Confirming Herschel candidate protoclusters from ALMA/VLA CO
  observations
  ALMA 870$\mu$m continuum imaging has uncovered a population of blends of
multiple dusty star-forming galaxies (DSFGs) in sources originally detected
with the Herschel Space Observatory. However, their pairwise separations are
much smaller that what is found by ALMA follow-up of other single-dish surveys
or expected from theoretical simulations. Using ALMA and VLA, we have targeted
three of these systems to confirm whether the multiple 870$\mu$m continuum
sources lie at the same redshift, successfully detecting $^{12}$CO($J = 3$-2)
and $^{12}$CO($J = 1$-0) lines and being able to confirm that in the three
cases all the multiple DSFGs are likely physically associated within the same
structure. Therefore, we report the discovery of two new gas-rich dusty
protocluster cores (HELAISS02, $z = 2.171 \pm 0.004$; HXMM20, $z = 2.602 \pm
0.002$). The third target is located in the well known COSMOS overdensity at $z
= 2.51$ (named CL J1001+0220 in the literature), for which we do not find any
new secure CO(1-0) detection, although some of its members show only tentative
detections and require further confirmation. From the gas, dust, and stellar
properties of the two new protocluster cores, we find very large molecular gas
fractions yet low stellar masses, pushing the sources above the main sequence,
while not enhancing their star formation efficiency. We suggest that the
sources might be newly formed galaxies migrating to the main sequence. The
properties of the three systems compared to each other and to field galaxies
may suggest a different evolutionary stage between systems.
