On the accretion of a new group of galaxies on to Virgo: I. Internal kinematics of nine in-falling dEs

Galaxy environment has been shown to play an important role in transforming late-type, star-forming galaxies to quiescent spheroids. This transformation is expected to be more severe for low-mass galaxies ( $M \lt 10^{10}\, \mathrm{M}_\odot$ ) in dense galaxy groups and clusters, mostly due to the influence of their past host haloes (also known as pre-processing) and their present-day environments. For the first time, in this study, we investigate a sample of nine early-type dwarf galaxies (dEs) that were accreted as a likely bound group on to the Virgo galaxy cluster about 2-3 Gyr ago. Considering this special condition, these nine dEs may provide a test bed for distinguishing between the influence of the Virgo galaxy cluster and the effects of the previous host halo on their current properties. Specifically, we use VLT/MUSE integral-field unit spectra to derive their kinematics and specific angular momentum (λ_R) profiles. We observe a spread in the λ_R profiles of our sample dEs, finding that the λ_R profiles of half of them are as high as those of low-mass field galaxies. The remaining dEs exhibit λ_R profiles as low as those of Virgo dEs that were likely accreted longer ago. Moreover, we detect nebular emission in one dE with a gas velocity offset suggesting ongoing gas stripping in Virgo. We suggest that the low-λ_R dEs in our sample were processed by their previous host halo, prior to their infall to Virgo, and that the high-λ_R dEs may be experiencing ram pressure stripping in Virgo.