On ths assembly history of stellar components in massive galaxies
Jaehyun Lee, Sukyoung K. Yi

TL;DR
This study uses semi-analytic models to explain the growth and assembly history of massive galaxies, reconciling observational data with hierarchical merger theories and highlighting the dominant role of mergers in the most massive galaxies.
Contribution
The paper demonstrates that hierarchical merger models can reproduce observed galaxy growth patterns and details the varying contributions of mergers and star formation across galaxy masses.
Findings
Most massive galaxies acquire ~70% of their stars via mergers.
Merger contribution decreases with galaxy mass.
Merger-driven growth dominates at high redshift (~z=2).
Abstract
Matsuoka & Kawara (2010) showed that the number density of the most massive galaxies (log M/M_sun=11.5-12.0) increases faster than that of the next massive group (log M/M_sun=11.0-11.5) during 0 < z < 1. This appears to be in contradiction to the apparent "downsizing effect". We attempt to understand the two observational findings in the context of the hierarchical merger paradigm using semi-analytic techniques. Our models closely reproduce the result of Matsuoka & Kawara (2010). Downsizing can also be understood as larger galaxies have, on average, smaller assembly ages but larger stellar ages. Our fiducial models further reveal details of the history of the stellar mass growth of massive galaxies. The most massive galaxies (log M/M_sun=11.5-12.0 at z=0), which are mostly brightest cluster galaxies, obtain roughly 70% of their stellar components via merger accretion. The role of merger…
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