AAS 204th Meeting, June 2004
Session 80 Nearby Galaxies
Poster, Thursday, June 3, 2004, 9:20am-4:00pm, Ballroom

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[80.02] Neon and Oxygen Abundances in M33

N. R. Crockett, D. R. Garnett (University of Arizona), P. Massey (Lowell Observatory), G. Jacoby (WIYN Observatory)

We present new spectroscopic observations of 13 H II regions in the Local Group spiral galaxy M33. The regions observed range in distance between 1 and 7 kpc from the nucleus. Of the 13 H II regions observed, we were able to detect the [O~III] 4363 Å\ line in six regions, and so were able to determine electron temperatures directly from the spectra using the 5007/4363 line ratio. Based on these temperature measurements we computed abundances for O and Ne for the six regions, and derived radial abundance gradients for both elements. We find that our new measurements lead to a shallower oxygen abundance gradient , --0.03±0.02 dex/kpc, than was derived by earlier studies. We attribute the difference partly to the use of uncertain extrapolations of O/H vs. ([O II] + [O III])/H\beta used in earlier studies to derive abundances for nebulae without measured electron temperatures. The shallower O/H gradient is in much better agreement with the Ne/H gradient derived from ISO spectra by Willner and Nelson-Patel, as expected from predictions of stellar nucleosynthesis. We also identify two new He II-emitting H II regions, the first to be discovered in M33.

The author(s) of this abstract have provided an email address for comments about the abstract: dgarnett@as.arizona.edu

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