Analytic expressions for the dark matter-baryon relations

Abstract

Recently, some very strong correlations between the distribution of dark matter and baryons (the dark matter-baryon relations) in galaxies with very different morphologies, masses, sizes, and gas fractions have been obtained. Some models have been suggested to explain why the dark matter contribution is fully specified by that of the baryons. In this article, we derive two analytic expressions to explain the observed dark matterbaryon relations based on the cold dark matter (CDM) model. The resultant expressions give excellent agreement with the observational data. The parameters involved in the analytic expressions are closely related to the amount of the baryon content. This model can provide a theoretical understanding of the strong correlations observed. We suggest that the observed relation represents the end product of galaxy formation.

The analytic radial acceleration relation for galaxy clusters

“…Nevertheless, the enclosed dynamical mass profile (M DM + M bar ) derived in the NFW framework is somewhat different from the hydrostatic dynamical mass in Eq. (6). Therefore, in the followings, we also derive an analytic RAR relation within the NFW framework.…”

“…The close relations between dark matter and baryons are not intuitively expected because the standard cold dark matter model suggests that the interaction between dark matter and baryons (except gravity) is almost negligible. Therefore, although some studies are able to reproduce these relations using the cold dark matter framework [6][7][8], the close relations between dark matter and baryons generally more favor the modified gravity theories because many of these theories suggest that baryonic mass and dynamical mass are inter-related [9][10][11][12][13].…”

A tight correlation between the enclosed gravitational mass and hot gas mass in galaxy clusters at intermediate radii

“…The RAR is a very important discovery because it indicates a very general tight correlation between gravitational mass and baryonic mass at different small and intermediate radii, not just for large radii of galaxies. Although some studies can produce these relations based on the CDM model [10,11,12], some of the parameters involved have to be adjusted to match the observed properties of galaxies. Therefore, a satisfactory explanation is still required to account for the observed strong coupling between dark matter and baryons.…”