Characterizing the Circumgalactic Medium of the Lowest-Mass Galaxies: A
  Case Study of IC 1613
  Using 10 sightlines observed with the Hubble Space Telescope/Cosmic Origins
Spectrograph, we study the circumgalactic medium (CGM) and outflows of IC1613,
which is a low-mass ($M_*\sim10^8~M_\odot$), dwarf irregular galaxy on the
outskirts of the Local Group. Among the sightlines, 4 are pointed towards
UV-bright stars in IC1613, and the other 6 sightlines are background QSOs at
impact parameters from 6 kpc ($<0.1R_{200}$) to 61 kpc ($0.6R_{200}$). We
detect a number of Si II, Si III, Si IV, C II, and C IV absorbers, most of
which have velocities less than the escape velocity of IC1613 and thus are
gravitationally bound. The line strengths of these ion absorbers are consistent
with the CGM absorbers detected in dwarf galaxies at low redshifts. Assuming
that Si II, Si III, and Si IV comprise nearly 100% of the total silicon, we
find 3% ($\sim$8$\times$10$^3~{\rm M_\odot}$), 2% ($\sim$7$\times$10$^3~{\rm
M_\odot}$), and 32--42% [$\sim$(1.0--1.3)$\times$10$^5~{\rm M_\odot}$] of the
silicon mass in the stars, interstellar medium, and within $0.6R_{200}$ of the
CGM of IC1613. We also estimate the metal outflow rate to be ${\rm
\dot{M}_{out, Z}\geq1.1\times10^{-5}~M_\odot~yr^{-1}}$ and the instantaneous
metal mass loading factor to be $\eta_{\rm Z}\geq0.004$, which are in broad
agreement with available observation and simulation values. This work is the
first time a dwarf galaxy of such low mass is probed by a number of both QSO
and stellar sightlines, and it shows that the CGM of low-mass gas-rich galaxies
can be a large reservoir enriched with metals from past and ongoing outflows.
