利用哈勃空间望远镜的Y矮星群体：解开我们最冷邻居的奥秘——III. 近红外光度学
The Y Dwarf Population with HST: unlocking the secrets of our coolest neighbours -- III. Near-Infrared Photometry
AI总结：
本研究利用哈勃空间望远镜的近红外光度学数据，揭示了Y矮星的色-光度图序列，发现其与大气模型存在系统性差异，强调了高精度数据对理解最冷天体物理过程的重要性。
摘要：
Y矮星代表了最冷的棕矮星类别，其有效温度低于500K，并提供了独特的类冷巨行星类比。我们呈现了一组来自哈勃空间望远镜的统一近红外光度学数据，涵盖21个Y矮星在多个WFC3/IR滤光片中的观测，包括F105W、F125W和F160W波段。我们采用了改进的PSF拟合和校准程序，使大多数目标的光度学误差达到0.02-0.05mag的水平。结合精确的视差测量，我们的数据揭示了近红外色-光度图中清晰定义的Y矮星序列，观测到显著改善的紧密性。已知的光度学趋势在最小的散射下显现，包括在F125W-F160W波段中随着温度降低而持续向红端移动，以及在F105W-F125W波段中向蓝端趋势，可能有在350K附近反转的暗示。与ATMO、Sonora Elf Owl和Lacy & Burrows大气模型的比较突显了系统性的差异，特别是F105W-F12 MERCHANTABILITY和F105W-F160W颜色被预测得过红。低金属licity网格提供了对全球Y矮星群体的最佳拟合，尽管在不同波长上更仔细的检查显示，这些偏好可能反映了缺失或不完整的物理过程的补偿效应，而不是真正的群体水平丰度。尽管Y矮星之间预期存在一些大气多样性，但它们紧密的观测序列和系统性的模型预测偏移揭示了关键的物理和化学过程在当前网格中仍然不够充分。我们的结果强调了高精度、内部一致的数据集在稳健地追踪Y矮星冷却序列和提供理论模型所需的经验约束方面的重要性。
英文摘要：
Y dwarfs represent the coldest class of brown dwarfs, with effective temperatures below 500K, and provide unique analogues to cold giant exoplanets. We present a large compilation of uniform near-infrared photometry from the Hubble Space Telescope for 21 Y dwarfs across multiple WFC3/IR filters, including the F105W, F125W and F160W bands. We employed refined PSF-fitting and calibration procedures to reach photometric uncertainties at the 0.02-0.05 mag level for most targets. Combined with precise parallax measurements, our data reveal well-defined Y-dwarf sequences in near-infrared colour-magnitude diagrams, observed with a markedly improved tightness. Known photometric trends emerge with minimal scatter, including the continuous redward progression in F125W-F160W with decreasing temperature, and the blueward trend in F105W-F125W with possible hints of a reversal around 350K. Comparisons to the ATMO, Sonora Elf Owl, and Lacy & Burrows atmospheric models highlight systematic discrepancies, in particular F105W-F125W and F105W-F160W colours predicted to be too red. Low-metallicity grids provide the best fits to the global Y-dwarf population, although closer inspection across wavelengths shows that these preferences likely reflect compensating effects in missing or incomplete physics rather than true population-level abundances. While some atmospheric diversity is expected among Y dwarfs, their tight observational sequences and systematic offsets from model predictions reveal that key physical and chemical processes remain inadequately captured in current grids. Our results underscore the importance of high-precision, internally consistent datasets in robustly tracing the Y-dwarf cooling sequence and providing the empirical constraints needed to advance theoretical models at the lowest temperatures.
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。
