发表机构
Observatório Nacional/MCTI; Instituto de Física, Universidade de São Paulo; Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo; Escola Politécnica, Universidade de São Paulo; European Southern Observatory (ESO); CONICET. Instituto de Astronomía Teórica y Experimental (IATE); Universidad Nacional de Córdoba (UNC). Observatorio Astronómico de Córdoba (OAC); International Gemini Observatory/NSF NOIRLab（国家天文台/科技部; 圣保罗大学物理研究所; 圣保罗大学天文学、地球物理学和大气科学研究所; 圣保罗大学理工学院; 欧洲南方天文台; 阿根廷国家科学研究委员会理论及实验天体物理研究所; 科尔多瓦国立大学科尔多瓦天文台; 国际双筒望远镜观测站/美国国家光学红外天文实验室）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究推出CLAS+星表，通过比对S-PLUS窄带成像与光谱合成测光，从98139个类星体中筛选出3554个高置信度变貌活动星系核候选体，大幅扩充了候选样本，为后续观测研究提供目标列表。
AI 中文摘要
变貌活动星系核（CLAGN）会在数月到数年的时间尺度上表现出快速的光谱跃迁，这对标准的活动星系核统一模型提出了挑战，也为研究吸积盘的光变特性和遮蔽过程提供了独特视角。尽管这类天体具有重要的科学价值，但受限于多历元光谱数据的稀缺性，以及难以高效构建大样本，针对CLAGN的系统性搜寻工作仍然十分有限。\n 我们推出CLAS+星表，该星表通过将DESI DR1和SDSS DR1的光谱得到的合成测光结果，与S-PLUS巡天的同期窄带成像数据进行比对构建而成。\n 我们将这套处理流程应用于包含98139个类星体的母样本，以约化卡方$\u03c7_r^2 > 15$为阈值，筛选出高置信度的CLAGN候选体。\n 我们共识别出3554个强CLAGN候选体，占母样本的3.6%。这一筛选比例取决于所采用的判据，不能被解读为CLAGN的内禀发生率。与现有CLAGN汇编星表的交叉匹配结果显示，CLAS+识别出了大量此前未被报道的高优先级候选体（共3481个）。在具有可靠时间分类的光谱-测光比对结果中，40%被归类为测光型增亮（turn-on），41%为中间型，19%为测光型变暗（turn-off）。我们还发现相对比例存在明显的红移依赖关系：在CLAS+的筛选样本中，红移越高，测光型增亮候选体的占比越高。\n 因此，窄带测光为大规模识别CLAGN候选体提供了一种强大且高效的替代方案，可取代纯光谱搜寻方式。CLAS+大幅扩充了已知的CLAGN候选体数量，为后续的光谱观测跟进，以及利用Rubin/LSST等设备开展时域研究提供了宝贵的目标列表。
英文摘要
Changing-look active galactic nuclei (CLAGN) exhibit rapid spectral transitions on timescales of months to years, challenging standard AGN unification models and providing unique insight into accretion-disk variability and obscuration processes. Despite their scientific importance, systematic searches for CLAGN remain limited by the scarcity of multi-epoch spectroscopy and the difficulty of constructing large samples efficiently. We introduce CLAS+, a catalog constructed by comparing synthetic photometry derived from DESI DR1 and SDSS DR17 spectra with contemporaneous narrow-band imaging from the S-PLUS survey. Applying our pipeline to a parent sample of 98,139 quasars, we select high-confidence CLAGN candidates above a threshold of reduced chi-squared $χ_r^2 > 15$. We identify 3,554 strong CLAGN candidates, corresponding to 3.6\% of the parent sample. This selected fraction is conditional on the adopted criterion and should not be interpreted as an intrinsic CLAGN occurrence rate. Cross-matching with existing CLAGN compilations shows that CLAS+ identifies a large population of previously unreported high-priority candidates (3,481). Among the spectroscopic--photometric comparisons with reliable temporal classification, 40\% are classified as photometric turn-on, 41\% as intermediate, and 19\% as turn-off. We also find an apparent redshift dependence in the relative fractions, with photometric turn-on candidates becoming more common at higher redshifts within the CLAS+ selected sample. Therefore, narrow-band photometry provides a powerful and efficient alternative to purely spectroscopic searches for identifying CLAGN candidates at scale. CLAS+ substantially expands the known CLAGN candidate population and provides a valuable target list for future spectroscopic follow-up and time-domain studies with facilities such as Rubin/LSST.
CommentsAccepted in ApJ. Crossmatch of CLAS+ with LSST is available in https://marixko.github.io/CLAS_lsst_fup/
