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arXiv 2607.00543astro-ph.SRastro-ph.EPastro-ph.GA
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SPHEREx 0.75至5微米邻近褐矮星序列光谱

SPHEREx 0.75 to 5 $μ$m Spectra for a Sequence of Nearby Brown Dwarfs

IPAC, California Institute of Technology（加州理工学院 IPAC）；Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；Department of Physics, California Institute of Technology（加州理工学院物理系）；Department of Physics & Astronomy, University of California Irvine（加州大学欧文分校物理与天文系）
Zafar Rustamkulov, J. Kirkpatrick, Rachel Akeson, Michael W Werner, Matthew Ashby, Tzu-Ching Chang, Shuang-Shuang Chen, Asantha Cooray, Brendan Crill, Olivier D… 展开作者

Zafar Rustamkulov, J. Kirkpatrick, Rachel Akeson, Michael W Werner, Matthew Ashby, Tzu-Ching Chang, Shuang-Shuang Chen, Asantha Cooray, Brendan Crill, Olivier Dore, C. Dowell, Andreas Faisst, Howard Hui, Woong-Seob Jeong, Miju Kang, Phil Korngut, Carey Lisse, Daniel Masters, Gary Melnick, Chi Nguyen, Roberta Paladini, Volker Tolls, Yujin Yang, Michael Zemcov

备注：
27 pages, 20 figures
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AI总结：

利用SPHEREx巡天获取37颗L0至Y4型褐矮星的中红外光谱，通过与五种大气模型对比，发现模型在J/H/K峰值和4微米不透明度窗口拟合不佳，尤其在L/T过渡天体及CO₂和CO特征处偏差最大。

摘要：

SPHEREx全天巡天现已测量了数千颗邻近褐矮星在化学丰富的0.75-5微米范围内的R~40-100红外光谱。该巡天宽光谱覆盖和高信噪比允许测量捕获多个宽带分子吸收特征，以及大多数褐矮星总辐射光度的80%以上。已知大气模型在推断褐矮星温度和半径时存在系统性差异，因此需要以观测为基准。在这项工作中，我们展示了跨越37颗邻近场褐矮星（从L0到Y4，约2500-250 K）的SPHEREx光谱，并将其与理论预期进行比较。我们还为独立的低重力和低金属丰度天体编译了光谱，并展示了它们如何随恒定光谱型变化。我们将测量光谱拟合到著名的前向模型网格Sonora Diamondback、Elf Owl、BT-Settl、ATMO2020和ATMO2020++，并比较它们作为波长、光谱型以及云和化学处理函数的拟合优度。我们发现这些模型仍然难以同时拟合J/H/K峰值和4微米不透明度窗口，尤其是在L/T过渡天体中。最大偏差出现在对化学敏感的CO₂和CO特征附近。尽管存在这些偏移，模型大致捕捉了它们在L/T过渡中的趋势，观测到的场矮星样本强烈偏好弱垂直混合（k_zz = 10^4 cm² s⁻¹）的Elf Owl模型而非强混合模型。这里展示的光谱以及未来的SPHEREx数据将有助于指导模型的改进。

英文摘要：

The SPHEREx all-sky survey has now measured the R$\sim$40-100 infrared spectra of thousands of nearby brown dwarfs in the chemically rich 0.75-5 $μ$m range. The survey's wide spectral coverage and high S/N permits flux measurements that capture several broadband molecular absorption features, and upwards of 80$\%$ of the total bolometric luminosity of most brown dwarfs. Atmospheric models are known to yield systematic disagreements in the inferred temperatures and radii of brown dwarfs, necessitating benchmarking against observations. In this work, we present SPHEREx spectra across a broad sequence of 37 nearby field brown dwarfs, ranging from L0 to Y4 ($\sim$2500-250 K) and compare them to theoretical expectations. We additionally compile spectra for separate low-gravity and low-metallicity objects, and show how they trend with constant spectral type. We fit the measured spectra to the well-known forward model grids Sonora Diamondback, Elf Owl, BT-Settl, ATMO2020 and ATMO2020++ and compare their goodness-of-fit as a function of wavelength, spectral type, and treatment of clouds and chemistry. We find that the models continue to struggle to simultaneously fit the J/H/K peaks and the 4 $μ$m opacity window, especially in L/T transition objects. The largest deviations appear around the chemistry-sensitive CO$_2$ and CO features. Despite these offsets, the models broadly capture their trends across the L/T transition, with the observed sample of field dwarfs strongly preferring the weak vertical mixing ($k_\mathrm{zz}$ = 10$^4$ cm$^2$s$^{-1}$) Elf Owl models over strong mixing. The spectra shown here along with future SPHEREx data will help guide improvements to models.

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