Kavli Affiliate: Yingjie Peng
| First 5 Authors: Min Du, Hong-Chuan Ma, Wen-Yu Zhong, Luis C. Ho, Shihong Liao
| Summary:
Utilizing a kinematic decomposition of simulated galaxies, we focus on
galaxies with tiny kinematically inferred stellar halos, indicative of weak
external influences. We investigate the intricate interplay between internal
(natural) and external (nurture) processes in shaping the scaling relationships
of specific angular momentum ($j_star$), stellar mass ($M_star$), and size of
disk galaxies within the IllustrisTNG simulation. The correlation among mass,
size, and angular momentum of galaxies is examined by comparing simulations
with observations and the theoretical predictions of the exponential
hypothesis. Galaxies with tiny stellar halos exhibit a large scatter in the
$j_star$-$M_star$ relation, which suggests that it is inherently present in
their initial conditions. The analysis reveals that the disks of these galaxies
adhere to the exponential hypothesis, resulting in a tight fiducial
$j_star$-$M_star$-scale length (size) relation that is qualitatively
consistent with observations. The inherent scatter in $j_star$ provides a
robust explanation for the mass-size relation and its substantial variability.
Notably, galaxies that are moderately influenced by external processes closely
adhere to a scaling relation akin to that of galaxies with tiny stellar halos.
This result underscores the dominant role of internal processes in shaping the
overall $j_star$-$M_star$ and mass-size relation, with external effects
playing a relatively minor role in disk galaxies. Furthermore, the correlation
between galaxy size and the virial radius of the dark matter halo exists but
fails to provide strong evidence of the connection between galaxies and their
parent dark matter halos.
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