The First Mid-Infrared Detection of a Source Coincident with Sagittarius A*

Abstract

We present the first mid-infrared detection of a source coincident with the black hole candidate Sgr A* in a deep image of the inner parsec of the Galaxy. These data were obtained with SpectroCam-10 at the 200 inch (5.08 m) Hale telescope. The source was detected at 8.7 μm on two separate occasions using different observing techniques. The spatial resolution is ~07 and the noise level is 1.6 mJy beam-1 in the combined mosaic near Sgr A*. A source at Sgr A* is weakly apparent in the raw data but is difficult to identify due to strong diffuse dust emission with a mean flux density of 500 mJy arcsec-2. Several deconvolution techniques were applied to achieve the diffraction limit of 044, all of which revealed a peak on a narrow NW-SE ridge of emission. The peak is coincident with Sgr A* within the ±03 uncertainty in locating Sgr A* relative to IRS 7. We estimate the flux density of the Sgr A* source above the ridge to be 25 ± 5 mJy. The extinction-corrected 8.7 μm flux density of ~100 mJy is significantly greater than what is predicted by dustless accretion disk models. The excess emission is best explained by warm dust which may be associated with Sgr A* or heated by local stellar sources.