极贫金属星系I ZW 18中的尘气比
Dust-to-Gas Ratio in the Extremely Metal Poor Galaxy I ZW 18
摘要：
蓝色致密矮星系I Zw 18是宇宙中已知的最贫金属的系统之一（12 + log（O/H）$=$ 7.17）。本文利用{ \it Spitzer}、{ \it Herschel空间望远镜}和IRAM Plateau de Bure干涉仪的观测数据对I Zw 18进行了研究。我们的数据集包括最敏感的地图I ZW 18，迄今为止，在这两个远红外和CO $J=1\rightarrow0$过渡。我们使用粉尘排放模型推导出的粉尘质量上限只有M $_{dust}\leq1.1\times10^4$ M $_{\odot}$（$3σ$限制）。这个上限是由在160 $μ$ m处未检测到驱动的，并且它比先前的估计值小4-10倍（取决于所使用的模型）。我们还估计了一个上限的总粉尘气体质量比M $_{Dust}$ /M $_{gas}\leq5.0\times10^{-5}$。如果尘气质量比与金属丰度（以O/H衡量）之间存在线性相关关系，我们预计比值为3.9 $\times10^{-4}$。我们还表明，红外SED是类似的星爆系统。
英文摘要：
The blue compact dwarf galaxy I Zw 18 is one of the most metal poor systems known in the local Universe (12 + log(O/H) $=$ 7.17). In this work we study I Zw 18 using data from {\it Spitzer}, {\it Herschel Space Telescope} and IRAM Plateau de Bure Interferometer. Our data set includes the most sensitive maps of I Zw 18, to date, in both, the far infrared and the CO $J=1\rightarrow0$ transition. We use dust emission models to derive a dust mass upper limit of only M$_{dust}\leq1.1\times10^4$ M$_{\odot}$ ($3σ$ limit). This upper limit is driven by the non-detection at 160 $μ$m, and it is a factor of 4-10 times smaller than previous estimates (depending upon the model used). We also estimate an upper limit to the total dust-to-gas mass ratio of M$_{Dust}$/M$_{gas}\leq5.0\times10^{-5}$. If a linear correlation between the dust-to-gas mass ratio and metallicity (measure as O/H) were to hold, we would expect a ratio of 3.9$\times10^{-4}$. We also show that the infrared SED is similar to that of starbursting systems.
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