标题： 斯必泽光谱线映射研究原恒星喷流：II L1157中的H2发射 显示英文标题

标题： Spitzer spectral line mapping of protostellar outflows: II H2 emission in L1157

摘要： 我们对L1157原恒星喷流的Spitzer-IRS光谱图进行了分析，研究了从S(0)到S(7)的H2纯转动线。 本工作的目的是推导与温暖分子气体相关的物理条件，并研究这些条件在喷流中的变化。 中红外H2发射遵循进动喷流的形态，峰值与单独的CO团块和H2 2.12{\mu }m振转发射相关。 仅在低能级跃迁中检测到描绘CO空腔的更弥散发射，其中J(下)小于或等于2。 利用H2线图像构建了二维地图，包括N(H2)、H2正-间比和温度谱指数beta，在假设气体温度分层的情况下，H2柱密度随T^(beta)变化。 在喷流中观察到这些参数的变化。 特别是，正-间比范围从0.6到2.8，突显了存在近期冲击区域，其中正-间比尚未达到平衡值。 近红外光谱数据结合了中红外数据，并用于推导最亮的蓝移和红移发射结中的额外冲击参数。 根据观测到的H2柱密度，假设n(H2)值由独立的SiO观测得出，暗示原子氢（H/H2约为0.1-0.3）具有高丰度。 存在高比例的原子氢表明，在这些局部区域的H2激发中应考虑部分解离的冲击组分。 然而，平面冲击模型，无论是C型还是J型，都无法一致地再现我们从H2发射分析中得到的所有物理参数。 总体而言，H2发射占L1157喷流总冲击辐射能量的大约50%。 显示英文摘要

摘要： We present an analysis of Spitzer-IRS spectroscopic maps of the L1157 protostellar outflow in the H2 pure-rotational lines from S(0) to S(7). The aim of this work is to derive the physical conditions pertaining to the warm molecular gas and study their variations within the flow. The mid-IR H2 emission follows the morphology of the precessing flow, with peaks correlated with individual CO clumps and H2 2.12{\mu}m ro-vibrational emission. More diffuse emission delineating the CO cavities is detected only in the low-laying transitions, with J(lower) less or equal to 2. The H2 line images have been used to construct 2D maps of N(H2), H2 ortho-to-para ratio and temperature spectral index beta, in the assumption of a gas temperature stratification where the H2 column density varies as T^(beta). Variations of these parameters are observed along the flow. In particular, the ortho-to-para ratio ranges from 0.6 to 2.8, highlighting the presence of regions subject to recent shocks where the ortho-to-para ratio has not had time yet to reach the equilibrium value. Near-IR spectroscopic data on ro-vibrational H2 emission have been combined with the mid-IR data and used to derive additional shock parameters in the brightest blue- and red-shifted emission knots. A high abundance of atomic hydrogen (H/H2 about 0.1-0.3) is implied by the observed H2 column densities, assuming n(H2) values as derived by independent SiO observations. The presence of a high fraction of atomic hydrogen, indicates that a partially-dissociative shock component should be considered for the H2 excitation in these localized regions. However, planar shock models, either of C- or J-type, are not able to consistently reproduce all the physical parameters derived from our analysis of the H2 emission. Globally, H2 emission contributes to about 50% of the total shock radiated energy in the L1157 outflow.