MG 0414+0534: A dusty gravitational lens

The gravitational lens system MG 0414+0534 has an unexceptional four-image lensing geometry; however, the optical counterparts of the radio images are exceedingly red, with spectra unlike that of any previously observed active nucleus. New infrared spectra reveal broad Balmer lines at a redshift of 2.639±0.002. We use these spectra, in combination with infrared and HST images, IRAS flux densities, the radio images of Hewitt et al. [AJ, 104, 968 (1992)] and Katz & Hewitt [ApJL, 409, L9 (1993)], and the optical spectrum of Hewitt et al. (1992), to argue that the background source in MG 0414+0534 is a typical high-redshift quasar heavily reddened by dust in the lens. Inferred values of visual extinction (A_V) along the path of the brightest image range up to 6 mag, depending on the assumed shape of the unreddened spectrum and the redshift of the lens. Extinction along one of the other image paths is somewhat larger, along the other two somewhat smaller. The image paths all lie roughly 5 kpc from the core of the lens. The presence of large quantities of dust in the lenses of both MG 0414+0534 and MG 1131+0456 [Larkin et al. ApJL, 420, L9 (1994)] suggests that a significant fraction of massive galaxies at high redshifts is dusty. This has important implications for our understanding of galaxies at high redshift, as well as for optical searches for gravitational lensing.