CO detection of the extremely red galaxy HR10

CO J = 5 - 4 and J = 2 - 1 emission lines were detected towards the extreme ly red galaxy (ERG) HR10 (J164502+4626.4) at z = 1.44. The CO intensities i mply a molecular gas mass M(H-2) of 1.6 x 10(11) h(50)(-2) M., and, combine d with the intensity of the dust continuum, a gas-to-dust mass ratio around 200-400 (assuming galactic values for the conversion factors). The peak of the CO lines are at the same redshift as the [OII]3727 line, but blue-shif ted by 430 km s(-1) from the H alpha line. These CO detections confirm the previous results that HR10 is a highly obscured object with a large thermal far-infrared luminosity and a high star-formation rate. The overall proper ties of HR10 (CO detection, L-FIR to L'(CO) ratio, and FIR to radio flux ra tio) clearly favour the hypothesis that its extreme characteristics are rel ated to star-formation processes rather than to a hidden AGN.