http://arxiv.org/abs/2201.08579
The IllustrisTNG simulations reproduce well the observed scaling relation between specific angular momentum (sAM) $j_{\rm s}$ and mass $M_{\rm s}$ of galaxies, i.e., the $j_{\rm s}$-$M_{\rm s}$ relation. This relation develops in disk galaxies at redshift $z\lesssim 1$ via forming disk structures whose sAM are nearly conserved from their parent dark matter halos. We provide a simple model that describes well the connection between halos and galaxies, giving ${\rm log} j_{\rm s} = 0.54\ {\rm log} M_{\rm s} – 2.53 + b$, where $b$ quantifies how well sAM is retained. This model suggests that the power-law index 0.54 of the $j_{\rm s}$-$M_{\rm s}$ relation is determined by (i) the change of the halo angular momentum-mass relation $j \propto M^{\alpha}$, whose index $\alpha$ grows from 0.68 to 0.80 under the effect of baryonic processes, and (ii) the mass dependence of the luminous-dark mass ratio. This model is different from the traditional expectation using a constant luminous-dark mass ratio and $\alpha=2/3$. We further suggest that a significant loss of sAM, which manifests as a decrease in $b$, leads to the parallel offset of elliptical galaxies (relative to disk galaxies) in the $j_{\rm s}$-$M_{\rm s}$ relation.
M. Du, L. Ho, H. Yu, et. al.
Mon, 24 Jan 22
39/59
Comments: 8 pages, 5 figures, submitted to ApJL
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