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Astron. Astrophys. 353, 72-76 (2000)


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A unified image of dust grains for the warped spiral galaxy in the merger Centaurus A *

D.L. Block 1 and M. Sauvage 2

1 Department of Computational and Applied Mathematics, University of the Witwatersrand, Private Bag 3, WITS, South Africa
2 CEA/DSM/DAPNIA/Service d'Astrophysique, C.E. Saclay, 91191 Gif-sur-Yvette Cedex, France

Received 5 November 1998 / Accepted 2 November 1999

Abstract

A unified view of dust grains of all sizes and temperatures in Centaurus A has been generated by combining ISOCAM mid-infrared images with optical data. In our unified V-15µm ratio image, a symmetrical bar-like structure and spiral arms of size 1.5 kpc surround the nucleus. We have overlaid the (H-K) model colour map of Quillen et al. (1993) and find a striking correspondence with the ridges seen in emission 15 µm and the dark lanes which they find in the near-infrared. The inference is that the morphology of large cold dust grains, responsible for the extinction at V, H and K, closely follows that of the hot dust over the full projected 3kpc diameter of the mini-spiral galaxy. From the spatial distribution of our V-15µm map, we derive a dust mass of approximately 2 106 [FORMULA], similar to the dust mass of the Triangulum galaxy NGC 598 (M33). A further intercomparison of optical and ISO images reveals that the morphology of the warp of the central spiral may be optically traced: the contours of an entire one half of the spiral lie on the same warped ridge as that found in optical photographs.

Key words: galaxies: individual: NGC 5128 – ISM: dust, extinction – infrared: ISM: continuum – infrared: ISM: lines and bands

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

Send offprint requests to: M. Sauvage (msauvage@cea.fr)

© European Southern Observatory (ESO) 2000

Online publication: December 8, 1999

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