发表机构
Istituto Nazionale di Astrofisica (INAF) - Osservatorio Astronomico di Palermo; Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências, Universidade de Lisboa; SUPA, School of Physics & Astronomy, University of St Andrews; European Southern Observatory; The University of Texas at Austin, Department of Astronomy; Space Telescope Science Institute; Department of Astronomy, University of Florida（意大利国家天体物理研究所（INAF）- 巴勒莫天文台; 里斯本大学科学学院空间科学与天体物理研究所; 圣安德鲁斯大学物理与天文学学院; 欧洲南方天文台; 德克萨斯大学奥斯汀分校天文学系; 太空望远镜科学研究所; 佛罗里达大学天文学系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用JWST/NIRCam对Westerlund 2开展深场观测，通过测光与SED拟合证认出353个亚恒星候选体，其中含73个带星周盘的候选体，为后续研究提供了关键样本。
AI 中文摘要
研究年轻大质量星团中的亚恒星族群可为褐矮星（BDs）的形成以及环境条件在塑造其性质中的作用提供关键见解。Westerlund 2（Wd2）作为银河系中最近的致密大质量星团之一，是研究高恒星密度和大质量恒星电离辐射对褐矮星形成影响的理想实验室。本文呈现了JWST/NIRCam对Wd2在1.15至4.1μm范围内多个滤光片的深场观测。我们的分析重点是证认和表征星团内的褐矮星族群。我们使用DOLPHOT对在4个宽滤光片和6个中带滤光片下获取的JWST/NIRCam深场数据进行了点扩散函数（PSF）测光。所得星表通过结合大气模型的光谱能量分布（SED）拟合来证认Wd2中的褐矮星候选体。在Wd2的距离、年龄和消光条件下，我们的NIRCam星表的50%探测极限约为0.015-0.02 M☉，提供了迄今为止对超大质量星团的最深观测。我们证认出353个亚恒星候选体，其中大多数（301个）在赫罗图中位于10 Myr等时线上方，与星团成员身份一致，被定义为强候选体。与控制场的比较显示，强候选体样本在低至约0.01-0.015 M☉质量时的污染水平≤5%。我们证认出73个呈现红外超的候选体，表明存在星周盘；这些天体在消光改正后的色-色图中占据预期的红外超轨迹，占F410M滤光片探测到的候选体的27.7%（误差范围+3.4/-3.2）。所得星表为后续光谱证认及Wd2亚恒星族群的进一步研究提供了特征明确的样本。
英文摘要
[Abridged] Investigating substellar populations in young massive clusters offers crucial insights into the formation of brown dwarfs (BDs) and the role of environmental conditions in shaping their properties. Westerlund 2 (Wd2), as one of the nearest dense and massive clusters in the Milky Way, represents an ideal laboratory for studying the effects of high stellar density and ionizing radiation from massive stars on BD formation. This paper presents deep JWST/NIRCam observations of Wd2 in a large number of filters between 1.15 and 4.1 $μm$. Our analysis focuses on identifying and characterizing the BD population within the cluster. We carried out PSF photometry on deep JWST/NIRCam data obtained in 4 wide and 6 medium-band filters, using DOLPHOT. The resulting catalog was used to identify BD candidates in Wd2 through spectral energy distribution (SED) fitting with atmospheric models. The 50\% detection limit of our NIRCam catalog is $\sim$0.015-0.02 $M_\odot$, at the distance, age, and extinction of Wd2, providing the deepest view of a supermassive star cluster to date. We identify 353 substellar candidates. Most candidates (301) lie above the 10 Myr isochrone in the Hertzsprung--Russell diagram consistent with cluster membership, which are defined as strong candidates. Comparison with a control field indicates a contamination level of $\lesssim$5\% for the strong candidate sample down to masses of $\sim$0.01--0.015~$M_\odot$. We identify 73 candidates exhibiting infrared excess indicative of circumstellar disks. These objects occupy the expected infrared-excess locus in de-reddened color diagrams and represent $27.7^{+3.4}_{-3.2}$\% of the candidates detected in F410M. The resulting catalog provides a well-characterized sample for future spectroscopic confirmation and subsequent studies of the substellar population of Wd2.
CommentsAccepted for publication at A&A
