Stephan五重奏中强大的H $_2$线路冷却：I -绘制组范围冲击中的重要冷却路径
Powerful H$_2$ Line-cooling in Stephan's Quintet : I - Mapping the Significant Cooling Pathways in Group-wide Shocks
摘要：
我们目前的结果，从中红外光谱映射斯蒂芬的五重奏使用斯皮策太空望远镜。1000公里/秒的碰撞产生了一个群范围的冲击，并首次揭示了温暖的分子氢发射的大规模分布，以及其与已知的冲击结构的密切联系。仅在主震区，我们就发现了5.0 $\times10^{8}$ M $_{\odot}$的暖H $_2$分布在$\sim$ 480 kpc $^2$上，另外还报告发现了第二个主震激发的H $_2$特征。这使得该组的总H $_2$线光度超过10 $^42$ erg/s。在主震中，H $_2$谱线的光度超过了热冲击气体的X射线光度的三倍，这证实了H $_2$冷却路径在X射线中占主导地位。[Si在H $_2$的1/10光度下检测到的34.82 $μ$ m发射，似乎密切地跟踪了整个群的激波，此外，我们从激波的最X射线发光部分检测到了微弱的[Fe II]25.99 $μ$ m发射。与冲击模型的比较表明，这种发射与快速冲击（100 < $V_{s}$ < 300 km/s）的区域是一致的，这些区域经历了铁和硅在尘埃颗粒上的耗尽。冲击波中的恒星形成（通过离子线、PAH和尘埃辐射追踪）出现在入侵者星系中，但最引人注目的是在射电冲击波的两端。激波脊本身几乎没有显示出恒星的形成，这与一个模型是一致的，在这个模型中，巨大的H $_{2}$能量是由激波后层运动的湍流能量转移驱动的。在快速星系尺度的冲击中，氢分子谱线相对于其他测量到的冷却源的重要性，可能对第一个星系组装中气体的冷却有着至关重要的影响。
英文摘要：
We present results from the mid-infrared spectral mapping of Stephan's Quintet using the Spitzer Space Telescope. A 1000 km/s collision has produced a group-wide shock and for the first time the large-scale distribution of warm molecular hydrogen emission is revealed, as well as its close association with known shock structures. In the main shock region alone we find 5.0 $\times10^{8}$ M$_{\odot}$ of warm H$_2$ spread over $\sim$ 480 kpc$^2$ and additionally report the discovery of a second major shock-excited H$_2$ feature. This brings the total H$_2$ line luminosity of the group in excess of 10$^42$ erg/s. In the main shock, the H$_2$ line luminosity exceeds, by a factor of three, the X-ray luminosity from the hot shocked gas, confirming that the H$_2$-cooling pathway dominates over the X-ray. [Si II]34.82$μ$m emission, detected at a luminosity of 1/10th of that of the H$_2$, appears to trace the group-wide shock closely and in addition, we detect weak [FeII]25.99$μ$m emission from the most X-ray luminous part of the shock. Comparison with shock models reveals that this emission is consistent with regions of fast shocks (100 < $V_{s}$ < 300 km/s) experiencing depletion of iron and silicon onto dust grains. Star formation in the shock (as traced via ionic lines, PAH and dust emission) appears in the intruder galaxy, but most strikingly at either end of the radio shock. The shock ridge itself shows little star formation, consistent with a model in which the tremendous H$_{2}$ power is driven by turbulent energy transfer from motions in a post-shocked layer. The significance of the molecular hydrogen lines over other measured sources of cooling in fast galaxy-scale shocks may have crucial implications for the cooling of gas in the assembly of the first galaxies.
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