The 15-µM Isogal Survey of the Inner Galactic Disc

Abstract

We report on an ongoing 15 µm ISOCAM survey of about 12 deg² distributed along the inner Galactic disc (|b|)<0.50°,|l|<30°). The sensitivity and the resolution are 2 orders of magnitude better than IRAS. The data will be combined with those of the I JK DENIS survey also in progress. The revolutionary performances of ISOCAM should allow the detection of M giants as far as the Galactic Centre. They will be good tracers of inner obscured Galactic structures: central regions close to the Galactic Centre, bar, old disc, molecular ring, young disc and spiral arms, etc. ISO-GAL will also detect several thousands of rarer infrared bright stars, will map the spectacular 15 µm diffuse emission and, combined with DENIS, will provide information on interstellar extinction at small angular scales. The data reduction is difficult because of the complex time behaviour of the detectors, persistence effects after observation of strong sources, patchy background emission and source confusion. A preliminary analysis of the first data indicates that the expectations are being met.