---
title: "Pea galaxy"
chunk: 4/11
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"
---

=== 2013–2015 ===
In January 2013, authors S. Parnovsky et al. published a paper in A&SS titled "H alpha and UV luminosities and star formation rates in a large sample of luminous compact galaxies". In it, they present a statistical study of the star formation rates (SFR) derived from the GALEX observations in the Ultraviolet continuum and in the H alpha emission line for a sample of ~800 luminous compact galaxies (LCGs). Within the larger set of LCGs, including the GPs, SFR of up to ~110 M☉/yr (~110 solar masses a year) are found, as well as estimates of the ages of the starbursts.
In April 2013, authors A. Jaskot and M. Oey published a paper in the ApJ titled "The Origin and Optical Depth of Ionizing Radiation in the "Green Pea" Galaxies". Six "extreme" GPs are studied. Using these, the authors endeavour to narrow down the list of possibilities about what is producing the radiation and the substantial amounts of high-energy photon that might be escaping from the GPs. Following on from this paper, observations on the Hubble Space Telescope, totalling 24 orbits, were taken in December 2013. The Cosmic Origins Spectrograph and the Advanced Camera for Surveys were used on four of the "extreme" GPs. For more details see: Two papers by Jaskot and Oey
In January 2014, authors Y. Izotov et al. published a paper in A&A entitled "Multi-wavelength study of 14000 star-forming galaxies from the Sloan Digital Sky Survey". In it they use a variety of sources to demonstrate "that the emission emerging from young star-forming regions is the dominant dust-heating source for temperatures to several hundred degrees in the sample star-forming galaxies". The first source of data is SDSS from which 14,610 spectra with strong emission lines are selected. Those spectra were then cross-identified with sources from photometric sky surveys in other wavelength ranges, which are: i) GALEX for the ultraviolet, ii) The 2MASS survey for the near-infrared, iii) The WISE All-Sky Source Catalog for infrared at differing wavelengths, iv) The IRAS survey for the far-infrared and the v) NVSS Survey at radio-wavelengths. Only a small fraction of the SDSS objects were detected in the last two surveys. Among the results is a list of 20 galaxies with the highest magnitudes which have hot dust of several hundred degrees. Of these 20, all could be classified as GPs and/or LCGs. Also among the results, the luminosity is obtained in the sample galaxies in a wide wavelength range. At the highest luminosities, the sample galaxies had luminosites approaching those of high-redshift Lyman-break galaxy.
In January 2014, authors A. Jaskot et al. gave a presentation titled "Neutral Gas and Low-Redshift Starbursts: From Infall to Ionization" to the AAS at their meeting #223. The presentation included data from The Arecibo Observatory Legacy Fast ALFA Survey (ALFALFA). The authors analyzed the optical spectra of the GPs and concluded "While the ALFALFA survey demonstrates the role of external processes in triggering starbursts, the Green Peas show that starbursts' radiation can escape to affect their external environment", finding "that the Peas are likely optically thin to Lyman continuum (LyC) radiation."
In June 2014, authors A. Jaskot and M. Oey published a conference report titled "The Origin and Optical Depth of Ionizing Photons in the Green Pea Galaxies". This appears in "Massive Young Star Clusters Near and Far: From the Milky Way to Reionization", based on the 2013 Guillermo Haro Conference. For more details see: Two papers by Jaskot and Oey.
In May 2015, authors A. Henry, C et al. published a paper in the ApJ entitled, "Lyα Emission from Green Peas: The Role of Circumgalactic Gas Density, Covering, and Kinematics". In this paper, ten Green Peas were studied in the ultraviolet, using high-resolution spectroscopy with the Hubble Space Telescope using the Cosmic Origins Spectrograph. This study showed, for the first time, that Green Peas have strong Lyα emission much like distant, high-redshift galaxies observed in a younger universe. Henry et al. explored the physical mechanisms that determine how Lyα escapes from the Green Peas, and concluded that variations in the neutral hydrogen column density were the most important factor. For more details see: Lyman Alpha Emission from Green Peas.

=== 2016–2017 ===
In May 2016, author Miranda C. P. Straub published a research paper in the open access journal Citizen Science: Theory and Practice called 'Giving Citizen Scientists a Chance: A Study of Volunteer-led Scientific Discovery'. The abstract states: "The discovery of a class of galaxies called Green Peas provides an example of scientific work done by volunteers. This unique situation arose out of a science crowdsourcing website called Galaxy Zoo."
In April 2016, Yang et al. published "Green Pea Galaxies Reveal Secrets of Lyα Escape." Archival Lyman-alpha spectra of 12 GPs that have been observed with the HST/COS were analysed and modelled with radiative transfer models. The dependence of Lyman-alpha (LyA) escape fractions on various properties were explored. All 12 GPs show LyA lines in emission, with a LyA equivalent width distribution similar to high-redshift emitters. Among the findings are that the LyA escape fraction depends strongly on metallicity and moderately on dust extinction. The papers results suggest that low H1 column density and low metallicity are essential for LyA escape. "In conclusion, GPs provide an unmatched opportunity to study LyA escape in LyA Emitters."