近红外线和连续天空发射：用GIANO-TNG从深高光谱分辨率光谱的观测约束
Lines and continuum sky emission in the near infrared: observational constraints from deep high spectral resolution spectra with GIANO-TNG
摘要：
目的确定H波段谱线强度和连续气辉辐射强度对弱目标红外光谱仪的设计具有重要意义。现有的低/中分辨率光谱无法将真实的天空连续谱与仪器效应（例如强谱线翅膀中的漫射光）分开。我们的目标是获得，第一次，一个高分辨率的红外光谱足够深，以设置显着的限制在H波段的线之间的连续发射。方法在La Palma天文台的GIANO高分辨率红外光谱仪第二次调试运行期间，我们将仪器直接指向天空，获得了从0.97到2.4微米的深光谱。结果光谱显示约1500条发射线，比以前的工作增加了两倍。其中，80%被确定为OH跃迁;其中一半是来自高度激发的分子（热OH组分），这些分子不包括在通常用于天文应用的OH气辉发射模型中。其他线归因于O2或未识别。一些微弱的谱线位于以前被认为没有谱线发射的光谱区域。H波段的连续谱在大约300光子/m^2/s/arcsec^2/μ m的水平上被勉强探测到，相当于20.1 AB等/arcsec^2。观测到的光谱和观测到的天际线列表以电子格式发布。我们的测量表明，H波段的天空连续体可能比以前认为的还要暗。然而，无数的气辉发射线严重限制了光谱范围，其中非常低的背景可以有效地实现低/中分辨率光谱仪。我们确定了一些光谱带，在VLT-MOONS的分辨能力（R ~6,600）下仍然可以保持相当暗。
英文摘要：
Aims Determining the intensity of lines and continuum airglow emission in the H-band is important for the design of faint-object infrared spectrographs. Existing spectra at low/medium resolution cannot disentangle the true sky-continuum from instrumental effects (e.g. diffuse light in the wings of strong lines). We aim to obtain, for the first time, a high resolution infrared spectrum deep enough to set significant constraints on the continuum emission between the lines in the H-band. Methods During the second commissioning run of the GIANO high-resolution infrared spectrograph at La Palma Observatory, we pointed the instrument directly to the sky and obtained a deep spectrum that extends from 0.97 to 2.4 micron. Results The spectrum shows about 1500 emission lines, a factor of two more than in previous works. Of these, 80% are identified as OH transitions; half of these are from highly excited molecules (hot-OH component) that are not included in the OH airglow emission models normally used for astronomical applications. The other lines are attributable to O2 or unidentified. Several of the faint lines are in spectral regions that were previously believed to be free of line emission. The continuum in the H-band is marginally detected at a level of about 300 photons/m^2/s/arcsec^2/micron, equivalent to 20.1 AB-mag/arcsec^2. The observed spectrum and the list of observed sky-lines are published in electronic format. Conclusions Our measurements indicate that the sky continuum in the H-band could be even darker than previously believed. However, the myriad of airglow emission lines severely limits the spectral ranges where very low background can be effectively achieved with low/medium resolution spectrographs. We identify a few spectral bands that could still remain quite dark at the resolving power foreseen for VLT-MOONS (R ~6,600).
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