Molecular hydrogen abundances of galaxies in the EAGLE simulations

By C. Lagos, Robert A. Crain, Joop Schaye, Michelle Furlong, Carlos S. Frenk, Richard G. Bower, Matthieu Schaller, Tom Theuns, James W. Trayford, Yannick Bahé and 1 more. 2015

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We investigate the abundance of galactic molecular hydrogen (H$_2$) in the "Evolution and Assembly of GaLaxies and their Environments" (EAGLE) cosmological hydrodynamic simulations. We assign H$_2$ masses to gas particles in the simulations in post-processing using two different prescriptions that depend on the local dust-to-gas ratio and the interstellar radiation field. Both result in H$_2$ galaxy mass functions that agree well with observations in the local and high-redshift Universe. The simulations reproduce the observed scaling relations between the mass of H$_2$ and the stellar mass, star formation rate and stellar surface density. Towards high edshifts, galaxies in the simulations display larger H$_2$ mass fractions, and correspondingly lower H$_2$ depletion timescales, also in good agreement with observations. The comoving mass density of H$_2$ in units of the critical density, $\Omega_{\rm H_2}$, peaks at $z\approx 1.2-1.5$, later than the predicted peak of the cosmic star formation rate activity, at $z\approx 2$. This difference stems from the decrease in gas metallicity and increase in interstellar radiation field with redshift, both of which hamper H$_2$ formation. We find that the cosmic H$_2$ budget is dominated by galaxies with $M_{\rm H_2}>10^9\,\rm M_{\odot}$, star formation rates $>10\,\rm M_{\odot}\,\rm yr^{-1}$ and stellar masses $M_{\rm stellar}>10^{10}\,\rm M_{\odot}$, which are readily observable in the optical and near-IR. The match between the H$_2$ properties of galaxies that emerge in the simulations and observations is remarkable, particularly since it involves no adjustable parameters.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/bbe36d9c6f1cbe00fce602dba6b6f2bf4d6251c8

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Citations in the corpus

xCOLD GASS: The Complete IRAM 30 m Legacy Survey of Molecular Gas for Galaxy Evolution Studies (2017, methodology): “For the EAGLE simulation, Lagos et al. (2015) implement the recipes of Gnedin & Kravtsov (2011) and Krumholz (2013); both have a dependence on the radiation field and the amount of metals in the ISM, but the latter has an additional dependence on the atomic gas column density.”
The eagle simulations of galaxy formation: Public release of halo and galaxy catalogues (2015, methodology): “The trees are stored in memory following themethod introduced by Lemson and Springel (2006) for the Millennium Simulation (see also the supplementary material of Springel et al.”
xGASS: total cold gas scaling relations and molecular-to-atomic gas ratios of galaxies in the local Universe (2018, methodology): “For the EAGLE simulations, the partition of the ISM into its different phases was implemented by Lagos et al. (2015) in post-processing.”
The formation and assembly history of the Milky Way revealed by its globular cluster population (2018, background): “…of galaxy stellar masses and sizes (Furlong et al. 2015, 2017), their photometric properties (Trayford et al. 2015) and cold gas content (e.g. Lagos et al. 2015; Bahé et al. 2016; Crain et al. 2017), and key properties of the circumgalactic medium (e.g. Rahmati et al. 2015; Oppenheimer et…”
Size evolution of normal and compact galaxies in the EAGLE simulation (2015, background): “…rates (SFRs; Schaye et al. 2015), galaxy colours (Trayford et al. 2015), rotation curves (Schaller et al. 2015b), the gas content of galaxies (Lagos et al. 2015; Bahé et al. 2016), and the intergalactic hydrogen and metal absorption lines (Schaye et al. 2015; Rahmati et al. 2015), as well…”
PHIBSS: Unified Scaling Relations of Gas Depletion Time and Molecular Gas Fractions (2017, background): “97 detections of CO 2-1 or 3-2 in main sequence SFGs between z=0.5 and 2.7, as part of the PHIBSS2 survey with the updated IRAM NOEMA interferometer (G15, Freundlich et al. 2018, and PHIBSS2 team, in preparation).”
Bimodality of low-redshift circumgalactic O VI in non-equilibrium EAGLE zoom simulations (2016, background): “Furthermore, because EAGLE reproduces key stellar and cold ISM properties of galaxies (e.g. S15; Furlong et al. 2015, 2016; Lagos et al. 2015a,b; Trayford et al. 2015; Bahé et al. 2016; Segers et al. 2015), while explicitly following the hydrodynamics, it is an ideal testbed for this study and…”
The EAGLE simulations of galaxy formation: the importance of the hydrodynamics scheme (2015, background): “…other observables such as the Tully-Fisher relation and specific star formation rates (Schaye et al. 2015), the H2 and H I properties of galaxies (Lagos et al. 2015, Bahe et al. submitted), the evolution of the galaxy stellar mass function (Furlong et al. 2015), the column density distribution…”