General descriptions

We provide a new database of absorption and emission-line measurements based on the entire spectral atlas from the Sloan Digital Sky Survey (SDSS) 7th data release of galaxies (0.0 ‹ z ‹ 0.2).

Our analysis of the SDSS spectra consisted of three separate steps.

First, we extracted the stellar kinematics by directly matching the spectra with a set of stellar templates, while excluding the spectral regions potentially affected by nebular emission.

We then measured the gaseous kinematics and assessed the strength of each emission-line (see table 1 in our paper) by fitting the entire spectrum, simultaneously using the stellar templates that were broadened and shifted by the previously derived stellar kinematics and a set of Gaussian templates representing the nebular emission. Foreground Galactic extinction is implicitly treated, whereas reddening in the SDSS galaxies is included in the form of a simple dust screen component affecting the entire spectrum that is accompanied by a second reddening component affecting only the ionised gas emission.

Finally, we subtracted, from the SDSS spectra, our best model for the nebular emission and measured the strength of various stellar absorption lines (see table 2 in our paper) from the observed spectra following standard line-strength index definitions.

 

 

 

 

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