Matches in SemOpenAlex for { <https://semopenalex.org/work/W3103184143> ?p ?o ?g. }
- W3103184143 abstract "Using Chandra and HST archival data, we have studied the individual Spectral Energy Distribution (SED) of 11 quasars. All UV spectra show a spectral break around 1100A. 5 X-ray spectra show the presence of a ``soft excess'' and 7 spectra showed an intrinsic absorption. We found that for most quasars a simple extrapolation of the far-UV powerlaw into the X-ray domain generally lies below the X-ray data and that the big blue bump and the soft X-ray excess do not share a common physical origin. We explore the issue of whether the observed SED might be dust absorbed in the far and near-UV. We fit the UV break, assuming a powerlaw that is absorbed by cubic nanodiamond dust grains. We then explore the possibility of a universal SED (with a unique spectral index) by including further absorption from SMC-like extinction. Using this approach, satisfactory fits to the spectra can be obtained. The hydrogen column densities required by either nanodiamonds or amorphous dust models are all consistent, except for one object, with the columns deduced by our X-ray analysis, provided that the C depletion is ~0.6. Because dust absorption implies a flux recovery in the extreme UV (<700A), our modeling opens the possibility that the intrinsic quasar SED is much harder and more luminous in the extreme UV than inferred from the near-UV data, as required by photoionization models of the broad emission line region. We conclude that the intrinsic UV SED must undergo a sharp turn-over before the X-ray domain." @default.
- W3103184143 created "2020-11-23" @default.
- W3103184143 creator A5010018395 @default.
- W3103184143 creator A5021988166 @default.
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- W3103184143 creator A5072765402 @default.
- W3103184143 creator A5084587116 @default.
- W3103184143 creator A5089810152 @default.
- W3103184143 date "2007-06-10" @default.
- W3103184143 modified "2023-09-23" @default.
- W3103184143 title "Energy Distribution of Individual Quasars from Far‐Ultraviolet to X‐Rays. I. Intrinsic Ultraviolet Hardness and Dust Opacities" @default.
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