Matías Blaña Díaz

Dwarfs in the Milky Way Halo Outer Rim: first in-fall or backsplash satellites?

We study the secular evolution of gas rich dwarfs that interact with the Milky Way hot halo through ram pressure and KH stripping. For this we implemented wind tunnel models, setting up multicomponent models in equillibrium with DICE for a dwarf galaxy, containing a stellar component (Plummer), a gas component (also Plummer), and a dark matter component (Burkert halo). Then we run the hydrosimulations with the grid code Ramses, which is well suited for modelling the discontinouities like shocks. The wind is injected with a gas density and temperature according to observational models of the MW corona. For now we assume here that the hot halo is static (some observations might indicate some coronal flow) and the galactic wind is given by the relative motion of the dwarf in the medium. In this simulations we test the effects of stellar feedback. Dwarfs like Leo T or Phoenix contain a dozen of AGB stars, where each star can produce a wind between 5 and 20km/s with a mass outflow of Mdot=1E-6Msun/yr and 1E-5Msun/yr.

We test if this stellar wind in combination with the galactic wind of 100km/s could generate the HI morphology observed in these dwarfs. AGB wind here has 10x 1E-5Msun/yr vwind=20km/s, and position shift of stars from DM center of 140pc

Here we explore a velocity wind of 200km/s (many more values to be tested).

In this simulations we test the effects of stellar feedback. Dwarfs like Leo T or Phoenix contain a few dozen of AGB stars, where each star can produce a wind between 5 and 20km/s with a mass outflow of Mdot=1E-6Msun/yr and 1E-5Msun/yr. We test if this stellar wind in combination with the galactic wind of 300km/s could generate the HI morphology observed in these dwarfs.

In this simulations we test an extreme ABG wind of 50km/s and Mdot corresponding to 100 AGB stars, resulting in a complete gas loss in the dwarf. The galaactic wind is set to 80km/s.

Dwarfs in the Halo Outer Rim:
Leo T -- first in-fall or backsplash Milky Way satellite?
Part I

Preface: cosmological galaxy simulations predict that beyond the virial radius of the Milky Way there are two types of populations of dwarf galaxies: the field galaxies, which currently are in their first in-fall to the Milky Way, and therefore they evolved mostly in isolation; and the population of back-splash satellites, which already passed whithin the Milky Way halo in the past. Tidal and ram pressure stripping by the host (MW) influenced the evolution of these two populations in different ways, resulting in substansial differences in some of their main properties.

The gas rich dwarf LeoT (M_gas=5.4x10⁵M_⊙) is an ideal laboratory to study the formation and evolution of dSph galaxies in the Local Group. Given its location at 409kpc (1.4R_vir) from the MW, its large gas-to-stellar mass fraction (~2) and its negative GSR LOS velocity (-65km/s), it is assumed to be a field dwarf on its first in fall. However, its proper motion is unknown making this a backsplash satellite candidate as well. Here we present proper motion and orbital constraints using dynamical and hydrodynamical constraints. In the video you may watch our Nbody simulation of particle models for Leo T and the Milky Way following a backsplash orbit for 12Gyr. We note here that, despite the dark matter stripping, the stellar component of the satellite protected in the inner part of the subhalo, results effectivly un-affected.