Quantifying scatter in galaxy formation at the lowest masses. Munshi, F., Brooks, A., Applebaum, E., Christensen, C., Sligh, J. P., & Quinn, T. arXiv e-prints, 2101:arXiv:2101.05822, January, 2021.
Quantifying scatter in galaxy formation at the lowest masses [link]Paper  abstract   bibtex   
We predict the stellar mass – halo mass (SMHM) relationship for dwarf galaxies, using simulated galaxies with peak halo masses of M\$_\{{\textbackslash}rm peak\} = 10{\textasciicircum}\{11\}\$ M\$_\{{\textbackslash}odot\}\$ down into the ultra-faint dwarf range to M\$_\{{\textbackslash}rm peak\} =\$ 10\${\textasciicircum}7\$ M\$_\{{\textbackslash}odot\}\$. Our simulated dwarfs have stellar masses of M\$_\{{\textbackslash}rm star\} = \$ 790 M\$_\{{\textbackslash}odot\}\$ to \$8.2 {\textbackslash}times 10{\textasciicircum}8\$ M\$_\{{\textbackslash}odot\}\$, with corresponding \$V\$-band magnitudes from \$-2\$ to \$-18.5\$. For M\$_\{{\textbackslash}rm peak\} {\textgreater} 10{\textasciicircum}\{10\}\$ M\$_\{{\textbackslash}odot\}\$, the simulated SMHM relationship agrees with literature determinations, including exhibiting a small scatter of 0.3 dex. However, the scatter in the SMHM relation increases for lower-mass halos. We first present results for well-resolved halos that contain a simulated stellar population, but recognize that whether a halo hosts a galaxy is inherently mass resolution dependent. We thus adopt a probabilistic model to populate "dark" halos below our resolution limit to predict an "intrinsic" slope and scatter for the SMHM relation. We fit linearly growing log-normal scatter in stellar mass, which grows to more than 1 dex at M\$_\{{\textbackslash}rm peak\}\$ \$=\$ 10\${\textasciicircum}8\$ M\$_\{{\textbackslash}odot\}\$. At the faintest end of the SMHM relation probed by our simulations, a galaxy cannot be assigned a unique halo mass based solely on its luminosity. Instead, we provide a formula to stochastically populate low-mass halos following our results. Finally, we show that our growing log-normal scatter steepens the faint-end slope of the predicted stellar mass function.
@article{munshi_quantifying_2021,
	title = {Quantifying scatter in galaxy formation at the lowest masses},
	volume = {2101},
	url = {http://adsabs.harvard.edu/abs/2021arXiv210105822M},
	abstract = {We predict the stellar mass -- halo mass (SMHM) relationship for dwarf galaxies, using simulated galaxies with peak halo masses of M\$\_\{{\textbackslash}rm peak\} = 10{\textasciicircum}\{11\}\$ M\$\_\{{\textbackslash}odot\}\$ down into the ultra-faint dwarf range to M\$\_\{{\textbackslash}rm peak\} =\$ 10\${\textasciicircum}7\$ M\$\_\{{\textbackslash}odot\}\$. Our simulated dwarfs have stellar masses of M\$\_\{{\textbackslash}rm star\} = \$ 790 M\$\_\{{\textbackslash}odot\}\$ to \$8.2 {\textbackslash}times 10{\textasciicircum}8\$ M\$\_\{{\textbackslash}odot\}\$, with corresponding \$V\$-band magnitudes from \$-2\$ to \$-18.5\$. For M\$\_\{{\textbackslash}rm peak\} {\textgreater} 10{\textasciicircum}\{10\}\$ M\$\_\{{\textbackslash}odot\}\$, the simulated SMHM relationship agrees with literature determinations, including exhibiting a small scatter of 0.3 dex. However, the scatter in the SMHM relation increases for lower-mass halos. We first present results for
well-resolved halos that contain a simulated stellar population, but recognize that whether a halo hosts a galaxy is inherently mass
resolution dependent. We thus adopt a probabilistic model to populate "dark" halos below our resolution limit to predict an "intrinsic" slope and scatter for the SMHM relation. We fit linearly growing log-normal scatter in stellar mass, which grows to more than 1 dex at M\$\_\{{\textbackslash}rm peak\}\$ \$=\$ 10\${\textasciicircum}8\$ M\$\_\{{\textbackslash}odot\}\$. At the faintest end of the SMHM relation probed by our simulations, a galaxy cannot be assigned a unique halo mass based solely on its luminosity. Instead, we provide a formula to stochastically populate low-mass halos following our results. Finally, we show that our growing log-normal scatter steepens the faint-end slope of the predicted stellar mass function.},
	urldate = {2021-02-03},
	journal = {arXiv e-prints},
	author = {Munshi, Ferah and Brooks, Alyson and Applebaum, Elaad and Christensen, Charlotte and Sligh, Jordan P. and Quinn, T.},
	month = jan,
	year = {2021},
	keywords = {Astrophysics - Astrophysics of Galaxies},
	pages = {arXiv:2101.05822},
}

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