The Herschel revolution: unveiling the morphology of the high mass star formation sites N44 and N63 in the LMC

Abstract

We study the structure of the medium surrounding sites of high-mass star formation to determine the interrelation between the HII regions and the environment from which they were formed. The density distribution of the surroundings is key in determining how the radiation of the newly formed stars interacts with the surrounds in a way that allows it to be used as a star formation tracer. We present new Herschel/SPIRE 250, 350 and 500 mum data of LHA 120-N44 and LHA 120-N63 in the LMC. We construct average spectral energy distributions (SEDs) for annuli centered on the IR bright part of the star formation sites. The annuli cover ~10-~100 pc. We use a phenomenological dust model to fit these SEDs to derive the dust column densities, characterise the incident radiation field and the abundance of polycyclic aromatic hydrocarbon molecules. We see a factor 5 decrease in the radiation field energy density as a function of radial distance around N63. N44 does not show a systematic trend. We construct a simple geometrical model to derive the 3-D density profile of the surroundings of these two regions. Herschel/SPIRE data have proven very efficient in deriving the dust mass distribution. We find that the radiation field in the two sources behaves very differently. N63 is more or less spherically symmetric and the average radiation field drops with distance. N44 shows no systematic decrease of the radiation intensity which is probably due to the inhomogeneity of the surrounding molecular material and to the complex distribution of several star forming clusters in the region.

Accepted for publication in A&A letters (Herschel special issue)

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• The Behavior of the Aromatic Features in M101 HII Regions: Evidence for Dust Processing
• A Problem with the Clustering of Recent Measures of the Distance to the Large Magellanic Cloud
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Cited by in corpus (6)

• Non-Standard Grain Properties, Dark Gas Reservoir, and Extended Submillimeter Excess, Probed by Herschel in the Large Magellanic Cloud
• Submillimeter to centimeter excess emission from the Magellanic Clouds. II. On the nature of the excess
• Herschel Inventory of The Agents of Galaxy Evolution (HERITAGE): the Large Magellanic Cloud dust
• Unbound Young Stellar Systems: Star Formation on the loose
• Star-formation rates from young-star counts and the structure of the ISM across the NGC346/N66 complex in the SMC
• Measuring Young Stars in Space and Time -- I. The Photometric Catalog and Extinction Properties of N44