# Stellar population analysis on the stacked spectra of double-peaked emission-line galaxies

## TL;DR

This study analyzes the stellar populations of double-peaked emission-line galaxies using stacked spectra from large surveys, revealing their association with older stellar environments and diverse star formation histories.

## Contribution

It introduces a comparative analysis of stellar populations in double-peaked versus single-peaked emission galaxies using spectral stacking and population synthesis.

## Key findings

- Double-peaked galaxies are linked to older stellar populations.
- Different BPT components show varied star formation histories.
- Strong correlation between spectral class and stellar population age.

## Abstract

The double-peaked emission-line galaxies has long been perceived as objects related with merging galaxies or other phenomena of disturbed dynamical activities, such as outflows and disk rotation. In order to find the connection between the unique activities happening in these objects and their stellar population physics, we study the stellar populations of the stacked spectra drawn from double-peaked emission-line galaxies in the Large Sky Area Multi-object Fiber Spectroscopic Telescope (LAMOST) Data Release 4 (DR4) and Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7) database. We group the selected double-peaked emission-line objects into 10 different types of pairs based on the Baldwin-Phillips-Terlevich (BPT) diagnosis for each pair of blue-shifted and red-shifted components, and then stack the spectra of each group for analysis. The software STARLIGHT is employed to fit each stacked spectra, and the contributions of stars at different ages and metallicities are quantified for subsequent comparative study and analysis. To highlight the commonness and uniqueness in these double-peaked emitting objects, we compare the population synthesis results of the stacked spectra of double-peaked emission-line galaxies with that of their counterpart reference samples appearing single-peaked emission features. The reference sample are also selected from LAMOST DR4 and SDSS DR7 databases, respectively. From the comparison results, we confirm the strong correlations between the stellar populations and its spectral classes, and find that the double-peaked emitting phenomena is more likely to occur in the `older' stellar environment and the subgroups hosting different BPT components will show obvious heterogeneous star formation history.