  Supernovae remnants (SNRs) represent a major feedback source from stars on
the interstellar medium of galaxies. During the latest stage of supernovae
explosions, shock waves produced by the initial blast modify the chemistry of
gas and dust, inject kinetic energy in the surroundings, and may alter star
formation characteristics. Simultaneously, gamma-ray emission is generated by
the interaction between the ambiant medium and the cosmic rays. We study the
stellar and interstellar contents of IC443, an evolved shell type SNR at a
distance of 1.9 kpc, with an estimated age of 30 kyr. We aim to measure the
mass of the gas within the extended G region, which corresponds to the peak of
gamma-ray emission detected by VERITAS and Fermi. We performed 10'x10' mapped
observations of 12CO and 13CO J=1-0, J=2-1 and J=3-2 pure rotational lines, as
well as C18O J=1-0 and J=2-1 obtained with the IRAM-30m and APEX telescopes. We
first compared our data with local thermodynamic equilbrium (LTE) models. We
estimated the optical depth of each line from the emission of the isotopologues
13CO and C18O. We used the population diagram and large velocity gradient (LVG)
assumption to measure the column density, mass, and kinetic temperature of the
gas using 12CO and 13CO lines. We used complementary data (stars, gas, and dust
at multiple wavelengths) and infrared point source catalogues to search for
protostar candidates. Our results emphasize how the mass associated with the
ring-like structure and the cloudlet cannot be overlooked when quantifying the
interaction of cosmic rays with the dense local medium. Additionally, the
presence of numerous possible protostars in the region might represent a fresh
source of CR, which must also be taken into account in the interpretation of
gamma-ray observations in this region.
