AI 中文总结
该研究利用SDSS-IV/eBOSS数据识别33817个[Ne V]星系，发现低红移日冕线星系中[Ne V]/[O III]与AGN光度强反相关，高红移AGN仅部分遵循该关系，为AGN诊断提供新依据。
AI 中文摘要
传统窄线诊断在高红移处失效，低金属度会导致恒星形成星系与活动星系核（AGN）在Baldwin-Phillips-Terlevich（BPT）图中重叠。电离势超过100 eV的日冕线提供了可靠替代：它们无法由正常恒星产生，几乎仅来自AGN或快激波，且对丰度演化不敏感。其中，[Ne V]双线是AGN活动最亮的光学日冕线示踪物。现有日冕线星表仅包含约1750个天体，数量过少无法统计评估[Ne V]选AGN样本的完备性与纯度。我们在斯隆数字巡天IV扩展重子振荡光谱巡天（SDSS-IV/eBOSS）中，识别出红移z=0.147-1.12范围内33817个[Ne V]信噪比S/N>5的星系，超过文献总合的一个数量级以上。[Ne V]优先选择吸积迅速、相对未被遮挡的AGN；仅41.5%的BPT AGN存在可探测发射。通过在黑洞质量与[O III]光度的网格上堆叠无[Ne V]的光谱，我们在多数区间中恢复出[Ne V]，说明未探测到[Ne V]是巡天灵敏度有限所致，而非日冕发射缺失。我们发现[Ne V]/[Ne III]与[O III]/[O II]仅弱相关。在给定[O III]/[O II]比值下，[Ne V]/[Ne III]较高的星系爱丁顿比率更低，更可能被归类为低电离核发射线区（LIER）或复合星系。[Ne V]/[O III]比值与[O III]光度呈强反相关，最极端的日冕线强度出现在光度最低的AGN中，与恒星质量黑洞的吸积态类似。与z=2-9的[Ne V]探测星系样本对比显示，部分（非全部）高红移AGN遵循相同关系。
英文摘要
Traditional narrow-line diagnostics fail at high redshift, where low metallicity drives star-forming galaxies and Active Galactic Nuclei (AGN) into overlapping regions of the Baldwin-Phillips-Terlevich (BPT) diagram. Coronal lines, with ionization potentials exceeding 100 eV, offer a robust alternative: they cannot be produced by normal stellar populations, arise almost exclusively from AGN or fast shocks, and are insensitive to abundance evolution. Among these, the [Ne V] doublet is the brightest optical coronal line tracer of AGN activity. Existing coronal line catalogs contain only about 1750 objects, too few to statistically assess the completeness and purity of [Ne V]-selected AGN samples. We identify 33,817 galaxies with [Ne V] S/N > 5 at z = 0.147-1.12 in the Sloan Digital Sky Survey IV extended Baryon Oscillations Spectroscopic Survey (SDSS-IV/eBOSS), exceeding the combined literature total by more than an order of magnitude. [Ne V] preferentially selects rapidly accreting, relatively unobscured AGN; only 41.5% of BPT AGN show detectable emission. By stacking spectra that lack [Ne V] on a grid of black hole mass and [O III] luminosity, we recover [Ne V] in the majority of bins, implying that non-detections reflect limited survey sensitivity rather than a deficit of coronal emission. We find [Ne V]/[Ne III] is only weakly correlated with [O III]/[O II]. Galaxies with high [Ne V]/[Ne III] for their [O III]/[O II] ratio have lower Eddington ratios and are more likely classified as LIERs or Composites. The [Ne V]/[O III] ratio shows a strong anticorrelation with [O III] luminosity, with the most extreme coronal-line strengths found among the lowest-luminosity AGN, in analogy with the accretion states of stellar-mass black holes. Comparison with a sample of z=2-9 [Ne V]-detected galaxies suggests some, but not all, high-redshift AGN follow the same relations.
Comments23 pages, 16 figures, 5 tables. Submitted to The Open Journal of Astrophysics. For the eBOSS-DAP catalog and associated data products, see https://datalab.noirlab.edu/data/sdss#sdss-iv-eboss-dap-value-added-catalog ; for the eBOSS-DAP source code, see https://github.com/owenmatthewsa/ebossdap
