Vol 15, No 6

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

Guan-Wen Fang, Zhong-Yang Ma, Yang Chen, Xu Kong


Abstract Utilizing a BzK-selection technique, we obtain 14 550 star-forming galaxies (sBzKs) and 1763 passive galaxies (pBzKs) at z ~ 2 from the K-selected (KAB < 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 the high (low) mass end. Moreover, we find that the star formation rate and stellar mass of sBzKs follow the relation of the main sequence. Based on HST/Wide Field Camera 3 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 have elliptical-like compact morphologies with lower M20, smaller size and higher G, indicating a 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 models and mass assembly histories.


Keywords galaxies: evolution — galaxies: fundamental parameters — galaxies: structure — galaxies: high-redshift

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