KUIPER WIDEFIELD INFRARED CAMERA FAR-INFRARED IMAGING OF THE GALACTlC CENTER: THE CIRCUMNUCLEAR DISK REVEALED

摘要

We present images of the Galactic center in the dust continuum at 3l.5 and 37.7 mu m obtained with the Kuiper Widefield Infrared Camera on the Kuiper Airborne Observatory. The raw images have a spatial resolution of ~8."5 and cover a region roughly 10' (R.A.) by 24' (decl.) in extent. Here we discuss the innermost 2.'8 x 3.'6 (6.9 x 9.1 pc) regions roughly centered on Sagittarius A*, where the high signal-to-noise ratio permits image restoration to ~3."6-5."7 spatial resolution at 3l.5 and 37.7 mu m, respectively. These images clearly delineate the warm dust in the "minispiral" but also show an elliptical structure centered on Sgr A* and intersecting the minispiral at the western arc that we identify as the photo-dissociated inner rim of the circumnuclear disk (CND) or ring. This is the first image of the complete disk and the first image of both the minispiral and CND in a single tracer, thereby permitting detailed studies of the intimate association between these two structures. The 3l.5/37.7 mu m color temperature map indicates that most of the far-UV flux required to heat the dust grains must come from centrally located sources. The cluster of He I emission-line stars recently identified near Sgr A* is sufficient to provide half the heating for the far-IR ring and minispiral structures, the balance likely being provided by O and B stars associated with the cluster. We also find ~16 color temperature peaks distributed within the CND that we suggest are the locations of early type (B4 to O9) main-sequence stars. To match the observed far-IR fluxes fro