Correlations between Nebular Emission and the Continuum Spectral Shape in SDSS Galaxies

TL;DR

This study analyzes the relationships between nebular emission lines and the continuum spectral shape in SDSS galaxies, revealing that three principal components can effectively describe emission line variations and enabling improved photometric redshift estimates.

Contribution

It introduces a principal component-based method to model emission line strengths from spectral shape, enhancing photometric redshift accuracy in galaxy surveys.

Findings

Three principal components explain emission line variations.

Empirical relations predict emission lines from spectral shape.

Method improves photometric redshift estimation accuracy.

Abstract

We present a statistical study of the correlations and dimensionality of emission lines carried out on a sample of over 40,000 Sloan Digital Sky Survey (SDSS) galaxies. Using principal component analysis, we found that the equivalent widths of the 11 strongest lines can be well represented using three parameters. We also explore correlations of the emission pattern with the eigenspace representation of the continuum spectrum. The observed relations are used to provide an empirical prescription for expectation values and variances of emission-line strengths as a function of spectral shape. We show that this estimation of emission lines has a sufficient accuracy to make it suitable for photometric applications. The method has already proved useful in SDSS photometric redshift estimation.