ISOCAM observations of NGC 6946: Mid-IR structure.

November 1996 • 1996A&A...315L.161M

Authors • Malhotra, S. • Helou, G. • van Buren, D. • Kong, M. • Beichman, C. A. • Dinerstein, H. • Hollenbach, D. J. • Hunter, D. A. • Lo, K. Y. • Lord, S. D. • Lu, N. Y. • Rubin, R. H. • Stacey, G. J. • Thronson, H. A., Jr. • Werner, M. W.

Abstract • The nearby spiral galaxy NGC 6946 was observed with ISO-CAM in the mid-infrared, achieving 7" resolution and sub-MJy/sr sensitivity. Images taken with CAM filters LW2 (7μm) and LW3 (15μm) are analysed to determine the morphology of this galaxy and understand better the emission mechanisms. The mid-infrared emission follows an exponential disk with a scale length 75". This is 60% of the scale length in the optical R-band and radio continuum. The nuclear starburst region is too bright for reliable measurement in these images. Its surface brightness exceeds the inner disk by at least a factor of 12. The arms and interarm regions are clearly detected, with each of these components contributing about equally to the disk emission. The arm-interarm contrast is 2-4 in the mid-IR, close to that measured in the visible R band light and lower than the contrast in Hα, suggesting that non-ionizing radiation contributes significantly to dust heating.

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George Helou

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