Sarah Pearson – University of Copenhagen

03 January 2018

Sarah Pearson

Observational surveys of low mass, dwarf galaxy pairs and groups are increasing. The surveys find that dwarf pairs are gas rich in the field, despite exhibiting elevated star formation rates. However, a substantial amount of this gas can reside in extended tidal features. Lacking are dynamically matched models of observed dwarf galaxy pairs to disentangle the physical processess involved with regulating the baryon cycle in low mass galaxies. In this talk I present a detailed theoretical model of an observed tidal encounter between two isolated low mass galaxies, NGC 4490 and NGC 4485. This system is an isolated analog of the Magellanic Clouds that is surrounded by a massive, ~50 kpc extended HI envelope. We use hybrid N-body and test particle simulations along with a visulization interface (Identikit) to simultaneously reproduce the observed present-day morphology and kinematics of the HI data for NGC4490/85. This is the first detailed model of tidal stripping between a known pair of low mass galaxes, independent of environmental effects. Our results demonstrate how the mutual interaction between two dwarf galaxies can "park" baryons at very large distances. Our best match to the data is a 1:8 mass ratio encounter where the smallest galaxy is on a polar, prograde orbit and its tidal debris forms the extended tidal structure matchiing the morphology and kinematics of the real system. We predict that the low mass galaxy pair will fully merge in 370 Myr, but that the extended tidal features will continue to persist and evolve for >5 Gyr. This pre-processing of baryons will affect the efficiency of gas stripping if the dwarfs eventually get accreted by a more massice galaxy. In contrast, if the galaxies remain in an isolated environment our work demonstrate how dwarf-dwarf interactions can create a long-lived supply of low metallicity gas to the merger remnant, and we predict an inflow rate of 10ˆ-2 Msun/yr.