We combine star-formation histories derived from observations of high redshift galaxies with measurements of the z~0 relation between gas-phase metallicity, stellar mass, and star formation rate to make an explicit and completely empirical connection between near-field and distant galaxy observations. Our approach relies on two basic assumptions: 1) galaxies' average paths through time in stellar mass vs. star formation rate space are represented by a family of smooth functions that are determined by the galaxies' final stellar mass, and 2) galaxies grow and become enriched with heavy elements such that they always evolve along the mass--metallicity--star formation rate relation. By integrating over these paths, we can track the chemical evolution of stars in galaxies in a model independent way, without the need for explicit assumptions about gas inflow, outflow, or star formation efficiency. Using this approach, we present predictions of stellar metallicity (i.e., O/H) distribution functions for present day star-forming galaxies of different stellar masses and the evolution of the alpha-element stellar metallicity-mass relation since z~1. The metallicity distribution functions are fairly well described as Gaussians, truncated at high metallicity, with power-law tails to low metallicity. We find that the stellar metallicity distribution for Milky Way mass galaxies is in reasonable agreement with observations for our Galaxy, and that the predicted stellar mass vs. mean stellar metallicity relation at z=0 agrees quite well with results derived from galaxy surveys. This validates the assumptions that are implicit in our simple approach. Upcoming observations will further test these assumptions and their range of validity, by measuring the mean stellar mass-metallicity relation up to z~1, and by measuring the stellar metallicity distributions over a range of galaxy masses.
Integral field spectroscopy of supernova explosion sites: constraining mass and metallicity of the progenitors -- II. Type II-P and II-L supernovae
利用积分场光谱学已经观测到了附近星系中II-P和II-L型超新星的13个爆炸点，使得对爆炸点的空间和光谱研究成为可能。我们利用同时代超新星祖先星的母恒星星族的性质来推导它的金属丰度和初始质量（c.f. Paper I）。母恒星星族的光谱通过强线方法得到金属丰度的估计，并通过与简单的恒星星族（SSP）模型的比较得到年龄。这些金属丰度和年龄参数被采用的祖星。通过与恒星演化模型的比较，利用恒星的年龄或寿命来推导恒星的初始质量。利用这种技术，我们能够确定我们样品中SN祖细胞的金属丰度和初始质量。我们的结果表明，一些II型超新星的祖先可能是质量与SN Ib/c祖先相当的恒星。
Carbon Stars as Standard Candles: An Empirical Test for the Reddening, Metallicity, and Age Sensitivity of the J-region Asymptotic Giant Branch (JAGB) Method
The superluminous supernova SN 2017egm in the nearby galaxy NGC 3191: a metal-rich environment can support a typical SLSN evolution
在红移z=0.03时，最近发现的SN 2017 egm是迄今为止距离最近的I型超亮超新星（SLSN），也是第一个靠近大质量螺旋星系（NGC 3191）中心的超新星。利用NGC 3191的SDSS光谱，我们发现其核的金属丰度为~2 Z $_\odot$，而在与SN 2017 egm相似的径向偏移量上，恒星形成区的金属丰度为~ 1.3Z $_\odot$。存档的无线电-紫外测光显示恒星形成速率约为15 M $_\odot$ yr $^{-1}$（约70%被尘埃遮蔽），这可以解释斯威夫特X射线探测，恒星质量约为$10^{10.7}$ M $_\odot$。我们使用贝叶斯光曲线拟合工具MOSFiT，用磁星中心引擎模型模拟早期的紫外光光曲线。拟合表明，喷出物质量为2-4 M $_\odot$，自旋周期为4-6 ms，磁场为（0.7-1.7）$\times 10^{14}$ G，动能为1-2 $\times10^{51}$ erg。这些参数与Nicholl等人（2017）建模的SLSNe的总体分布一致，尽管导出的质量和自旋接近低端，可能表明爆炸前质量和角动量的损失增加。这有两个含义：（i）SLSNe可以发生在太阳的金属丰度，虽然有一个低分数~10%;和（ii）金属丰度最多有适度的影响，他们的属性。这两个结论都与长伽马射线暴的结果一致。假设一个单调上升给出一个爆炸日期MJD $57889\pm1…
