Background Infrared Sources for Studying the Galactic Center’s Interstellar Gas
Background Infrared Sources for Studying the Galactic Center’s Interstellar Gas
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用于研究银河系中心星际气体的背景红外源
DOI：
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发表时间：
2015
影响因子：
4.9
通讯作者：
F. Najarro
中科院分区：
文献类型：
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作者：
T. Geballe;E. Lambrides;B. Schlegelmilch;S. Yeh;M. Goto;C. Westrick;T. Oka;F. Najarro
我们简要地描述了一个K波段光谱调查的结果，超过500个高度红化的点状物体的视线朝向中央分子区（CMZ）的银河系。目标是找到光谱无特征或几乎无特征的恒星，适合银河系中心星际气体的近红外和中红外吸收光谱，视线遍布CMZ。直到最近，在五重星系团和中央星系团附近非常局部的视线之外，只有少数这样的恒星被发现。我们已经使用斯皮策太空望远镜银河遗产红外中面巡天和2微米全天巡天测光来选择有希望的候选者，在过去的10年里，我们一直在获取它们的低分辨率K波段光谱。正如预期的那样，绝大多数是冷的和/或高度变红的红巨星，具有复杂的光球光谱，不适合测量微弱的星际线。其中大约10%的观测结果在这里报告，具有无特征或几乎无特征的光谱。虽然这些恒星在银河经度上分布不均匀，但它们分散在CMZ上。它们中的许多是发光的恒星，深深地嵌入温暖的尘埃茧中，并且具有K波段连续谱，波长急剧上升到更长。其中相当一部分是各种光谱类型的热星，包括至少五颗新发现的沃尔夫-拉叶星。所有这些都应该适合于在大于3 μm的红外波长处的星际吸收线的光谱学，并且许多也适合于更短的波长。
We briefly describe the results of a K-band spectroscopic survey of over 500 highly reddened point-like objects on sightlines toward the Central Molecular Zone (CMZ) of the Galaxy. The goal was to find stars with featureless or nearly featureless spectra suitable for near- and mid-infrared absorption spectroscopy of the Galactic center’s interstellar gas on sightlines spread across the CMZ. Until recently only a few such stars have been known outside of very localized sightlines in the vicinity of the Quintuplet and Central clusters. We have used Spitzer Space Telescope Galactic Legacy Infrared Midplane Survey Extraordinaire and Two-Micron All-Sky Survey photometry to select promising candidates, and over the last 10 years have been acquiring low-resolution K-band spectra of them. As expected, the vast majority are cool and/or highly reddened red giants with complex photospheric spectra unsuitable for measuring faint interstellar lines. Approximately 10% of them, whose observations are reported here, have featureless or nearly featureless spectra. Although not evenly distributed in Galactic longitude, these stars are scattered across the CMZ. Many of them are luminous stars that are deeply embedded in warm dust cocoons, and have K-band continua rising steeply to longer wavelengths. A significant fraction of them are hot stars of a variety of spectral types, including at least five newly discovered Wolf–Rayet stars. All of them should be suitable for spectroscopy of interstellar absorption lines at infrared wavelengths greater than 3 μm and many are also suitable at shorter wavelengths.