Abundances in the H I Envelope of the Extremely Low Metallicity Blue Compact Dwarf Galaxy SBS 0335–052 from Far Ultraviolet Spectroscopic Explorer Observations
Abundances in the H I Envelope of the Extremely Low Metallicity Blue Compact Dwarf Galaxy SBS 0335–052 from Far Ultraviolet Spectroscopic Explorer Observations
复制标题
远紫外光谱探测器观测中极低金属丰度蓝矮星星系 SBS 0335–052 的 H I 包层中的丰度
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发表时间：
2004
期刊：
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通讯作者：
Y. Izotov
中科院分区：
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作者：
T. Thuan;A. Lecavelier des Etangs;Y. Izotov
我们展示了SBS 0335-052的远紫外光谱，SBS 0335-052是已知的第二缺乏金属的蓝致密矮星（BCD）星系[log(O/H) = -4.70]。除了H I Lyman系列外，我们还检测到C II， N I, N II, O I, Si II， Ar I和Fe II吸收线，主要是由于SBS 0335-052嵌入的扩展的H I包络线。未见H2吸收谱线。漫射H2的缺失意味着通过红外发射探测到的温暖H2一定是非常块状的，并且与恒星形成区域有关。团块密度应大于~1000 cm-3，温度应大于~1000 K，占总H I质量≥5%。虽然SBS 0335-052可能是一个年轻的星系，但它的中性气体并不是原始的。其中性气体的金属丰度与其电离气体相似，等于log(O/H) ~ -5。这种金属丰度与其他四个bcd的H I包层中发现的金属丰度相当，这些bcd的电离气体金属丰度范围从log(O/H) = -4.8到-3.8不等，并且在Lyα吸收体中也发现了这种金属丰度，这使人们猜测，可能之前有原始中性气体富集到log(O/H) ~ -5的常见金属丰度水平，可能是由III星族恒星产生的。
We present Far Ultraviolet Spectroscopic Explorer spectroscopy of SBS 0335-052, the second most metal-deficient blue compact dwarf (BCD) galaxy known [log(O/H) = -4.70]. In addition to the H I Lyman series, we detect C II, N I, N II, O I, Si II, Ar I, and Fe II absorption lines, mainly arising from the extended H I envelope in which SBS 0335-052 is embedded. No H2 absorption lines are seen. The absence of diffuse H2 implies that the warm H2 detected through infrared emission must be very clumpy and associated with the star-forming regions. The clumps should be denser than ~1000 cm-3 and hotter than ~1000 K and account for ≥5% of the total H I mass. Although SBS 0335-052 is a probable young galaxy, its neutral gas is not pristine. The metallicity of its neutral gas is similar to that of its ionized gas and is equal to log(O/H) ~ -5. This metallicity is comparable to that found in the H I envelopes of four other BCDs with ionized gas metallicities spanning the wide range from log(O/H) = -4.8 to -3.8, and in Lyα absorbers, fueling the speculation that there may have been previous enrichment of the primordial neutral gas to a common metallicity level of log(O/H) ~ -5, possibly by Population III stars.