APM 08279+5255: Keck Near‐ and Mid‐Infrared High‐Resolution Imaging

We present Keck high-resolution near-IR (2.2 microns; FWHM~0.15") and mid-IR(12.5 microns; FWHM~0.4") images of APM08279+5255, a z=3.91 IR-luminous BALQSOwith a prodigious apparent bolometric luminosity of 5x10^{15} Lsun, the largestknown in the universe. The K-band image shows that this system consists ofthree components, all of which are likely to be the gravitationally lensedimages of the same background object, and the 12.5 micron image shows amorphology consistent with such an image configuration. Our lens model suggeststhat the magnification factor is ~100 from the restframe UV to mid-IR, wheremost of the luminosity is released. The intrinsic bolometric luminosity and IRluminosity of APM08279+5255 are estimated to be 5x10^{13} Lsun and 1x10^{13}Lsun, respectively. This indicates that APM 08279+5255 is intriniscallyluminous, but it is not the most luminous object known. As for its dustcontents, little can be determined with the currently available data due to theuncertainties associated with the dust emissivity and the possible effects ofdifferential magnification. We also suggest that the lensing galaxy is likelyto be a massive galaxy at z~3.Comment: 32 pages, 4 tables, 11 figures; Accepted for publication in Ap