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Eigenspectra of the SDSS DR1 quasars

Ching-Wa Yip·Andrew Connolly·Daniel Vanden Berk·Zhaoming Ma·Joshua Frieman·Mark SubbaRao·Alex Szalay
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Abstract

We construct eigenspectra from the DR1 quasars in the SDSS using the Karhunen-Loève (KL) transform (or Principal Component Analysis, PCA) in different redshift and luminosity bins. We find that the quasar spectra can be classified, by the first two eigenspectra, into a continuous sequence in the variation of the spectral slope. We also find a dependence on redshift and luminosity in the eigencoefficients. The dominant redshift effect is the evolution of the blended Fe~II emission (optical) and the Balmer continuum (the ``small-bump'', $λ_{rest} \approx 2000-4000$Å), while the luminosity effect is related to the Baldwin effect. Correlations among several major broad emission lines are found, including the well-known ``Eigenvector-1''.

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Ching-Wa Yip, Andrew Connolly, Daniel Vanden Berk, Zhaoming Ma, Joshua Frieman, Mark SubbaRao, Alex Szalay. 2004-03-23. Eigenspectra of the SDSS DR1 quasars. https://arxiv.org/abs/astro-ph/0403560

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