[PPS07-P21] Measurement of Size Distribution of Cold Classical Trans-Neptunian Objects
Keywords:Trans-Neptunian objects, size distribution, Subaru Telescope
Our study is to measure the luminosity function (corresponding to the size distribution) of CCs down to a diameter of 100 km or less. Since TNOs are so far/faint, their sky number density with the same detection limit is very low compared with other small-body populations. Therefore, a combination of a large aperture telescope and a wide-field imaging instrument is required to obtain sufficient data for deriving the luminosity function with high accuracy. We performed an optical survey observation for TNOs using the 8.2-m Subaru Telescope and Hyper Suprime-Cam, a gigantic mosaic CCD camera with a wide field-of-view of 1.5 deg in diameter, around the ecliptic sky area of 14 deg2 with two (g- and r-band) filters on January 26, 2015 UT. Few have ever reported the absolute magnitude distribution of the CC population around 100 km in diameter from a single survey. Our homogeneous survey data acquired with the same instrument, at the same field, and by the same technique allows us to obtain a precise statistical sample.
We detected 173 TNOs from our survey data. The 50%-completeness detection limit is 25.0 mag in r band, corresponding to 80 km in diameter at heliocentric distance of 45 au assuming a geometric albedo of 0.1. We extracted a debiased sample containing 47 of the CC candidates based on their sky motion, brightness, and color. The absolute magnitude distribution derived from our CC sample are well fitted by a broken power law as pointed out by previous studies, but the bright-end slope looks shallower than those of the previous studies. We will discuss the similarity and difference between the obtained size distribution and that of other small-body populations such as Jupiter Trojans and Neptune Trojans.