Remarks on the properties of elliptical galaxies in modified Newtonian dynamics

TL;DR

This paper investigates properties of elliptical galaxies under MOND, showing that flat velocity curves at high accelerations are possible and that their dark halo scaling relations resemble MONDian phantom halos.

Contribution

It demonstrates that elliptical galaxies can have flat velocity curves at high accelerations in MOND and that their dark halo scaling relations match those of MONDian phantom halos.

Findings

Flat circular velocity curves can occur at high accelerations in MOND.

Dark halo scaling relations of ellipticals resemble MONDian phantom halos.

Baryonic distributions described by Jaffe profiles produce flat velocity curves.

Abstract

Two incorrect arguments against MOND in elliptical galaxies could be that the equivalent circular velocity curves tend to become flat at much larger accelerations than in spiral galaxies, and that the Newtonian dark matter halos are more concentrated than in spirals. Here, we compare published scaling relations for the dark halos of elliptical galaxies to the scaling relations expected for MONDian phantom halos. We represent the baryonic content of galaxies by spherical profiles, and their corresponding MONDian phantom halos by logarithmic halos. We then derive the surface densities, central densities, and phase space densities and compare them with published scaling relations. We conclude that it is possible to get flat circular velocity curves at high acceleration in MOND, and that this happens for baryonic distributions described by Jaffe profiles in the region where the circular velocity curve is flat. Moreover, the scaling relations of dark halos of ellipticals are remarkably similar to the scaling relations of phantom halos of MOND.