论文标题
在潮汐麦哲伦桥中发现O星的恒星：恒星参数，丰富和反馈最近的金属贫困巨星及其对麦哲伦系统生态学的影响
Discovery of O stars in the tidal Magellanic Bridge: Stellar parameters, abundances, and feedback of the nearest metal-poor massive stars and their implication for the Magellanic System ecology
论文作者
论文摘要
SMC和LMC之间伸展的麦哲伦桥是最近剥离的潮汐间环境环境，其平均金属性低为$ z〜0.1z _ {\ odot} $。在这里，我们报告了使用ESO/VLT上的火焰收集的档案光谱在桥上首次发现三个O型星。我们使用POWR模型分析光谱，该模型提供了物理参数，电离光子通量和表面丰度。这一发现表明，潮汐剥离的低密度气体能够产生巨大的O恒星，其年龄意味着桥梁中正在进行的恒星形成。多个上述光谱表明所有三个恒星都是二进制的。尽管它们彼此之间的空间接近度，但这些O恒星在化学上是不同的。其中一个是一个快速旋转的巨人，几乎像LMC一样丰富。另外两个是主要序列恒星，它们旋转非常缓慢，并且被强大的金属耗尽。这包括迄今为止最新的氮气恒星最贫穷的O。考虑到桥梁中B恒星的先前分析，我们将各种金属丰度解释为化学不均匀的星体介质的特征，这表明该气体可能在云之间的潮汐相互作用的多个发作中积聚。将最低的派生金属含量归因于原始气体，桥梁初始形成的时间可能会追溯到几个GYR。使用Gaia和Galex颜色标记图，我们粗略地估计了桥上的恒星总数及其总电离辐射。与扩散ISM的能量相比，我们发现热星对桥梁电离辐射场的贡献小于10％，得出结论，电离光子的主要来源是LMC和SMC的泄漏。我们估计从这两个矮星系中逃脱的电离辐射的比例。
The Magellanic Bridge stretching between the SMC and LMC is the nearest tidally stripped intergalactic environment and has a low average metallicity of $Z~0.1Z_{\odot}$. Here we report the first discovery of three O-type stars in the Bridge using archival spectra collected with FLAMES at ESO/VLT. We analyze the spectra using the PoWR models, which provide the physical parameters, ionizing photon fluxes, and surface abundances. This discovery suggests that the tidally stripped low density gas is capable of producing massive O stars and their ages imply ongoing star formation in the Bridge. The multi-epoch spectra indicate that all three O stars are binaries. Despite their spatial proximity to each other, these O stars are chemically distinct. One of them is a fast-rotating giant with nearly LMC-like abundances. The other two are main-sequence stars that rotate extremely slowly and are strongly metal depleted. This includes the most nitrogen-poor O star known up to date. Taking into account the previous analyses of B stars in the Bridge, we interpret the various metal abundances as the signature of a chemically inhomogeneous interstellar medium, suggesting that the gas might have accreted during multiple episodes of tidal interaction between the Clouds. Attributing the lowest derived metal content to the primordial gas, the time of initial formation of the Bridge may date back to several Gyr. Using the Gaia and Galex color-magnitude diagrams we roughly estimate the total number of O stars in the Bridge and their total ionizing radiation. Comparing with the energetics of the diffuse ISM, we find that the contribution of the hot stars to the ionizing radiation field in the Bridge is less than 10%, and conclude that the main sources of ionizing photons are leaks from the LMC and SMC. We estimate a lower limit for the fraction of ionizing radiation that escapes from these two dwarf galaxies.
