Infrared profile of central region of our Galaxy at 2.47 µm

Abstract

SEVERAL investigators have described the features around the galactic centre in some infrared wavelength regions^1–3. Their results demonstrate the conspicuous peak and several humps around it. These observations, however, are confined to a rather small region mainly because of the terrestrial background radiation. So the overall feature of the central bulge of our Galaxy could not be derived. Studies of the central bulge have been carried out only with the aid of the distribution of RR Lyrae variables through the ‘galactic window’⁴, but the distribution does not necessarily represent that of general stars which are responsible for the galactic structure. On the contrary, near infrared observation reveals the structure of the central bulge more directly, because the main constituents of the bulge are probably late-type stars which radiate their energy effectively in the infrared region, as inferred from external galaxies. Much weaker interstellar extinction in the infrared region also enables us to observe the whole central bulge through thick interstellar dust clouds. The surface brightness at 2.4 µm in the range of 75° > l > 23°, |b| <20° was attained by our previous balloon experiment^5,6. We have now attempted further similar observations aiming mainly to derive the surface brightness of the central bulge of our Galaxy.