AI 中文总结
本研究利用JWST的NIRSpec探测到普遍存在的星际中性氦发射线，发现其具有高度时间变异性，揭示了冷银河系气体穿过太阳系的相关特征，为星际气体研究提供了新方法。
AI 中文摘要
我们报告了一项发现：在詹姆斯·韦布空间望远镜（JWST）的近红外光谱仪（NIRSpec）获取的天空光谱中，探测到了普遍存在的中性氦发射线。该发射线波长为1.0833微米，类似于地面观测站观测到的“天空谱线”之一。我们检查了公共档案中所有合适的NIRSpec光谱，总曝光时间达22天。结果发现，这种氦I（He I）发射线几乎始终存在：在80%的观测中均可清晰探测到，在53%的单独曝光中也能被检测到。该发射线具有高度时间变异性：在同一指向天区，其谱线强度在一天内可变化数倍。当JWST穿过太阳引力聚焦的星际中性氦锥时，He I发射线强度最强；锥穿越期间的强度与太阳活动呈反相关。He I线的低红移、窄速度宽度，以及JWST穿越聚焦锥时强度升高的特征，共同表明该He I发射线的起源是穿过太阳系的冷银河系气体。JWST为研究这种星际气体提供了新途径，揭示了此前未被报道的新见解，例如在小时至天的时间尺度上存在极端变异性。
英文摘要
We report the discovery of ubiquitous neutral helium emission in sky spectra taken with JWST's NIRSpec instrument. The emission, with a wavelength of 1.0833 micron, resembles one of the "sky lines" that are seen by ground-based observatories. We examine this emission in all suitable NIRSpec spectra in the public archive, totaling 22 days of exposure time. We find that this He I emission is almost always present: it is well-detected in 80 percent of the observations, and in 53 percent of the individual exposures. The emission is highly time-variable: at a given pointing, the line intensity can vary by factors of several over the course of a day. The He I emission is strongest when JWST crosses through the cone of interstellar neutral helium that is gravitationally focused by the sun; intensity during the cone crossing is anti-correlated with solar activity. The low redshift and narrow velocity width of the He I line, and the elevated intensity when JWST crosses through the focusing cone, together indicate that origin of the He I emission is cold Milky Way gas passing through our solar system. JWST provides a new way to study this interstellar gas, revealing new insights such as extreme variability on timescales of hours to days, which has not been previously reported.
Commentssubmitted to the AAS journals; 23 pages, 17 figures, 4 tables
