Origin of Weak MgII and Higher Ionization Absorption Lines in an Outflow
  from an Intermediate-Redshift Dwarf Satellite Galaxy
  Observations at intermediate redshifts reveal the presence of numerous,
compact, weak MgII absorbers with near to super-solar metallicities, often
surrounded by more extended regions that produce CIV and/or OVI absorption in
the circumgalactic medium at large impact parameters from luminous galaxies.
Their origin and nature remains unclear. We hypothesize that undetected,
satellite dwarf galaxies are responsible for producing some of these weak MgII
absorbers. We test our hypothesis using gas dynamical simulations of galactic
outflows from a dwarf satellite galaxy with a halo mass of $5\times10^{9}$
M$_{\odot}$, which could form in a larger $L^{*}$ halo at z=2, to study the gas
interaction in the halo. We find that thin, filamentary, weak MgII absorbers
are produced in two stages: 1) when shocked core collapse supernova (SNII)
enriched gas descending in a galactic fountain gets shock compressed by upward
flows driven by subsequent SNIIs and cools (phase 1), and later, 2) during an
outflow driven by Type Ia supernovae that shocks and sweeps up pervasive SNII
enriched gas, which then cools (phase 2). The width of the filaments and
fragments are $\lesssim~100$ pc, and the smallest ones cannot be resolved at
12.8 pc resolution. The MgII absorbers in our simulations are continuously
generated for >150 Myr by shocks and cooling, though each cloud survives for
only ~60 Myr. Their metallicity is 10-20% solar metallicity and column density
is $<10^{12}$ cm$^{-2}$. They are also surrounded by larger (0.5-1 kpc) CIV
absorbers that seem to survive longer. In addition, larger-scale (>1 kpc) CIV
and OVI clouds are produced in both expanding and shocked SNII enriched gas
which is photoionized by the UV metagalactic radiation at intermediate
redshift. Our simulation highlights the possibility of dwarf galactic outflows
producing highly enriched multiphase gas.
