Detection of CO(4-3), CO(9-8), and dust emission in the BAL quasar APM 08279+5255 at a redshift of 3.9

Abstract

We detected with the IRAM interferometer the lines of CO(4-3) and CO(9-8) from the recently-discovered broad absorption line quasar APM 08279+5255. The molecular lines are at a redshift of 3.911, which we take to be the true cosmological redshift of the quasar's host galaxy. This means the quasar emission lines at z=3.87 are blueshifted by a kinematic component of -2500 km/s, and, along with the broad absorption lines, are probably emitted in the quasar's wind or jet, moving toward us. The CO line ratios suggest the molecular gas is at a temperature of about 200 K, at a density of about 4000 cm^-3. We also detected the dust emission at 94 and 214 GHz (emitted wavelengths 650 and 290 microns). The spectral index of the mm/submm continuum is +3.2, indicating the dust emission is optically thin in this part of the spectrum. The extremely high CO and dust luminosities suggest magnification by gravitational lensing. Using the optical extent and our limit on the size of the CO region, we estimate a magnification of 7 to 30 for the CO lines and the far-IR continuum, and 14 to 60 for the optical/UV. In this interpretation, the molecular gas and dust is in a nuclear disk of radius 90 to 270 pc around the quasar. The quasar is 25 to 100 times stronger than, but otherwise resembles, the nucleus of Mrk 231.