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 Brammer, Ivelina Momcheva, Arjen van der Wel, Katherine E. Whitaker, Erica Nelson, Rachel Bezanson, Adam Muzzin, Marijn Franx, John MacKenty, Joel Leja, Mariska Kriek, Danilo Marchesini

*Corresponding author for this work

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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 (03 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 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 , with 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
Article number57
JournalAstrophysical Journal
Issue number1
Number of pages27
Publication statusPublished - 2019


  • Galaxies: evolution
  • Galaxies: high-redshift
  • Galaxies: photometry
  • Galaxies: structure

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