标题： 分子氢在红外环状尘埃中 显示英文标题

标题： Molecular Hydrogen in Infrared Cirrus

摘要： 我们将最近针对50个高银纬活动星系核的FUSE星际分子氢吸收数据与COBE校正后的IRAS 100微米发射图结合，以研究红外星云与H2的相关性。 H2柱密度与红外星云强度的图表显示了与总氢柱密度N_H相同的分子分数f_H2的转变。 这种转变通常归因于H2的自屏蔽作用，并表明许多弥散星云云含有显著比例的H2，f_H2 = 1-30%。 这些云覆盖了银纬b > 30度的北天约50%，在温度校正后的100微米强度D_100 > 1.5 MJy/sr处。 片状星云云，氢密度n_H > 30 cm^-3，可能在盘-晕界面的动力过程作用下被压缩，并有利于在尘埃表面形成H2。 利用N(H2)与100微米强度之间的相关性，我们估计银纬b > 30的星云中含有约3000 M_sun的H2。 外推到银河系内部，星云可能含有10^7 M_sun的H2和10^8 M_sun的总气体质量。 如果提升到100 pc，它们的引力势能约为10^53 erg。 显示英文摘要

摘要： We combine data from our recent FUSE survey of interstellar molecular hydrogen absorption toward 50 high-latitude AGN with COBE-corrected IRAS 100 micron emission maps to study the correlation of infrared cirrus with H2. A plot of the H2 column density vs. IR cirrus intensity shows the same transition in molecular fraction, f_H2, as seen with total hydrogen column density, N_H. This transition is usually attributed to H2 self-shielding, and it suggests that many diffuse cirrus clouds contain H2 in significant fractions, f_H2 = 1-30%. These clouds cover approximately 50% of the northern sky at latitudes b > 30 degrees, at temperature-corrected 100 micron intensities D_100 > 1.5 MJy/sr. The sheetlike cirrus clouds, with hydrogen densities n_H > 30 cm^-3, may be compressed by dynamical processes at the disk-halo interface, and they are conducive to H2 formation on grain surfaces. Exploiting the correlation between N(H2) and 100 micron intensity, we estimate that cirrus clouds at b > 30 contain approximately 3000 M_sun in H2. Extrapolated over the inner Milky Way, the cirrus may contain 10^7 M_sun of H2 and 10^8 M_sun in total gas mass. If elevated to 100 pc, their gravitational potential energy is ~10^53 erg.