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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Blueberry galaxy | 3/3 | https://en.wikipedia.org/wiki/Blueberry_galaxy | reference | science, encyclopedia | 2026-05-05T06:51:23.966099+00:00 | kb-cron |
While some authors continue to name these blue low-redshift compact starforming galaxies as BBs, some have broadened the original criteria for GPs and, perhaps confusingly, call BBs as GPs. An example of this is the study "New Insights on Lyα and Lyman Continuum Radiative Transfer in the Greenest Peas" (Jaskot et al. 2019) in which blue objects at very low redshifts are named as GPs . In this study, 13 blue and green galaxies at various redshifts are observed using the Hubble Space Telescope Cosmic Origins Spectrograph (COS) from which spectra are produced. The authors seek the levels of the ionizing Lyman continuum photons which might be important when considering the epoch of reionization in the early universe. In a 2011 study, Izotov et al. classified BBs as 'Luminous Compact Galaxies' but did not refer to them by name, stating that blue, purple and green Pea galaxies were the same type of object at distances between redshifts z=~0.02 to ~0.63.
In the publication: "Proceedings of the conference 'The Interplay between Local and Global Processes in Galaxies', Cozumel, Mexico, 2016-4" (Hidalgo-Gámez et al. 2017a ), the authors in an accompanying presentation call galaxies similar to BBs 'Blue marbles' or purple Pea galaxies 'Purple marbles'. They state: "Although some authors have concluded that all three are the same kind of galaxies, we have studied them carefully and found out that there are important differences among the properties, including the scaling relations." "Chemical Abundances of a Sample of Oxygen-dominated Galaxies" (Miranda-Pérez et al. 2023) seeks to determine the chemical abundances of 88 Extreme Emission Line Galaxies by spectroscopy. The sample of 88 compact, oxygen-dominated galaxies were taken from SDSS DR7 and were selected because of their large equivalent width of [O III]λ5007 (more than 200 Å). The authors determined oxygen, nitrogen, sulphur, neon, argon, iron and chlorine levels and found a mean metallicity of 12 + log(O/H) ≈ 8. Their sample contained objects that they placed into 3 colour sets: 23 blue, 29 purple and 36 green. The galaxies were those colours because of where the strong [OIII] emission line fell in the SDSS spectrum according to redshift of the object: blue nearby, then purple with green the furthest away at redshift z < 0.35. 12% of the galaxies were found to Extremely Metal Poor (XMP). It became clear that "that there is a lack of evolution in the chemical abundance for all the elements for such a long time, about 4.6 Gyr" while "it is expected that galaxies at high redshift might have lower metallicities". See also "Chemical abundances of a sample of coloured galaxies" (Hidalgo-Gámez et al. 2017b), and "Coloured galaxies" (Hidalgo-Gámez et al. 2019) presentation at "Small Galaxies, Cosmic Questions", Durham University.
== Purple pea galaxies ==
Purple Pea galaxies (PPs) are counterparts of Green Pea galaxies and Blueberry galaxies, often being termed 'Purple Grapes'. The PPs sample shown in the image to the right has 15 dwarf starburst galaxies and was taken from a list on the Galaxy Zoo website. As in other samples, these PPs are at a distance of redshit 0.05 ≤ z < 0.112 which places them about halfway in distance between GPs and BBs. The 24 galaxies named 'Purple marbles' in Hidalgo-Gámez et al. 2017a are at an average distance of redshift z = 0.09 and so fall within the range of PPs.
== Little blue dots == The study "Little Blue Dots in the Hubble Space Telescope Frontier Fields: Precursors to Globular Clusters?" (Elmegreen et al. 2017) examines images from the HST Frontier Fields Parallels, finding galaxies they name as Little Blue Dots (LBDs). When compared to BBs, LBDs are less massive and have a higher specific star formation rate, suggesting that their entire stellar mass has formed in only 1% of the local age of the universe. They are considered to be low-mass analogs of BBs. The authors find 55 LBDs between redshifts z=~0.73 and ~4.09 that appear as different colour objects because of their distance. They suggest that "objects like this are the long-sought progenitors of low-metallicity globular clusters, which formed in dwarf galaxies and were assimilated into the halos of today's spirals and ellipticals."
== See also == Citizen science Galaxy formation and evolution Faint blue galaxy Gems of the Galaxy Zoos Haro 11 Irregular galaxy Little red dot (galaxy) Lyman-alpha forest
== References ==
== External links == "February 2024: Blueberries and Peas" - Podcast from the Jodrell Bank Centre for Astrophysics featuring an interview about Blueberries and Green Peas (22m45s - 32m43s). February 2024. "What are Green Peas? - Article about Green Peas from the BBC Sky at Night magazine. November 2024.