Oral Presentation

The Second Acceleration Scale in Dark Matter Problem

Author(s): Yong Tian (Graduate Institute of Astronomy, National Central University)

Presenter: Yong Tian (National Central University)

A characteristic acceleration scale is identified in galaxies with tight dynamical and kinematic scaling relations in the dark matter problem. For example, the radial acceleration relation (RAR) is a tight correlation between dynamical and baryonic acceleration, with the acceleration scale as a turning point between high and low acceleration regions. In addition, the low acceleration limit of the RAR recovers the famous baryonic Tully-Fisher relation (BTFR) and baryonic Faber-Jackson relation (BFJR) as the kinematic counterparts. However, such a characteristic acceleration scale fails to explain the “missing mass” in galaxy clusters. In this talk, I will present our recent discoveries of the tight parallel RAR and BFJR in brightest cluster galaxies (BCGs) and galaxy clusters, albeit with a larger second acceleration scale. In our studies, both velocity dispersion profiles of BCGs and clusters illustrate a flat tail. Moreover, the existence of the second acceleration scale raises issues on both the dark matter model and modified gravity on BCG-cluster scales.