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Astron. Astrophys. 315, L85-L88 (1996)

NGC5195 - a look into the hot dusty ISM of an interacting SB0 galaxy with ISOCAM*

O. Boulade1, M. Sauvage1, B. Altieri2, J. Blommaert2, P. Gallais1,2, S. Guest2, L. Metcalfe2, K. Okumura2, S. Ott2, D. Tran1, and L. Vigroux1

1 CEA/DSM/DAPNIA/Service d'Astrophysique, C.E. Saclay, F-91191 Gif-sur-Yvette Cedex, France
2 ESA/Villafranca Satellite Tracking Station, PO Box 50727, E-28080 Madrid, Spain

Received 16 July 1996 / Accepted 31 July 1996

Abstract. We present broad-band images and a CVF spectrum of NGC5195, the companion of M51. NGC5195 appears as a very strong point source while its spectrum is dominated by the so-called PAH features at 6.2, 7.7, 8.6, and 11.3 img1.gifm. No hot continuum is detected longward of 14 img1.gifm, and infrared ionic lines are absent from the spectrum. We examine in turn possibilities for the generation of this infrared emission: (1) photospheres or circumstellar envelopes, (2) an embedded current starburst, (3) a LINER, and (4) the evolved starburst population. We find that only 3 and 4 are compatible with the data and tend to prefer 4 since ionic lines expected in LINERs are absent. We also show that, to produce the detected flux, the dust has to take a substantial fraction of its heating energy from optical photons, eventhough PAH features dominate the emission.

Key words: galaxies: individual: NGC5195 - galaxies: ISM - galaxies: spiral - infrared: ISM: 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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Last change: December 16, 1996
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