Measurements of the angular momentum-mass relations in the Simba simulation

TL;DR

This paper uses Simba simulations to study the specific angular momentum of galaxies, revealing tight j-mass relations across different components and confirming observational trends about the influence of HI content.

Contribution

It provides new measurements of angular momentum-mass relations in simulated galaxies and links these to HI content and other scaling relations.

Findings

Tight j-M relations for stellar, HI, and baryonic matter.

HI content significantly influences stellar angular momentum scatter.

Simba simulations effectively model galaxy angular momentum properties.

Abstract

We present measurements of the specific angular momentum content (j) of galaxies drawn from the Simba cosmological hydrodynamic simulations. For the stellar, HI and baryonic matter components we demonstrate the existence of extremely tight relations between j and the mass contained within the radius at which the HI mass surface density decreases to 1 Msun/pc^2. These relations are broadly consistent with a variety of empirical measurements. We confirm the observational result that the scatter in the stellar j-M relation is driven largely by HI content, and measure the dependence of its scatter on the deviations of galaxies from other important scaling relations. For a given stellar mass, HI-rich/poor galaxies have more/less-than-average stellar specific angular momentum. A similar, yet weaker, correlation exists for HI mass fraction. Overall, our results demonstrate the utility of the Simba simulations as a platform for understanding and contextualising the data and results from forthcoming large galaxy surveys.