SIMBAD references

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.


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, Th and Tc. For large temperature differences, the values of t2 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 t2 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 t2 values typically inferred for H II regions.

Abstract Copyright:

Journal keyword(s): ISM: general - ISM: HII regions

Status at CDS:  

Simbad objects: 6

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