Emission-Line Galaxies from the PEARS Hubble Ultra Deep Field: A 2-D   Detection Method and First Results
  The Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) grism PEARS (Probing Evolution And Reionization Spectroscopically) survey provides a large dataset of low-resolution spectra from thousands of galaxies in the GOODS North and South fields. One important subset of objects in these data are emission-line galaxies (ELGs), and we have investigated several different methods aimed at systematically selecting these galaxies. Here we present a new methodology and results of a search for these ELGs in the PEARS observations of the Hubble Ultra Deep Field (HUDF) using a 2D detection method that utilizes the observation that many emission lines originate from clumpy knots within galaxies. This 2D line-finding method proves to be useful in detecting emission lines from compact knots within galaxies that might not otherwise be detected using more traditional 1D line-finding techniques. We find in total 96 emission lines in the HUDF, originating from 81 distinct "knots'' within 63 individual galaxies. We find in general that [OIII] emitters are the most common, comprising 44% of the sample, and on average have high equivalent widths (70% of [OIII] emitters having rest-frame EW>100A). There are 12 galaxies with multiple emitting knots--with different knots exhibiting varying flux values, suggesting that the differing star formation properties across a single galaxy can in general be probed at redshifts z~0.2-0.4. The most prevalent morphologies are large face-on spirals and clumpy interacting systems, many being unique detections owing to the 2D method described here, thus highlighting the strength of this technique. 
Amber N. Straughn, Gerhardt R. Meurer, Norbert Pirzkal, Seth H. Cohen,   Sangeeta Malhotra, James Rhoads, Rogier A. Windhors...