Blueberry and Green Pea galaxies live in low density environments

TL;DR

This study investigates the clustering and environmental density of Green Pea and Blueberry galaxies, revealing they predominantly reside in isolated, low-density regions, supporting internal or gas accretion-driven starburst scenarios.

Contribution

It provides the first large-scale analysis of the environments of GPs and BBs, linking their low clustering to their starburst activity and potential early Universe analogues.

Findings

GPs and BBs are found in low-density, isolated environments.

Clustering depends strongly on star-formation activity, with high SFR galaxies less clustered.

Low metallicities and weak clustering support internal or gas accretion-driven starbursts.

Abstract

Little is currently known about the large-scale environments of Green Pea (GP) and Blueberry (BB) galaxies, which are low-mass, compact systems with extreme specific star-formation rates (sSFR). Their environments are inherently linked to their formation mechanism, and they may serve as crucial local analogues for high-redshift, reionizing galaxies. This paper aims to investigate the clustering properties of GPs and BBs, leveraging large-scale survey data to quantify their spatial distribution relative to the broader galaxy population. We here investigate a sample of these galaxies, consisting of 339 GPs $\rm (0.1 < z \le 0.33)$ and 56 BBs $\rm (0 < z \le 0.1)$, whose clustering properties we analyse relative to an extensive control sample derived from the SDSS MPA-JHU DR8 catalogue, binned by stellar mass and sSFR. We use the number of neighbours within a 5 Mpc radius as a proxy for environmental density, i.e. clustering, and employ a pair-matching and bootstrapping methodology to ensure statistical robustness. We observe that galaxy clustering depends strongly on star-formation activity, with passive galaxies being more clustered than their high star-formation rate counterparts, with GPs and BBs lying at the extreme end of this relation, exhibiting the lowest neighbour counts among all subsamples. The nearest neighbours of BBs also tend to have lower masses than other classes of dwarf galaxies. GPs and BBs predominantly reside in isolated, low-density environments, suggesting that their intense starbursts are unlikely to be triggered by common environmental processes such as mergers or starburst cycles. Their low metallicities and weak clustering instead support scenarios in which recent starbursts are driven by internal processes or pristine gas accretion, reinforcing their role as nearby analogues of young, low-mass galaxies in the early Universe.