行星状星云和M81中HII区域的人口。金属丰度径向梯度与化学演化研究
The population of planetary nebulae and HII regions in M81. A study of radial metallicity gradients and chemical evolution
摘要：
我们分析了行星状星云和HII区的化学丰度的M81磁盘洞察星系演化，并比较它与其他星系，包括银河系。我们获得了39个PNe和20个HII区域的Hectospec/MMT光谱，其中33个光谱可用于温度和丰度分析。我们的PN观测代表了有史以来发表的M81中的第一个PN谱，而之前已经发表了几个HII区谱，尽管没有直接的电子温度测定。我们确定氦，氮，氧，氖，硫和氩的元素丰度在PNE和HII区域，并确定其平均值和径向梯度。PNe的平均O/H比与HII区的平均O/H比相比，表明M81在最后~10 Gyr普遍富氧。M81盘的PN金属丰度梯度为-0.055 ± 0.02dex/kpc。氖和硫在PNe中的径向分布类似于氧的径向分布，具有类似的梯度斜率。如果我们将我们的HII样本与文献中的样本相结合，我们会发现梯度斜率可能会发生温和的演变，其结果与梯度随时间变陡一致。需要额外的光谱来证实这一趋势。在我们的M81样本中没有I型PNE，这与PNLF，星系金属丰度和后AGB壳层演化的最亮仓的观测一致。年轻和年老的M81星群都显示出较浅但可检测到的负径向金属丰度梯度，年轻星群的金属丰度梯度可能稍陡，因此不排除自星系形成以来随着时间的推移而逐渐变陡的温和梯度。在其演化过程中，M81一直在产生氧气，其总的氧富集度超过了附近的其他星系。
英文摘要：
We analyze the chemical abundances of planetary nebulae and HII regions in the M81 disk for insight on galactic evolution, and compare it with that of other galaxies, including the Milky Way. We acquired Hectospec/MMT spectra of 39 PNe and 20 HII regions, with 33 spectra viable for temperature and abundance analysis. Our PN observations represent the first PN spectra in M81 ever published, while several HII region spectra have been published before, although without a direct electron temperature determination. We determine elemental abundances of helium, nitrogen, oxygen, neon, sulfur, and argon in PNe and HII regions, and determine their averages and radial gradients. The average O/H ratio of PNe compared to that of the HII regions indicates a general oxygen enrichment in M81 in the last ~10 Gyr. The PN metallicity gradient in the disk of M81 is -0.055+-0.02 dex/kpc. Neon and sulfur in PNe have a radial distribution similar to that of oxygen, with similar gradient slopes. If we combine our HII sample with the one in the literature we find a possible mild evolution of the gradient slope, with results consistent with gradient steepening with time. Additional spectroscopy is needed to confirm this trend. There are no Type I PNe in our M81 sample, consistently with the observation of only the brightest bins of the PNLF, the galaxy metallicity, and the evolution of post-AGB shells. Both the young and the old populations of M81 disclose shallow but detectable negative radial metallicity gradient, which could be slightly steeper for the young population, thus not excluding a mild gradients steepening with the time since galaxy formation. During its evolution M81 has been producing oxygen; its total oxygen enrichment exceeds that of other nearby galaxies.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
