用于活动星系核的HII-CHI-mistry：无需经验电离校正因子的光学硫丰度
HII-CHI-mistry for active galactic nuclei: optical sulphur abundances without empirical ionisation correction factors
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中文总结 AI 辅助
本研究扩展HII-CHI-mistry方法，无需经验电离校正因子，推导活动星系核的硫丰度，发现硫可作为气相金属丰度的可靠示踪剂，揭示赛弗特与LINER的电离条件差异。
中文摘要 AI 辅助
活动星系核（AGN）中硫丰度的测定存在不确定性，因为电离校正因子（ICFs）通常是针对HII区校准的。我们扩展了HII-CHI-mistry（HCm）方法，通过与光电离模型对比，从光学发射线推导AGN中的总S/H。对采用直接法离子丰度的赛弗特星系的测试表明，α_ox=-1.2且自由电子停止判据为98%的模型更优。虽然O/H与之前的测定结果一致，但HCm得出的S/H比使用经典ICFs的直接法分析系统更大，这表明这些公式低估了AGN中更高电离阶段的硫。将该方法应用于MaNGA的赛弗特和LINER类区域后，发现存在共同的正S/O-金属丰度关系。在高O/H时，赛弗特的中位S/O比恒星形成区略大，而LINER处于中间位置。当使用S/H而非O/H作为金属丰度示踪剂时，这些差异会减弱，不过赛弗特仍倾向于分布在上包络。因此，硫可能是气相金属丰度的可靠示踪剂，而赛弗特与LINER之间的差异可能反映了它们电离条件和电离SED的不同。
英文摘要
> The determination of sulphur abundances in active galactic nuclei (AGN) is uncertain because ionisation correction factors (ICFs) are commonly calibrated for HII regions. We extend the HII-CHI-mistry methodology to derive total S/H in AGN from optical emission lines through comparison with photoionisation models. Tests against Seyfert galaxies with direct-method ionic abundances favour models with alpha_ox=-1.2 and a 98% free-electron stopping criterion. While O/H agrees with previous determinations, HCm yields systematically larger S/H than direct-method analyses using classical ICFs, suggesting that these prescriptions underestimate higher sulphur ionisation stages in AGN. Applied to MaNGA Seyfert and LINER-like regions, the method reveals a common positive S/O-metallicity relation. Seyferts show slightly larger median S/O than star-forming regions at high O/H, while LINERs occupy an intermediate position. These differences become weaker when S/H rather than O/H is used as the metallicity tracer, although Seyferts still tend to populate the upper envelope. Sulphur may therefore provide a robust tracer of gas-phase metallicity, while the differences between Seyferts and LINERs may reflect differences in their ionisation conditions and ionising SEDs.
