ALPINE-CRISTAL-JWST巡天：揭示高红移星系中质量更小的黑洞
The ALPINE-CRISTAL-JWST Survey: Revealing Less Massive Black Holes in High-Redshift Galaxies
AI总结：
本研究通过ALPINE-CRISTAL-JWST巡天在高红移大质量恒星形成星系中识别出7个暗弱宽线AGN候选体，发现其黑洞质量接近或低于局域标度关系，揭示了选择偏差对高红移黑洞研究的影响，为AGN与宿主星系共演化提供新认知。
摘要：
我们对红移z=4.4-5.7的18个恒星形成星系（恒星质量M⋆>10^9.5 M⊙）组成的ALPINE-CRISTAL-JWST样本开展了宽线活动星系核（AGN）的系统搜寻。利用JWST/NIRSpec积分场单元（IFU），我们从以光度峰值为中心的33个孔径光谱中，通过探测宽Hα发射线识别出7个AGN候选体。这些候选体包括1个可靠性极高的AGN探测结果，其全宽半高（FWHM）约为2800 km/s，另有6个呈现出FWHM约600-1600 km/s的宽线成分，其中2个位于并合系统中。我们强调，由于这些候选体均处于恒星形成星系与AGN重叠的窄发射线比值诊断图范围内，因此只有宽线探测是有效的。根据候选体的可靠性不同，宽线AGN占比在5.9%到33%之间。假设其中绝大多数为AGN，相对较高的AGN占比可能源于我们以大质量星系为观测目标，模拟研究表明这类星系中宽线探测更易实现。它们的黑洞质量范围为10^6到10^7.5 M⊙，爱丁顿比L_bol/L_Edd约为0.1到1。此前JWST的高红移研究发现黑洞相对于其宿主星系质量过大，而我们的候选体质量接近甚至低于局域M_BH-M⋆标度关系，由此证明了选择偏差的影响。本研究通过在星系样本中识别暗弱的宽线AGN，为高红移下AGN与宿主星系的共同演化提供了新见解，凸显了考虑质量依赖的选择偏差的重要性，同时表明存在大量质量偏低的AGN族群，且JWST刚刚开始探测到这类天体。
英文摘要：
We present a systematic search for broad-line active galactic nuclei (AGNs) in the ALPINE-CRISTAL-JWST sample of 18 star-forming galaxies ($M_\star>10^{9.5}~M_{\odot}$) at redshifts $z=4.4-5.7$. Using JWST/NIRSpec IFU, we identify 7 AGN candidates through the detection of broad \Ha\ emission lines from 33 aperture spectra centred on photometric peaks. These candidates include one highly robust AGN detection with FWHM $\sim$ 2800 \kms\ and six showing broad components with FWHM $\sim 600-1600$ \kms, with two in a merger system. We highlight that only broad-line detection is effective since these candidates uniformly lie within narrow emission-line ratio diagnostic diagrams where star-forming galaxies and AGNs overlap. The broad-line AGN fraction ranges from 5.9\% to 33\%, depending on the robustness of the candidates. Assuming that the majority are AGNs, the relatively high AGN fraction is likely due to targeting high-mass galaxies, where simulations demonstrate that broad-line detection is more feasible. Their black hole masses range from $10^6$ to $10^{7.5}~M_{\odot}$ with $0.1 \lesssim L_{\rm bol}/L_{\rm Edd}\lesssim 1$. Counter to previous JWST studies at high redshift that found overmassive black holes relative to their host galaxies, our candidates lie close to or below the local $M_{\rm BH}-M_\star$ scaling relations, thus demonstrating the effect of selection biases. This study provides new insights into AGN-host galaxy co-evolution at high redshift by identifying faint broad-line AGNs in galaxy samples, highlighting the importance of considering mass-dependent selection biases and the likelihood of a large population of AGNs being undermassive and just now being tapped by JWST.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
