Recovering the Physical Properties of Molecular Gas in Galaxies from CO SLED Modeling
Recovering the Physical Properties of Molecular Gas in Galaxies from CO SLED Modeling
复制标题
DOI：
10.3847/1538-4357/aab3e2
复制
发表时间：
2018-03
期刊：
影响因子：
--
通讯作者：
J. Kamenetzky;G. Privon;D. Narayanan
中科院分区：
文献类型：
--
作者：
J. Kamenetzky;G. Privon;D. Narayanan
CO分子谱线能量分布（SLED）的模拟可以揭示银河系云和其他星系中分子气体的物理条件（温度和密度）。最近，赫歇尔空间天文台和阿尔马首次提供了J = 4−3到J = 13−12转动谱线的综合视图，这些谱线产生于复杂多样的物理条件，在建模时必须简化为一个、两个或三个分量。在这里，我们调查的物理条件的可恢复性从SLEDs产生的星系演化模拟包含一个大的动态范围内的物理性质。这些模拟的SLED一般适合一个组成部分的气体，其性质在很大程度上类似于或稍微低估了模拟的亮度加权属性时，由于非热速度分散的结块考虑。如果只对前三条旋转线进行建模，边缘化参数分布的中值可以更好地代表模拟的亮度加权特性，但拟合参数的不确定性几乎是一个数量级，而在J = 10−9的完全采样SLED的“最佳情况”下，近似为0.2 dex。这项研究表明，虽然常见的CO SLED建模技术不能揭示分子气体的潜在复杂性，但如果检测到足够数量的线并进行建模，则可以区分随星星形成表面密度和星系演化而变化的体积亮度加权特性。
Modeling of the spectral line energy distribution (SLED) of the CO molecule can reveal the physical conditions (temperature and density) of molecular gas in Galactic clouds and other galaxies. Recently, the Herschel Space Observatory and ALMA have offered, for the first time, a comprehensive view of the rotational J = 4−3 through J = 13−12 lines, which arise from a complex, diverse range of physical conditions that must be simplified to one, two, or three components when modeled. Here we investigate the recoverability of physical conditions from SLEDs produced by galaxy evolution simulations containing a large dynamical range in physical properties. These simulated SLEDs were generally fit well by one component of gas whose properties largely resemble or slightly underestimate the luminosity-weighted properties of the simulations when clumping due to nonthermal velocity dispersion is taken into account. If only modeling the first three rotational lines, the median values of the marginalized parameter distributions better represent the luminosity-weighted properties of the simulations, but the uncertainties in the fitted parameters are nearly an order of magnitude, compared to approximately 0.2 dex in the “best-case” scenario of a fully sampled SLED through J = 10−9. This study demonstrates that while common CO SLED modeling techniques cannot reveal the underlying complexities of the molecular gas, they can distinguish bulk luminosity-weighted properties that vary with star formation surface densities and galaxy evolution, if a sufficient number of lines are detected and modeled.