AKARI Near-infrared Spectroscopic Survey for CO2 in 18 Comets
AKARI Near-infrared Spectroscopic Survey for CO2 in 18 Comets
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AKARI 近红外光谱调查 18 颗彗星中的二氧化碳
DOI：
10.1088/0004-637x/752/1/15
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发表时间：
2012
影响因子：
4.9
通讯作者：
Tomohiko; and 4 coauthors
中科院分区：
文献类型：
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作者：
Ootsubo;Takafumi; Kawakita;Hideyo; Hamada;Saki; Kobayashi;Hitomi; Yamaguchi;Mitsuru; Usui;Fumihiko; Nakagawa;Takao; Ueno;Munetaka; Ishiguro;Masateru; Sekiguchi;Tomohiko; and 4 coauthors
我们用日本AKARI红外卫星上的红外照相机在2.5 - 5 μm波长范围内对彗星挥发物进行了光谱测量。在我们的调查中，从2008年6月到2010年1月，观测到了18颗彗星，包括奥尔特云彗星和彗星族彗星，其中大多数至少观测了两次。在观测到的光谱中，主要的发射带是水（H2O）在2.7 μm和二氧化碳（CO2）在4.3 μm的基本振动带。一些彗星在3.3-3.5 μm附近还可以识别出4.7 μm附近的一氧化碳（CO）的基本振动带和可能与含碳氢分子有关的宽发射特征。除了29 P/Schwassmann-Wachmann 1彗星外，其它17颗彗星的CO2气体生成率都是由H2O的气体生成率计算出来的。我们的数据集提供了迄今为止获得的彗星中CO2/H2O产生速率比的最大均匀数据库。当彗星在日心距为100 Au 2.5时，由于H2 O冰在那里完全升华，因此CO2/H2 O产生率比被认为反映了彗星冰的组成。在Au < 2.5的彗星（17颗彗星中的13颗）中，彗星冰中的CO2/H2 O比值从几个到30%不等。另外，根据我们的观测，彗星中CO/CO2的比值似乎小于1，尽管我们在大多数彗星中只获得了CO的上限。
We conducted a spectroscopic survey of cometary volatiles with the Infrared Camera on board the Japanese infrared satellite AKARI in the wavelength range from 2.5 to 5 μm. In our survey, 18 comets, including both the Oort cloud comets and the Jupiter-family comets, were observed in the period from 2008 June to 2010 January, most of which were observed at least twice. The prominent emission bands in the observed spectra are the fundamental vibrational bands of water (H 2 O) at 2.7 μm and carbon dioxide (CO 2) at 4.3 μm. The fundamental vibrational band of carbon monoxide (CO) around 4.7 μm and the broad emission feature, probably related to carbon–hydrogen-bearing molecules, can also be recognized around the 3.3–3.5-μm region in some of the comets. With respect to H 2 O, gas production rate ratios of CO 2 have been derived in 17 comets, except for the comet 29P/Schwassmann-Wachmann 1. Our data set provides the largest homogeneous database of CO 2/H 2 O production rate ratios in comets obtained so far. The CO 2/H 2 O production rate ratios are considered to reflect the composition of cometary ice when a comet is observed at a heliocentric distance within∼ 2.5 AU, since H 2 O ice fully sublimates there. The CO 2/H 2 O ratio in cometary ice spans from several to∼ 30% among the comets observed at< 2.5 AU (13 out of the 17 comets). Alternatively, the ratio of CO/CO 2 in the comets seems to be smaller than unity based on our observations, although we only obtain upper limits for CO in most of the comets.