Comets are always masked by the coma when they approach the Sun. The development of coma makes it difficult to characterize the cometary nuclei directly by ground-based observations. Using a large telescope, we can detect more distant comets, which have less outgassing activity and more likely bare nuclei. The Hyper-Suprime Cam, a powerful wide-field camera mounted on the Subaru 8-m telescope in Mauna Kea, provides a 1.5-degree field of view in diameter and can detect a 24-mag point source in a single snapshot. The dedicated Hyper-Suprime Cam Subaru Strategic Program (HSC-SSP, Aihara et al. 2017) and other individual projects obtained thousands of comet detections during the observing period since the public operation in 2014. The systematical observation, calibration, and photometric pipeline inspire an excellent opportunity to study solar system objects in the same standard.
In this presentation, we will introduce our nuclei size estimation by analyzing the Subaru Hyper-Suprime Cam (HSC) archives: the third Public Data Release of HSC-SSP (PDR3, Aihara et al. 2022) and the Hyper Suprime-Cam Legacy Archive (HSCLA, Tanaka et al. 2021). More than 40,000 individual wide-field images are open for public access so far. We have retrieved 2521 postamp images on 240 known comets that had ever entered the HSC field of view, according to the JPL orbital ephemeris. Since it is not a dedicated project to observe solar system targets, we manually exclude defects or low SNR images, and comets shown as high-level active behavior. We derive the nuclei size of 60 comets, less than half of which had previously been reported. A good consistency can be found between our estimation and the previous studies (Bauer et al., 2017; Knight et al., 2023), meaning that our analytic method gives reliable results and can be applied for the upcoming observation by LSST, the next-generation synoptic all-sky survey.
The size distribution of solar system bodies is an indicative signature of the formation, collision, and evolutionary history. We combined our size-estimating result with the previous measurements and produced the size-frequency distribution. We will briefly summarize our work in this presentation.