On the electron temperatures in high-metallicity H iiregions

Authors: Pilyugin, L. S.; Mattsson, L.¹; Vílchez, J. M.²; Cedrés, B.²

Source: Monthly Notices of the Royal Astronomical Society, Volume 398, Number 1, September 2009 , pp. 485-496(12)

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Abstract:

The electron temperatures of high-metallicity [12 + log (O/H) > 8.2] H ii regions have been studied. The empirical flux-flux relations which express the nebular-to-auroral [O iii] line ratio Q_3,O (as well as the nebular-to-auroral [O ii] line ratio Q_2,O , and the nebular-to-auroral [N ii] line ratio Q_2,N ) in terms of the nebular R₃ and R₂ line fluxes in spectra of high-metallicity H iiregions are derived, and the electron temperatures t_3,O, t_2,O and t_2,N in a number of extragalactic H iiregions are also determined. Furthermore, the t₂-t₃ diagram is discussed. It is found that there is a one-to-one correspondence between t₂ and t₃ electron temperatures for H iiregions with a weak nebular R₃ lines (log R₃≲ 0.5) . The derived t_2,N-t_3,O relation for these H iiregions is similar to commonly used t₂-t₃ relations. The H iiregions with a strong nebular R₃ line flux (log R₃≳ 0.5) do not follow this relation. A discrepancy between t_2,N and t_2,O temperatures is found, being the t_2,N temperatures systematically lower than the t_2,O ones. The differences are small at low electron temperatures, and increase with increasing electron temperatures up to 10 per cent at t= 1 . The uncertainties in the atomic data may be the cause of this discrepancy.

Keywords: ISM: abundances; H iiregions; galaxies: abundances

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15182.x

Affiliations: 1: Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden 2: Instituto de Astrofísica de Andalucía, CSIC, Apdo, 3004, 18080 Granada, Spain

Publication date: 2009-09-01