MMT Extremely Metal Poor Galaxy Survey I. An Efficient Technique to Identify Metal Poor Galaxies

TL;DR

This paper presents an efficient method for identifying extremely metal poor galaxies, revealing a sample with very low metallicity and properties similar to gamma-ray burst host galaxies, which could inform GRB environment studies.

Contribution

The study introduces a successful technique for selecting extremely metal poor galaxies and characterizes their properties, linking them to GRB host environments.

Findings

Identified 10 metal poor galaxies from 24 candidates.

Some galaxies have among the lowest metallicities known.

Metal poor galaxies resemble GRB host properties.

Abstract

We demonstrate a successful strategy for identifying extremely metal poor galaxies. Our preliminary survey of 24 candidates contains 10 metal poor galaxies of which 4 have 12+log(O/H)<7.65, some of the lowest metallicity blue compact galaxies known to date. Interestingly, our sample of metal poor galaxies have systematically lower metallicity for their luminosity than comparable samples of blue compact galaxies, dIrrs, and normal star-forming galaxies. Our metal poor galaxies share very similar properties, however, with the host galaxies of nearby long-duration gamma-ray bursts (GRBs), including similar metallicity, stellar ages, and star formation rates. We use H\beta to measure the number of OB stars present in our galaxies and estimate a core-collapse supernova rate of ~10^-3 yr^-1. A larger sample of metal poor galaxies may provide new clues into the environment where GRBs form and may provide a list of potential GRB hosts.