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Astron. Astrophys. 315, L93-L96 (1996)

ISOCAM observations of the Antennae Galaxies*

L. Vigroux1, F. Mirabel1, B. Altiéri3, F. Boulanger2, C. Cesarsky1, D. Cesarsky2, A. Claret1, C. Fransson3, P. Gallais1, D. Levine3, S. Madden1, K. Okumura3, and D. Tran1

1 CEA/DSM/DAPNIA Service d'Astrophysique, F-91191 Gif-sur-Yvette, France
2 Institut d'Astrophysique Spatiale, F-91405 Orsay, France
3 ISO Science Operation center,Astrophysics Division of ESA, Villafranca del Castillo, P.O. Box 50727, E-28080 Madrid, Espagne

Received 16 July 1996 / Accepted 29 August 1996

Abstract. We have mapped the Antennae Galaxies (NGC4038/39) in the 6.7 and 15 img1.gifm continuum emission using ISOCAM (see Cesarsky et al., 1996) with img2.gif resolution. Spectrophotometric observations with the CVF in the spectral range 5.5 to 16.5 img1.gifm 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 img1.gifm 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 img1.gifm. The brightest knot in the overlap region has a surface brightness at 15 img1.gifm 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.

Key words: galaxies: individual: NGC4038/39 - galaxies: individual: Antennae Galaxies - infrared: interstellar: continuum - stars: formation

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with participation of ISAS and NASA.

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