MOLECULAR GAS IN LENSED z 2 QUASAR HOST GALAXIES AND THE STAR FORMATION LAW FOR GALAXIES WITH LUMINOUS ACTIVE GALACTIC NUCLEI

摘要

We report the detection of luminous CO(J?= 2→1), CO(J?= 3→2), and CO(J?= 4→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 μL 11-170, and thus allow us to probe the 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'CO?= 0.65-21×109?K?km?s-1?pc2, translating to H2 masses of M(H2)?= 0.52-17 × 109?(αCO/0.8) M ☉. To investigate whether or not the active galactic nucleus (AGN) in luminous quasars substantially contributes to L FIR, we study the L'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).