On the triggering of extreme starburst events in low-metallicity galaxies: a deep search for companions of Green Peas

TL;DR

This study investigates whether interactions with companion galaxies trigger starburst events in Green Pea galaxies by conducting deep spectroscopic surveys, finding no significant difference in companion frequency compared to typical star-forming galaxies.

Contribution

The paper provides the first systematic deep search for companions of Green Pea galaxies using MUSE, showing that their starbursts are not predominantly caused by galaxy interactions.

Findings

Green Pea galaxies have a companion fraction of about 11%.

Control star-forming galaxies show a similar companion fraction.

No statistical evidence links companions to starburst activity in Green Peas.

Abstract

Green pea galaxies are starbursting, low-mass galaxies that are good analogues to star-forming galaxies in the early universe. We perform a survey of 23 Green Peas using the MUSE Integral Field Unit spectrograph on the VLT to search for companion galaxies. The survey reaches an average point-source depth of $\sim 10^{-18}$ erg cm$^{-2}$ s$^{-1}$ for emission lines. The MUSE field of view allows us to probe a 1$\times$1 arcmin$^2$ field around these galaxies and to search their surroundings for faint companions that could have interacted with them and induced their starburst episodes. We search for companions using a variety of methods including template matching to emission and absorption line spectra. When restricting the search to the same physical area (R = 78 kpc) for all galaxies, we find that the fraction of green pea galaxies with companions is $0.11_{-0.05}^{+0.07}$. We define a control sample of star-forming galaxies with the same stellar masses and redshifts as the green peas, but consistent with the star-formation main sequence. We find that green pea galaxies are as likely to have companions as the control sample; for which the fraction of objects with companions is $0.08_{-0.03}^{+0.05}$. Given that we do not find statistical evidence for an elevated companion fraction in the green peas in this study, we argue that the ``companions" are likely unrelated to the bursts in these galaxies.