2007A&A...464..631Z -
Astronomy and Astrophysics, volume 464, 631-634 (2007/3-3)
Temperature fluctuations in H II regions: t2 for the two-phase model.
ZHANG Y., ERCOLANO B. and LIU X.-W.
Abstract (from CDS):
We investigate temperature fluctuations in HII regions in terms of a two-phase model, which assumes that the nebular gas consists of a hot and a cold phase. We derive general formulae for T([OIII]), the [OIII] forbidden line temperature, and T(HI), the hydrogen Balmer jump temperature, in terms of the temperatures of the hot and cold phases, T
h and T
c. For large temperature differences, the values of t
2 required to account for the observed difference between T([OIII]) and T(HI) are much lower than those deduced using the classical formulae that assume random and small amplitude temperature fluctuations. One should therefore be cautious when using a two-phase model to account for empirically derived t
2 values. We present a correction of a recent work by Giammanco & Beckman (
2005A&A...437L..11G), who use a two-phase model to estimate the ionization rate of HII regions by cosmic rays. We show that a very small amount of cold gas is sufficient to account for t
2 values typically inferred for H II regions.
Abstract Copyright:
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Journal keyword(s):
ISM: general - ISM: HII regions
Simbad objects:
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