[Previous] | [Session 77] | [Next]
Z. Shang, B. Wills, E. Robinson, J. Yuan (University of Texas at Austin)
We have performed a spectral principal component analysis (SPCA) of a complete sample of 22 low redshift QSOs from Ly\alpha to H\alpha, and found three significant principal components, which account for 50% of the total variance in the sample. The first component suggests an anticorrelation between emission line strength and QSO luminosity. It is closely related to the Baldwin effect (e.g. Baldwin, 1977, Espey & Andreadis 1999) which is an anticorrelation between broad emission line equivalent width and the QSO luminosity. But in our result, only the narrow components of the broad emission lines are involved. This principal component is probably driven by QSO luminosity (i.e. accretion rate). The second component represents the variations in UV continuum slope, which could be due to the intrinsic variation in the emitted continuum, external dust reddening or star light. The third principal component, involving broad components of broad emission lines, shows consistent change in the widths of emission lines, and a strong anticorrelation between strength of optical and UV FeII emissions. It is related to the Boroson & Green (1992) ``Eigenvector 1'' (or 1st principal component), and seems to be driven directly by black hole mass (MBH) or through Eddington ratio (L/LEdd \propto L/MBH).