Extremely strong C iv λ1550 nebular emission in the extremely low-metallicity star-forming galaxy J2229+2725

Q1 Earth and Planetary Sciences Monthly Notices of the Royal Astronomical Society: Letters Pub Date : 2023-11-07 DOI:10.1093/mnrasl/slad166

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

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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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极低金属丰度恒星形成星系J2229+2725中极强的C iv λ1550星云发射

利用哈勃太空望远镜(HST)/宇宙起源光谱仪(COS)对当地宇宙中最缺乏金属的矮星形成星系(J2229+2725)之一的观测，我们发现了一个极其强大的星云CIV 1549, 1551发射线双线，其等效宽度为43A，比迄今为止在低红移的SFG中观测到的值高几倍。再加上从光谱学中获得的其他极端特征(氧丰度12+log(O/H)=7.085+/-0.031，比值O32 = I([OIII]5007)/I([OII]3727) ~ 53，以及Hbeta发射线的等效宽度EW(Hbeta) = 577A)，该星系极大地增加了矮SFGs在低红移时的物理性质范围，很可能与导致宇宙再电离的高红移矮SFGs类似。我们发现J2229+2725的电离辐射来自恒星，高EW(CIV 1549,1551)是由于极端电离条件和高碳丰度造成的，相应的log C/O = -0.38，比附近低金属丰度SFGs的平均值高0.4个指数。

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来源期刊

Monthly Notices of the Royal Astronomical Society: Letters Earth and Planetary Sciences-Space and Planetary Science

CiteScore

8.80

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0.00%

发文量

136

期刊介绍： For papers that merit urgent publication, MNRAS Letters, the online section of Monthly Notices of the Royal Astronomical Society, publishes short, topical and significant research in all fields of astronomy. Letters should be self-contained and describe the results of an original study whose rapid publication might be expected to have a significant influence on the subsequent development of research in the associated subject area. The 5-page limit must be respected. Authors are required to state their reasons for seeking publication in the form of a Letter when submitting their manuscript.

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