Molecular gas in two companion cluster galaxies at z=1.2
  We study the molecular gas properties of two star-forming galaxies separated
by 6 kpc in the projected space and belonging to a galaxy cluster selected from
the Irac Shallow Cluster Survey, at a redshift $z=1.2$, i.e., $\sim2$ Gyr after
the cosmic star formation density peak. This work describes the first CO
detection from $1<z<1.4$ star forming cluster galaxies with no reported clear
evidence of AGN. We exploit observations taken with the NOEMA interferometer at
$\sim3$ mm to detect CO(2-1) line emission from the two selected galaxies,
unresolved by our observations. Based on the CO(2-1) spectrum we estimate a
total molecular gas mass $M({\rm H_2})=(2.2^{+0.5}_{-0.4})\times10^{10}$
$M_\odot$ and dust mass $M_{\rm dust}<4.2\times10^8~M_\odot$ for the two
blended sources. The two galaxies have similar stellar masses and a large
relative velocity of $\sim$400 km/s estimated from the CO(2-1) line width.
These findings tend to privilege a scenario where both sources contribute to
the observed CO(2-1). By using the archival Spitzer MIPS flux at 24$\mu$m we
estimate an ${\rm SFR(24\mu m)}=(28^{+12}_{-8})~M_\odot$/yr for each of the two
galaxies. Assuming that the two sources equally contribute to the observe
CO(2-1) our analysis yields a depletion time scale $\tau_{\rm
dep}=(3.9^{+1.4}_{-1.8})\times10^8$ yr, and a molecular gas to stellar mass
ratio $0.17\pm0.13$ for each of two sources, separately. Our results are in
overall agreement with those of other distant cluster galaxies. The two target
galaxies have molecular gas mass and depletion time that are marginally
compatible with, but smaller than those of main sequence field galaxies,
suggesting that the molecular gas has not been refueled enough. Higher
resolution and higher frequency observations will enable us to spatially
resolve the two sources and possibly distinguish between different gas
processing mechanisms.
