Electron temperature fluctuations in 30 Doradus

¹ Laboratório de Análise Numérica e Astrofísica, Departamento de Matemática, Universidade Federal de Santa Maria, 97119-900 Santa Maria, RS, Brazil
² Physics Department, University of Cincinnati, Cincinnati OH 45221-0011, USA

Corresponding author: M. V. F. Copetti, angela,mvfc@lana.ccne.ufsm.br

Received: 13 December 2001
Accepted: 18 February 2002

Abstract

We present an observational study of the spatial variation of the electron temperature in the 30 Doradus Nebula. We used the ratio to estimate the electron temperature at 135 positions in the nebula across three different directions. We analysed long-slit spectrophotometric data of high signal-to-noise in the range of 4100 to 5030 Å obtained with the Cassegrain spectrograph attached to the 1.60 m telescope of the Laboratório Nacional de Astrofísica, Brazil. No large-scale electron temperature gradient was detected in 30 Doradus. The electron temperature estimates obtained are fairly homogeneous with a mean value of K. The compatibility between the present estimates with optical and radio temperature determinations found in the literature for other positions or for the entire nebula corroborates this conclusion. Temperature fluctuations of small amplitude were observed with a variance relative to the mean of or equivalently with a dispersion of only 5%. The areas with lower surface brightness seem to present slightly higher electron temperatures. This would indicate that the bright arcs of 30 Doradus, which correspond to the densest regions, would have lower electron temperatures than the most diffuse areas. regions – ISM: individual objects: 30 Doradus Nebula