用HeII $λ$ 4686谱线揭示MaNGA恒星形成星系中隐藏的活动核
Unveiling hidden active nuclei in MaNGA star-forming galaxies with HeII$λ$4686 line emission
摘要：
星云HeII $λ$ 4686 γ ~谱线发射对于揭示活跃星系核（AGN）是有用的，这些活动星系核位于恒星形成活跃的（SF）星系中，通常被标准的BPT分类所遗漏。在这里，我们采用HeII诊断，以确定隐藏的活动星系核在本地宇宙中使用的第一次空间分辨的数据，从数据发布15映射附近的Galerkin在APO调查（MANGA DR 15）。通过结合HeII和BPT诊断的结果，我们总共选择了459个活动星系核候选者（$\sim$ 10%在MaNGA DR 15），其中27个仅由HeII图确定为活动星系核。只有HeII的活动星系核由大质量（M $_*\gtrsim10^{10}$ M $_{\odot}$）SF主序星星系组成，平均亮度低于BPT选择的活动星系核。由于HeII线模糊，我们重新审视我们的人口普查会计不完整的影响，由于HeII的灵敏度限制的MANGA。因此，我们得到的MANGA中活动星系核的比例（11%）比仅BPT普查（9%）增加了，对于质量比$10^{10}$ M $_{\odot}$更大的星系，这一比例进一步增加到14%;有趣的是，在SF主序星上，这一比例增加了约2倍。大量的活动星系核在SF星系点显着的，同时代的恒星形成和黑洞吸积，一致的流体动力学模拟的结果和淬火方案的重要影响。鉴于探索前所未有的高红移与JWST和新的地面设施，通过新的发射线诊断重新审视标准的BPT分类是发现活动星系核在高SF环境的基础。
英文摘要：
Nebular HeII$λ$4686Å~line emission is useful to unveil active galactic nuclei (AGN) residing in actively star-forming (SF) galaxies, typically missed by the standard BPT classification. Here we adopt the HeII diagnostic to identify hidden AGN in the Local Universe using for the first time spatially-resolved data from the Data Release 15 of the Mapping Nearby Galaxies at APO survey (MaNGA DR15). By combining results from HeII and BPT diagnostics, we overall select 459 AGN host candidates ($\sim$10% in MaNGA DR15), out of which 27 are identified as AGN by the HeII diagram only. The HeII-only AGN population is hosted by massive (M$_*\gtrsim10^{10}$ M$_{\odot}$) SF Main Sequence galaxies, and on average less luminous than the BPT-selected AGN. Given the HeII line faintness, we revisit our census accounting for incompleteness effects due to the HeII sensitivity limit of MaNGA. We thus obtain an overall increased fraction (11%) of AGN in MaNGA compared to the BPT-only census (9%), which further increases to 14% for galaxies more massive than $10^{10}$ M$_{\odot}$; interestingly, on the SF Main Sequence the increase is by about a factor of 2. A substantial number of AGN in SF galaxies points to significant, coeval star formation and black hole accretion, consistently with results from hydrodynamical simulations and with important implications on quenching scenarios. In view of exploring unprecedented high redshifts with JWST and new ground-based facilities, revisiting the standard BPT classification through novel emission-line diagnostics is fundamental to discover AGN in highly SF environments.
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