) with the majority being between 0 < n < 2. The distribution is similar to the distribution of Sersic indices seen locally. A visual inspection of the images suggests a qualitative morphological transition at n ~ 2, with small-n LAEs having extended or multimodal light distributions and relatively little diffuse emission and large-n LAEs have compact central components surrounded by diffuse emission.
