Morphology and structure of BzK-selected galaxies at z~2 in the CANDELS-COSMOS field

TL;DR

This study analyzes the morphology, structure, and evolution of BzK-selected star-forming and passive galaxies at z~2 using multi-wavelength data, revealing diverse morphologies and different evolutionary paths.

Contribution

It provides a detailed morphological and structural comparison of sBzKs and pBzKs at z~2, highlighting their different sizes, structures, and evolutionary modes.

Findings

sBzKs follow the main sequence of star formation.

pBzKs are more compact and elliptical-like.

Sizes of pBzKs are 2-3 times smaller than local early-type galaxies.

Abstract

Utilizing a BzK-selected technique, we obtain 14550 star-forming galaxies (sBzKs) and 1763 passive galaxies (pBzKs) at z~2 from the K-selected (K<22.5) catalog in the COSMOS/UltraVISTA field. The differential number counts of sBzKs and pBzKs are consistent with the results from the literature. Compared to the observed results, semi-analytic models of galaxy formation and evolution provide too few (many) galaxies at high (low)-mass end. Moreover, we find that the star formation rate (SFR) and stellar mass of sBzKs follow the relation of main sequence. Based on the HST/Wide Field Camera 3 (WFC3) F160W imaging, we find a wide range of morphological diversities for sBzKs, from diffuse to early-type spiral structures, with relatively high M20, large size and low G, while pBzKs are elliptical-like compact morphologies with lower M20, smaller size and higher G, indicating the more concentrated and symmetric spatial extent of stellar population distribution in pBzKs than sBzKs. Furthermore, the sizes of pBzKs (sBzKs) at z~2 are on average two to three (one to two) times smaller than those of local early-type (late-type) galaxies with similar stellar mass. Our findings imply that the two classes have different evolution modes and mass assembly histories.