Near-infrared interferometric images of the hot inner disk surrounding the massive young star MWC 349A

We present images of the massive young star MWC 349A at 1.65, 2.16, and 2.27, and 3.08 mum, reconstructed from complex visibility data obtained with an aperture-masking interferometric technique on the Keck I telescope. These images have an approximately elliptical appearance and are consistent with the expected shape of a nearly edge-on disk. Visibility data at 1.65, 2.27, and 3.08 mum were fitted with uniform ellipses with major axes 36 +/- 2, 47 +/- 2, and 62 +/- 1 mas in length, respectively. The major axis is at a position angle of 100 degrees +/- 3 degrees, consistent with the position angle of the dark lane observed previously in VLA radio continuum maps at 8 and 22 GHz. This axis is also perpendicular to the symmetry axis of the bipolar lobes of H66 alpha recombination line emission and is consistent with positions of the recombination line maser spots at 1.3 mm. At an assumed distance of 1.2 kpc, the linear sizes of the disk are 44 and 57 AU at 1.65 and 2.27 mum, respectively. These images are consistent with a dust disk having an angle between the symmetry axis of the disk and the plane of the sky of 15 degrees and thickness of 6 AU, or an angle of 20 degrees and thickness of 1.4 AU, giving an upper bound to the mass of the disk of M(d) < 5.7 or respectively.