M81外盘的氧吸收梯度
An Oxygen Abundance Gradient into the Outer Disk of M81
摘要：
M81的扩展HI盘和潮汐尾为研究星系相互作用对大旋涡星系外盘恒星形成和化学演化的影响提供了一个有趣的环境。我们给出了M81外盘的Hα成像和大约3倍光学半径范围内40个HII区的亮度。我们还获得了MMT光谱的21个HII地区的两倍以上的光学半径。我们得到强线氧丰度的所有HII地区使用R_{23}为基础的和[NII]/[OII]为基础的校准和电子温度丰度的7个区域跨越银河系的距离在5.7和32千秒差距。我们还评论了KDG 61附近的HII区和“潮矮”候选者HoIX的丰度。我们的研究结果构成了迄今为止对M81的最径向扩展的金属丰度研究。利用这个扩展的数据集，我们发现在整个径向范围内的总体氧丰度梯度为-0.013 dex/kpc。这比以前仅限于光盘的研究中发现的要平坦得多。从我们的温度为基础的丰度，我们发现一个梯度-0.020德克斯/千秒差距，并提出了一个破碎的梯度从这些数据的可能性，但注意到需要获得更多的温度为基础的丰度在中间银河系距离（~10-20千秒差距），以验证是否可能是这种情况。我们讨论了我们的主要结果，一个相当平坦的梯度M81的背景下，在其他星系的丰度梯度的模拟和观测。我们发现，M81的浅丰度梯度可能是该星系相互作用历史的结果。
英文摘要：
The extended HI disk and tidal tails of M81 present an interesting environment to study the effects of galaxy interaction on star formation and chemical evolution of the outer disk of a large spiral galaxy. We present Hα imaging of the outer disk of M81 and luminosities for 40 HII regions out to about 3 times the optical radius. We have also obtained MMT spectra for 21 HII regions out to more than twice the optical radius. We derive strong line oxygen abundances for all HII regions using R_{23} based and [NII]/[OII] based calibrations and electron temperature abundances for seven regions spanning a galactocentric distance between 5.7 and 32 kpc. We also comment on the abundances of HII regions near KDG 61 and the "tidal dwarf" candidate HoIX. Our results constitute the most radially extended metallicity study for M81 to date. With this extended data set, we find an overall oxygen abundance gradient of -0.013 dex/kpc over the entire radial range. This is significantly flatter than what has been found in previous studies which were limited to the optical disk. From our temperature based abundances, we find a gradient of -0.020 dex/kpc and present the possibility of a broken gradient from these data, but note the need to obtain more temperature based abundances at intermediate galactocentric distances (~10-20 kpc) to verify whether or not this may be the case. We discuss our main result of a rather flat gradient for M81 in the context of simulations and observations of abundance gradients in other galaxies. We find that the shallow abundance gradient of M81 is likely a result of the interaction history of this galaxy.
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。
