Morphological Classification of High-redshift Massive Galaxies in the COSMOS/UltraVISTA Field

摘要

Utilizing the multi-band photometric data of the COSMOS (Cosmic Evolution Survey)/UltraVISTA (Ultra-deep Visible and Infrared Survey Telescope for Astronomy) field and the high-resolution HST WFC3 (Hubble Space Telescope Wide Field Camera 3) near-infrared images in the CANDELS (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey) field, we have selected 362 galaxies with the redshifts of 1≤ z ≤3 and the stellar masses of M_? ≥ 10~(10.5)M_⊙, and made the classification study on the morphologies of these massive galaxies. The results from the UVJ ((U–V) vs (V–J)) two-color diagram classification, visual classification, non-model based classification (Gini coefficient G and moment index M_(20)), and model based classification (Sérsic index n ) are in good agreement with each other. Compared with the star-forming galaxies (SFGs), the quiescent galaxies (QGs) defined by the UVJ two-color diagram exhibit the compact elliptical structures, and generally have larger n and G, but smaller M_(20) and galaxy’s effective radius r_e. The evolution of galaxy size with the redshift is obvious for various QG and SFG samples defined by the different classification systems (two-color diagram classification system, model and non-model based classification systems), and this evolutionary tendency is stronger for QGs in comparison with SFGs, independent to the selection of galaxy classification methods.