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arXiv · 2311.02015

Extremely strong CIV 1550 nebular emission in the extremely low-metallicity star-forming galaxy J2229+2725

Y. I. Izotov·D. Schaerer·N. G. Guseva·T. X. Thuan·G. Worseck
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Abstract

Using Hubble Space Telescope (HST)/Cosmic Origins Spectrograph (COS) observations of one of the most metal-poor dwarf star-forming galaxies (SFG) in the local Universe, J2229+2725, we have discovered an extremely strong nebular CIV 1549, 1551 emission-line doublet, with an equivalent width of 43A, several times higher than the value observed so far in low-redshift SFGs. Together with other extreme characteristics obtained from optical spectroscopy (oxygen abundance 12+log(O/H)=7.085+/-0.031, ratio O32 = I([OIII]5007)/I([OII]3727) ~ 53, and equivalent width of the Hbeta emission line EW(Hbeta) = 577A), this galaxy greatly increases the range of physical properties for dwarf SFGs at low redshift and is a likely analogue of the high-redshift dwarf SFGs responsible for the reionization of the Universe. We find the ionizing radiation in J2229+2725 to be stellar in origin and the high EW(CIV 1549,1551) to be due to both extreme ionization conditions and a high carbon abundance, with a corresponding log C/O = -0.38, that is ~ 0.4 dex higher than the average value for nearby low-metallicity SFGs.

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Y. I. Izotov, D. Schaerer, N. G. Guseva, T. X. Thuan, G. Worseck. 2023-11-03. Extremely strong CIV 1550 nebular emission in the extremely low-metallicity star-forming galaxy J2229+2725. https://doi.org/10.1093/mnrasl%2Fslad166

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