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首页> 外文期刊>The Astrophysical journal >VERY LARGE ARRAY OBSERVATIONS OF HIGH-VELOCITY H Ⅰ IN L1551
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VERY LARGE ARRAY OBSERVATIONS OF HIGH-VELOCITY H Ⅰ IN L1551

机译：L1551中高速HⅠ的非常大的阵列观测

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摘要

We report Very Large Array (VLA) observations of the 21 cm continuum and H Ⅰ line emission of the neutral wind in the prototypical molecular outflow source L1551. The intermediate-velocity gas observed with the VLA has a velocity with respect to the ambient cloud in the range 10-50 km s~(-1). Although the blueshifted flow appears weaker than the red one, the maps are indicative of a bipolar morphology confined inside the large-scale CO bipolar lobes. This morphology strongly suggests that the atomic wind is driving the bipolar CO outflow. We fit to the H Ⅰ line profiles, at four different positions along the redshifted flow axis, a model of a decelerating conical wind that entrains ambient cloud material in a mixing layer at the walls of the cone. This model has a velocity at the axis v_0 = 200 km s~(-1), a mass-loss rate M_* approx= 9 x 10~(-7) solar mass yr~(-1), and a momentum rate P approx= 2 x 10~(-4) solar mass yr~(-1) km s~(-1). This is sufficient to drive the observed molecular flow, provided an age ≥8 x 10~4 yr. We find that the continuum emission spectrum of IRS 5, on scales of 10″, is similar to those of H Ⅱ regions. This can be explained if most of the emission comes from material ionized by UV radiation from shock fronts due to the interaction of the stellar wind against the ambient cloud. The momentum rate required to produce the extended centimeter emission agrees well with the wind P obtained by fitting the line profiles. Finally, the location of a background extragalactic continuum source in the red lobe allows us to probe the physical conditions of the neutral wind. We find that the most probable H Ⅰ spin temperature in the wind is in the range 25-50 K, in agreement with predictions of the thermal structure of such winds.
机译：我们报告了典型分子流出源L1551中21 cm连续谱和中性风的HⅠ线发射的甚大阵列（VLA）观测结果。用VLA观测到的中速气体相对于周围云的速度范围为10-50 km s〜（-1）。尽管蓝移的流动似乎比红移的流动弱，但是这些图表明了双极性形态只局限在大规模的CO双极性叶内。这种形态强烈表明，原子风正在推动双极CO的流出。我们在沿红移流轴的四个不同位置拟合了HⅠ线轮廓，这是一个锥形风减速模型，该锥形风将环境云物质夹带在锥体壁的混合层中。该模型的轴速度为v_0 = 200 km s〜（-1），质量损失率M_ *大约为9 x 10〜（-7）太阳质量yr〜（-1），动量率为P大约= 2 x 10〜（-4）太阳质量yr〜（-1）km s〜（-1）。只要年龄≥8x 10〜4岁，这足以驱动观察到的分子流动。我们发现，IRS 5的连续谱在10“范围内与HⅡ区相似。如果大多数发射来自恒星风与周围云的相互作用，则来自冲击前沿的紫外线辐射使材料电离，则可以解释这一点。产生延长的厘米辐射所需的动量速率与通过拟合线轮廓获得的风P非常吻合。最后，背景河外连续体源在红色波瓣中的位置使我们能够探测中性风的物理条件。我们发现，风中最可能的HⅠ自旋温度在25-50 K范围内，这与此类风的热结构预测相符。

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