Helium and hydrogen excitation in starburst galaxies – infrared and optical line ratios
Open Access
- 15 November 1995
- journal article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 277 (2) , 577-593
- https://doi.org/10.1093/mnras/277.2.577
Abstract
We present infrared spectra for a heterogeneous sample of 22 starburst galaxies. Line fluxes are measured for the prominent He I 2.058-μm and Br γ lines, and their ratio is compared with theoretical predictions of the behaviour of the He I 2.058 μm/Br γ line ratio with stellar effective temperature. The observed line ratios are lower than those found in individual compact H II regions. For a subset of these galaxies optical measurements of HeI/Hβ were derived from the literature. The combination of optical and infrared HeI/HI line ratios suggests effective temperatures for the UV field of at least 40 000 K, consistent with existing results from metal-line excitation.Keywords
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