Observational Evidence for a Thick Disk of Dark Molecular Gas in the
  Outer Galaxy
  We present the serendipitous discovery of an extremely broad ($\Delta V_{LSR}
\sim 150$ km/s), faint ($T_{mb} < 10 \textrm{mK}$), and ubiquitous 1667 and
1665 MHz ground-state thermal OH emission towards the 2nd quadrant of the outer
Galaxy ($R_{gal}$ > 8 kpc) with the Green Bank Telescope. Originally discovered
in 2015, we describe the redundant experimental, observational, and data
quality tests of this result over the last five years. The longitude-velocity
distribution of the emission unambiguously suggests large-scale Galactic
structure. We observe a smooth distribution of OH in radial velocity that is
morphologically similar to the HI radial velocity distribution in the outer
Galaxy, showing that molecular gas is significantly more extended in the outer
Galaxy than previously expected. Our results imply the existence of a thick
($-200< z < 200$ pc) disk of diffuse ($n_{H_{2}}$ $\sim$ 5 $\times$ 10$^{-3}$
cm$^{-3}$) molecular gas in the Outer Galaxy previously undetected in all-sky
CO surveys.
