X-ray Group and cluster mass profiles in MOND: Unexplained mass on the group scale

Understand

Although very successful in explaining the observed conspiracy between the baryonic distribution and the gravitational field in spiral galaxies without resorting to dark matter (DM), the modified Newtonian dynamics (MOND) paradigm still requires DM in X-ray bright systems.

• Here, to get a handle on the distribution and importance of this DM, and thus on its possible form, we deconstruct the mass profiles of 26 X-ray emitting systems in MOND, with temperatures ranging from 0.5 to 9 keV.
• Initially we compute the MOND dynamical mass as a function of radius, then subtract the known gas mass along with a component of galaxies which includes the cD galaxy with $M/L_K=1$.
• Next we test the compatibility of the required DM with ordinary massive neutrinos at the experimental limit of detection ($m_{\nu}=2$ eV), with density given by the Tremaine-Gunn limit.