论文标题
直接测量[CI]亮度对高红移星形星系中的分子气体质量转化因子
Direct measurement of the [CI] luminosity to molecular gas mass conversion factor in high-redshift star-forming galaxies
论文作者
论文摘要
高红移星系中的冷，分子气的量通常是根据分子氢（H $ _2 $）的代理来推断的，例如一氧化碳（CO）或中性原子碳（[CI]）和分子气体质量转化因子。但是，这些代理的使用依赖于未直接在本地宇宙之外进行测量的建模和观测值。在这里，我们使用H $ _2 $的圆柱密度从圆柱密度来确定此转换因子$α_ {\ rm [ci]} $的最新样品来确定此转换因子$α_ {\ rm [ci]} $。这项技术使我们能够直接测量高红移吸收选择的星系中的相对丰度。我们的样品跨越Z = 1.9-3.4的红移，覆盖了气相金属性的两个数量级。我们发现$α_ {\ rm [ci]} $与金属性：$ \logα_ {\ rm [ci]} = -1.13 \ times \ times \ log（z/z _ {z/z _ {\ odot}） dex。使用[CI]和CO线检测的Z〜0-5的发射选择星系样本，我们将$α_ {\ rm [CI]} $转换应用于分子气体和$α_ {\ rm CO} $的独立估计。我们发现，与典型的$α_ {\ rm co} $相比，从吸收来源的$α_ {\ rm [ci]} $推断出的分子气体质量之间达成了一个显着的一致性，基于典型的$α_ {\ rm co} $ - 基于$α_ {\ rm co} $ a____的推断金属演化和$ rm co a__的推断金属演化文献估计。因此，这些结果支持使用吸收衍生的$α_ {\ rm [ci]} $转换因子用于发射选择的星形星系，并证明这两种方法都探测了局部和高红色宇宙中分子气的相同通用性能。
The amount of cold, molecular gas in high-redshift galaxies is typically inferred from proxies of molecular hydrogen (H$_2$), such as carbon monoxide (CO) or neutral atomic carbon ([CI]) and molecular gas mass conversion factors. The use of these proxies, however, relies on modeling and observations that have not been directly measured outside the local universe. Here, we use recent samples of high-redshift gamma-ray burst (GRB) and quasar molecular gas absorbers to determine this conversion factor $α_{\rm [CI]}$ from the column density of H$_2$, which gives us the mass per unit column, and the [CI]($J=1$) column density, which provides the luminosity per unit column. This technique allows us to make direct measurements of the relative abundances in high-redshift absorption-selected galaxies. Our sample spans redshifts of z=1.9-3.4 and covers two orders of magnitude in gas-phase metallicity. We find that $α_{\rm [CI]}$ scales linearly with the metallicity: $\log α_{\rm [CI]} = -1.13\times \log(Z/Z_{\odot}) + 1.33$, with a scatter of $σ_{α_{\rm [CI]}} = 0.2$ dex. Using a sample of emission-selected galaxies at z~0-5, with both [CI] and CO line detections, we apply the $α_{\rm [CI]}$ conversion to derive independent estimates of the molecular gas mass and $α_{\rm CO}$. We find a remarkable agreement between the molecular gas masses inferred from the absorption-derived $α_{\rm [CI]}$ compared to typical $α_{\rm CO}$-based estimates, and an inferred metallicity evolution of $α_{\rm CO}$ that is consistent with $α_{\rm [CI]}$ and previous estimates from the literature. These results thus support the use of the absorption-derived $α_{\rm [CI]}$ conversion factor for emission-selected star-forming galaxies and demonstrate that both methods probe the same universal properties of molecular gas in the local and high-redshift universe.
