Galaxy Cold Gas Contents in Modern Cosmological Hydrodynamic Simulations. (arXiv:2002.07226v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Dave_R/0/1/0/all/0/1">Romeel Dav&#xe9;</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Crain_R/0/1/0/all/0/1">Robert A. Crain</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Stevens_A/0/1/0/all/0/1">Adam R. H. Stevens</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Narayanan_D/0/1/0/all/0/1">Desika Narayanan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Saintonge_A/0/1/0/all/0/1">Amelie Saintonge</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Catinella_B/0/1/0/all/0/1">Barbara Catinella</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cortese_L/0/1/0/all/0/1">Luca Cortese</a>

We present a comparison of galaxy atomic and molecular gas properties in
three recent cosmological hydrodynamic simulations, Simba, EAGLE, and
IllustrisTNG, versus observations from $zsim 0-2$. All simulations
qualitatively reproduce the observed z=0 HI and H$_2$ mass functions (HIMF,
H2MF), CO(1-0) luminosity functions (COLF), and gas scaling relations versus
stellar mass, specific star formation rate, and stellar surface density
$mu_*$. Quantitatively, Simba and TNG show significantly more cold gas than
EAGLE, particularly in massive systems. To compare to the COLF, we employ a
prescription for the H$_2$-to-CO conversion factor $alpha_{CO}$ from Narayanan
et al (2012), yielding substantial variations in $alpha_{CO}$ and significant
differences between models. Predicted $z=0$ COLFs agree better with data than
predicted H2MFs. Out to $zsim 2$, EAGLE’s and Simba’s HIMF and COLF strongly
increase, while TNG’s HIMF declines and COLF evolves slowly. EAGLE and Simba
reproduce high $L_{rm CO1-0}$ galaxies at $zsim 1-2$ as observed, owing
partly to a median $alpha_{CO}(z=2)sim 1$ versus $alpha_{CO}(z=0)sim 3$.
Examining HI, H$_2$, and CO scaling relations, their trends with $M_*$ are
broadly reproduced in all models, but EAGLE tends to produce somewhat too
little HI, TNG overproduces cold gas in massive galaxies, and Simba
overproduces molecular gas. Specifically in Simba, we test how individual black
hole feedback modules impact cold gas contents. We find that Simba’s AGN jet
feedback is primarily responsible by lowering cold gas contents from $zsim
1to0$ by suppressing cold gas in $M_*>sim 10^{10}M_odot$ galaxies, while
X-ray feedback suppresses the formation of high-$mu_*$ systems.

We present a comparison of galaxy atomic and molecular gas properties in
three recent cosmological hydrodynamic simulations, Simba, EAGLE, and
IllustrisTNG, versus observations from $zsim 0-2$. All simulations
qualitatively reproduce the observed z=0 HI and H$_2$ mass functions (HIMF,
H2MF), CO(1-0) luminosity functions (COLF), and gas scaling relations versus
stellar mass, specific star formation rate, and stellar surface density
$mu_*$. Quantitatively, Simba and TNG show significantly more cold gas than
EAGLE, particularly in massive systems. To compare to the COLF, we employ a
prescription for the H$_2$-to-CO conversion factor $alpha_{CO}$ from Narayanan
et al (2012), yielding substantial variations in $alpha_{CO}$ and significant
differences between models. Predicted $z=0$ COLFs agree better with data than
predicted H2MFs. Out to $zsim 2$, EAGLE’s and Simba’s HIMF and COLF strongly
increase, while TNG’s HIMF declines and COLF evolves slowly. EAGLE and Simba
reproduce high $L_{rm CO1-0}$ galaxies at $zsim 1-2$ as observed, owing
partly to a median $alpha_{CO}(z=2)sim 1$ versus $alpha_{CO}(z=0)sim 3$.
Examining HI, H$_2$, and CO scaling relations, their trends with $M_*$ are
broadly reproduced in all models, but EAGLE tends to produce somewhat too
little HI, TNG overproduces cold gas in massive galaxies, and Simba
overproduces molecular gas. Specifically in Simba, we test how individual black
hole feedback modules impact cold gas contents. We find that Simba’s AGN jet
feedback is primarily responsible by lowering cold gas contents from $zsim
1to0$ by suppressing cold gas in $M_*>sim 10^{10}M_odot$ galaxies, while
X-ray feedback suppresses the formation of high-$mu_*$ systems.

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