THE INTERPRETATION OF ASYMMETRIC DEPOLARIZATION IN EXTRAGALACTIC RADIO-SOURCES

被引:143
作者
GARRINGTON, ST
CONWAY, RG
机构
[1] University of Manchester, Nuffield Radio Astronomy Laboratories, Jodrell Bank, Macclesfield, Cheshire
基金
俄罗斯科学基金会;
关键词
D O I
10.1093/mnras/250.1.198
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We discuss various interpretations of the effect found in powerful double radio sources with one-sided jets whereby the depolarization is systematically stronger on the counter-jet side. Depolarization by gas located within the sources is unlikely to be the cause of the asymmetry. Line-emitting gas, though often associated with depolarization in radio galaxies, is not systematically stronger on the counter-jet side. We interpret the asymmetry in terms of a halo of hot gas surrounding the radio source. If the visible jet is on the near side of the source, as required for the relativistic beaming hypothesis, it will be seen through less depolarizing gas. We have investigated halo models, using density information from X-ray data and assuming the magnetic-field energy to scale as the gas density. Tangling of the magnetic field due to turbulence is shown to be important chiefly on scales of a few kpc. To produce the observed depolarization asymmetry the halo core diameter must be within a factor 2 of the source size, of order 100 kpc. Haloes of this size are associated with poor groups of galaxies. The correlation of depolarization asymmetry with redshift implies that the median halo size decreases by more than a factor of 2 at redshifts z > 1. Central values of n0B0 are about 1 x 10(-3) cm-3 mu-G at low redshift, increasing to 40 x 10(-3) cm-3 mu-G for clusters at z > 1. For the most distant clusters, we estimate n0 approximately 3.0 x 10(-2) cm-3 and B0 approximately 1-mu-G.
引用
收藏
页码:198 / 208
页数:11
相关论文
共 55 条
[1]   EXTENDED OPTICAL-LINE-EMITTING GAS IN RADIO GALAXIES - BROAD-BAND OPTICAL NARROW-BAND OPTICAL, AND RADIO IMAGING OF A REPRESENTATIVE SAMPLE [J].
BAUM, SA ;
HECKMAN, T ;
BRIDLE, A ;
VANBREUGEL, W ;
MILEY, G .
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 1988, 68 (04) :643-714
[2]   TWIN-EXHAUST MODEL FOR DOUBLE RADIO-SOURCES [J].
BLANDFORD, RD ;
REES, MF .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1974, 169 (03) :395-415
[3]   RELATIVISTIC JETS AS COMPACT RADIO-SOURCES [J].
BLANDFORD, RD ;
KONIGL, A .
ASTROPHYSICAL JOURNAL, 1979, 232 (01) :34-48
[4]   COLLIMATION AND POLARIZATION OF THE JETS IN 3C-219 [J].
BRIDLE, AH ;
PERLEY, RA ;
HENRIKSEN, RN .
ASTRONOMICAL JOURNAL, 1986, 92 (03) :534-545
[5]   EXTRAGALACTIC RADIO JETS [J].
BRIDLE, AH ;
PERLEY, RA .
ANNUAL REVIEW OF ASTRONOMY AND ASTROPHYSICS, 1984, 22 :319-358
[6]  
BRIDLE AH, 1988, ACTIVE GALACTIC NUCL, P329
[7]   MULTIFREQUENCY STUDIES OF 7 3CR RADIO-SOURCES .2. RESULTS AND INTERPRETATION [J].
BURCH, SF .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1979, 186 (02) :519-553
[9]   RADIO-SOURCES WITH SUPERLUMINAL VELOCITIES [J].
COHEN, MH ;
KELLERMANN, KI ;
SHAFFER, DB ;
LINFIELD, RP ;
MOFFET, AT ;
ROMNEY, JD ;
SEIELSTAD, GA ;
PAULINYTOTH, IIK ;
PREUSS, E ;
WITZEL, A ;
SCHILIZZI, RT ;
GELDZAHLER, BJ .
NATURE, 1977, 268 (5619) :405-409
[10]   MULTIFREQUENCY OBSERVATIONS OF LINEAR-POLARIZATION IN 94 SOURCES FROM THE 3CR CATALOG .1. OBSERVATIONS [J].
CONWAY, RG ;
BIRCH, P ;
DAVIS, RJ ;
JONES, LR ;
KERR, AJ ;
STANNARD, D .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1983, 202 (02) :813-823