Browsing by Subject "qsos"

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    The Black Hole Mass-Galaxy Luminosity Relationship For Sloan Digital Sky Survey Quasars
    (2015-02) Salviander, Sarah; Shields, Gregory A.; Bonning, E. W.; Salviander, Sarah; Shields, Gregory A.
    We investigate the relationship between the mass of the central supermassive black hole, M-BH, and the host galaxy luminosity, L-gal, in a sample of quasars from the Sloan Digital Sky Survey Data Release 7. We use composite quasar spectra binned by black hole mass and redshift to assess galaxy features that would otherwise be overwhelmed by noise in individual spectra. The black hole mass is calculated using the photoionization method, and the host galaxy luminosity is inferred from the depth of the Ca II H+K features in the composite spectra. We evaluate the evolution in the M-BH-L-gal relationship by examining the redshift dependence of Delta log M-BH, the offset in M-BH from the local M-BH-L-gal relationship. There is little systematic trend in. log MBH out to z = 0.8. Using the width of the [O III] emission line as a proxy for the stellar velocity dispersion, sigma(*), we find agreement of our derived host luminosities with the locally observed Faber-Jackson relation. This supports the utility of the width of the [O III] line as a proxy for sigma(*) in statistical studies.
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    In Search Of The Largest Velocity Dispersion Galaxies
    (2008-11) Salviander, Sarah; Shields, Gregory A.; Gebhardt, Karl; Bernardi, M.; Hyde, J. B.; Salviander, Sarah; Shields, Gregory A.; Gebhardt, Karl
    We present Hobby-Eberly Telescope (HET) observations for galaxies at redshift z < 0:3 from the Sloan Digital Sky Survey (SDSS) showing large velocity dispersions while appearing to be single galaxies in HSTimages. The high signal-to-noise HET spectra provide more definitive velocity dispersions. The maximum velocity dispersion we find is sigma(*) = 444 km s(-1). Emission-line widths in QSOs indicate that black holes can exist with masses M-center dot exceeding 5 billion M-circle dot, implying sigma(*) > 500 km s(-1) by the local M-center dot sigma(*) relationship. This suggests either that QSO black hole masses are overestimated or that the black hole-bulge relationship changes at high black hole mass. The latter option is consistent with evidence that the increase in sigma(*) with luminosity levels off for the brightest elliptical galaxies.