Statistics – Applications
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003aas...203.7823m&link_type=abstract
American Astronomical Society Meeting 203, #78.23; Bulletin of the American Astronomical Society, Vol. 35, p.1328
Statistics
Applications
Scientific paper
The study of the UV Fe 2 multiplets in quasar spectra has broad potential applications. In principle, the ratio of Fe 2 to Mg 2 in high redshift quasars permits a probe of the chemical evolution in the Universe. The complicated multiplets of Fe 2 potentially hold information about the excitation and optical depths for low-ionization line emission in the broad-line region. Narrow-line quasars are the best objects to use to study low-ionization line emission, because these lines are frequently strong, and because the narrow lines reduce ambiguity arising from blending.
We present an analysis of the near-UV spectra of ˜ 900 narrow-line quasars from the Sloan Digital Sky Survey. The sample was choosen from quasars with redshifts between 1.2 and 1.8, and with Mg 2 FWHM less than 3000 km s-1. Further screening rejected objects with lines having FWHM greater than 2600 km s-1, poor signal-to-noise ratios, and intrinsic Mg 2 absorption lines. After refining the redshifts using the narrow Mg 2 line, and removing Galactic absorption lines, a composite spectrum was constructed. Fitting the Fe 2 using a template created from HST spectrum of I Zw 1 revealed an Fe 2-to-Mg 2 ratio of 3.9 in the composite. This is comparable to values measured in high redshift quasars, somewhat lower than in nearby Narrow-line Seyfert 1 galaxies, and somewhat larger than in the SDSS early-release quasar composite spectrum.
Further analysis, including a study of the distribution of Fe 2 to Mg 2 ratios, correlations with continuum shape, line width, and luminosity, and a systematic search for objects with Fe 2 emission differing from that of I Zw 1 (and therefore potentially revealing different conditions in the low-ionization line emitting gas) will be presented.
Casebeer Darrin
Leighly Karen M.
Moore Jeffrey R.
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