The correlation of line strength with luminosity and redshift from composite QSO spectra

Croom, SM
Rhook, K
Corbett, EA
Boyle, BJ
Netzer, H
Loaring, NS
Miller, L
Outram, PJ
Shanks, T
Smith, RJ

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Publication date

July 2002

DOI

10.1046/j.1365-8711.2002.05910.x

Publisher

Wiley

Journal

Monthly Notices of the Royal Astronomical Society

Abstract

We have generated a series of composite QSO spectra using over 22000 individual low resolution (~8A) QSO spectra obtained from the 2dF (18.25<bj<20.85) and 6dF (16<bj<18.25) QSO Redshift Surveys. The large size of the catalogue has enabled us to construct composite spectra in narrow redshift (dz=0.25) and absolute magnitude (dMb=0.5) bins. The median number of QSOs in each composite is ~200, yielding typical S/N of ~100. For a given redshift interval, the composite spectra cover a factor of over 25 in luminosity. Using the composite spectra we have measured the equivalent widths (EWs) of the major broad and narrow emission lines, and the CaII K absorption feature due to the host galaxy of the AGN. Assuming a fixed host galaxy spectral energ...