PHYSICAL CONDITIONS IN THE CENTRAL PARSEC DERIVED FROM MID-INFRARED IMAGING PHOTOMETRY

Dan Gezari, Eli Dwek and Frank Varosi

NASA/Goddard Space Flight Center, Infrared Astrophysics Branch, Code 685, Greenbelt, MD 20771

E-mail contact: gezari@astrolab.gsfc.nasa.gov

Array camera images of the central 1 parsec of the Galactic Center at eight mid-infrared wavelengths between 4.8 and 20.0 um with ~1 arcsec resolution are used to model the temperature, opacity and bolometric luminosity distributions of the emitting dust in the central parsec, and the extinction in the line of sight. We use the results to discriminate between two mechanisms for heating the dust: heating by radiation from a "central engine" (possibly a massive black hole associated with Sgr A*), or internal heating by luminous stars embedded in or among the dust clouds. The temperature and opacity distributions are consistent with the presence of self-luminous objects imbedded at prominent the IRS source positions. However, temperatures on the northern arm and east-west bar are highest along the inner flank of those structures surrounding the central cavity, while the dust opacity peaks further out from the central cavity. The warm inner ridge suggests heating by centrally located concentrated luminous sources, including IRS3 and IRS7. The of the model results are compared with the distributions of the various stellar populations in the central parsec. There is evidence for physical interaction between the warm emitting dust and luminous stars, including dozens of hot HeI emission line stars and B[e] stars. The combined contributions of embedded stars at the IRS source positions and the luminous stars distributed throughout Sgr A West can account for the temperature enhancements and the luminosity distribution in the central parsec computed by the model.