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Astron. Astrophys. 338, L29-L32 (1998)


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Letter to the Editor

The LMC stellar complexes in luminosity slices

Star formation indicators

F. Maragoudaki 1, 2, M. Kontizas 1, E. Kontizas 2, A. Dapergolas 2 and D.H. Morgan 3

1 Section of Astrophysics Astronomy & Mechanics, Department of Physics, University of Athens, GR-157 83 Athens, Greece
2 Astronomical Institute, National Observatory of Athens, P.O. Box 20048, GR-118 10 Athens, Greece
3 UK Schmidt Telescope Unit, Royal Observatory of Edinburgh, EH9 3HJ, UK

Received 16 July 1998 / Accepted 4 August 1998

Abstract

An approach towards the investigation of the star formation mechanisms in galaxies can be achieved through the search of stellar complexes and the determination of their properties. A method has been developed for the detection of stellar complexes and the derivation of their fundamental properties in the LMC.

Photographic plates taken with the 1.2m U.K. Schmidt Telescope have been digitized by the APM and SuperCosmos machines to produce homogeneous data for extended regions. Star counts have been performed for extended areas in selected luminosity slices and colours (U, HeII, R filters). Isodensity contours have been used to identify the various structures with enhanced stellar number density (3[FORMULA] above the mean background density).

About 50 large stellar groupings have been revealed showing: 1) hierarchical structure, where the smallest are found within the large ones. 2) their size distribution has peaks at 250[FORMULA]50 pc (aggregates) and 600[FORMULA]50 pc (complexes), there are also a few cases with size 1200[FORMULA]50 pc (supercomplexes). 3) there is evidence that at the fainter magnitudes these structures are aligned to a general trend whereas at the most bright end (B1, O spectral types) they become more clumpy and symmetrical in shape. The relationship between the above complexes' properties and the various scenarios of star formation are discussed.

Key words: galaxies: stellar content – Magellanic Clouds – star formation

Send offprint requests to: F. Maragoudaki (e-mail: fmarag@titan.astro.noa.gr)

© European Southern Observatory (ESO) 1998

Online publication: September 8, 1998

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