Galaxy Zoo Green Peas: discovery of a class of compact extremely star-forming galaxies

By C. Cardamone, Kevin Schawinski, M. Sarzi, Steven Bamford, N. Bennert, C. Urry, Chris J. Lintott, William Keel, J. Parejko, Robert Nichol and 8 more. 2009

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We investigate a class of rapidly growing emission line galaxies, known as “Green Peas,” first noted by volunteers in the Galaxy Zoo project because of their peculiar bright green colour and small size, unresolved in SDSS imaging. Their appearance is due to very strong optical emission lines, namely [O III] �5007 ˚ A, with an unusually large equivalent width of up to �1000 ˚ A. We discuss a well-defined sample of 251 colour-selected ob jects, most of which are strongly star forming, although there are some AGN interlopers including 8 newly discovered Narrow Line Seyfert 1 galaxies. The star-forming Peas are low mass galaxies (M� 10 8.5 10 10 M⊙) with high star formation rates (� 10 M⊙yr −1 ), low metallicities (log[O/H] + 12 �8.7) and low reddening (E(B V) 6 0.25) and they reside in low density environments. They have some of the highest specific star for mation rates (up to � 10 −8 yr −1 ) seen in the local Universe, yielding doubling times for their stellar mass of hundreds of Myrs. The few star-forming Peas with HST imaging appear to have several clumps of bright star-forming regions and low surface density features that may indicate recent or ongoing mergers. The Peas are similar in size, mass, luminosity and metallicity to Luminous Blue Compact Galaxies. They are also similar to high redshift UV-luminous galaxies, e.g., Lymanbreak galaxies and Lyman-� emitters, and therefore provide a local laboratory with which to study the extreme star formation processes that occur in high-redshift galaxies. Studying starbursting galaxies as a function of redshift is essential to u nderstanding the build up of stellar mass in the Universe.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

Ionization state of inter-stellar medium in galaxies: evolution, SFR-M * -Z dependence, and ionizing photon escape (2013, methodology): “We use 80 GPs given by Cardamone et al. (2009) that are free from AGN contamination.”
J1154+2443: a low-redshift compact star-forming galaxy with a 46 per cent leakage of Lyman continuum photons (2017, background): “The subsample of these galaxies in the redshift range z ∼ 0.1 – 0.3 is often referred to as “Green Pea” (GP) galaxies because of their green colour in the composite SDSS images (Cardamone et al. 2009).”
Detection of high Lyman continuum leakage from four low-redshift compact star-forming galaxies (2016, methodology): “Cardamone et al. (2009) used colour-colour diagrams to select a sample of “Green Pea” (GP) compact galaxies from the Sloan Digital Sky Survey (SDSS) named for their green colour.”
The Rhetoric and Reality of Anthropomorphism in Artificial Intelligence (2019, background): “2014) and discover new astronomical objects (Cardamone et al. 2009; Watson and Floridi 2018).”
Galaxy Zoo: the fraction of merging galaxies in the SDSS and their morphologies (2009, background): “…2009), the relationships between environment, morphology and colour (Bamford et al. 2008a; Skibba et al. 2008), to study optically blue early-type galaxies at very low redshift (Schawinski et al. 2009) and has also lead to some serendipitous discoveries (Lintott et al. 2009; Cardamone et al. 2009).”
HYDROGEN-POOR SUPERLUMINOUS SUPERNOVAE AND LONG-DURATION GAMMA-RAY BURSTS HAVE SIMILAR HOST GALAXIES (2013, background): “The blue-green color of the dwarf galaxy is due to strong [O iii] emission in r-band, similar to the “Green Pea” galaxies found in SDSS (Cardamone et al. 2009).”
Using Lyman-α to detect galaxies that leak Lyman continuum (2014, background): “Recently, UV spectra of green peas (Cardamone et al. 2009) acquired with HST/COS have become available through the MAST archive (GO 12928, PI: A. Henry, GO 13293, PI: A. Jaskot, Jaskot & Oey 2014).”
Galaxy Zoo 1: data release of morphological classifications for nearly 900 000 galaxies (2010, background): “Its usefulness is demonstrated both by the catalogue presented here, but also by the serendipitous discovery of unusual objects and classes of object discussed el - where (e.g. Lintott et al. 2009; Cardamone et al. 2009).”
An extreme [O III] emitter at z = 3.2: a low metallicity Lyman continuum source (2015, background): “1010.5M ), low metallicity (12 + log(O/H) = 8.05 ± 0.14, Amorı́n et al. 2010, 2012), high sSFR (sSFR=SFR/stellar mass, 1 to 10 Gyr−1, Cardamone et al. 2009), young age (few Myr), showing Wolf-Rayet signatures (e.g., bumps and He ii]λ4686 emission line), and extremely large Hα and [O iii]λ5007…”
Spectroscopy of superluminous supernova host galaxies. A preference of hydrogen-poor events for extreme emission line galaxies (2014, background): “An offset of 0.3 dex has also been found between SDSS galaxies and Green Peas of similar masses (Amorı́n et al. 2010).”
IMPROVED AND QUALITY-ASSESSED EMISSION AND ABSORPTION LINE MEASUREMENTS IN SLOAN DIGITAL SKY SURVEY GALAXIES (2011, background): “An early application and description of this fitting strategy can be found in Schawinski et al. (2007) and Cardamone et al. (2009).”
STRONG NEBULAR LINE RATIOS IN THE SPECTRA of z ∼ 2–3 STAR FORMING GALAXIES: FIRST RESULTS FROM KBSS-MOSFIRE (2014, background): “…that in many respects resembles both typical and extreme members of the KBSSMOSFIRE sample at z' 2.3: the so-called “green pea” (GP) galaxies (e.g., Cardamone et al. 2009) are relatively rare z ' 0.2 objects selected by their distinctive colors caused by unusually large [O III] equivalent widths.”
Star formation sustained by gas accretion (2014, background): “ite images (Cardamone et al. 2009).”
The green valley is a red herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early-and late-type galaxies (2014, background): “…(e.g. Bamford et al. 2009; Skibba et al. 2009), mergers (Darg et al. 2010a, b; Kaviraj et al. 2012; Teng et al. 2012), unusual galaxy types (Cardamone et al. 2009; Lintott et al. 2009; Keel et al. 2012) and specific morphological features such as bars (e.g. Hoyle et al. 2011; Masters et…”
The Keck Lyman Continuum Spectroscopic Survey (KLCS): The Emergent Ionizing Spectrum of Galaxies at z ∼ 3 (2018, background): “…Space Telescope (HST) of low-redshift galaxies that have been identified as likely analogs of the high redshift objects (e.g., Borthakur et al. 2014; Izotov et al. 2016a,b; Leitherer et al. 2016), such as ‘Lyman break analogs” (LBAs; Overzier et al. 2009), and “Green Peas” (Cardamone et al. 2009.)”
THE ORIGIN AND OPTICAL DEPTH OF IONIZING RADIATION IN THE “GREEN PEA” GALAXIES (2013, methodology): “Cardamone et al. (2009) assume an intrinsic Hα/Hβ ratio appropriate for Te = 10 4 K for all the Peas, whereas the six extreme Peas have temperatures of ∼15000 K (Table 2).”
The Milky Way Project First Data Release: a bubblier Galactic disc (2012, methodology): “This has been shown by the serendipitous discovery of Hanny’s Voorwerp (Lintott et al. 2009) and the case of the Galaxy Zoo ‘Green Peas’ (Cardamone et al. 2009).”