标题： 从ALMA获得的木卫四多频段全球热特性视图 显示英文标题

标题： A multi-frequency global view of Callisto's thermal properties from ALMA

摘要： 我们展示了使用阿塔卡马大型毫米波/亚毫米波阵列(ALMA)在0.87毫米(343 GHz)、1.3毫米(233 GHz)和3毫米(97 GHz)波长下获得的木卫三前导和后导半球的热观测数据。这些观测的角分辨率范围为0.09-0.24角秒，对应于木卫三上的约420-1100公里。全球表面特性是通过一个热物理模型(de Kleer等，2021年)从观测中得出的，该模型受到航天器数据的约束。我们发现，与欧罗巴和甘尼米德在这些波长下的0.75-0.85相比，木卫三的毫米波发射率较高，代表性值为0.85-0.97。很明显，由单一热惯性参数化的模型不足以模拟木卫三的热辐射，并且以系统的方式偏离数据中的温度分布。相反，采用两个热惯性成分或将电皮肤深度作为自由参数的更复杂模型比单一热惯性模型更能准确地拟合数据。全局最佳拟合模型的残差揭示了热异常；特别是，与周围地形相比局部冷3-5 K的亮度温度与撞击坑有关。我们识别出瓦尔哈拉撞击盆地以及包括洛恩在内的多个大撞击坑作为这些数据中的关键冷异常(~3-5 K)和地质特征。这些数据为木卫三的詹姆斯·韦伯太空望远镜结果(Cartwright等，2024年)以及其他ALMA伽利略卫星观测(de Kleer等，2021年，Trumbo等，2017年，2018年，Thelen等，2024年)提供了背景，并可能对即将进行的伽利略卫星任务(JUICE，欧罗巴快船)有用地基背景。 显示英文摘要

摘要： We present thermal observations of Callisto's leading and trailing hemispheres obtained using the Atacama Large Millimeter/submillimeter Array (ALMA) at 0.87 mm (343 GHz), 1.3 mm (233 GHz), and 3 mm (97 GHz). The angular resolution achieved for these observations ranged from 0.09-0.24 arcseconds, corresponding to ~420-1100 km at Callisto. Global surface properties were derived from the observations using a thermophysical model (de Kleer et al. 2021) constrained by spacecraft data. We find that Callisto's millimeter emissivities are high, with representative values of 0.85-0.97, compared to 0.75-0.85 for Europa and Ganymede at these wavelengths. It is clear that models parameterized by a single thermal inertia are not sufficient to model Callisto's thermal emission, and clearly deviate from the temperature distributions in the data in systematic ways. Rather, more complex models that adopt either two thermal inertia components or that treat electrical skin depth as a free parameter fit the data more accurately than single thermal inertia models. Residuals from the global best-fit models reveal thermal anomalies; in particular, brightness temperatures that are locally 3-5 K colder than surrounding terrain are associated with impact craters. We identify the Valhalla impact basin and a suite of large craters, including Lofn, as key cold anomalies (~3-5 K) and geologic features of interest in these data. These data provide context for Callisto JWST results (Cartwright et al. 2024) as well as the other ALMA Galilean moon observations (de Kleer et al. 2021, Trumbo et al. 2017, 2018, Thelen et al. 2024), and may be useful ground-based context for upcoming Galilean satellite missions (JUICE, Europa Clipper).