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Astron. Astrophys. 361, 685-694 (2000)

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Study of the ammonia emission in the NGC 6334 region

A. Caproni 1, Z. Abraham 1 and J.W.S. Vilas-Boas 2

1 Instituto Astronômico e Geofísico, Universidade de São Paulo, Av. M. Stéfano 4200, CEP 04301-904, São Paulo, SP, Brazil
2 Centro de Radio Astronomia e Aplicações Espaciais (CRAAE-INPE), CRAAM, Inst. Presbiteriano Mackenzie, R. Consolacão 89, CEP 01302-000, São Paulo, SP, Brazil

Received 20 March 2000 / Accepted 24 July 2000

Abstract

The region centered in the NGC 6334 I(N) radio continuum source was surveyed in an extension of 6´ in right ascension and 12´ in declination, in the NH3(J,K) = (1,1) transition, using the Itapetinga radio telescope. The spectra show non-LTE behavior, and gradients of velocity and line-width were detected along the region. A detailed analysis of the spectra showed that the surveyed region is composed of at least three overlapped sources related to regions that are in different stages of star formation: NGC 6334 I, associated with an already known molecular bipolar outflow, NGC 6334 I(N)w, the brightest ammonia source, coincidental with the continuum source NGC 6334 I(N), and NGC 6334 I(N)e, weaker, more extended and probably less evolved than the others. The physical parameters of the last two sources were calculated in non-LTE conditions, assuming that their spectra are the superposition of the narrow line spectra produced by small dense clumps. The H2 density, NH3 column density, kinetic temperature, diameter and mass of the clumps were found to be very similar in the two regions, but the density of clumps is lower in the probably less evolved source NGC 6334 I(N)e. Differences between the physical parameters derived assuming LTE and non-LTE conditions are also discussed in this work.

Key words: stars: formation – ISM: abundances – ISM: clouds – ISM: H ii regions – ISM: molecules

Send offprint requests to: A. Caproni (acaproni@andromeda.iagusp.usp.br)

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© European Southern Observatory (ESO) 2000

Online publication: October 2, 2000
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