THE GRISM LENS-AMPLIFIED SURVEY FROM SPACE (GLASS). V. EXTENT AND SPATIAL DISTRIBUTION OF STAR FORMATION INz∼ 0.5 CLUSTER GALAXIES

Abstract

We present the first study of the spatial distribution of star formation in z ∼ 0.5 cluster galaxies. The analysis is based on data taken with the Wide Field Camera 3 as part of the Grism Lens-Amplified Survey from Space (GLASS). We illustrate the methodology by focusing on two clusters (MACS0717.5+3745 and MACS1423.8+2404) with different morphologies (one relaxed and one merging) and use foreground and background galaxies as field control sample. The cluster+field sample consists of 42 galaxies with stellar masses in the range 10 8 -10 11 M , and star formation rates in the range 1-20 M yr −1 . Both in clusters and in the field, Hα is more extended than the rest-frame UV continuum in 60% of the cases, consistent with diffuse star formation and inside out growth. In ∼ 20% of the cases, the Hα emission appears more extended in cluster galaxies than in the field, pointing perhaps to ionized gas being stripped and/or star formation being enhanced at large radii. The peak of the Hα emission and that of the continuum are offset by less than 1 kpc. We investigate trends with the hot gas density as traced by the X-ray emission, and with the surface mass density as inferred from gravitational lens models and find no conclusive results. The diversity of morphologies and sizes observed in Hα illustrates the complexity of the environmental process that regulate star formation. Upcoming analysis of the full GLASS dataset will increase our sample size by almost an order of magnitude, verifying and strengthening the inference from this initial dataset.

K-CLASH: Strangulation and ram pressure stripping in galaxy cluster members at 0.3 < z < 0.6

“…They also concluded that these objects have been ram-pressure stripped, leading to an extended star-forming halo around the stellar component and complicated morphologies. As discussed in Section 3.2, the limiting SFR surface density of our observations is ≈ 0.03 − 0.1 M yr −1 kpc −2 , shallower than the studies of Vulcani et al (2015Vulcani et al ( , 2016 which reach 0.01 M yr −1 kpc −2 . The reason for the apparent disagreement between the studies, therefore, could be due to the fact that we are insensitive to extended low surface brightness Hα emission.…”

“…On the other hand, Vulcani et al (2015Vulcani et al ( , 2016 found a small number of cluster galaxies at redshift 0.3 < z < 0.7 with extended Hα compared to the stellar continuum, using HST grism observations and rest-frame UV, optical and infrared HST imaging. Of the galaxies with "spiral" morphologies in their sample, 7 out of 25 have Hα sizes more than twice their size in the HST F475W band.…”

“…Two further recent examples are Vulcani et al (2015Vulcani et al ( , 2016, who used data from the Grism Lens-Amplified Survey from Space (GLASS) to study the morphologies and star formation rates of 76 Hα emitters in 10 clusters from the Cluster Lensing and Supernova survey with Hubble (CLASH; Postman et al 2012). They found that Hα emitters are observed with a wide variety of morphologies, including a number undergoing ram-pressure stripping, and that their cluster samples follow a mass-star formation rate (SFR) relation similar to that of a matched sample of galaxies in the field.…”

RETURN TO [Log-]NORMALCY: RETHINKING QUENCHING, THE STAR FORMATION MAIN SEQUENCE, AND PERHAPS MUCH MORE

“…Pilot surveys of this nature are underway-GLASS (Treu et al 2015;Jones et al 2015;Vulcani et al 2015b), GASP (Poggianti et al, in preparation), ATLAS3D (Cappellari et al 2011), 3D-HST (Brammer et al 2012;Nelson et al 2015), CALIFA (Sánchez et al 2012), MANGA (Bundy et al 2015), SAMI (Allen et al 2015), KROSS (Magdis et al 2016)-and proving quite powerful. Hence, the "dimensionality problem" at small scales may itself soon be reduced.…”

The Grism Lens-amplified Survey from Space (GLASS). XII. Spatially Resolved Galaxy Star Formation Histories and True Evolutionary Paths at z > 1*

“…Exploiting space's low IR backgrounds, lack of seeing limitations, and lensing's additional resolution and S/N boosts, GLASS provides rest-optical continuum spectra for SFRunbiased, z 1 galaxy samples resolved out to ∼2 half-light radii. These IFU-like data (Vulcani et al 2015b(Vulcani et al , 2016(Vulcani et al , 2017Wang et al 2017) enable individual systems' size, mass, and SFR evolution to be inferred over Gyr timescales, providing new spatio-temporal empirical windows on how galaxies wove their way through the cosmic narrative.…”