X-ray and multiwavelength insights into the inner structure of high-luminosity disc-like emitters

B. Luo, W. N. Brandt, M. Eracleous, Jian Wu, P. B. Hall, A. Rafiee, D. P. Schneider, Jianfeng Wu

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

We present X-ray and multiwavelength studies of a sample of eight high-luminosity active galactic nuclei (AGN) with disc-like HΒ emission-line profiles selected from the Sloan Digital Sky Survey Data Release 7. These sources have higher redshift (z ≈ 0.6) than the majority of the known disc-like emitters, and they occupy a largely unexplored space in the luminosity-redshift plane. Seven sources have typical AGN X-ray spectra with power-law photon indices of γ ≈ 1.4-2.0; two of them show some X-ray absorption (column density NH ≈ 1021-1022 cm-2 for neutral gas). The other source, J0850+4451, has only three hard X-ray photons detected and is probably heavily obscured (NH ≳; 3 × 1023 cm-2). This object is also identified as a low-ionization broad absorption line (BAL) quasar based on Mg II γ2799 absorption; it is the first disc-like emitter reported that is also a BAL quasar. The infrared-to-ultraviolet (UV) spectral energy distributions (SEDs) of these eight sources are similar to the mean SEDs of typical quasars with a UV 'bump', suggestive of standard accretion discs radiating with high efficiency, which differs from low-luminosity disc-like emitters. Studies of the X-ray-tooptical power-law slope parameters (αOX) indicate that there is no significant excess X-ray emission in these high-luminosity disc-like emitters. Energy budget analysis suggests that for disc-like emitters in general, the inner disc must illuminate and ionize the outer disc efficiently (≈15 per cent of the nuclear ionizing radiation is required on average) via direct illumination and/or scattering. Warped accretion discs are probably needed for direct illumination to work inhigh-luminosity objects, as their geometrically thin inner discs decrease the amount of direct illumination possible fora flat disc.

Original languageEnglish (US)
Pages (from-to)1479-1493
Number of pages15
JournalMonthly Notices of the Royal Astronomical Society
Volume429
Issue number2
DOIs
StatePublished - Feb 21 2013

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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