Circular polarimetry and the line of sight to the Becklin–Neugebauer object     

D. K. Aitken  J. H. Hough  A. Chrysostomou 《Monthly notices of the Royal Astronomical Society》2006,366(2):491-498

The 3.1-μm absorption feature of water-ice has been observed spectroscopically in many molecular clouds and, when it has been observed spectropolarimetrically, usually a corresponding polarization feature is seen. Typically, on these occasions, and particularly for the Becklin–Neugebauer (BN) object, a distinct position angle shift between the feature and continuum is seen, which indicates both a fractionation of the icy material and a changing alignment direction along the line of sight.
Here, the dependence of circular polarimetry on fractionation along the line of sight is investigated and it is shown that the form of its spectrum, together with the sign of the position angle shift, indicates where along the line of sight the icy material lies. More specifically, a coincidence between the sign of the position angle displacement in the ice feature, measured north through east, and that of the circular polarization ice feature means that the icy grains are overlaid by bare grains. Some preliminary circular polarimetry of BN has this characteristic, and a similar situation is found in the only two other cases for which relevant observations so far exist.  相似文献   

类星体3C 273的射电流量和偏振度关系     

毛李胜 《天文研究与技术》2007,4(3):216-220

利用UMRAO数据平台,研究了类星体3C273的射电流量密度与偏振度的关系（包括4.8GHz,8GHz和14.5GHz3个频段）,结果发现偏振度与射电流量在3个频段都具有很强的负相关性。这些结果可能表明3C273的射电流量密度和偏振度的变化与聚束效应无关。一般,偏振度与流量密度的强负相关现象可以用喷流成分＋激波成分的双成分模型来解释：在喷流成分与激波成分的偏振角相互垂直并且偏振度基本相同的情况下,激波在喷流中的传播产生了这些偏振度与流量密度的强负相关性。  相似文献   

A new approach for a Galactic synchrotron polarized emission template in the microwave range     

G. Bernardi  E. Carretti  R. Fabbri  C. Sbarra  S. Poppi  S. Cortiglioni 《Monthly notices of the Royal Astronomical Society》2003,344(2):347-357

  相似文献   

MERLIN polarimetry of the OH masers in OH17.7–2.0     

I. Bains  T. M. Gledhill  J. A. Yates  A. M. S. Richards 《Monthly notices of the Royal Astronomical Society》2003,338(2):287-302

  相似文献   

Equatorial scattering and the structure of the broad-line region in Seyfert nuclei: evidence for a rotating disc     

J. E. Smith  A. Robinson †  S. Young  D. J. Axon †  Elizabeth A. Corbett 《Monthly notices of the Royal Astronomical Society》2005,359(3):846-864

We present detailed scattering models confirming that distinctive variations in polarization across the broad Hα line, which are observed in a significant fraction of type 1 Seyfert galaxies, can be understood in terms of a rotating line-emitting disc surrounded by a coplanar scattering region (the equatorial scattering region). The predicted polarization properties are: (i) averaged over wavelength, the position angle (PA) of polarization is aligned with the projected disc rotation axis and hence also with the radio source axis; (ii) the polarization PA rotates across the line profile, reaching equal but opposite (relative to the continuum PA) rotations in the blue and red wings; and (iii) the degree of polarization peaks in the line wings and passes through a minimum in the line core. We identify 11 objects that exhibit these features to different degrees. In order to reproduce the large-amplitude PA rotations observed in some cases, the scattering region must closely surround the emission disc and the latter must itself be a relatively narrow annulus – presumably the Hα-emitting zone of a larger accretion disc. Asymmetries in the polarization spectra may be attributable to several possible causes, including bulk radial infall in the equatorial scattering region, or contamination by polar scattered light. The broad Hα lines do not, in general, exhibit double-peaked profiles, suggesting that a second Hα-emitting component of the broad-line region is present, in addition to the disc.  相似文献   

Late reionizations of the Universe and their manifestation in the WMAP and future Planck data     

Pavel Naselsky  Lung-Yih Chiang 《Monthly notices of the Royal Astronomical Society》2004,347(3):795-801

  相似文献   

Magnetic field limits and spectral variability in the Circinus galaxy H₂O megamasers     

J. N. McCallum  S. P. Ellingsen  J. E. J. Lovell 《Monthly notices of the Royal Astronomical Society》2007,376(2):549-556

We have used the Australia Telescope Compact Array (ATCA) to search for polarized emission from the Circinus galaxy H₂O megamasers. No linear or circular polarized emission was detected with 3σ upper limits of 24 and 39 mJy, respectively, corresponding to fractional polarizations of 0.6 and 0.9 per cent for the strongest line. These results allow us to place upper limits on the strength of the nuclear magnetic field of ≤150 mG near the outer edge of the masing disc and ≤360 mG at the inner edge.
Rapid variability, thought to be due to interstellar scintillation, is a well-known feature of the Circinus H₂O megamasers. Our Stokes-I data show evidence for changes in the shape of the maser line spectral profiles, as well as their intensity. In addition to the rapid variations, the maser light curves also exhibit variations with a time-scale of the order of days (although our observations are too short to characterize this well). These behaviours support the hypothesis that the Circinus H₂O megamasers undergo diffractive interstellar scintillation, which has previously only been observed in pulsars and in one active galactic nucleus.  相似文献   

The effect of differential refraction on wave propagation in rotating pulsar magnetospheres     

D. Fussell  Q. Luo 《Monthly notices of the Royal Astronomical Society》2004,349(3):1019-1026

  相似文献   

VLT spectropolarimetry of two powerful radio galaxies at z∼ 1.4: ultraviolet continuum, emission-line properties and the nature of high-redshift dust     

C. Solórzano-Iñarrea  P. N. Best  H. J. A. Röttgering  A. Cimatti 《Monthly notices of the Royal Astronomical Society》2004,351(3):997-1014

  相似文献   

Scientific optimization of a ground-based CMB polarization experiment     

M. Bowden  A. N. Taylor  K. M. Ganga  P. A. R. Ade  J. J. Bock  G. Cahill  J. E. Carlstrom  S. E. Church  W. K. Gear  J. R. Hinderks  W. Hu  B. G. Keating  J. Kovac  A. E. Lange  E. M. Leitch  B. Maffei  O. E. Mallie  S. J. Melhuish  J. A. Murphy  G. Pisano  L. Piccirillo  C. Pryke  B. A. Rusholme  C. O'Sullivan  K. Thompson 《Monthly notices of the Royal Astronomical Society》2004,349(1):321-335

  相似文献