Astronomy and Astrophysics Letters dedicated to ISO

ISOCAM Observations of the Antennae Galaxies

L. Vigroux, F. Mirabel,, B. Altiéri , F.Boulanger,C. Cesarsky, D. Cesarsky, A.Claret, C. Fransson, , P. Gallais, D. Levine, S. Madden, K. Okumura, D. Tran


We have mapped the Antennae Galaxies (NGC4038/39) in the 6.7 and 15 micron continuum emission using ISOCAM with ~ 5 - 8" resolution. Spectrophotometric observations with the CVF in the spectral range 5.5 to 16.5 microns have also been obtained. We compare the distribution of the infrared emission in the 2 nuclei and in the overlap region where the disks of the galaxies collide. The emission longward of 12.5 microns is dominated by ionized gas and by reprocessing of UV flux by dust. The overlap region is the most active star forming area in the system and contributes to more than half of the total infrared luminosity between 12.5 and 18 microns. The brightest knot in the overlap region has a surface brightness at 15 microns which is 5 times larger than the nuclei of the parent galaxies. From the [NeIII] and [NeII] lines, we estimate a lower limit to the effective temperature of the ionizing stars of 39,500 K and 37,000 K in the overlap region and the nuclei, respectively.

Galaxies: individual: NGC4038/39 - Galaxies: individual: Antennae Galaxies - Infrared: interstellar: continuum - Stars: formation

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