论文标题
基于星系中晶粒尺寸分布的演变的灰尘和PAH的光谱能分布
Spectral energy distributions of dust and PAHs based on the evolution of grain size distribution in galaxies
论文作者
论文摘要
基于银河系中晶粒尺寸分布的单区进化模型，我们计算了红外光谱分布（SED）的演化，考虑硅酸盐，碳质粉尘和多环芳族烃（PAHS）。星际介质（ISM）的密集气体分数（$η_\ MathRM {lot} $），星形形成时间尺度（$τ_\ Mathrm {sf} $）以及星际辐射场强度正常于银河系值（$ u $）是主要参数。我们发现，在星系进化的早期，SED形状通常具有弱的中红外（miR）发射，因为灰尘丰度由大谷物主导。在中级阶段（$ t \ sim 1 $ gyr for $τ_\ mathrm {sf} = 5 $ gyr），由于气相金属的积聚大大增加了mir发射的迅速增长。我们还将结果与附近和高红移（$ z \ sim 2 $）星系的观察数据进行了比较。我们在各种频段中广泛地重现了金属性的函数。我们发现，小$η_\ mathrm {lote} $（即\ \ \ \ iSM由弥散阶段主导）是为了再现由PAHS主导的8 $μ$ m强度的附近和$ z \ sim \ sim \ sim \ sim 2 $ 2 $ 2 $ 2 $ 2。一个长$τ_\ mathrm {sf} $将8 $μ$ m的排放提高到与附近的低金属星系一致的水平。理论计算与观察结果之间的广泛匹配支持了我们对晶粒尺寸分布的理解，但是弥漫性ISM对PAH发射的重要性意味着需要对ISM进行空间解决的处理。
Based on a one-zone evolution model of grain size distribution in a galaxy, we calculate the evolution of infrared spectral energy distribution (SED), considering silicate, carbonaceous dust, and polycyclic aromatic hydrocarbons (PAHs). The dense gas fraction ($η_\mathrm{dense}$) of the interstellar medium (ISM), the star formation time-scale ($τ_\mathrm{SF}$), and the interstellar radiation field intensity normalized to the Milky Way value ($U$) are the main parameters. We find that the SED shape generally has weak mid-infrared (MIR) emission in the early phase of galaxy evolution because the dust abundance is dominated by large grains. At an intermediate stage ($t\sim 1$ Gyr for $τ_\mathrm{SF}=5$ Gyr), the MIR emission grows rapidly because the abundance of small grains increases drastically by the accretion of gas-phase metals. We also compare our results with observational data of nearby and high-redshift ($z\sim 2$) galaxies taken by \textit{Spitzer}. We broadly reproduce the flux ratios in various bands as a function of metallicity. We find that small $η_\mathrm{dense}$ (i.e.\ the ISM dominated by the diffuse phase) is favoured to reproduce the 8 $μ$m intensity dominated by PAHs both for the nearby and the $z\sim 2$ samples. A long $τ_\mathrm{SF}$ raises the 8 $μ$m emission to a level consistent with the nearby low-metallicity galaxies. The broad match between the theoretical calculations and the observations supports our understanding of the grain size distribution, but the importance of the diffuse ISM for the PAH emission implies the necessity of spatially resolved treatment for the ISM.
