First Detection of HCO$^+$ Absorption in the Magellanic System
  We present the first detection of HCO$^+$ absorption in the Magellanic
System. Using the Australia Telescope Compact Array (ATCA), we observed 9
extragalactic radio continuum sources behind the Magellanic System and detected
HCO$^+$ absorption towards one source located behind the leading edge of the
Magellanic Bridge. The detection is located at LSR velocity of $v=214.0 \pm
0.4\rm\,km\,s^{-1}$, with a full width at half maximum of $\Delta v=4.5\pm
1.0\rm\,km\,s^{-1}$ and optical depth of $\tau(\rm HCO^+)=0.10\pm 0.02$.
Although there is abundant neutral hydrogen (HI) surrounding the sightline in
position-velocity space, at the exact location of the absorber the HI column
density is low, $<10^{20}\rm\,cm^{-2}$, and there is little evidence for dust
or CO emission from Planck observations. While the origin and survival of
molecules in such a diffuse environment remains unclear, dynamical events such
as HI flows and cloud collisions in this interacting system likely play an
important role.
