NGC5195 - A look into the hot dusty ISM of an interacting SB0 galaxy with ISOCAM.

O.Boulade - M. Sauvage - B. Altieri - J. Blommaert - P. Gallais1 - S. Guest - L. Metcalfe - K. Okumura - S. Ott - D. Tran - L. Vigroux

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 microns. No hot continuum is detected longward of 14 microns, 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.

Keywords:
Galaxies: individual: NGC5195 - Galaxies: ISM - Galaxies: spiral - Infrared: ISM: continuum - Stars: formation

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