Green Peas in the Southern Sky: Broadband Color Selection and Spectroscopic Follow-up

Abstract We present a systematic search for 1696 green pea (GP) galaxy candidates in the southern hemisphere selected from the Dark Energy Survey Data Release 2 and provide preliminary results from spectroscopic follow-up observations of 26 targets chosen among them. Our selection criteria include the colors in the gri bands and compact morphology in the color-composite images. The multiwavelength spectral energy distribution fitting shows that the selected GP candidates exhibit star formation rates up to several tens of M ⊙ yr −1 . With the mean stellar mass of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>log</mml:mi> <mml:mspace width="0.25em"/> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>*</mml:mo> </mml:msub> <mml:mo>/</mml:mo> <mml:msub> <mml:mi>M</mml:mi> <mml:mo>⊙</mml:mo> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>8.6</mml:mn> </mml:math> , GP candidates are located at roughly 1 dex above the main sequence of star-forming galaxies at z ∼ 0.3. Spectroscopic follow-up observations of the GP candidates with Gemini/Gemini Multi-Object Spectrograph are underway. All 26 targets are spectroscopically confirmed to be at z = 0.3–0.41 and have an [O iii ] equivalent width larger than 85 Å, classified to be starbursts with low-to-moderate dust attenuation. These confirmed GPs show a lower metallicity offset from the mass–metallicity relation of local star-forming galaxies, indicating that GPs are less chemically evolved systems at their early stage of evolution.