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Date and Time of the Query: 2019-06-26 T17:01:02 PDT
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For refcode 2009ApJ...702..767W:
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2009ApJ...702..767W Probing The Origins of the C IV and Fe K{alpha} Baldwin Effects Wu, Jian; Vanden Berk, Daniel E.; Brandt, W. N.; Schneider, Donald P.; Gibson, Robert R.; Wu, Jianfeng Abstract. We use UV/optical and X-ray observations of 272 radio-quiet Type 1 active galactic nuclei and quasars to investigate the C IV Baldwin Effect (BEff). The UV/optical spectra are drawn from the Hubble Space Telescope, International Ultraviolet Explorer and Sloan Digital Sky Survey archives. The X-ray spectra are from the Chandra and XMM-Newton archives. We apply correlation and partial-correlation analyses to the equivalent widths (EWs), continuum monochromatic luminosities, and {alpha}_ox_, which characterizes the relative X-ray to UV brightness. The EW of the C IV {lambda}1549 emission line is correlated with both {alpha}_ox_ and luminosity. We find that by regressing l_{nu}_(2500 Angstrom) with EW(C IV) and {alpha}_ox_, we can obtain tighter correlations than by regressing l_{nu}_(2500 Angstrom) with only EW(C IV). Both correlation and regression analyses imply that l_{nu}_(2500 Angstrom) is not the only factor controlling the changes of EW(C IV); {alpha}_ox_ (or, equivalently, the soft X-ray emission) plays a fundamental role in the formation and variation of C IV. Variability contributes at least 60% of the scatter of the EW(C IV)-l_{nu}_(2500 Angstrom) relation and at least 75% of the scatter of the of the EW(C IV)-{alpha}_ox_ relation. In our sample, narrow Fe K{alpha} 6.4 keV emission lines are detected in 50 objects. Although narrow Fe K{alpha} exhibits a BEff similar to that of C IV, its EW has almost no dependence on either {alpha}_ox_ or EW(C IV). This suggests that the majority of narrow Fe K{alpha} emission is unlikely to be produced in the broad emission-line region. We do find suggestive correlations between the emission-line luminosities of C IV and Fe K{alpha}, which could be potentially used to estimate the detectability of the Fe K{alpha} line of quasars from rest-frame UV spectroscopic observations. Key words: quasars: emission lines
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