---
title: "Pea galaxy"
chunk: 6/11
source: "https://en.wikipedia.org/wiki/Pea_galaxy"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T04:15:28.328105+00:00"
instance: "kb-cron"
---

The JWST image used by Rhoads et al. is called SMACS 0723 and within it three galaxies that looked particularly far away were followed up using spectroscopic observations. This caught the attention of Rhoads et al. as the spectra of the three galaxies resembled GPs. Astronomer Trinh Thuan from the University of Virginia says he was amazed to see the similarity between the distant trio and GPs. Before JWST, the furthest GPs were measured at about 10 billion years after the Big Bang. Daniel Schaerer, an astronomer at the University of Geneva said that GPs can now be measured from only 700 million years after the Big Bang – "It's completely mind-boggling". As reported in Nature back in 2016, GPs are strong sources of ionizing radiation that are thought to be able to free the early universe from its 'dark ages'. Thuan said: "Now I really do think that these star-forming dwarf galaxies are the agent of reionization".
A study published in the ApJ  by Bhat et al. in January 2024 investigates the influence of jets on GPs and Green Beans. Using 12 subjects selected from the SDSS and Radio Sky at 20 cm survey, the team use the  Large Binocular Telescope–Multi-Object Double Spectrograph long-slit spectroscopy at two position angles for each galaxy: one aligned with the jet direction and another perpendicular to it. By tracing the [OIII] emission along these slits, the team aimed to assess the extension of the jets, which revealed that there was no preferred direction on the EELRs. When comparing the extension of [OIII] emission with that [OII], it was found that [OII] emission extended along a greater extension along the galactic plane, suggesting a stronger association of [OII] with stellar processes.
In the 2024 study "Ubiquitous broad-line emission and the relation between ionized gas outflows and Lyman
continuum escape in Green Pea galaxies" R. Amorin et al. report evidence obtained by observations of ionized gas kinematics in a sample of 20 LyC emitters. These were made up of GPs from 3 different studies i) 14 from the Low-z Lyman Continuum (Flury et al. 2022a,b & Saldana-Lopez et al. 2022.) ii) 5 from Izotov et al. (2016a,b & 2018a) iii) 1 from Wang et al. (2021). A subsample of 13 spectra were obtained with the X-shooter instrument at the Very Large Telescope, while a subsample of 7 used spectra from the William Herschel Telescope's ISIS. Presenting new high-resolution optical spectra of 6 strong, 11 weak and 3 insignificant LyC leakers, they performed a first kinematic analysis of resolved emission-line profiles using multicomponent Gaussian fitting. They find a significant correlation between the intrinsic velocity dispersion and maximum line-width velocities of galaxies and their LyC escape fraction. Their results strongly suggest "that the physical mechanisms driving the observed kinematic complexity play a significant role in the escape of ionizing photons in galaxies."

== Blueberry galaxies ==

Blueberry galaxies (BBs) are fainter, less massive and lower distance counterparts of GPs. They are generally very small dwarf starburst galaxies that have very high ionisation rates and also have some of the lowest stellar masses and metallicities of starburst galaxies, although a massive BB has been studied. Two BBs are among the most metal-poor galaxies known, while the larger sample exist in low-density environments, similar to GPs. BBs are more compact than GPs being less than 1/3000 the size of the Milky Way. BBs form one of the youngest classes of star-forming galaxies with median ages ≤70 Myr. In 2011, Izotov and fellow authors wrote that GPs, BBs and 'Purple Grapes' were Luminous Compact Galaxies at different distances (see below).
While Huan (2017) identified a sample of 40 BBs, a much larger sample was acquired using data from the LAMOST DR9 survey. Siqi Liu and fellow authors found 270 BBs, as well as GPs and 'Purple Grapes'. The observations found 1,417 new compact galaxies, nearly twice as many as formerly known.  Researchers undertook a systematic study of the star formation rates, metallicities and environments of the compact galaxies that have different colours because of the different positions of emission lines in the photometric bands.

== Little red dots ==

Recent observations by the JWST have revealed a population of small red galaxies known as Little Red Dots (LRD) that exist between 600 million years and 1.5 billion years after the Big Bang . It is thought that these objects have AGN within them caused by supermassive black holes, though other theories exist.
A study published in the ApJ letters by Ruqiu Lin et al. (2025) link LRDs to GPs. Using data gathered from previous work, Lin et al. theorise local analog GPs that host broad-line AGNs (BLGPs) are similar to LRDs. These galaxies with 'over massive' black holes have spectra similar to that found with LRDs. They conclude: "GPs provide a local subsample that can be considered analogs to LRDs and high-z broad-line AGNs. Combined with follow-up observation, including spectroscopic and imaging observations with high sensitivity and high spatial resolution in the UV and optical bands, this V-shaped BLGP sample can help to address several unclear questions for LRDs, such as the UV emission origin."