HST/WFC3 Grism Observations of

Jasleen Matharu, Adam Muzzin, Gabriel B. Brammer, Erica J. Nelson, Matthew W. Auger, Paul C. Hewett, Remco van der Burg, Michael Balogh, Ricardo Demarco, Danilo Marchesini, Allison G. Noble, Gregory Rudnick, Arjen van der Wel, Gillian Wilson, Howard K.C. Yee

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We present and publicly release (www.gclasshst.com) the first spatially resolved Hα maps of star-forming cluster galaxies at z ∼ 1, made possible with the Wide Field Camera 3 (WFC3) G141 grism on the Hubble Space Telescope (HST). Using a similar but updated method to 3D-HST in the field environment, we stack the Hα maps in bins of stellar mass, measure the half-light radius of the Hα distribution, and compare it to the stellar continuum. The ratio of the Hα to stellar continuum half-light radius, , is smaller in the clusters by (6 ± 9)%, but statistically consistent within 1σ uncertainties. A negligible difference in R[Hα/C] with environment is surprising, given the higher quenched fractions in the clusters relative to the field. We postulate that the combination of high quenched fractions and no change in R[Hα/C] with environment can be reconciled if environmental quenching proceeds rapidly. We investigate this hypothesis by performing similar analysis on the spectroscopically confirmed, recently quenched cluster galaxies. 87% have Hα detections, with star formation rates 8 ± 1 times lower than star-forming cluster galaxies of similar stellar mass. Importantly, these galaxies have an R[Hα/C] that is (81 ± 8)% smaller than coeval star-forming field galaxies at fixed stellar mass. This suggests the environmental quenching process occurred outside-in. We conclude that disk truncation due to ram pressure stripping is occurring in cluster galaxies at z ∼ 1, but more rapidly and/or efficiently than in z ≲ 0.5 clusters, such that the effects on R[Hα/C] become observable just after the cluster galaxy has recently quenched.

Original languageEnglish (US)
Article number222
JournalAstrophysical Journal
Issue number2
StatePublished - Dec 20 2021

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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