The mass dependence of structure, star formation rate, and mass assembly mode at 0.5<z< 2.5

TL;DR

This study examines how galaxy structure, star formation, and mass assembly depend on stellar mass across redshifts 0.5 to 2.5, revealing transitional phases and morphological transformations during quenching.

Contribution

It provides new insights into the mass-dependent structural and morphological evolution of galaxies during quenching at intermediate redshifts.

Findings

Structural parameters correlate with stellar mass.

Green galaxies are transitional, with properties between blue and red galaxies.

Morphological transformation sequences vary with redshift.

Abstract

To investigate the mass dependence of structural transformation and star formation quenching, we construct three galaxy samples using massive ($M_* > 10^{10} M_{\odot}$) red, green, and blue galaxy populations at $0.5<z<2.5$ in five 3D--{\it HST}/CANDELS fields. The structural parameters, including effective radius ($r_{\rm e}$), galaxy compactness ($\Sigma_{1.5}$), and second order moment of 20\% brightest pixels ($M_{20}$) are found to be correlated with stellar mass. S\'{e}rsic index ($n$), concentration ($C$), and Gini coefficient ($G$) seem to be insensitive to stellar mass. The morphological distinction between blue and red galaxies is found at a fixed mass bin, suggesting that quenching processes should be accompanied with transformations of galaxy structure and morphology. Except for $r_e$ and $\Sigma_{1.5}$ at high mass end, structural parameters of green galaxies are intermediate between red and blue galaxies in each stellar mass bin at $z < 2$, indicating green galaxies are at a transitional phase when blue galaxies are being quenched into quiescent statuses. The similar sizes and compactness for the blue and green galaxies at high-mass end implies that these galaxies will not appear to be significantly shrunk until they are completely quenched into red QGs. For the green galaxies at $0.5<z<1.5$, a morphological transformation sequence of bulge buildup can be seen as they are gradually shut down their star formation activities, while a faster morphological transformation is verified for the green galaxies at $1.5<z<2.5$.