The implications of the surprising existence of a large, massive CO disk
  in a distant protocluster
  It is not yet known if the properties of molecular gas in distant
protocluster galaxies are significantly affected by their environment as
galaxies are in local clusters. Through a deep, 64 hours of effective on-source
integration with the Australian Telescope Compact Array (ATCA), we discovered a
massive, M_mol=2.0+-0.2x10^11 M_sun, extended, ~40 kpc, CO(1-0)-emitting disk
in the protocluster surrounding the radio galaxy, MRC1138-262. The galaxy, at
z_CO=2.1478, is a clumpy, massive disk galaxy, M_star~5x10^11 M_sun, which lies
250 kpc in projection from MRC1138-262 and is a known H-alpha emitter, HAE229.
HAE229 has a molecular gas fraction of ~30%. The CO emission has a kinematic
gradient along its major axis, centered on the highest surface brightness
rest-frame optical emission, consistent with HAE229 being a rotating disk.
Surprisingly, a significant fraction of the CO emission lies outside of the
UV/optical emission. In spite of this, HAE229 follows the same relation between
star-formation rate and molecular gas mass as normal field galaxies. HAE229 is
the first CO(1-0) detection of an ordinary, star-forming galaxy in a
protocluster. We compare a sample of cluster members at z>0.4 that are detected
in low-order CO transitions with a similar sample of sources drawn from the
field. We confirm findings that the CO-luminosity and FWHM are correlated in
starbursts and show that this relation is valid for normal high-z galaxies as
well as those in overdensities. We do not find a clear dichotomy in the
integrated Schmidt-Kennicutt relation for protocluster and field galaxies. Not
finding any environmental dependence in the "star-formation efficiency" or the
molecular gas content, especially for such an extended CO disk, suggests that
environmentally-specific processes such as ram pressure stripping are not
operating efficiently in (proto)clusters. (abridged)
