SPITZER INFRARED SPECTROGRAPH DETECTION OF MOLECULAR HYDROGEN ROTATIONAL EMISSION TOWARDS TRANSLUCENT CLOUDS
SPITZER INFRARED SPECTROGRAPH DETECTION OF MOLECULAR HYDROGEN ROTATIONAL EMISSION TOWARDS TRANSLUCENT CLOUDS
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DOI：
10.1088/0004-637x/743/2/174
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发表时间：
2011-09
期刊：
影响因子：
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通讯作者：
J. Ingalls;T. Bania;F. Boulanger;B. Draine;E. Falgarone;P. Hily-Blant
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文献类型：
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作者：
J. Ingalls;T. Bania;F. Boulanger;B. Draine;E. Falgarone;P. Hily-Blant
利用斯皮策太空望远镜上的红外光谱仪，我们在两个半透明的高银河系纬度云DCld 300.2−16.9和LDN 1780中探测到了氢分子（H2）的S（0）、S（1）和S（2）纯转动（v = 0-0）跃迁向六个位置的发射。这些线的检测提出了关于远离紫外线辐射源的低消光云内部的物理条件的重要问题。在这6个位置上，7.9 μm处S（2）通量与多环芳烃（PAHs）通量的比值平均为0.007。这比斯皮策红外近地星系巡天中对非活动星系中心区域测量的相同比率高出约4倍。因此，这些半透明云的环境比整个星系盘更有效地产生每个PAH激发光子的旋转激发H2。激发分析发现，S（1）和S（2）发射区是温暖的（T ≈ 300 K），但包括不超过2%的气体质量。我们发现紫外光子不能成为这些区域唯一的激发源，并建议通过冲击或湍流耗散进行机械加热是发射的主要原因。这些云位于天蝎座-半人马座OB协会的外围，可能正在消散最近超新星爆炸产生的机械能爆发。我们认为，温暖的气体在弥漫或半透明的云，集成在磁盘的星系，口袋可能是一个主要的来源，所有非活跃的星系H2排放。
Using the Infrared Spectrograph on board the Spitzer Space Telescope, we have detected emission in the S(0), S(1), and S(2) pure-rotational (v = 0–0) transitions of molecular hydrogen (H2) toward six positions in two translucent high Galactic latitude clouds, DCld 300.2−16.9 and LDN 1780. The detection of these lines raises important questions regarding the physical conditions inside low-extinction clouds that are far from ultraviolet radiation sources. The ratio between the S(2) flux and the flux from polycyclic aromatic hydrocarbons (PAHs) at 7.9 μm averages 0.007 for these six positions. This is a factor of about four higher than the same ratio measured toward the central regions of non-active Galaxies in the Spitzer Infrared Nearby Galaxies Survey. Thus, the environment of these translucent clouds is more efficient at producing rotationally excited H2 per PAH-exciting photon than the disks of entire galaxies. Excitation analysis finds that the S(1) and S(2) emitting regions are warm (T ≳ 300 K), but comprise no more than 2% of the gas mass. We find that UV photons cannot be the sole source of excitation in these regions and suggest mechanical heating via shocks or turbulent dissipation as the dominant cause of the emission. The clouds are located on the outskirts of the Scorpius-Centaurus OB association and may be dissipating recent bursts of mechanical energy input from supernova explosions. We suggest that pockets of warm gas in diffuse or translucent clouds, integrated over the disks of galaxies, may represent a major source of all non-active galaxy H2 emission.