Optical spectroscopy of the extremely metal-deficient star-forming galaxy HSC J1631+4426: a test of the strong-line method

ABSTRACT Recently, Kojima and co-authors have reported a record low oxygen abundance, 12 + logO/H = 6.90 ± 0.03, or 1.6 per cent of solar metallicity, in the low-mass star-forming galaxy HSC J1631 + 4426. This exceptionally low oxygen abundance was obtained by the direct method, using the [O iii]λ43...

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Published in:Monthly notices of the Royal Astronomical Society. Letters 2022-10, Vol.516 (1), p.L81-L85
Main Authors: Thuan, T X, Guseva, N G, Izotov, Y I
Format: Article
Language:English
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Summary:ABSTRACT Recently, Kojima and co-authors have reported a record low oxygen abundance, 12 + logO/H = 6.90 ± 0.03, or 1.6 per cent of solar metallicity, in the low-mass star-forming galaxy HSC J1631 + 4426. This exceptionally low oxygen abundance was obtained by the direct method, using the [O iii]λ4363Å emission line. However, using the strong-line method by Izotov et al. (2019b), these authors have derived a significantly higher metallicity 12 + logO/H = 7.175 ± 0.005. To clarify the situation, we have obtained new observations of HSC J1631 + 4426 with the Large Binocular Telescope (LBT)/Multi-Object Dual Spectrograph (MODS). We have derived a higher oxygen abundance, 12 + logO/H = 7.14 ± 0.03, using the direct method, a value similar to the oxygen abundance obtained by the strong-line method. Thus, HSC J1631 + 4426 has a metallicity close to that of the well known blue compact dwarf galaxy I Zw 18.
ISSN:1745-3925
1745-3933
DOI:10.1093/mnrasl/slac095