Seyfert 1 Composite Spectrum using SDSS Legacy Survey Data

TL;DR

This paper constructs a median composite spectrum for Seyfert 1 galaxies using SDSS data, analyzing spectral features and comparing it with quasar spectra to understand active galactic nuclei.

Contribution

It provides the first large-scale composite Seyfert 1 spectrum from SDSS, including spectral measurements and comparison with quasar spectra, advancing AGN unification studies.

Findings

The composite spectrum matches well with quasar spectra in the blue region.

There is a flux offset in the red part of the spectrum compared to quasars.

Spectral index and emission line properties are characterized.

Abstract

We present a rest-frame composite spectrum for Seyfert 1 galaxies using spectra obtained from the DR12 release of the Sloan Digital Sky Survey (SDSS). The spectrum is constructed by combining data from a total of 10,112 galaxies, spanning a redshift range of 0 to 0.793. We produce an electronic table of the median and geometric mean composite Seyfert 1 spectrum. We measure the spectral index of the composite spectrum, and compare it with that of the composite quasar spectrum. We also measure the flux and width of the strong emission lines present in the composite spectrum. We compare the entire spectrum with the quasar spectrum in the context of the AGN unification model. The two composite spectra match extremely well in the blue part of the spectrum, while there is an offset in flux in the red portion of the spectrum.