AI 中文总结
该研究利用SPHEREx获取94颗年轻低重力L、T型矮星的3-5微米光谱，分析其大气多样性，发现低重力天体的3-5微米色指数更红，部分巨行星与低重力天体轨迹一致，部分差异显著。
AI 中文摘要
巨行星的出射光谱在热红外波长（3-5微米）处达到峰值，该波段包含反映碳化学、垂直混合、云层及成分的大气特征。然而，该光谱区域难以从地面观测，且借助詹姆斯·韦伯空间望远镜（JWST）通常需要对每个目标单独指向。SPHEREx正在提供0.75-5微米范围内数百万个天体的全天光谱，使得对孤立及宽距亚恒星天体的个体和种群水平研究成为可能。本研究中，我们发布了包含94颗年轻（年龄小于3亿年）低重力L型和T型矮星的SPHEREx分光光度图集，以在相对未被探索的3-5微米波长范围内研究其大气多样性。这些天体包括年龄、质量和温度各异的自由漂浮行星质量天体，它们常被JWST探测，也将可通过即将上线的凯克望远镜/SCALES和欧洲极大望远镜（ELT）/METIS等设备观测。我们计算了22个滤光片对应的JWST/NIRCam和MKO合成测光及色指数，并研究了基于物理动机的色指数、绝对星等和光谱型的趋势。我们发现，最低重力的天体通常具有最红的3-5微米色指数，且在给定光谱型下比场L型矮星更亮，扩展了最初在近红外波长建立的模式。与自由漂浮天体的低重力样本相比，一些巨行星紧密遵循低重力轨迹，而另一些则表现出更大的离散度和更极端的色指数，这表明它们在云层特性、温度、金属丰度或垂直混合方面存在差异。本研究开发的SPHEREx数据提取代码与提取的光谱及合成测光一同公开。
英文摘要
The emergent spectra of giant planets peak at thermal infrared wavelengths (3-5um) and possess atmospheric features in this regime that trace carbon chemistry, vertical mixing, clouds, and composition. However, this spectral region is challenging to access from the ground, and with JWST generally requires an independent pointing for each target. SPHEREx is providing all-sky spectra of millions of sources from 0.75-5um, enabling both individual and population-level studies of isolated and widely bound substellar objects. In this work we present a SPHEREx spectrophotometric atlas of 94 young (<300Myr) low-gravity L and T dwarfs to study their atmospheric diversity in the relatively unexplored wavelength range from 3-5um. These include free-floating planetary-mass objects in a range of ages, masses, and temperatures regularly probed with JWST and which will be accessible with upcoming instruments such as Keck/SCALES and ELT/METIS. We compute synthetic JWST/NIRCam and MKO photometry and colors across 22 filters, and examine trends in physically-motivated sets of colors, absolute magnitudes, and spectral types. We find that the lowest-gravity objects generally have the reddest 3-5um colors and tend to be brighter than field L dwarfs for a given spectral type, extending previous patterns originally established at near-infrared wavelengths. Compared to the low-gravity sample of free-floating objects, some giant planets closely follow the low-gravity locus, while others show larger scatter and more extreme colors, pointing to differences in cloud properties, temperature, metallicity, or vertical mixing. The SPHEREx data extraction code developed in this work is made available together with the extracted spectra and synthetic photometry.
CommentsSubmitted to AJ. 20 pages, 8 figures, 3 tables
