Modified Gravity Spins Up Galactic Halos

TL;DR

This study shows that modified gravity models, specifically f(R) gravity, lead to galactic halos with higher specific angular momentum compared to standard cosmology, especially in low-mass, isolated halos.

Contribution

It demonstrates that specific angular momentum of galactic halos can serve as an independent test for modified gravity models like f(R).

Findings

Galactic halos in f(R) gravity have higher angular momentum than in LCDM.

Largest differences occur in low-mass, isolated halos less than 10^{11}M_sun/h.

Potential use of low surface brightness galaxies as a test for gravity models.

Abstract

We investigate the effect of modified gravity on the specific angular momentum of galactic halos by analyzing the halo catalogs at z=0 from high-resolution N-body simulations for a f(R) gravity model that meets the solar-system constraint. It is shown that the galactic halos in the f(R) gravity model tend to acquire significantly higher specific angular momentum than those in the standard LCDM model. The largest difference in the specific angular momentum distribution between these two models occurs for the case of the isolated galactic halos with mass less than 10^{11}M_sun/h, which are likely least shielded by the chameleon screening mechanism. As the specific angular momentum of galactic halos is rather insensitive to the other cosmological parameters, it can in principle be an independent discriminator of modified gravity. We speculate a possibility of using the relative abundance of the low surface brightness galaxies (LSBGs) as a test of GR given that the formation of the LSBGs befalls in the fast spinning dark halos.