Dynamical Properties of Molecular Cloud Complexes in Galaxies at the Epoch of Reionization. (arXiv:1907.02972v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Leung_T/0/1/0/all/0/1">T. K. Daisy Leung</a> (Cornell, Flatiron CCA), <a href="http://arxiv.org/find/astro-ph/1/au:+Pallottini_A/0/1/0/all/0/1">Andrea Pallottini</a> (Centro Fermi, SNS), <a href="http://arxiv.org/find/astro-ph/1/au:+Ferrara_A/0/1/0/all/0/1">Andrea Ferrara</a> (SNS, Kavli IPMU), <a href="http://arxiv.org/find/astro-ph/1/au:+Low_M/0/1/0/all/0/1">Mordecai-Mark Mac Low</a> (Flatiron CCA, AMNH)

We study the properties of molecular cloud complexes (MCCs) at the epoch of
reionization using cosmological zoom-in simulations. We identify MCCs in a z~6
prototypical (“Althaea”) using an H2 density-based clump finder. We compare
their mass, size, velocity dispersion, gas surface density, and virial
parameter (alpha_vir) to observations. In Althaea, the typical MCC mass and
size are Mgas~10^6.5 Msun and R~45-100 pc, which are comparable to those found
in nearby spirals and starburst galaxies. MCCs are highly supersonic and
supported by turbulence, with r.m.s velocity dispersions of sigma_gas~20-100
km/s and pressure of P/K_B~10^7.6 K cm^-3 (i.e., > 1000x with respect to the
Milky Way), similar to those found in nearby and z~2 gas-rich starburst
galaxies. In addition, we perform stability analysis to understand the origin
and dynamical properties of MCCs. We find that MCCs are globally stable in the
main disk of Althaea. Densest regions where star formation is expected to take
place in clumps and cores on even smaller scales instead have lower alpha_vir
and Toomre-Q values. Detailed studies of the star-forming gas dynamics at the
epoch of reionization thus require a spatial resolution of <40 pc (~0.01"), which is within reach with the Atacama Large (sub-)Millimeter Array (ALMA) and the Next Generation Very Large Array (ngVLA).

We study the properties of molecular cloud complexes (MCCs) at the epoch of
reionization using cosmological zoom-in simulations. We identify MCCs in a z~6
prototypical (“Althaea”) using an H2 density-based clump finder. We compare
their mass, size, velocity dispersion, gas surface density, and virial
parameter (alpha_vir) to observations. In Althaea, the typical MCC mass and
size are Mgas~10^6.5 Msun and R~45-100 pc, which are comparable to those found
in nearby spirals and starburst galaxies. MCCs are highly supersonic and
supported by turbulence, with r.m.s velocity dispersions of sigma_gas~20-100
km/s and pressure of P/K_B~10^7.6 K cm^-3 (i.e., > 1000x with respect to the
Milky Way), similar to those found in nearby and z~2 gas-rich starburst
galaxies. In addition, we perform stability analysis to understand the origin
and dynamical properties of MCCs. We find that MCCs are globally stable in the
main disk of Althaea. Densest regions where star formation is expected to take
place in clumps and cores on even smaller scales instead have lower alpha_vir
and Toomre-Q values. Detailed studies of the star-forming gas dynamics at the
epoch of reionization thus require a spatial resolution of <40 pc (~0.01″),
which is within reach with the Atacama Large (sub-)Millimeter Array (ALMA) and
the Next Generation Very Large Array (ngVLA).

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