Friday, July 26, 2013

1307.6799 (Rajib Ganguly et al.)

A Census of Quasar-Intrinsic Absorption in the Hubble Space Telescope Archive: Systems from High Resolution Echelle Spectra    [PDF]

Rajib Ganguly, Ryan S. Lynch, Jane C. Charlton, Michael Eracleous, Todd M. Tripp, Christopher Palma, Kenneth R. Sembach, Toru Misawa, Joseph R. Masiero, Nikola Milutinovic, Benjamin D. Lackey, Therese M. Jones
We present a census of z(abs) < 2, intrinsic (those showing partial coverage) and associated [z(abs) ~ z(em)] quasar absorption-line systems detected in the Hubble Space Telescope archive of Space Telescope Imaging Spectrograph echelle spectra. This work complements the Misawa et al. (2007) survey of 2 < z(em) < 4 quasars that selects systems using similar techniques. We confirm the existence of so-called "strong N V" intrinsic systems (where the equivalent width of H I Ly alpha is small compared to N V 1238) presented in that work, but find no convincing cases of "strong C IV" intrinsic systems at low redshift/luminosity. Moreover, we also report on the existence of "strong O VI" systems. From a comparison of partial coverage results as a function of ion, we conclude that systems selected by the N V ion have the highest probability of being intrinsic. By contrast, the C IV and O VI ions are poor selectors. Of the 30 O VI systems tested, only two of the systems in the spectrum on 3C 351 show convincing evidence for partial coverage. However, there is a 3-sigma excess in the number of absorbers near the quasar redshift (|Delta v| <= 5000 km/s) over absorbers at large redshift differences. In at least two cases, the associated O VI systems are known not to arise close to the accretion disk of the quasar.
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