Collaborative Research: Determining Properties of Brown Dwarf Atmospheres With High-Precision Spectro-Polarimetry

在银河系中形成的质量小于太阳质量约8%的物体无法进行核聚变，这是形成真正恒星所必需的。这些被称为棕矮星(BDS)的恒星下天体在许多方面与我们太阳系中的气态巨行星相似，但也有显著的不同。加州理工学院和加州大学伯克利分校的一项研究合作将对太阳系外的棕矮星和巨行星(太阳系外巨行星：EGP)进行观测，以更好地了解这些相似和不同之处。研究人员将使用望远镜对BDS和EGP进行广泛的天文测量。他们的新观测将提供必要的信息，帮助理解EGP的形成和物理性质。这项工作将涉及两所大学的研究生和本科生，研究人员将在帕洛玛天文台的格林威游客中心开发一个关于BDS和系外行星的新展览，利用他们的研究活动和成果。棕矮星和太阳系外巨行星的近红外(NIR)发射光谱是由凝聚云和阴霾形成的，但缺乏对这些云的空间分布和微物理的详细描述。因此，当应用于当前典型的低分辨率、低信噪比的EGP光谱时，大气反演码产生简并的丰度结果。该计划将为BDS和EGP提供光谱偏振近红外序列，以便为新一代三维建模工具提供信息，其中包括全球环流模型和云微物理。其结果将是在近红外波段(J和H波段)对BDS的光谱偏振云图特征进行大规模调查，同时对伴生的BDS和EGP进行较小的光谱偏振调查。与光度法相比，旋光法对云和阴霾的存在和表面分布更敏感。这项拟议的调查最终将有助于区分恒星状云坍塌、行星状圆盘不稳定和核心吸积等形成途径。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Objects that form in the Galaxy with masses less than about 8% that of the Sun cannot sustain the nuclear fusion necessary to become a true star. These substellar objects, called brown dwarfs (BDs), are similar in many ways to the gas giant planets in our own Solar System, but there are significant differences. A research collaboration between California Institute of Technology and the University of California-Berkeley will observe both brown dwarfs and giant planets outside the solar system (extra-solar giant planets: EGPs) to better understand these similarities and differences. The researchers will carry out an extensive astronomical survey of BDs and EGPs using telescopes. Their new observations will provide essential information to help understand the formation and physical properties of EGPs. The work will involve graduate and undergraduate students at both universities, and the investigators will develop a new exhibit on BDs and exoplanets at Palomar Observatory's Greenway Visitor Center, drawing on activities and results from their research. The near-infrared (NIR) emission spectra of brown dwarfs and extra-solar giant planets are shaped by condensate clouds and hazes, but a detailed description of these clouds' spatial distributions and microphysics is lacking. As a result, atmospheric retrieval codes yield degenerate abundance results when applied to current typically low-resolution, low signal-to-noise EGP spectroscopy. This program will provide a spectro-polarimetric NIR sequence for BDs and EGPs in order to inform a new generation of three-dimensional modeling tools, incorporating global circulation models and cloud microphysics. The outcome will be a large-scale survey of spectro-polarimetric cloud signatures in BDs, complemented with a smaller spectro-polarimetric survey of companion BDs and EGPs, in the NIR (J and H bands). Compared with photometry, polarimetry is more sensitive to the presence and surface distribution of clouds and hazes. The proposed survey will ultimately help differentiate between formation pathways such as star-like cloud collapse, planet-like disk instability, and core accretion.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.