ALFALFA DISCOVERY of the MOST METAL-POOR GAS-RICH GALAXY KNOWN: AGC 198691

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

doi:10.3847/0004-637X/822/2/108

ALFALFA DISCOVERY of the MOST METAL-POOR GAS-RICH GALAXY KNOWN: AGC 198691

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

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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 10⁶-10^7.2 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.

Original language	English (US)
Article number	108
Journal	Astrophysical Journal
Volume	822
Issue number	2
DOIs	https://doi.org/10.3847/0004-637X/822/2/108
State	Published - May 10 2016

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© 2016. The American Astronomical Society. All rights reserved.

Keywords

galaxies: ISM
galaxies: abundances
galaxies: dwarf
galaxies: evolution
galaxies: star formation

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10.3847/0004-637X/822/2/108

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Hirschauer, A. S., Salzer, J. J., Skillman, E. D., Berg, D., McQuinn, K. B. W., Cannon, J. M., Gordon, A. J. R., Haynes, M. P., Giovanelli, R., Adams, E. A. K., Janowiecki, S., Rhode, K. L., Pogge, R. W., Croxall, K. V., & Aver, E. (2016). ALFALFA DISCOVERY of the MOST METAL-POOR GAS-RICH GALAXY KNOWN: AGC 198691. Astrophysical Journal, 822(2), Article 108. https://doi.org/10.3847/0004-637X/822/2/108

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title = "ALFALFA DISCOVERY of the MOST METAL-POOR GAS-RICH GALAXY KNOWN: AGC 198691",

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.",

keywords = "galaxies: ISM, galaxies: abundances, galaxies: dwarf, galaxies: evolution, galaxies: star formation",

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

year = "2016",

month = may,

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doi = "10.3847/0004-637X/822/2/108",

language = "English (US)",

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T1 - ALFALFA DISCOVERY of the MOST METAL-POOR GAS-RICH GALAXY KNOWN

T2 - AGC 198691

AU - Hirschauer, Alec S.

AU - Salzer, John J.

AU - Skillman, Evan D.

AU - Berg, Danielle

AU - McQuinn, Kristen B W

AU - Cannon, John M.

AU - Gordon, Alex J R

AU - Haynes, Martha P.

AU - Giovanelli, Riccardo

AU - Adams, Elizabeth A K

AU - Janowiecki, Steven

AU - Rhode, Katherine L.

AU - Pogge, Richard W.

AU - Croxall, Kevin V.

AU - Aver, Erik

PY - 2016/5/10

Y1 - 2016/5/10

N2 - 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.

AB - 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.

KW - galaxies: ISM

KW - galaxies: abundances

KW - galaxies: dwarf

KW - galaxies: evolution

KW - galaxies: star formation

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VL - 822

JO - Astrophysical Journal

JF - Astrophysical Journal

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M1 - 108

ER -

ALFALFA DISCOVERY of the MOST METAL-POOR GAS-RICH GALAXY KNOWN: AGC 198691

Abstract

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