Details

Autor(en) / Beteiligte

• Hirschauer, Alec S.
• Salzer, John J.
• Skillman, Evan D.
• Berg, Danielle
• McQuinn, Kristen B. W.
• Cannon, John M.
• Gordon, Alex J. R.
• Haynes, Martha P.
• Giovanelli, Riccardo
• Adams, Elizabeth A. K.
• Janowiecki, Steven
• Rhode, Katherine L.
• Pogge, Richard W.
• Croxall, Kevin V.
• Aver, Erik

Titel

ALFALFA DISCOVERY OF THE MOST METAL-POOR GAS-RICH GALAXY KNOWN: AGC 198691

Ist Teil von

• The Astrophysical journal, 2016-05, Vol.822 (2), p.108-108

Ort / Verlag

United States: The American Astronomical Society

Erscheinungsjahr

2016

Quelle

EZB Electronic Journals Library

Beschreibungen/Notizen

• ABSTRACT We present spectroscopic observations of the nearby dwarf galaxy AGC 198691. This object is part of the Survey of H i in Extremely Low-Mass Dwarfs project, which is a multi-wavelength study of galaxies with H i masses in the range of 106-107.2 M , discovered by the Arecibo Legacy Fast ALFA (ALFALFA) survey. We have obtained spectra of the lone H ii region in AGC 198691 with the new high-throughput KPNO Ohio State Multi-Object Spectrograph 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 [O iii]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 H i survey; this high yield of XMD galaxies represents a paradigm shift in the search for extremely metal-poor galaxies.