English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Observations of the cosmic evolution of different gas phases across timeindicate a marked increase in the molecular gas mass density towards $z\sim2-3$. Such a transformation implies an accompanied change in the globaldistribution of molecular hydrogen column densities ($N_{\rm{H_2}}$). Usingobservations by PHANGS-ALMA/SDSS and simulations by GRIFFIN/IllustrisTNG weexplore the evolution of this H$_2$ column density distribution function[$f(N_{\rm{H}_2})$]. The H$_2$ (and HI) column density maps for TNG50 andTNG100 are derived in post-processing and are made available through theIllustrisTNG online API. The shape and normalization of $f(N_{\rm{H}_2})$ ofindividual main-sequence star-forming galaxies are correlated with the starformation rate (SFR), stellar mass (${M_*}$), and H$_2$ mass ($M_{\rm{H}_2}$)in both observations and simulations. TNG100, combined with H$_2$post-processing models, broadly reproduces observations, albeit withdifferences in slope and normalization. Also, an analytically modelled $f(N)$,based on exponential gas disks, matches well with the simulations. The GRIFFINsimulation gives first indications that the slope of $f(N_{\rm{H}_2})$ mightnot majorly differ when including non-equilibrium chemistry in simulations. The$f(N_{\rm{H}_2})$ by TNG100 implies that higher molecular gas column densitiesare reached at $z=3$ than at $z=0$. Further, denser regions contribute more tothe molecular mass density at $z=3$. Finally, H$_2$ starts dominating comparedto HI only at column densities above log($N_{\rm{H}_2} / \rm{cm}^{-2}) \sim21.8-22$ at both redshifts. These results imply that neutral atomic gas is animportant contributor to the overall cold gas mass found in the ISM of galaxiesincluding at densities typical for molecular clouds at $z=0$ and $z=3$.

The Column Densities of Molecular Gas across Cosmic Time: Bridging Observations and Simulations