On the Triggering of Extreme Starburst Events in Low-metallicity Galaxies: A Deep Search for Companions of Green Peas

Abstract

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 Multi Unit Spectroscopic Explorer (MUSE) Integral Field Unit spectrograph on the Very Large Telescope to search for companion galaxies. The survey reaches an average point-source depth of ∼10−18 erg cm−2 s−1 for emission lines. The MUSE field of view allows us to probe a 1 × 1 arcmin2 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.