TEMPERATURE-FLUCTUATIONS AND ABUNDANCES IN H-II GALAXIES

There is evidence for temperature fluctuations in planetary nebulae an d in some Galactic H II regions. If such fluctuations occur in the low -metallicity, extragalactic H II regions used to probe the primordial helium abundance, the derived He-4 mass fraction, Y-p, could be system atically different from the true primordial value. For cooler, mainly high-metallicity H II regions, the derived helium abundance may be nea rly unchanged, but the oxygen abundance could have been seriously unde restimated. For hotter, mainly low-metallicity H II regions, the oxyge n abundance is likely accurate, but the helium abundance could be unde restimated. The net effect is to tilt the Y-versus-Z relation, making it flatter and resulting in a higher inferred Y-p. Although this effec t could be large, there are no data that allow us to estimate the size of the temperature fluctuations for the extragalactic H II regions. T herefore, we have explored this effect via Monte Carlo simulations of the data in which the abundances derived from a fiducial data set are modified by Delta T chosen from a distribution with 0 less than or equ al to Delta T less than or equal to Delta T-max where Delta T-max is v aried from 500 to 4000 K. It is interesting that, although this effect shifts the locations of the H II regions in the Y-versus-O/H plane, i t does not introduce any significant additional dispersion.