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Models of the continuum polarization in active galactic nuclei: Implications for unification schemes.

机译：活跃银河原子核中连续谱极化的模型：对统一方案的启示。

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摘要

I have computed the UBV RI-band thermal continuum polarization induced by gas and dust arranged in configurations compatible with current active galactic nuclei (AGNs) unification schemes. Both uniform-density tori and stratified-density disk-driven winds were considered. A Monte Carlo radiative transfer code was developed which includes the polarization mechanisms of electron and dust scattering as well as dichroic extinction by aligned grains. I propose a new interpretation of many of the observed polarization traits of Seyfert galaxies and QSOs: namely, that the polarization in these sources is induced by the same optically thick material which is assumed to obscure the central engine in unification schemes.; Stratified-density winds could provide a natural explanation of the polarization trends observed in Seyfert galaxies. Such winds display polarizations ({dollar}P sbsp{lcub}sim{rcub}{lcub}<{rcub}{dollar} 15%) oriented perpendicular to the axis along viewing angles inclined to the axis by {dollar}thetasb{lcub}o{rcub} sbsp{lcub}sim{rcub}{lcub}>{rcub}{dollar} 45{dollar}spcirc{dollar}; this polarization shifts to smaller magnitudes ({dollar}P sbsp{lcub}sim{rcub}{lcub}<{rcub}{dollar} 2%) and parallel orientations for more face-on viewing, consistent with the patterns observed in Seyfert 2 and Seyfert 1 sources, respectively. Simple torus models cannot produce these viewing angle-dependent changes in P and the position angle.; The magnitude of P depends on the opening angle and optical depth of the torus or wind, the degree of grain alignment, and the location of the continuum source within the obscuring material. The polarization position angle is defined by the primary photon scattering planes within the gas and dust and the direction of grain alignment. It may be oriented either perpendicular or parallel to the symmetry axis, or along an intermediate angle determined by the grain alignment. {dollar}P(lambda{dollar}) may rise into the blue, rise into the red, or remain roughly constant depending on the torus/wind optical depth, degree of grain alignment, and viewing angle.; I also consider the collimation of the central continuum emission by the obscuring dust and gas. I show that disk-driven winds are effective collimators which can produce apparent cones of ionizing photons even though they lack the sharp edges of uniform-density tori.
机译：我已经计算出由气体和尘埃引起的UBV RI波段热连续谱极化，这些气体和尘埃的排列方式与当前的主动银河核（AGNs）统一方案兼容。均密度花托和分层密度圆盘驱动风都被考虑了。研制了蒙特卡罗辐射转移码，其中包括电子和尘埃散射的极化机制以及取向晶粒的二向色性消光。我对塞弗特星系和QSO的许多极化特性提出了新的解释：即，这些源中的极化是由相同的光学厚度的材料引起的，假定该材料在统一方案中会遮挡中央引擎。分层密度风可以自然解释塞弗特星系中的极化趋势。这样的风显示极化（{dollar} P sbsp {lcub} sim {rcub} {lcub} <{rcub} {dollar} 15％）沿垂直于轴的观察角沿{dollar} thetasb {lcub}倾斜的方向取向。 o {rcub} sbsp {lcub} sim {rcub} {lcub}> {rcub} {dollar} 45 {dollar} spcirc {dollar};这种极化移动到较小的幅度（{dollar} P sbsp {lcub} sim {rcub} {lcub} <{rcub} {dollar} 2％）和平行方向以实现更多的正面观看，这与Seyfert 2中观察到的模式一致和Seyfert 1资料来源。简单的环面模型无法在P和位置角上产生这些与视角相关的变化。 P的大小取决于圆环或风的张开角度和光学深度，晶粒排列的程度，以及连续光源在遮盖材料中的位置。偏振位置角由气体和灰尘中的主要光子散射平面以及晶粒排列的方向定义。它可以垂直于或平行于对称轴定向，也可以沿由晶粒排列确定的中间角定向。 {dol} P（lambda {dollar}）可能升为蓝色，升为红色，或大致保持恒定，具体取决于圆环/风的光学深度，晶粒取向度和视角。我还考虑通过遮盖灰尘和气体来使中央连续体发射准直。我证明了磁盘驱动的风是有效的准直器，即使它们缺少均匀密度花托的尖锐边缘，它们也可以产生明显的电离光子锥。

著录项

  • 作者

    Kartje, John Francis.;

  • 作者单位

    The University of Chicago.;

  • 授予单位 The University of Chicago.;
  • 学科 Physics Astronomy and Astrophysics.
  • 学位 Ph.D.
  • 年度 1995
  • 页码 65 p.
  • 总页数 65
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 天文学;
  • 关键词

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