The extent of chemically enriched gas around star-forming dwarf galaxies
  Supernova driven winds are often invoked to remove chemically enriched gas
from dwarf galaxies to match their low observed metallicities. In such shallow
potential wells, outflows may produce massive amounts of enriched halo gas
(circum-galactic medium or CGM) and pollute the intergalactic medium (IGM).
Here, we present a survey of the CGM and IGM around 18 star-forming field
dwarfs with stellar masses of $\log\,M_*/M_\odot\approx8-9$ at $z\approx0.2$.
Eight of these have CGM probed by quasar absorption spectra at projected
distances, $d$, less than the host virial radius, $R_{\rm h}$. Ten are probed
in the surrounding IGM at $d/R_{\rm h}=1-3$. The absorption measurements
include neutral hydrogen, the dominant silicon ions for diffuse cool gas
($T\sim10^4$ K; Si II, Si III, and Si IV), moderately ionized carbon (C IV),
and highly ionized oxygen (O VI). Metal absorption from the CGM of the dwarfs
is less common and $\approx4\times$ weaker compared to massive star-forming
galaxies though O VI absorption is still common. None of the dwarfs probed at
$d/R_{\rm h}=1-3$ have definitive metal-line detections. Combining the
available silicon ions, we estimate that the cool CGM of the dwarfs accounts
for only $2-6\%$ of the expected silicon budget from the yields of supernovae
associated with past star-formation. The highly ionized O VI accounts for
$\approx8\%$ of the oxygen budget. As O VI traces an ion with expected
equilibrium ion fractions of $\lesssim 0.2$, the highly ionized CGM may
represent a significant metal reservoir even for dwarfs not expected to
maintain gravitationally shock heated hot halos.
