Session 14 - Milky Way Galaxy.
Display session, Monday, January 15
North Banquet Hall, Convention Center

## [14.09] Interstellar Extinction in the Vicinity of the Galactic Center

A. S. Cotera (NASA/JPL), J. P. Simpson, E. F. Erickson, S. W. J. Colgan (NASA/ARC), M. G. Burton (UNSW)

Observations have been made at the Anglo-Australian Observatory using the facility Infrared Imaging Spectrometer (IRIS) of the regions surrounding the Arched and Straight Filaments, and the compact radio emission regions northeast of Sgr A, H1-H8 and A-D. Broad band J, H and K^\prime images were obtained in good conditions with seeing \sim 1''. The sensitivity for the images is limited by confusion at K^\prime\sim14.5 mag, H\sim16, and J\sim17.5, increasing by \sim3 mag the sensitivity of previous extinction studies (Catchpole, Whitelock amp; Glass 1990, M.N.R.A.S., 247, 479). Localized variations in the extinction are examined by means of color--magnitude diagrams and statistical variation with position of stellar densities and colors. Preliminary results of the average H-K^\prime values in regions of \sim2.4 pc^2 show considerable variations, ranging between 1.5 and 3.0, with little correlation to the position of the radio emission features.

In addition, observations were made of the thermal radio emission regions located within the broad band images. Observing in spectral mode using a 70''\times2.0'' slit (resolution R\sim250) at fixed right ascension while the telescope drifted in declination, data cubes (with axes \alpha, \delta and \lambda) are obtained from which images in Br\gamma (2.166 \mum) are extracted. Br\gamma images were obtained of G0.15-0.05 (the \lq Pistol\rq), G0.18-0.04 (the \lq Sickle\rq), G0.10+0.02, the compact radio emission regions A-D near Sgr A East, and H1, H2, H5-H8 north of Sgr A. Recombination theory is used to predict the expected Br\gamma emission from the measured radio emission. By comparing the predicted and the measured Br\gamma emission we have a second measure of the extinction in these regions. Taken together, these measurements allow us to determine the extent of any small scale variations in the interstellar extinction of these complex regions.