Black Hole Winds: the case of PDS 456. Abstract:
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XMM-Newton observations of the nearby, luminous quasar PDS 456 have revealed a massive X-ray outflow whose primary observational signature is deep absorption in the iron K-shell band. The UV spectrum of PDS 456 also shows spectral features consistent with out-flowing material. The combined RGS and EPIC spectra are best fit by a model in which a large column of highly ionized gas (NH = 5 x 1023 cm-2 , log = 2.5) is out-flowing at a velocity of 50000 km s-1 . Assuming a conservative covering factor of 0.1 steradian, we derive a mass-outflow rate of ~10 M year-1 . The kinetic energy of the outflow is equivalent to ~10% of the bolometric luminosity of PDS 456. The outflow may be driven by radiation and/or magnetic field.
Observations of other type-1 AGN with XMM-Newton have revealed similar high-mass, highly ionized outflows, or “black hole winds. Such black hole winds are capable of providing a substantial input of both energy and mass to the surroundings of the black hole, and may be a source of gas for the BLR and NLR. Future observations are planned to study how the outflow properties correlate with the accretion rate, to determine the driving mechanism and to further investigate the geometry and dynamics of the outflow and how it relates to the continuum emission.
Paul O’Brien,X-ray and Observational Astronomy Group, University of Leicester