The GBT Diffuse Ionized Gas Survey (GDIGS): Survey Overview and First Data Release
The GBT Diffuse Ionized Gas Survey (GDIGS): Survey Overview and First Data Release
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DOI：
10.3847/1538-4365/abef65
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发表时间：
2021-03
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影响因子：
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通讯作者：
L. Anderson;M. Luisi;B. Liu;T. Wenger;D. Balser;T. Bania;L. M. Haffner;Dylan J. Linville;J. Ma
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作者：
L. Anderson;M. Luisi;B. Liu;T. Wenger;D. Balser;T. Bania;L. M. Haffner;Dylan J. Linville;J. Ma
绿色堤岸望远镜（GBT）的扩散电离气体巡天（GDIGS）通过测量4-8 GHz的无线电复合线（RRL）辐射来追踪银河系中平面的电离气体。标称测量区域为32.°3 > θ> − 5°，θ B θ < 0.°5，但覆盖范围在选定字段的平面上方和下方延伸，并额外包括W 47（θ 37.°5）和W 49（θ 43°）周围的区域。GDIGS同时观测到22个Hnα（15个可用）、25个Hnβ（18个可用）和8个Hnγ RRL（全部可用），以及多个分子线跃迁（包括H2 CO和CH 3OH）。在这里，我们描述了GDIGS调查参数和RRL数据的特点，主要集中在Hnα数据。我们通过对可用的RRL进行平均来产生敏感数据立方体，在第一次平滑到0.5 km s−1的共同光谱分辨率和Hnα的2.65的空间分辨率、Hnβ的2.62的空间分辨率和Hnγ的2.09的空间分辨率之后。在Hnα数据立方体中，每个空间的平均光谱噪声为100 mK（150 mJy束-1）。这种灵敏度使GDIGS能够从整个内星系的血浆中检测RRL。GDIGS的Hnα数据对发射测量值EM = 1100 cm−6 pc敏感，这对应于平均电子密度EM = 30 cm−3（1 pc路径长度）或EM = 1 cm−3（1 kpc路径长度）。
The Green Bank Telescope (GBT) Diffuse Ionized Gas Survey (GDIGS) traces ionized gas in the Galactic midplane by measuring 4–8 GHz radio recombination line (RRL) emission. The nominal survey zone is 32.°3 > ℓ > − 5°, ∣b∣ < 0.°5, but coverage extends above and below the plane in select fields and additionally includes the areas around W47 (ℓ ≃ 37.°5) and W49 (ℓ ≃ 43°). GDIGS simultaneously observes 22 Hnα (15 usable), 25 Hnβ (18 usable), and 8 Hnγ RRLs (all usable), as well as multiple molecular line transitions (including those of , H2CO, and CH3OH). Here, we describe the GDIGS survey parameters and characterize the RRL data, focusing primarily on the Hnα data. We produce sensitive data cubes by averaging the usable RRLs, after first smoothing to a common spectral resolution of 0.5 km s−1 and a spatial resolution of 2.′65 for Hnα, 2.′62 for Hnβ, and 2.′09 for Hnγ. The average spectral noise per spaxel in the Hnα data cubes is ∼10 mK (∼5 mJy beam−1). This sensitivity allows GDIGS to detect RRLs from plasma throughout the inner Galaxy. The GDIGS Hnα data are sensitive to emission measures EM ≳ 1100 cm−6 pc, which corresponds to a mean electron density 〈n e 〉 ≳ 30 cm−3 for a 1 pc path length or 〈n e 〉 ≳ 1 cm−3 for a 1 kpc path length.