(Proposal ID) S15A-050

(PI) Terai, Tsuyoshi

(Proposal Title)
 Deep Imaging Survey for Faint Trans-Neptunian Objects

(Abstract)
Trans-neptunian objects (TNOs) are remnants of planetesimals and their 
fragments in the outer solar system. Large objects free from destructive 
collisions maintain the primordial size distribution, while small objects 
have collisionally evolved. The two populations could induce a "break" in 
the shape of TNOs' size distribution, which is expected to be located around 
60--100 km in diameter. Determination of the break size and the size 
distribution slope of the collisionally evolved population provides important 
constraints on the collisional evolution and internal structure of TNOs. 
We propose to perform a deep survey with a total integration time of 4 hours 
covering 3.5 square degree of the ecliptic fields using Hyper Suprime-Cam. 
We aim to achieve a limiting magnitude of r = 27.0 mag corresponding to TNO 
diameter of 30 km. This survey allows us to detect about 300 small TNOs and 
to measure the shape of size distribution much more accurately than the 
current estimates. The results could be helpful to construct an advanced model 
of the formation and evolution histories of planetesimals in the outer solar 
system.