The effect of pre-processing on the stellar population content of early-type dwarf galaxies

According to the CDM model, galaxy clusters grow through the accretion of individual galaxies and galaxy groups. Thus, it is a true challenge to distinguish the possible role of the present-day host halo from that of previous ones, in the transformation of accreted galaxies. Dwarf early-type galaxies (dEs) are often regarded as statistically meaningful testbeds for investigating environmental effects mainly due to their high number density and shallow potential well. To study the imprint of pre-processing on the stellar population content of dEs, we analyzed a sample of  nine Virgo dEs that, based on their distribution on the projected phase-space diagram (PSD) and predictions from N-body simulations, have been accreted to Virgo as gravitationally bound members of a massive galaxy group, about 2-3 Gyr ago. We derived stellar population properties of  these dEs (i.e., their age, [M/H], and [alpha/Fe]) using their MUSE spectra. We found that the dEs of our sample is considerably [alpha/Fe] enhanced (at an 8 sigma level) and metal-poorer (at a 2-3 sigma level) than equally-massive dEs of the Coma and Virgo clusters that have similar or even larger exposure to their host clusters. We also noted that 6 out of 9 dEs have experienced enhanced star formation (SF) at their accretion time or later, possibly due to shocks and thermal instabilities exerted by ram pressure inside Virgo. Based on this, we speculate that the short episode of star formation  that occurred at infall into Virgo might be responsible for the relatively high [alpha/Fe] ratios observed in the six dEs of our sample. Our results also indicate that the rest of our sample were accreted onto Virgo already quenched (hence pre-processed). In this talk, I take advantage of these results and discuss how pre-processing in previous host halos, and early processing in clusters may affect the physical properties of cluster dEs.

15/11/2022 - 12:30
Dr. Bahar Bidaran
Universidad de Granada, Spain