Molecular CO(1-0) Gas in the z ~ 2 Radio Galaxy MRC 0152-209
Villar-Martín, M.; Morganti, R.; Ekers, R. D.; Tadhunter, C. N.; Saikia, D. J.; Röttgering, H. J. A.; Norris, R. P.; Emonts, B. H. C.; Mao, M. Y.; Miley, G.; Sadler, E. M.; Feain, I.; Oosterloo, T. A.; Rees, G.; Stevens, J. B.
Australia, Netherlands, Spain, United Kingdom, India
Abstract
We report the detection of molecular CO(1-0) gas in the high-z radio galaxy MRC 0152-209 (z = 1.92) with the Australia Telescope Compact Array Broadband Backend (ATCA/CABB). This is the third known detection of CO(1-0) in a high-z radio galaxy to date. CO(1-0) is the most robust tracer of the overall molecular gas content (including the widespread, low-density, and sub-thermally excited component), hence observations of CO(1-0) are crucial for studying galaxy evolution in the early universe. We derive L'CO = 6.6 ± 2.0 × 1010 K km s-1 pc2 for MRC 0152-209, which is comparable to that derived from CO(1-0) observations of several high-z submillimeter and star-forming BzK galaxies. The CO(1-0) traces a total molecular hydrogen mass of M_H_2 = 5 × 1010 (αx/0.8) M sun. MRC 0152-209 is an infrared bright radio galaxy, in which a large reservoir of cold molecular gas has not (yet) been depleted by star formation or radio source feedback. Its compact radio source is reliably detected at 40 GHz and has a steep spectral index of α = -1.3 between 1.4 and 40 GHz (4-115 GHz in the galaxy's rest frame). MRC 0152-209 is part of an ongoing systematic ATCA/CABB survey of CO(1-0) in high-z radio galaxies between 1.7 < z < 3.