Astron. Astrophys. 315, L89-L92 (1996)
ISOCAM mapping of the Whirlpool galaxy M 51*
M. Sauvage1, J. Blommaert2, F. Boulanger3, C.J. Cesarsky3, D.A. Cesarsky1, F.X. Désert3, D. Elbaz1, P. Gallais1,2, G. Joncas4, L. Metcalfe2, K. Okumura2, S. Ott2, R. Siebenmorgen2, J.L. Starck1, D. Tran1, and L. Vigroux1
1 CEA/DSM/DAPNIA/Service d'Astrophysique, C.E. Saclay, F-91191 Gif-sur-Yvette Cedex, France
Received 16 July 1996 / Accepted 29 August 1996
Abstract. We have obtained the first images of the 6.75 and 15 m continuum emission in the Whirlpool galaxy with ISOCAM, the infrared camera of the ISO (See Kessler et al. 1996). These data reveal the well-developed, spiral arms of the galaxy, in addition to diffuse emission between arms and in the outer regions of the disk. There is a striking correspondence with the 15 m emission and the H emission over the galaxy. We tighten this link by looking at the properties of the individual HII regions and show that the 15 m emission traces massive star formation and is not affected by extinction as is H . The data show systematic mid-infrared color variations perpendicular to the arms, which we interpret as two distinct dust components contributing to the mid-infrared emission. We examine the implication of these color variations in light of our current understanding of dust at these wavelength.
Key words: galaxies: individual: M 51 - galaxies: ISM - galaxies: spiral - 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.
Last change: December 16, 1996