The Grism Lens-Amplified Survey from Space (GLASS). I. Survey overview and first data release

TL;DR

The GLASS survey uses Hubble Space Telescope grism spectroscopy to study galaxy clusters at redshifts 0.3-0.7, providing extensive spectroscopic data and redshift catalogs, including new measurements for faint sources and multiple image systems.

Contribution

This paper presents the first data release of the GLASS survey, including a large spectroscopic catalog and software tools, advancing the study of galaxy clusters and gravitational lensing.

Findings

Catalog of 139 emission-line redshifts for extragalactic sources

Identification of three new redshifts of multiple image systems

High-quality spectra enabling detailed cluster and lensing studies

Abstract

We give an overview of the Grism Lens Amplified Survey from Space (GLASS), a large Hubble Space Telescope program aimed at obtaining grism spectroscopy of the fields of ten massive clusters of galaxies at redshift z=0.308-0.686, including the Hubble Frontier Fields (HFF). The Wide Field Camera 3 yields near infrared spectra of the cluster cores, covering the wavelength range 0.81-1.69mum through grisms G102 and G141, while the Advanced Camera for Surveys in parallel mode provides G800L spectra of the infall regions of the clusters. The WFC3 spectra are taken at two almost orthogonal position angles in order to minimize the effects of confusion. After summarizing the scientific drivers of GLASS, we describe the sample selection as well as the observing strategy and data processing pipeline. We then utilize MACSJ0717.5+3745, a HFF cluster and the first one observed by GLASS, to illustrate the data quality and the high-level data products. Each spectrum brighter than H_AB=23 is visually inspected by at least two co-authors and a redshift is measured when sufficient information is present in the spectra. Furthermore, we conducted a thorough search for emission lines through all the GLASS WFC3 spectra with the aim of measuring redshifts for sources with continuum fainter than H_AB=23. We provide a catalog of 139 emission-line based spectroscopic redshifts for extragalactic sources, including three new redshifts of multiple image systems (one probable, two tentative). In addition to the data itself we also release software tools that are helpful to navigate the data.