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Supernova remnant masers: Shock interactions with molecular clouds.

机译：超新星残余物：与分子云的激波相互作用。

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摘要

Maser emission from the 1720-MHz transition of hydroxyl (OH) has identified shock interactions in 10% of all supernova remnants (SNRs). Such maser-emitting SNRs are also bright in molecular line emission. Though somewhat rare, SNRs interacting with dense molecular clouds are an important class in which to study cosmic ray acceleration, SNR evolution, and effects on the energetics and chemistry of the interstellar medium. To study molecular shocks via a multiwavelength approach, the VLA, GBT, Spitzer Space Telescope have been used in the following ways: (i) With the GBT widespread OH (1720 MHz) emission and absorption in other OH lines is observed across the interaction site. Observations of all four ground-state transitions at 1720, 1667/5 and 1612 MHz allows us to model OH excitation, yielding the temperature, density and OH abundance in the post-shock gas. Maser emission is found to have a higher flux density with the GBT than with high-resolution VLA observations for 10 of 15 observed remnants, suggesting maser emission is present on large spatial scales. (ii) Sensitive VLA observations of select SNRs (W44, IC 443, Kes 69, 3C 391, G357.7+0.3) reveal the nature of enhanced 1720 MHz emission. Numerous weak compact masers as well as diffuse extended emission are detected tracing the shock-front. Zeeman splitting of masers permits the post-shock magnetic field strength and the line of sight field direction to be directly measured. (iii) Rotational lines of molecular hydrogen are detected at the position of several masers with Spitzer IRS spectroscopy between 5 and 35 mum. Excitation of the hydrogen lines requires the passage of a C-type shock through dense molecular gas, in agreement with the conditions derived from OH excitation. The presence of bright ionic lines requires multiple shocks present at the interaction site. (iv) A new survey for SNR-masers has identified four new interacting SNRs within 10 degrees of the Galactic Center. Maser-emitting SNRs are found to be preferentially distributed in the inner Galaxy, and preferentially associated with gamma-ray sources. To date, nine remnants with TeV or GeV-energy coincidences also harbor OH(1720 MHz) masers, making this signpost of interaction a potential signpost of cosmic-ray acceleration as well. The enhanced local cosmic ray density is a viable mechanism to produce the high columns of OH which are observed in these sources.
机译：来自羟基（OH）的1720 MHz跃迁的Maser发射已在所有超新星遗留物（SNR）的10％中确定了冲击相互作用。在分子线发射中，这种发射mass的SNR也很明亮。尽管与稀有分子云相互作用的信噪比虽然很少见，但却是研究宇宙射线加速，信噪比演变以及对星际介质的能量和化学的影响的重要一类。为了通过多波长方法研究分子冲击，已通过以下方式使用了VLA，GBT，Spitzer空间望远镜：（i）在GBT的作用下，在整个相互作用点观察到其他OH线中广泛的OH（1720 MHz）发射和吸收。在1720、1667 / 5和1612 MHz处观察到所有四个基态跃迁，使我们可以对OH激发进行建模，从而产生震荡后气体中的温度，密度和OH丰度。发现在15个观测残留物中，有10个残留物，GBT的Maser发射具有比高分辨率VLA观测更高的通量密度，这表明maser发射存在于较大的空间尺度。 （ii）对某些SNR（W44，IC 443，Kes 69、3C 391，G357.7 + 0.3）的敏感VLA观测揭示了增强的1720 MHz发射的性质。跟踪冲击前，可以检测到许多弱的紧凑型激射器以及弥散的扩展发射。激光激射器的塞曼分裂允许直接测量震后磁场强度和视线方向。 （iii）用Spitzer IRS光谱仪在5到35微米之间的几个激波位置检测到分子氢的旋转线。氢线的激发需要C型激波通过致密分子气体，这与从OH激发得到的条件一致。明亮的离子线的存在要求在相互作用部位存在多次电击。 （iv）一项针对SNR-masers的新调查确定了在银河中心10度以内的四个新的相互作用SNR。发现发射Maser的SNR优先分布在内部银河中，并优先与伽马射线源相关联。迄今为止，九个与TeV或GeV能量重合的残余物还带有OH（1720 MHz）masers，使这种相互作用的路标也成为宇宙射线加速的潜在路标。增强的局部宇宙射线密度是产生高OH柱的可行机制，在这些来源中观察到。

著录项

  • 作者

    Hewitt, John William.;

  • 作者单位

    Northwestern University.;

  • 授予单位 Northwestern University.;
  • 学科 Physics Astronomy and Astrophysics.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 228 p.
  • 总页数 228
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

  • 入库时间 2022-08-17 11:38:30

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