We report the detection of luminous CO ( J =2 \to 1 ) , CO ( J =3 \to 2 ) , and CO ( J =4 \to 3 ) emission in the strongly lensed high-redshift quasars B1938+666 ( z =2.059 ) , HE 0230–2130 ( z =2.166 ) , HE 1104–1805 ( z =2.322 ) , and B1359+154 ( z =3.240 ) , using the Combined Array for Research in Millimeter-wave Astronomy .
B1938+666 was identified in a ‘ blind ’ CO redshift search , demonstrating the feasibility of such investigations with millimeter interferometers .
These galaxies are lensing-amplified by factors of \mu _ { L } \simeq 11–170 , and thus allow us to probe molecular gas in intrinsically fainter galaxies than currently possible without the aid of gravitational lensing .
We report lensing-corrected intrinsic CO line luminosities of L ^ { \prime } _ { CO } =0.65–21 \times 10 ^ { 9 } K km s ^ { -1 } pc ^ { 2 } , translating to H _ { 2 } masses of M ( { H _ { 2 } } ) =0.52–17 \times 10 ^ { 9 } ( \alpha _ { CO } /0.8 ) M _ { \odot } .
To investigate whether or not the AGN in luminous quasars substantially contribute to L _ { FIR } , we study the L ^ { \prime } _ { CO } – L _ { FIR } relation for quasars relative to galaxies without a luminous AGN as a function of redshift .
We find no substantial differences between submillimeter galaxies and high- z quasars , but marginal evidence for an excess in L _ { FIR } in nearby low- L _ { FIR } AGN galaxies .
This may suggest that an AGN contribution to L _ { FIR } is significant in systems with relatively low gas and dust content , but only minor in the most far-infrared-luminous galaxies ( in which L _ { FIR } is dominated by star formation ) .