论文标题
氮核合成的经验约束
Empirical Constraints on the Nucleosynthesis of Nitrogen
论文作者
论文摘要
我们通过将n富集纳入我们先前开发和经验调节的多区域银河系化学演化模型中，从而对氮的核合成产量产生了经验约束。我们从大型恒星和金属依赖性（“次级”）N产量中采用金属性无关（“主要”）N产量。在我们的模型中，银河径向区域不会沿观察到的[n/o] - [o/h]关系进化，而是在大致恒定[n/o]下首次增加[o/h]，然后通过次级N产生在[n/o]中向上移动。在$ t \大约5 $ gyr的情况下，该模型接近平衡[n/o] - [o/h]关系，可追溯径向氧梯度。如果我们采用$ y_ \ text {n}^\ text {cc} = 3.6 \ times10^{ - 4} $，我们发现在半乳酸系统中观察到的[n/o] - [o/h]趋势都很好，如果我们采用$ y_ \ text {n}^\ text {cc} = 3.6 \ text { - 4} $，与快速旋转的后代和产生的预测一致$ y_ \ text {n}^\ text {agb} =（9 \ times10^{ - 4}）（m _*/m_ \ odot）（z _*/z__ \ odot）$。该模型重现了垂直调查中的银河系星星的[n/o] - [O/H]关系，并且随着年龄和[O/Fe]的趋势（尽管不完美）（尽管不完美）恒星[N/O]的趋势。金属依赖性的产量在塑造气相[n/o] - [o/h]关系中起主要作用，但是需要AGB时间段以匹配垂直恒星年龄和[o/fe]趋势。如果我们将$ \ sim $ 40 \％的振荡添加到恒星形成速率中，则该模型将在漫画中观察到的外部星系中的气相[n/o]中的散射。我们还使用已发表的AGB产量构建模型，并检查其经验成功和缺点。对于我们考虑的所有AGB收益率，简单的恒星种群仅在$ \ sim $ 250 MYR之后发布一半的N。
We derive empirical constraints on the nucleosynthetic yields of nitrogen by incorporating N enrichment into our previously developed and empirically tuned multi-zone galactic chemical evolution model. We adopt a metallicity-independent ("primary") N yield from massive stars and a metallicity-dependent ("secondary") N yield from AGB stars. In our model, galactic radial zones do not evolve along the observed [N/O]-[O/H] relation, but first increase in [O/H] at roughly constant [N/O], then move upward in [N/O] via secondary N production. By $t\approx5$ Gyr, the model approaches an equilibrium [N/O]-[O/H] relation, which traces the radial oxygen gradient. We find good agreement with the [N/O]-[O/H] trend observed in extra-galactic systems if we adopt an IMF-averaged massive star yield $y_\text{N}^\text{CC}=3.6\times10^{-4}$, consistent with predictions for rapidly rotating progenitors, and a fractional AGB yield that is linear in mass and metallicity $y_\text{N}^\text{AGB}=(9\times10^{-4})(M_*/M_\odot)(Z_*/Z_\odot)$. This model reproduces the [N/O]-[O/H] relation found for Milky Way stars in the APOGEE survey, and it reproduces (though imperfectly) the trends of stellar [N/O] with age and [O/Fe]. The metallicity-dependent yield plays the dominant role in shaping the gas-phase [N/O]-[O/H] relation, but the AGB time-delay is required to match the APOGEE stellar age and [O/Fe] trends. If we add $\sim$40\% oscillations to the star formation rate, the model reproduces the scatter in gas-phase [N/O] vs. [O/H] observed in external galaxies by MaNGA. We also construct models using published AGB yields and examine their empirical successes and shortcomings. For all AGB yields we consider, simple stellar populations release half their N after only $\sim$250 Myr.
