The Mass Assembly History of Field Galaxies

downsizing;evolution;galaxy;star formation

Bundy, Kevin A. ; Ellis, Richard S.

University:California Institute of Technology

Department:Physics, Mathematics and Astronomy

关键词: downsizing;    evolution;    galaxy;    star formation;   

Others  :  https://thesis.library.caltech.edu/907/1/thesis.pdf

美国|英语

来源: Caltech THESIS

【 摘 要 】

The work presented in this thesis utilizes the combination of near-IR photometry and spectroscopic redshifts to estimate the stellar masses of distant field galaxies in order to characterize their assembly history since z~1.The primary data set for this analysis comes from an extensive near-IR survey conducted at Palomar Observatory that includes over 12,000 galaxies detected in the Ks-band with DEEP2 spectroscopic redshifts in the range 0.2

New diagnostics are introduced to quantify this downsizing behavior including the quenching mass, M_Q, which traces the stellar mass scale above which star formation in galaxies is suppressed.M_Q decreases by a factor of ~5 after z~1, indicating that the quenching mechanism responsible for downsizing becomes more efficient in galaxies with lower masses as a function of time.This evolution is analyzed as a function of environmental density, and no environmental dependence is observed except in the most extreme environments, where downsizing appears to be slightly accelerated in high density regions.This weak environmental dependence suggests that the quenching mechanism for most galaxies is primarily driven by internal processes.The nature of the quenching mechanism is discussed in the context of CDM galaxy formation models, and additional motivation for this comparison is also presented in a direct study of the near-IR merger rate and an analysis of the relationship between stellar mass and dark matter in disk galaxies.