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ALFALFA Discovery of the Most Metal-Poor Gas-Rich Galaxy Known: AGC 198691 (2016)
  • Alec S. Hirschauer
  • John J. Salzer
  • Evan D. Skillman
  • Danielle Berg
  • Kristen B.W. McQuinn
  • John M Cannon, Macalester College
  • Alex J.R. Gordon, Macalester College
  • Martha P. Haynes
  • Riccardo Giovanelli
  • Elizabeth A.K. Adams
  • Steven Janowiecki
  • Katherine L. Rhode
  • Richard W. Pogge
  • Kevin V. Croxall
  • Erik Aver
"We present spectroscopic observations of the nearby dwarf galaxy AGC 198691. This object is part of the Survey of HI in Extremely Low-Mass Dwarfs (SHIELD) project, which is a multi-wavelength study of galaxies with HI masses in the range of 106-107.2~M discovered by the ALFALFA survey. We have obtained spectra of the lone HII region in AGC 198691 with the new high-throughput KPNO Ohio State Multi-Object Spectrograph (KOSMOS) on the Mayall 4-m as well as with the Blue Channel spectrograph on the MMT 6.5-m telescope. These observations enable the measurement of the temperature-sensitive [OIII]λ4363 line and hence the determination of a "direct" oxygen abundance for AGC 198691. We find this system to be an extremely metal-deficient (XMD) system with an oxygen abundance of 12+log(O/H) = 7.02 ± 0.03, making AGC 198691 the lowest-abundance star-forming galaxy known in the local universe. Two of the five lowest-abundance galaxies known have been discovered by the ALFALFA blind HI survey; this high yield of XMD galaxies represents a paradigm shift in the search for extremely metal-poor galaxies." from
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Citation Information
Alec S. Hirschauer, John J. Salzer, Evan D. Skillman, Danielle Berg, et al.. "ALFALFA Discovery of the Most Metal-Poor Gas-Rich Galaxy Known: AGC 198691" (2016)
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