演講資訊

摘要：

In the dark matter problem, a characteristic acceleration scale g_†=1.2×10^-10 ms^-2 is identified in galaxies with tight dynamical and kinematic scaling relations. For example, the radial acceleration relation (RAR) is a tight correlation between dynamical and baryonic acceleration, with g† 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. The RAR and its kinematic implications in galaxies play a similar role to Newton's and Kepler's laws law in the solar system. Besides, these tight empirical correlations pose challenges to the dark matter model. 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 the second acceleration scale g_‡=2.0×10^-9 ms^-2. 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. Finally, I will introduce our current projects and collaborations by investigating MaNGA, XXL, and eROSITA samples.