Searching for the lowest metallicity galaxies in the local universe

Hsyu, Tiffany; Cooke, Ryan J.; Prochaska, J. Xavier; Bolte, Michael

Abstract

We report a method of identifying candidate low-metallicity blue compact dwarf galaxies (BCDs) from the Sloan Digital Sky Survey (SDSS) imaging data, and present 3 m Lick Observatory and 10 m W.M. Keck Observatory optical spectroscopic observations of 94 new systems that have been discovered with this method. The candidate BCDs are selected from Data Release 12 (DR12) of SDSS on the basis of their photometric colors and morphologies. Using the Kast spectrometer on the 3 m telescope, we confirm that the candidate low-metallicity BCDs are emission-line galaxies, and we make metallicity estimates using the empirical R and S calibration methods. Follow-up observations on a subset of the lowest-metallicity systems are made at Keck using the Low Resolution Imaging Spectrometer, which allow for a direct measurement of the oxygen abundance. We determine that 45 of the reported BCDs are low-metallicity candidates with 12 + log(O/H) ≤ 7.65, including six systems which are either confirmed or projected to be among the lowest-metallicity galaxies known, at 1/30 of the solar oxygen abundance, or 12 + log(O/H) ~ 7.20.

Citation

Hsyu, T., Cooke, R. J., Prochaska, J. X., & Bolte, M. (2018). Searching for the lowest metallicity galaxies in the local universe. Astrophysical Journal, 863(2), Article 134. https://doi.org/10.3847/1538-4357/aad18a

• Journal Article Type: Article
• Acceptance Date: Jul 2, 2018
• Online Publication Date: Aug 17, 2018
• Publication Date: Aug 31, 2018
• Deposit Date: Aug 9, 2018
• Publicly Available Date: Aug 9, 2018
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 863
• Issue: 2
• Article Number: 134
• DOI: https://doi.org/10.3847/1538-4357/aad18a
• Public URL: https://durham-repository.worktribe.com/output/1323790