ACCRETION OF GASEOUS DISKS AT HIGH REDSHIFTS AND THE DEPOLARIZATION ASYMMETRY OF RADIO-LOUD QUASARS

A new scenario is explored to understand the striking depolarization a symmtery observed between the two lobes of powerful radio sources exhi biting one-sided jets. According to this tight correlation, commonly k nown as the Laing-Garrington effect, the lobe on the counter-jet side is found to depolarize more rapidly at longer radio wavelengths, compa red to the opposite lobe. Conventionally, this is explained by postula ting that distant radio sources are embedded within large halos of den se magneto-ionic plasma, with typical dimensions of the core of intra- cluster medium (ICM). Pointing out potential problems with this scheme , we argue that the depolarization asymmetry, instead of arising from the putative ICM cores at high redshifts, could occur more commonly du e to extended disks of dusty magneto-ionic medium surrounding elliptic al galaxies hosting quasars. Differring radically in their physical or igin from the postulated ICM haloes, such disks are likely to have bee n acquired in the events of capture of gas-rich galaxies, or their pro genitors, by massive radio-loud ellipticals. Radio and optical evidenc es for such disks an summarized and some aspects of their evolution ar e briefly discussed.