A Two-Dimensional Spectroscopic Study of Emission Line Galaxies in the Faint Infrared Grism Survey (FIGS) I: Detection Method and Catalog

TL;DR

This paper introduces EM2D, a novel two-dimensional emission line detection method applied to Hubble Space Telescope data, enabling detailed analysis of emission line galaxies and improving redshift accuracy and star formation studies.

Contribution

The paper presents the EM2D method for emission line detection, enhancing galaxy redshift measurements and enabling analysis of star formation regions within galaxies up to z~4.

Findings

Improved galaxy redshift accuracy approaching high-resolution data levels.

Identification of multiple star-formation sites within individual galaxies.

Enhanced reliability of high-redshift Lyman-alpha detections.

Abstract

We present the results from the application of a two-dimensional emission line detection method, EMission-line two-Dimensional (EM2D), to the near-infrared G102 grism observations obtained with the Wide-Field Camera 3 (WFC3) as part of the Cycle 22 {\em Hubble Space Telescope} Treasury Program: the Faint Infrared Grism Survey (FIGS). Using the EM2D method, we have assembled a catalog of emission line galaxies (ELGs) with resolved star formation from each of the four FIGS fields. Not only can one better assess the global properties of ELGs, but the EM2D method allows for the analysis and an improved study of the individual emission-line region {\it within} each galaxy. This paper includes a description of the methodology, advantages, and the first results of the EM2D method applied to ELGs in FIGS. The advantage of 2D emission line measurements includes significant improvement of galaxy redshift measurements, approaching the level of accuracy seen in high-spectral-resolution data, but with greater efficiency; and the ability to identify and measure the properties of multiple sites of star-formation and over scales of $\sim$ 1 kpc within individual galaxies out to z $\sim$ 4. The EM2D method also significantly improves the reliability of high-redshift ($z\sim7$) Lyman-$\alpha$ detections. Coupled with the wide field of view and high efficiency of space-based grism observations, EM2D provides a noteworthy improvement on the physical parameters that can be extracted from grism observations.