The Mystery of the $\sigma$-Bump -- A new Signature for Major Mergers in Early-type Galaxies?

摘要: The stellar velocity dispersion as a function of the galactocentric radius an early-type galaxy can generally be well approximated by power law $\sigma \propto r^{\beta}$. However, some observed profiles show deviation from this fit at intermediate radii, usually between one and three $R_{\mathrm{eff}}$, where remains constant with radius, showing bump-like behavior, which we term "$\sigma$-"bump. To understand origin $\sigma$-bump, study set simulated galaxies formed in major mergers. We find $\sigma$-bump all our galaxies, size position bump slightly varying to galaxy, leading assumption that is characteristic merger formation scenario. feature seen both intrinsic projected dispersions. In contrast shells form during event but evolve time finally disappear, stays nearly permanent preserved until end simulation. not dark matter gas components therefore conclude it purely remnants.