PEGASUS（昴星团望远镜PFS发射线星系巡天）：II. 高等值宽度窄带发射线天体中的贫金属活动星系核
PEGASUS (Pfs Emission-line GAlaxy SUrvey with Subaru): II. Metal Poor AGNs in High Equivalent-Width Narrow-Band Emitters
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中文总结 AI 辅助
本研究通过PFS光谱后续观测高EW窄带发射线星系，发现约34%为AGN，部分位于BPT图谷区且与亚太阳金属丰度一致，表明高EW选择可有效识别贫金属AGN候选体。
中文摘要 AI 辅助
我们展示了昴星团望远镜'Ōnohi'ula Prime Focus Spectrograph（PFS）对从Hyper Suprime-Cam Subaru Strategic Program中选出的高等值宽度（EW）窄带（NB）发射线星系的光学-近红外光谱后续观测，以评估高EW源是否优先承载低金属丰度活动星系核（AGN）。PFS光谱为583个目标提供了可靠的识别，包括581个具有可靠PFS红移解的天体和两个手动识别的$z\sim4$闯入者。我们为在所有四条BPT谱线中均有显著探测的70个天体构建了BPT诊断图。其中，约34%位于BPT图的AGN区域，表明AGN在该样本中占据显著比例。一个不可忽略的部分并未占据经典AGN分支，而是位于恒星形成序列与AGN序列之间的中间“谷”中。与Cloudy模型的比较表明，谷中星族与亚太阳金属丰度一致。在BPT图的恒星形成区域还发现了三个He II/[Ne V]探测源，它们延伸到较低金属丰度解，与$Z/Z_{\odot}\approx0.25-0.5$（$12+\log({\rm O/H})\approx8.1-8.4$）一致。一个天体显示出清晰的宽H$\alpha$成分；多成分拟合得出$M_{\rm BH}\approx8.8\times10^{6} M_{\odot}$和$\lambda_{\rm Edd}\approx0.035$，与近太阳窄线区金属丰度一致。母样本中类点源的比例（$22\\%\pm2\\%$）介于恒星形成星系（$12\\%\pm5\\%$）和AGN（$33\\%\pm10\\%$）之间，与致密成分的贡献一致。叠加的[O III]线轮廓未显示强外流的明确证据。我们的发现表明，高EW窄带选择能有效识别贫金属AGN候选体。
英文摘要
We present Subaru 'Ōnohi'ula Prime Focus Spectrograph (PFS) optical--NIR spectroscopic follow-up of high-equivalent-width (EW) narrow-band (NB) emission-line galaxies selected from Hyper Suprime-Cam Subaru Strategic Program, to assess whether high-EW sources preferentially host low-metallicity AGNs. PFS spectroscopy yielded secure identifications for 583 targets, including 581 sources with reliable PFS redshift solutions and two manually identified $z\sim4$ interlopers. We construct BPT diagnostics for the 70 objects with significant detections in all four BPT lines. Among them, $\sim34\%$ are located in the AGN region of the BPT diagram, suggesting that AGNs constitute a significant fraction of the sample. A non-negligible fraction does not populate the classical AGN branch; instead, it lies in the intermediate ``valley'' between the star-forming and AGN sequences. Comparison to Cloudy models suggests that the valley population is consistent with sub-solar metallicities. Three He II/[Ne V]-detected sources are also found in the star-forming region of the BPT diagram and extend to lower-metallicity solutions, consistent with $Z/Z_{\odot}\approx0.25-0.5$ ($12+\log({\rm O/H})\approx8.1-8.4$). One object shows a clear broad H$α$ component; a multi-component fit yields $M_{\rm BH}\approx8.8\times10^{6} M_{\odot}$ and $λ_{\rm Edd}\approx0.035$, consistent with near-solar narrow-line region metallicity. The fraction of point-like sources in the parent target sample ($22\%\pm2\%$) is intermediate between those of star-forming galaxies ($12\%\pm5\%$) and AGN ($33\%\pm10\%$), consistent with a contribution from compact components. Stacked [O III] line profiles show no clear evidence for strong outflows. Our findings suggest that high-EW NB selection efficiently identifies candidates for metal-poor AGNs.
发表机构
- Hosei University（法政大学）
- National Astronomical Observatory of Japan（日本国立天文台）
- Ehime University（爱媛大学）
- Kwansei Gakuin University（关西学院大学）
- Tohoku University（东北大学）
- Waseda University（早稻田大学）
机构由 AI 辅助整理，请以论文原文为准。
