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 wide-spread , low-density and subthermally excited component ) , hence observations of CO ( 1-0 ) are crucial for studying galaxy evolution in the Early Universe .
We derive L ^ { \prime } _ { CO } = 6.6 \pm 2.0 \times 10 ^ { 10 } { K~ { } km~ { } s ^ { -1 } ~ { } pc ^ { 2 } } for MRC 0152-209 , which is comparable to that derived from CO ( 1-0 ) observations of several high- z submillimeter and starforming BzK galaxies .
The CO ( 1-0 ) traces a total molecular hydrogen mass of M _ { H 2 } = 5 \times 10 ^ { 10 } ( \alpha _ { x } /0.8 ) M _ { \odot } .
MRC 0152-209 is an infra-red 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 \alpha = -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 .