A Chemical Evolution Model for the Fornax Dwarf Spheroidal Galaxy

¹ School of Physics and Astronomy, University of Minnesota, Minneapolis, MN, 55455, USA
² Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China
³ Center for Nuclear Astrophysics, INPAC, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai, 200240, China

^a e-mail: yuan@physics.umn.edu

Published online: 12 February 2016

Abstract

Fornax is the brightest Milky Way (MW) dwarf spheroidal galaxy and its star formation history (SFH) has been derived from observations. We estimate the time evolution of its gas mass and net inflow and outflow rates from the SFH usinga simple star formation law that relates the star formation rate to the gas mass. We present a chemical evolution model on a 2D mass grid with supernovae (SNe) as sources of metal enrichment. We find that a key parameter controlling the enrichment is the mass M_x of the gas to mix with the ejecta from each SN. The choice of M_x depends on the evolution of SN remnants and on the global gas dynamics. It differs between the two types of SNe involved and between the periods before and after Fornax became an MW satellite at time t = t_sat. Our results indicate that due to the global gas outflow at t > t_sat, part of the ejecta from each SN may directly escape from Fornax. Sample results from our model are presented and compared with data.