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Table · dataset · 2005

Millennium Arecibo 21-cm Survey. III.

Listed in IVOA Registry (Virtual Observatory)

We outline the theory and practice of measuring the four Stokes parameters of spectral lines in emission/absorption observations.

Description

We apply these concepts to our Arecibo H I absorption line data and present the results. We include a detailed discussion of instrumental effects arising from polarized beam structure and its interaction with the spatially extended emission line structure.

At Arecibo, linear polarization [Stokes (Q,U)] has much larger instrumental effects than circular (Stokes V). We show how to reduce the instrumental contributions to V and to evaluate upper limits to its remaining instrumental errors by using the (Q,U) results. These efforts work well for opacity spectra but not for emission spectra.

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Arecibo's large central blockage exacerbates these effects, particularly for emission profiles, and other telescopes with weaker sidelobes are not as susceptible. We present graphical results for 41 sources; we analyze these absorption spectra in terms of Gaussian components, which number 136, and present physical parameters including magnetic field for each.

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Catalogue records · 2

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Stated by source
Radio
Inferred from text
Astronomical sciences 72%
Provenance · 1 source records, 9 field assertions
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IVOA Registry (Virtual Observatory)ivo://cds.vizier/j/apjs/151/27111 d agoJSON v1
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