A SPECTROSCOPIC STUDY OF BLUE SUPERGIANT STARS IN THE SCULPTOR GALAXY NGC 55: CHEMICAL EVOLUTION AND DISTANCE
A SPECTROSCOPIC STUDY OF BLUE SUPERGIANT STARS IN THE SCULPTOR GALAXY NGC 55: CHEMICAL EVOLUTION AND DISTANCE
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DOI：
10.3847/0004-637x/829/2/70
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发表时间：
2016-07
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影响因子：
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通讯作者：
R. Kudritzki;M. Urbaneja;N. Castro;I. Ho;F. Bresolin;W. Gieren;G. Pietrzyński;N. Przybilla
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文献类型：
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作者：
R. Kudritzki;M. Urbaneja;N. Castro;I. Ho;F. Bresolin;W. Gieren;G. Pietrzyński;N. Przybilla
利用非LTE技术分析了分布在麦哲伦螺旋星系NGC 55盘上的58颗蓝超巨星的低分辨率（4.5-5 μ m）光谱，以确定恒星的温度、重力和金属丰度（从铁峰和α元素）。检测到的金属丰度梯度为−0.22 ± 0.06 dex/R25。中心金属丰度相对于太阳的对数标度为[Z] = −0.37 ± 0.03。一个化学演化模型，使用所观察到的恒星和星际介质气体质量的柱密度分布再现所观察到的金属丰度分布以及揭示了最近的历史，强大的星系质量吸积和风外流的吸积和质量损失率的顺序的星星形成率。有迹象表明金属丰度存在空间不均匀性。此外，相对较高的中心金属丰度的磁盘证实，两个平面外的金属贫H ii地区在以前的工作中检测到的银道面以上1.13至2.22千秒差距电离的大质量恒星在磁盘外原位形成。对于超巨星的子样本，哈勃空间望远镜测光可用，通量加权的重力-光度关系被用来确定26.85 ± 0.10等的距离模。
Low-resolution (4.5–5 Å) spectra of 58 blue supergiant stars distributed over the disk of the Magellanic spiral galaxy NGC 55 in the Sculptor group are analyzed by means of non-LTE techniques to determine stellar temperatures, gravities, and metallicities (from iron peak and α-elements). A metallicity gradient of −0.22 ± 0.06 dex/R25 is detected. The central metallicity on a logarithmic scale relative to the Sun is [Z] = −0.37 ± 0.03. A chemical evolution model using the observed distribution of column densities of the stellar and interstellar medium gas mass reproduces the observed metallicity distribution well and reveals a recent history of strong galactic mass accretion and wind outflows with accretion and mass-loss rates of the order of the star formation rate. There is an indication of spatial inhomogeneity in metallicity. In addition, the relatively high central metallicity of the disk confirms that two extraplanar metal-poor H ii regions detected in previous work 1.13 to 2.22 kpc above the galactic plane are ionized by massive stars formed in situ outside the disk. For a subsample of supergiants, for which Hubble Space Telescope photometry is available, the flux-weighted gravity–luminosity relationship is used to determine a distance modulus of 26.85 ± 0.10 mag.