IMAGING THE MOLECULAR GAS IN A z=3.9 QUASAR HOST GALAXY AT 0 ''.3 RESOLUTION: A CENTRAL, SUB-KILOPARSEC SCALE STAR FORMATION RESERVOIR IN APM 08279+5255

We have mapped the molecular gas content in the host galaxy of the strongly lensed high-redshift quasar APM 08279+5255 (z = 3.911) with the Very Large Array at 0 ''.3 resolution. The CO(J = 1--> 0) emission is clearly resolved in our maps. The CO(J = 1--> 0) line luminosity derived from these maps is in good agreement with a previous single-dish measurement. In contrast to previous interferometer-based studies, we find that the full molecular gas reservoir is situated in two compact peaks separated by less than or similar to 0 ''.4. Our observations reveal, for the first time, that the emission from cold molecular gas is virtually co-spatial with the optical/near-infrared continuum emission of the central active galactic nucleus (AGN) in this source. This striking similarity in morphology indicates that the molecular gas is situated in a compact region close to the AGN. Based on the high-resolution CO maps, we present a revised model for the gravitational lensing in this system, which indicates that the molecular gas emission is magnified by only a factor of 4 ( in contrast to previously suggested factors of 100). This model suggests that the CO is situated in a circumnuclear disk of similar to 550 pc radius that is possibly seen at an inclination of less than or similar to 25 degrees, i.e., relatively close to face-on. From the CO luminosity, we derive a molecular gas mass of M-gas = 1.3 x 10(11) M-circle dot for this galaxy. From the CO structure and linewidth, we derive a dynamical mass of M-dyn sin(2) i = 4.0 x 10(10) M-circle dot. Based on a revised mass estimate for the central black hole of M-BH = 2.3 x 10(10) M-circle dot and the results of our molecular line study, we find that the mass of the stellar bulge of APM 08279+ 5255 falls short of the local M-BH-sigma(bulge) relationship of nearby galaxies by more than an order of magnitude, lending support to recent suggestions that this relation may evolve with cosmic time and/or change toward the high-mass end.