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arXiv 2205.03069astro-ph.GA
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半解析谱拟合:同时模拟MaNGA旋涡星系的质量积累和化学演化

Semi-analytic spectral fitting: simultaneously modelling the mass accumulation and chemical evolution in MaNGA spiral galaxies

Shuang Zhou, Michael Merrifield, Alfonso Aragon-Salamanca

摘要:

我们开发了一种新的半解析光谱拟合方法来量化单个星系的恒星形成历史(SFHs)和化学富集历史(ChEHs)。我们构建了简单而通用的化学演化模型,考虑气体流入和流出过程以及恒星形成,以研究无合并恒星形成系统的演化。这些模型直接拟合到星系的吸收线光谱,而它们的发射线被用来限制当前的气相金属丰度和恒星形成率。我们将这种方法应用于从SDSS-IV MANGA调查中选择的螺旋星系。通过拟合每个星系的共同添加的吸收线光谱,并使用发射线对当今的金属丰度和恒星形成的约束,我们重建的SFHs和ChEHs的样本中的所有对象。我们可以使用这些重建,以获得考古措施的衍生相关性,如质量-金属丰度关系在任何红移,比较有利的直接观察。我们发现,SFHS和ChEHs有很强的质量依赖性:大质量星系积累恒星质量,并成为丰富的早期。这种质量依赖性导致了在较低的红移下观察到的质量-金属丰度关系的平坦化。该模型还再现了观测到的气体-恒星质量比及其质量依赖性。此外,我们能够确定,更大质量的星系有更早的气体流入时间和更短的流入时间尺度,以及早期的化学富集低质量星系被抑制强流出,而流出是不是很重要的大质量星系。

英文摘要:

We develop a novel semi-analytic spectral fitting approach to quantify the star-formation histories (SFHs) and chemical enrichment histories (ChEHs) of individual galaxies. We construct simple yet general chemical evolution models that account for gas inflow and outflow processes as well as star formation, to investigate the evolution of merger-free star-forming systems. These models are fitted directly to galaxies' absorption-line spectra, while their emission lines are used to constrain current gas phase metallicity and star formation rate. We apply this method to spiral galaxies selected from the SDSS-IV MaNGA survey. By fitting the co-added absorption-line spectra for each galaxy, and using the emission-line constraints on present-day metallicity and star formation, we reconstruct both the SFHs and the ChEHs for all objects in the sample. We can use these reconstructions to obtain archaeological measures of derived correlations such as the mass--metallicity relation at any redshift, which compare favourably with direct observations. We find that both the SFHs and ChEHs have strong mass dependence: massive galaxies accumulate their stellar masses and become enriched earlier. This mass dependence causes the observed flattening of the mass--metallicity relation at lower redshifts. The model also reproduces the observed gas-to-stellar mass ratio and its mass dependence. Moreover, we are able to determine that more massive galaxies have earlier gas infall times and shorter infall time-scales, and that the early chemical enrichment of low-mass galaxies is suppressed by strong outflows, while outflows are not very significant in massive galaxies.

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