Discovery of a z = 7.452 High Equivalent Width Lyα Emitter from the Hubble Space Telescope Faint Infrared Grism Survey

The Figs Team, Rebecca L. Larson, Steven L. Finkelstein, Norbert Pirzkal, Russell Ryan, Vithal Tilvi, Sangeeta Malhotra, James Rhoads, Keely Finkelstein, Intae Jung, Lise Christensen, Andrea Cimatti, Ignacio Ferreras, Norman Grogin, Anton M. Koekemoer, Nimish Hathi, Robert O'Connell, Göran Östlin, Anna Pasquali, John PharoBarry Rothberg, Rogier Windhorst

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


We present the results of an unbiased search for Lyα emission from continuum-selected 5.6 < z < 8.7 galaxies. Our data set consists of 160 orbits of G102 slitless grism spectroscopy obtained with the Hubble Space Telescope(HST)/WFC3 as part of the Faint Infrared Grism Survey (FIGS; PI: Malhotra), which obtains deep slitless spectra of all sources in four fields, and was designed to minimize contamination in observations of previously identified high-redshift galaxy candidates. The FIGS data can potentially spectroscopically confirm the redshifts of galaxies, and as Lyα emission is resonantly scattered by neutral gas, FIGS can also constrain the ionization state of the intergalactic medium during the epoch of reionization. These data have sufficient depth to detect Lyα emission in this epoch, as Tilvi et al. have published the FIGS detection of previously known Lyα emission at z = 7.51. The FIGS data use five separate roll angles of HST to mitigate the contamination by nearby galaxies. We created a method that accounts for and removes the contamination from surrounding galaxies and also removes any dispersed continuum light from each individual spectrum. We searched for significant (>4σ) emission lines using two different automated detection methods, free of any visual inspection biases. Applying these methods on photometrically selected high-redshift candidates between 5.6 < z < 8.7, we find two emission lines, one previously published by Tilvi et al., (2016) and a new line at 1.028 μm, which we identify as Lyα at z = 7.452 ± 0.003. This newly spectroscopically confirmed galaxy has the highest Lyα rest-frame equivalent width (EWLyα) yet published at z > 7 (140.3 ± 19.0 -).

Original languageEnglish (US)
Article number94
JournalAstrophysical Journal
Issue number2
StatePublished - May 10 2018


  • galaxies: distances and redshifts
  • galaxies: high-redshift
  • line: identification

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


Dive into the research topics of 'Discovery of a z = 7.452 High Equivalent Width Lyα Emitter from the Hubble Space Telescope Faint Infrared Grism Survey'. Together they form a unique fingerprint.

Cite this