State of the Universe
The radial acceleration relation in a LCDM universe
by Prof. Aseem Paranjape (IUCAA, India)
Friday, April 9, 2021 from to (Asia/Kolkata)
The `radial acceleration relation’ (RAR) between the total and baryonic centripetal acceleration profiles of galaxies has recently emerged as an intriguing new potential test of gravity at galactic scales. I will discuss the RAR in the framework of the Lambda-cold dark matter (LCDM) framework, presenting new analytical insights into the emergence of this relation from an interplay between baryonic feedback processes and the distribution of CDM in dark halos. I will show that, at high baryonic acceleration (i.e., in the baryon-dominated, inner halo region), the median RAR of central galaxies in LCDM is very sensitive to the backreaction of baryons on the dark matter profile of the host halo. On the other hand, the median at very low accelerations (halo outskirts) is determined by the abundance and distribution of diffuse gas affected by feedback processes. At all accelerations, the scatter around the median RAR is determined almost entirely by variations in host halo mass and concentration. These results follow from analytical arguments augmented by a realistic mock catalog of galactic rotation curves in a cosmological volume, and lead to a number of testable predictions of the LCDM paradigm at galactic scales.