Astronomy and Astrophysics – Astronomy
Scientific paper
Apr 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999apj...515l..53w&link_type=abstract
The Astrophysical Journal, Volume 515, Issue 2, pp. L53-L56.
Astronomy and Astrophysics
Astronomy
62
Accretion, Accretion Disks, Galaxies: Starburst, Galaxies: Quasars: Emission Lines, Galaxies: Quasars: General, Ultraviolet: Galaxies, X-Rays: Galaxies
Scientific paper
Two sets of relationships relate QSO UV to soft X-ray continua with the broad-line region. These are (i) the Baldwin relationships, which are inverse relationships between the broad-line equivalent width and the continuum luminosity, and (ii) Boroson & Green's optical ``Principal Component 1'' relationships, linking steeper soft X-ray spectra with narrower Hβ emission, stronger Hβ blue wings, stronger optical Fe II emission, and weaker [O III] lambda5007 lines. In order to understand these relationships, we extended the spectra into the UV for 22 QSOs with high-quality soft X-ray spectra. These are from the complete sample of QSOs from the Bright Quasar Survey for which Laor et al. demonstrated strong luminosity and X-ray-optical Principal Component 1 relationships. We show that these extend to a whole new set of UV relationships: Principal Component 1 (in the sense of steeper X-ray spectra) is related to narrower C III] lambda1909 lines, larger Si III] lambda1892/C III] lambda1909 ratios (a high-density indicator), stronger low-ionization lines, and weaker C IV lambda1549 but stronger N V lambda1240 lines. We speculate that high accretion rates are linked to high columns of dense (~10^11 cm^-3), nitrogen-enhanced, low-ionization gas from nuclear starbursts. Line width, inverse Fe II-[O III] and inverse Fe II-C IV relationships hint at the geometrical arrangement of this gas. These Principal Component 1 relationships appear to be independent of luminosity and therefore of the Baldwin relationships.
Brotherton Michael S.
Ferland Gary J.
Laor Ari
Shang Zhaohui
Wilkes Belinda J.
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