Letter to the Editor

On the relationship between auroral and nebular oxygen line intensities in spectra of H II regions

Main Astronomical Observatory of National Academy of Sciences of Ukraine, 27 Zabolotnogo str., 03680 Kiev, Ukraine e-mail: pilyugin@mao.kiev.ua

Received: January 1900
Accepted: 10 April 2005

Abstract

We investigate relationships between observed auroral and nebular oxygen line fluxes in spectra of H ii regions. We find a relation that is metallicity-dependent at low metallicities, but becomes independent of metallicity (within the uncertainties of the available data) above 12+logO/H ~ 8.25, i.e. there is one-to-one correspondence (the ff-relation) between auroral and nebular oxygen line fluxes in spectra of high-metallicity H ii regions. The ff-relation allows one to estimate the flux in the auroral line from strong oxygen line measurements only. This solves the problem of the electron temperature (and, consequently, abundance) determination in high-metallicity H ii regions. The ff-relation confirms the basic idea of the “empirical” method, proposed by Pagel et al. (1979, MNRAS, 189, 95) a quarter of a century ago, that the oxygen abundance in H ii region can be esimated from the strong oxygen lines measurements only.