High redshift radio quiet quasars - exploring the parameter space of accretion models. Part I: hot semi-spherical flow

M. A. Sobolewska; A. Siemiginowska; P. T. Zycki

doi:10.1086/392529

paper

High redshift radio quiet quasars - exploring the parameter space of accretion models. Part I: hot semi-spherical flow

arXiv:astro-ph/0410204 · doi:10.1086/392529

Abstract

Two families of models are currently considered to describe an accretion flow onto black holes and production of the observed X-ray radiation: (1) a standard cold accretion disk with a hot corona above it and (2) an outer truncated accretion disk with a hot semispherical inner flow. We compute spectra in the scenario with a hot inner flow surrounded by a truncated accretion disk covered by a hot corona and test the results on a sample of high redshift (z > 4) quasars observed with Chandra. We find that in order to reproduce the ratio of optical to X-ray fluxes (the $α_{ox}$ parameter), the optical depth of the Comptonizing plasma has to be rather low ( $τ = 0.02 - 0.15 in t h ecor o naab o v e t h e d i s k, an d$ τ= 0.15 - 0.70 in the hot inner flow). This, together with the observed X-ray photon indices, implies either a high temperature in a thermal plasma ( $k T_{e} = 90 - 500 k e V), or an o n t h er ma l e l ec t r o n d i s t r ib u t i o nin t h e pl a s ma . W e p u t an u pp er l imi t o n t h e d i s k t r u n c a t i o n r a d i u s,$ r_{\rm tr} \leq 40 R_{\rm S} $. T h e m o d e l e d a ccr e t i o n r a t e i s hi g h,$ \dot{m} > 0.2 Eddington rate, which may suggest that high-z radio quiet quasars are analogs of X-ray binaries in their high or very high state.

High redshift radio quiet quasars - exploring the parameter space of accretion models. Part I: hot semi-spherical flow

Abstract

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