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Paper: A Metallicity Map of M 33
Volume: 396, Formation and Evolution of Galaxy Disks
Page: 23
Authors: Simon, J.D.; Rosolowsky, E.
Abstract: We present initial results from the M 33 Metallicity Project. Out of the thousands of cataloged H II regions in M 33, only ∼ 30 have electron-temperature based abundances in the literature. We have obtained Keck spectroscopy of a sample of ∼ 200 H II regions in M 33, with 61 detections of the [O III]λ4363 Å line that can be used for determining electron temperatures, including measurements at small galactocentric radii where auroral lines are generally difficult to detect. We find an oxygen abundance gradient of −0.027 ± 0.012 dex kpc−1, in agreement with infrared measurements of the neon abundance gradient but much shallower than most previous oxygen gradient measurements. There is substantial intrinsic scatter of 0.11 dex in the metallicity at any given radius in M 33, which imposes a fundamental limit on the accuracy of gradient measurements that rely on small samples of objects. Finally, we present a two-dimensional map of oxygen abundances across the southern half of M 33 and discuss the evidence for deviations from axisymmetry.
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