COSMOS-DASH: The Evolution of the Galaxy Size-Mass Relation since z ∼ 3 from New Wide-field WFC3 Imaging Combined with CANDELS/3D-HST

Lamiya A. Mowla, Pieter Van Dokkum, Gabriel B. Brammer, Ivelina Momcheva, Arjen Van Der Wel, Katherine Whitaker, Erica Nelson, Rachel Bezanson, Adam Muzzin, Marijn Franx, John Mackenty, Joel Leja, Mariska Kriek, Danilo Marchesini

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110 Scopus citations


We present COSMOS-Drift And SHift (DASH), a Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) imaging survey of the COSMOS field in the H 160 filter. The survey comprises 456 individual WFC3 pointings corresponding to an area of 0.49 deg2 (0.66 deg2 when including archival data) and reaches a 5σ point-source limit of H 160 = 25.1 (0.″3 aperture). COSMOS-DASH is the widest HST/WFC3 imaging survey in the H 160 filter, tripling the extragalactic survey area in the near-infrared at HST resolution. We make the reduced H 160 mosaic available to the community. We use this data set to measure the sizes of 169 galaxies with at 1.5 < z < 3.0 and augment this sample with 749 galaxies at 0.1 < z < 1.5 using archival ACS imaging. We find that the median size of galaxies in this mass range changes with redshift as reff = (13.4 ± 0.5) × (1+z)(-0.95 ± 0.05 kpc. Separating the galaxies into star-forming and quiescent galaxies using their rest-frame U - V and V - J colors, we find no statistical difference between the median sizes of the most massive star-forming and quiescent galaxies at : they are 4.9 ± 0.9 kpc and 4.3 ± 0.3 kpc, respectively. However, we do find a significant difference in the Sèrsic index between the two samples, such that massive quiescent galaxies have higher central densities than star-forming galaxies. We extend the size-mass analysis to lower masses by combining it with the 3D-HST/CANDELS sample of van der Wel et al. and derive empirical relations between size, mass, and redshift. Fitting a relation of the form reff = A × m α, with m = M/5 × 1010 M and r eff in kpc, we find log A = -0.25 log(1 + z) + 0.80 and α = -0.13 log(1 + z) + 0.27. We also provide relations for the subsamples of star-forming and quiescent galaxies. Our results confirm previous studies that were based on smaller samples or ground-based imaging.

Original languageEnglish (US)
Article number57
JournalAstrophysical Journal
Issue number1
StatePublished - Jul 20 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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