The Effect of Many Minor Mergers on the Size Growth of Compact Quiescent Galaxies
Jeroen B\'edorf, Simon Portegies Zwart

TL;DR
This study uses N-body simulations to investigate how numerous minor mergers contribute to the size growth of compact quiescent galaxies, finding that small mass ratio mergers significantly increase galaxy size and central mass concentration.
Contribution
The paper demonstrates through simulations that many minor mergers with small mass ratios can explain the observed size evolution of compact galaxies from early to late universe.
Findings
Minor mergers with mass ratios of 1:5 to 1:10 cause sufficient size growth.
Mergers with ratios smaller than 1:20 lead to significant size increase, up to 17 times.
Mass from minor mergers tends to settle in the halo or central region depending on the merger ratio.
Abstract
Massive galaxies with a half-mass radius <~ 1kpc are observed in the early universe (z~>2), but not in the local universe. In the local universe similar-mass (within a factor of two) galaxies tend to be a factor of 4 to 5 larger. Dry minor mergers are known to drive the evolution of the size of a galaxy without much increasing the mass, but it is unclear if the growth in size is sufficient to explain the observations. We test the hypothesis that galaxies grow through dry minor mergers by simulating merging galaxies with mass ratios of q=1:1 (equal mass) to q=1:160. In our N-body simulations the total mass of the parent galaxy doubles. We confirm that major mergers do not cause a sufficient growth in size. The observation can be explained with mergers with a mass ratio of q=1:5--1:10. Smaller mass ratios cause a more dramatic growth in size, up to a factor of ~17 for mergers with a mass…
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