From Diversity to Dichotomy, and Quenching: Milky-Way-Like and Massive-Galaxy Progenitors at 0.5<z<3.0

TL;DR

This study investigates the evolutionary paths of Milky Way-like and massive galaxies from redshift 3 to 0.5 using multi-band imaging, revealing distinct growth and quenching patterns and their implications for galaxy formation.

Contribution

It introduces a radially resolved pixel SED fitting method and a new approach to assess morphological diversity, highlighting different evolutionary behaviors of galaxy progenitors.

Findings

Milky Way progenitors grow self-similarly in stellar mass.

Massive galaxy progenitors grow inside-out, accumulating most mass at larger radii.

Bulge formation and quenching occur earlier, with distinct timelines for MWs and MGs.

Abstract

Using the HST/WFC3 and ACS multi-band imaging data taken in CANDELS and 3D-HST, we study the general properties and the diversity of the progenitors of the Milky Way (MWs) and local massive galaxy (MGs) at 0.5 < z < 3.0, based on a constant cumulative number density analysis. After careful data reduction and stacking analysis, we conduct a radially resolved pixel SED fitting to obtain the radial distributions of the stellar mass and rest-frame colors. The stellar mass of MWs increases in self-similar way, irrespective of the radial distance, while that of MGs grows in inside-out way where they obtain ~ 75% of the total mass at outer (> 2.5 kpc) radius since z ~ 2. Although the radial mass profiles evolve in distinct ways, the formation and quenching of the central dense region (or bulge) ahead of the outer disk formation are found to be common for both systems. The sudden reddening of bulge at z ~ 1.6 and z ~ 2.4 for MWs and MGs, respectively, suggests the formation of bulge and would give a clue to the different gas accretion histories and quenching. A new approach to evaluate the morphological diversity is conducted by using the average surface density profile and its dispersion. The variety of the radial mass profiles for MGs peaks at higher redshift (z > 2.8), and then rapidly converges to more uniform shape at z < 1.5, while that for MWs remains in the outer region over the redshift. Compared with the observed star formation rates and color profiles, the evolution of variety is consistently explained by the star formation activities.