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Excess line broadening in various objects- a case for weak magnetic effects

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Abstract

I present updated compilations of both observational data and theoretical predictions concerning excess line width and sizes in astrophysical bodies. After removing two well-known broadening mechanisms (thermal width and width due to large scale motions such as expansion), I analyse statistically the excess line widthW excess. The excess line width shows a changing behavior with object sizeR, of the formW excess ~R q. Taking all objects together, I find thatq = 0.55 with s.d. = 0.05. This resultextends previous studies to cover 5 decades in sizes, from 0.01 pc up to 1000 pc. Taking only objects withR < 1 pc, I find thatq = 0.7 with s.d.=0.1, while taking only objects withR > 1 pc givesq = 0.5 with s.d.=0.1; thus a steeper (not flatter) value ofq at smallR may be possible. Previous claims to derive a law for objects of sizesR > 1 kpc are discussed, in relation to the problem of removing obvious large scale motions from the observed line width. Thus several models with predictedq values between 0 and 1 can be eliminated, and the remaining ones could allow weak magnetic effects on the line widths.

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  1. J.C.M.T. Group, Herzberg Institute of Astrophysics, National Research Council of Canada, Ottawa, Ontario, Canada

    J. P. Vallée

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  1. J. P. Vallée
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Vallée, J.P. Excess line broadening in various objects- a case for weak magnetic effects. Astrophys Space Sci 220, 289–297 (1994). https://doi.org/10.1007/BF00658059

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