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

Abstract

We present COSMOS-Drift And SHift (DASH), a Hubble Space Telescope 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 deg 2 (0.66 deg 2 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 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 dataset to measure the sizes of 162 galaxies with log(M /M ) > 11.3 at 1.5 < z < 3.0, and augment this sample with 748 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 r eff = (10.4 ± 0.4) × (1 + z) (−0.65±0.05) kpc. Separating the galaxies into star forming and quiescent galaxies using their restframe 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 z = 2.5: 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. (2014), and derive empirical relations between size, mass, and redshift. Fitting a relation of the form r eff = A × m α , with m = M /5 × 10 10 M and r eff in kpc, we find log A = −0.25 log (1 + z) + 0.79 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.

The OTELO survey as a morphological probe. Last ten Gyr of galaxy evolution

“…For the purpose of the comparison, presented in what follows, this selection is compatible with our ET-LT separation (van der Wel et al 2014). Our MSR for LT galaxies is consistent with those given by Mowla et al (2019), even taking into account the differences in the mass range studied in both works. However, the slope obtained by these authors in the case of ET galaxies is stepper than the fitted in this work for all redshift bins, with the largest difference in the last volume 1 ≤ z < 2 (0.73 and 0.56, in Mowla et al 2019 and in this work, respectively).…”

“…Among them, we can highlight the following: a census of ET galaxies with emission lines, a comprehensive study of the properties of compact galaxies, a comparison of extragalactic sources with and without detection of emission lines; and a recently published work on the machine learning techniques to separate ET from LT galaxies (de Diego et al 2020). Additionally, in this work, we study the MSR of galaxies up to z = 2 and down to stellar masses of log M * /M ∼ 8, which is ∼1 dex lower than the lower mass limit established in previous studies at the same redshift range (van der Wel et al 2014;Mowla et al 2019). In particular, we present insights on the median size evolution r e −z for LT and ET galaxies at a fixed stellar mass found in the OTELO field.…”

“…Thus, in all panels of Fig. 11 we additionally represent the fits from Mowla et al (2019) for star-forming (LT) and quiescent (ET) for the same redshift bins. Their separation onto star-forming and quiescent galaxies is based on U, V, and J rest-frame bands.…”

“…Furthermore, morphology is directly linked to the physical and chemical properties of galaxies, and, ultimately, to their evolution. In particular, the stellar mass-size relation (MSR) has been studied for several decades, and it has been shown that the galaxy size not only can vary significantly with stellar mass and morphology, but it also evolves with redshift depending on these two parameters (e.g., Kormendy & Bender 1996;Shen et al 2003;van der Wel et al 2014;Lange et al 2015;Roy et al 2018;Mowla et al 2019). For instance, early-type (ET) galaxies are typically more compact for the same mass, and more massive for the same size, than the late-type (LT) galaxies at given redshift.…”

The Fundamental Plane of Massive Quiescent Galaxies at z ∼ 2

“…From these observations rapid-size evolution has been inferred for field early-type galaxies across time (Newman et al 2012;van der Wel et al 2014;Faisst et al 2017;Morishita et al 2019;Mowla et al 2019). Simulations have shown dry mergers to be an efficient process for making galaxies larger (e.g., Hopkins et al 2009;Naab et al 2009;Bezanson et al 2009;Hilz et al 2012Hilz et al , 2013Remus et al 2017;Lagos et al 2018).…”