MCSED：一个灵活的光谱能量分布拟合程序及其对$z \sim 2$发射线星系的应用
MCSED: A flexible spectral energy distribution fitting code and its application to $z \sim 2$ emission-line galaxies
摘要：
我们提出了MCSED，一个新的光谱能量分布（SED）拟合代码，它匹配灵活的恒星演化计算与软件包emcee的马尔可夫链蒙特卡罗算法。MCSED采用宽波段、中波段和窄波段测光、发射线通量和/或吸收线光谱指数，并返回所有模型参数的概率分布和协方差图。MCSED包括各种各样的尘埃衰减曲线与参数变化的紫外线斜率和碰撞强度，处方的连续性和多环芳烃排放的尘埃，模型的连续性和线发射电离气体，固定和可变的恒星金属丰度的选项，并选择恒星形成率（SFR）的历史。该代码是非常适合探索参数的相互依赖性，在已知的红移，其中有多波段光度学和/或光谱学的星系集。我们应用MCSED的$\sim2000$ $1.90<z<2.35$星系的样本在五个坎德尔领域，这是通过他们的强[O III] $\lambda5007$发射选择，并探讨其SED的系统行为。我们发现星系随着恒星质量的增加而变得更红，这是由于内部衰减增加和老年恒星数量增加。紫外线消光曲线的斜率也会随着恒星质量的变化而变化，至少有一些星系在2175埃处表现出消光过剩。最后，我们证明，低于$M\lesssim10^9\,M_{\odot}$），恒星形成星系的主要序列的形状是高度依赖于星系的假设SFR的历史，作为计算，假设一个恒定的SFR产生恒星质量是$\sim1$ dex小于那些发现使用更现实的SFR的历史。
英文摘要：
We present MCSED, a new spectral energy distribution (SED)-fitting code, which mates flexible stellar evolution calculations with the Markov Chain Monte Carlo algorithms of the software package emcee. MCSED takes broad, intermediate, and narrow-band photometry, emission-line fluxes, and/or absorption line spectral indices, and returns probability distributions and co-variance plots for all model parameters. MCSED includes a variety of dust attenuation curves with parameters for varying the UV slopes and bump strengths, a prescription for continuum and PAH emission from dust, models for continuum and line emission from ionized gas, options for fixed and variable stellar metallicity, and a selection of star formation rate (SFR) histories. The code is well-suited for exploring parameter inter-dependencies in sets of galaxies with known redshifts, for which there is multi-band photometry and/or spectroscopy. We apply MCSED to a sample of $\sim2000$ $1.90<z<2.35$ galaxies in the five CANDELS fields, which were selected via their strong [O III] $\lambda5007$ emission, and explore the systematic behavior of their SEDs. We find the galaxies become redder with stellar mass, due to both increasing internal attenuation and a greater population of older stars. The slope of the UV extinction curve also changes with stellar mass, and at least some galaxies exhibit an extinction excess at 2175 Angstroms. Finally, we demonstrate that below $M\lesssim10^9\,M_{\odot}$), the shape of the star-forming galaxy main sequence is highly dependent on the galaxies' assumed SFR history, as calculations which assume a constant SFR produce stellar masses that are $\sim1$ dex smaller than those found using more realistic SFR histories.
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