Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2012
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21924307c&link_type=abstract
American Astronomical Society, AAS Meeting #219, #243.07
Astronomy and Astrophysics
Astronomy
Scientific paper
FeII emission poses a long-standing yet important problem in studies of quasar broad emission lines. FeII emission is a primary coolant of the broad-line region, a primary player in the set of emission line correlations known as Eigenvector 1, and it can yield information about metallicity in the early Universe. It is generally thought that UV FeII emission has the same shape in all quasars, varying only in equivalent width; however, Leighly et al. 2007 identified two characteristic shapes. Typical quasars exhibit FeII emission in the 2200-2600Å region. PHL 1811-like quasars exhibit additional FeII emission in the 2200-2600Å region and excess emission in the regions 2100-2200Å and 1950-2050Å. Leighly et al. hypothesized the difference in shape arises from differences in Fe excitation and ionization in these strong Fe emitters: the emission in typical spectra arises from low-excitation FeII, and in PHL 1811-like spectra the emission arises from additional high-excitation FeII and FeIII.
We investigate the near-UV Fe emission in quasars by modeling strong iron emitters with templates generated using the atomic data in the Kurucz database. By grouping lines of similar upper energy level, we populate the levels according to the Boltzmann factor, as in a thermal gas. A preliminary fit of the strong iron emitter SDSS J124244.37+624659.1 shows the expected lower-excitation levels dominating the FeII emission. Analysis of the PHL 1811 spectrum shows the expected higher-excitation levels contributing to the FeII emission, and additional FeIII flux relative to the SDSS J124244.37+624659.1 spectrum. More analysis is needed to interpret the spectrum in the 2000-2300Å range, where the excess of flux presents a challenge to model. Additional results will include a larger sample of strong Fe emitting quasars of both types.
This work is funded by NSF AST-0707703.
Cooper Erin M.
Leighly Karen
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