Radial Acceleration Relation by Dark Matter and Baryons in the Intermediate Acceleration Regime.- [PDF] - [Article]

Kyu-Hyun Chae, Mariangela Bernardi, Ravi K. Sheth

We report an empirical relation between the radial accelerations by baryons ($a_{\rm B}$) and dark matter ($a_{\rm DM}$) derived from kinematic analyses of $\sim 7000$ nearly round, pure bulge, non-rotating elliptical galaxies, selected from Sloan Digital Sky Survey DR7. For an acceleration range $a_0 < a_{\rm B} < 30 a_0$ above $a_0 =1.2 \times 10^{-10}$~m~s$^{-2}$, we find $a_{\rm DM}/a_{\rm B} = 10^{p} (a_{\rm B}/a_0)^q$ with $p = -0.08 \pm 0.02$ (stat) $\pm 0.1$ (sys) and $q=-0.93\pm 0.03$ (stat) $\pm 0.1$ (sys). This relation constrains the higher acceleration part of the radial acceleration relation observed for rotating galaxies near or below $a_0$. Our results point to a particular direction in theories of dark matter or modified gravity.