Astron. Astrophys. 336, 662-666 (1998)

Mid-IR mapping of the region of N 4 in the Large Magellanic Cloud with ISOCAM ^*

A. Contursi ¹, J. Lequeux ¹, M. Hanus ¹, M. Heydari-Malayeri ¹, C. Bonoli ², A. Bosma ³, F. Boulanger ⁴, D. Cesarsky ⁴, S. Madden ⁵, M. Sauvage ⁵, D. Tran ⁵ and L. Vigroux <sup>5

1</sup> Observatoire de Paris, 61 Av. de l'Observatoire, F-75014 Paris, France
² Osservatorio Astronomico, Viccolo Osservatorio, I-35122 Padova, Italy
³ Observatoire de Marseille, 2 Place Le Verrier, F-13248 Marseille Cedex 04, France
⁴ Institut d'Astrophysique Spatiale, Bat. 121, Université Paris XI, F-91450 Orsay Cedex, France
⁵ SAp/DAPNIA/DSM, CEA-Saclay, F-91191 Gif-sur-Yvette Cedex, France

Received 18 June 1997 / Accepted 24 September 1997

Abstract

We present images of the N 4 region in the Large Magellanic Cloud obtained with ISOCAM on board ISO through broad band filters centered at 6.75 and 15 µm. Far from the three H II   regions contained in the map, the emission at both wavelengths is due to the Unidentified Infrared Bands and associated continuum and originates in the external layers of a molecular cloud complex. The ratio between the intensities at 15 and 6.75 µm is 0.6-0.7 comparable to the 0.55-0.85 ratio found in our Galaxy. Closer to the H II   regions, this ratio increases when the ultraviolet radiation density reaches 10³ times the radiation density near the Sun, due to the contribution of very small grains to the flux near 15 µm. The emission at both wavelengths is maximum in the direction of an interface between the main H II   region N 4A and the molecular cloud, a region very similar to the classical interface of M 17 in our Galaxy. We have detected at both mid-IR wavelengths the emission of a M supergiant present in the field.

Key words: ISM: N 4 (LMC) Magellanic clouds infrared: ISM: continuum infrared: ISM: lines and bands ISM: clouds ISM: H ii   regions

* 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 the participation of ISAS and NASA.

Send offprint requests to: lequeux@mesioa.obspm.fr

This article contains no SIMBAD objects.

Contents

• 1. Introduction
• 2. Observations and reductions
• 3. ISO filter maps of the region of N 4
• 4. Discussion
• 5. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: July 20, 1998
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