The Milky Way is a barred spiral galaxy with "bar lanes" that bring gas
towards the Galactic Center. Gas flowing along these bar lanes often
overshoots, and instead of accreting onto the Central Molecular Zone, it
collides with the bar lane on the opposite side of the Galaxy. We observed G5,
a cloud which we believe is the site of one such collision, near the Galactic
Center at (l,b) = (+5.4, -0.4) with the ALMA/ACA. We took measurements of the
spectral lines 12CO J=2-1, 13CO J=2-1, C18O J=2-1, H2βCO
J=303β-202β, H2βCO J=322β-221β, CH3βOH
J=422β-312β, OCS J=18-17 and SiO J=5-4. We observed a velocity bridge
between two clouds at βΌ50 km/s and βΌ150 km/sin our position-velocity
diagram, which is direct evidence of a cloud-cloud collision. We measured an
average gas temperature of βΌ60 K in G5 using H2βCO integrated intensity
line ratios. We observed that the 12C/13C ratio in G5 is consistent
with optically thin, or at most marginally optically thick 12CO. We
measured 1.5 x 109 cmβ2(K km/s)β1 for the local XCOβ, 10-20x
less than the average Galactic value. G5 is strong direct observational
evidence of gas overshooting the Central Molecular Zone (CMZ) and colliding
with a bar lane on the opposite side of the Galactic center.Comment: Accepted to ApJ. 27 pages, 19 figure