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Abstract: We present the results of EVN+MERLIN VLBI polarization observations of 8Broad Absorption Line BAL quasars at 1.6 GHz, including 4 LoBALs and 4 HiBALswith either steep or flat spectra on VLA scales. Only one steep-spectrumsource, J1122+3124, shows two-sided structure on the scale of 2 kpc. The otherfour steep-spectrum sources and three flat-spectrum sources display either anunresolved image or a core-jet structure on scales of less than three hundredparsecs. In all cases the marginally resolved core is the dominant radiocomponent. Linear polarization in the cores has been detected in the range of afew to 10 percent. Polarization, together with high brightness temperaturesfrom 2*10^9-5*10^10 K, suggest a synchrotron origin for the radio emission.There is no apparent difference in the radio orphologies or polarizationbetween low-ionization and high-ionization BAL QSOs nor between flat- andsteep-spectrum sources. We discuss the orientation of BAL QSOs with both flatand steep spectra, and consider a possible evolutionary scenario for BAL QSOs.In this scenario, BAL QSOs are probably the young population of radio sources,which are Compact Steep Spectrum or GHz peaked radio source analog at the lowend of radio power.

Autor: Y. Liu, D. R.Jiang, T. G. Wang, F. G. Xie


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