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Date and Time of the Query: 2019-06-19 T21:22:16 PDT
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For refcode 2008A&A...478..321B:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
2008A&A...478..321B Evidence of a type 1/type 2 dichotomy in the correlation between quasar optical polarization and host-galaxy/extended emission position angles Borguet, B.; Hutsemekers, D.; Letawe, G.; Letawe, Y.; Magain, P. Abstract. Aims.For Seyfert galaxies, the AGN unification model provides a simple and well-established explanation of the type 1/type 2 dichotomy through orientation-based effects. The generalization of this unification model to the higher luminosity AGNs that quasars are remains a key question. The recent detection of type 2 radio-quiet quasars seems to support such an extension. We propose a further test of this scenario. Methods: On the basis of a compilation of quasar host-galaxy position angles consisting of previously published data and of new measurements performed using HST Archive images, we investigate the possible existence of a correlation between the linear polarization position angle and the host-galaxy/extended emission position angle of quasars. Results: We find that the orientation of the rest-frame UV/blue extended emission is correlated to the direction of the quasar polarization. For type 1 quasars, the polarization is aligned with the extended UV/blue emission, while these two quantities are perpendicular in type 2 objects. This result is independent of the quasar radio loudness. We interpret this (anti-)alignment effect in terms of scattering in a two-component polar+equatorial model that applies to both type 1 and type 2 objects. Moreover, the orientation of the polarization -and then of the UV/blue scattered light- does not appear correlated to the major axis of the stellar component of the host-galaxy measured from near-IR images. Key words: galaxies: quasars: general, polarization
Retrieve 135 NED objects in this reference.
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