Dense CO in Mrk 71-A: Superwind Suppressed in a Young Super Star Cluster
  We report the detection of CO(J=2-1) coincident with the super star cluster
(SSC) Mrk 71-A in the nearby Green Pea analog galaxy, NGC 2366. Our NOEMA
observations reveal a compact, ~7 pc, molecular cloud whose mass (10^5 M_sun)
is similar to that of the SSC, consistent with a high star-formation
efficiency, on the order of 0.5. There are two, spatially distinct components
separated by 11 km/s. If expanding, these could be due to momentum-driven,
stellar wind feedback. Alternatively, we may be seeing the remnant infalling,
colliding clouds responsible for triggering the SSC formation. The kinematics
are also consistent with a virialized system. These extreme, high-density,
star-forming conditions inhibit energy-driven feedback; the co-spatial
existence of a massive, molecular cloud with the SSC supports this scenario,
and we quantitatively confirm that any wind-driven feedback in Mrk 71-A is
momentum-driven, rather than energy-driven. Since Mrk 71-A is a candidate Lyman
continuum emitter, this implies that energy-driven superwinds may not be a
necessary condition for the escape of ionizing radiation. In addition, the
detection of the nebular continuum emission yields an accurate astrometric
position for the Mrk 71-A. We also detect four other massive, molecular clouds
in this giant star-forming complex.
