Unveiling the Nature of the 'Green Pea' Galaxies: Oxygen and Nitrogen Chemical Abundances

We present recent results on the oxygen and nitrogen chemical abundances in the extremely compact, low-mass starburst galaxies at redshifts 0.1-0.3 usually referred to as 'green pea' galaxies. We show that they are metal-poor galaxies (~1/5 solar) with lower oxygen abundances than star-forming galaxies of similar mass and N/O ratios unusually high for galaxies of the same metallicity. Recent, rapid, and massive inflows of cold gas, possibly coupled with enriched outflows from supernova winds, are used to explain the results. This is consistent with the known 'pea' galaxy properties and suggest that these rare objects are experiencing a short and extreme phase in their evolution.