Solar System Science with Subaru and HSC Matthew Lehner ASIAA

Subaru and HSC Large aperture and wide field Unique combination! Only existing facility capable of pushing outer Solar System science into unexplored parameter space Fainter objects (r’ < 24.5 → r’ < 26.5 to 27) More distant objects (q > 50 AU, out to 70 or 80 AU) Science questions Formation and collisional evolution of planetesimals Migration of giant planets Many others…

Proposal for Outer Solar System Survey with HSC Subaru workshop 2018 November 19 – 21 in Kobe Discussed plans for possible survey proposal Taiwan, Japan, South Korea, China, Canada ~100 deg.2 Fields both on and off ecliptic Expect >100 TNOs per pointing at ecliptic 3 year program 10 nights per semester

Outer Solar System survey with HSC??? Cadence is critical Needed for both discovery and tracking observations Need accurate orbits to determine dynamical class of discovered objects Need time for both follow up observations and sky coverage Fully characterized Known detection biases

Discovery and Tracking Images Triplet of images in one night Additional two images within two nights Tracking: Taken every 2 to 3 months while field is visible 2 – 3 images within 2 nights Coverage over 1.5 years (sometimes 2) Discovery and tracking images can be taken in random order Exact requirements depend on facility E.g. number of faint background stars Test with existing HSC data

Position uncertainty <1” over 4 years

Recent Experience: OSSOS and HSC SSP Outer Solar System Origins Survey CFHT large program (Canada, France, and Taiwan) 2013 January to 2016 July 168 deg.2 at different blocks on or near ecliptic Magnitude limit of r’ = 24.5 Ideal cadence for discovery and tracking 891 objects discovered All but two dynamically classified 30+ and counting refereed publications

Recent Experience: OSSOS and HSC SSP Hyper Suprime Cam Strategic Survey Program 2013 to 2018 1400 deg.2 at different regions on sky, much near ecliptic Magnitude limit of r’ = 26 Solar System science not considered when determining survey cadence Low detection efficiency, no tracking observations 231 objects discovered in 221 deg.2 No objects dynamically classified 1 refereed publication

Recent Experience: OSSOS and HSC SSP Conclusion Careful planning of cadence critical Need both discovery and tracking images 1 object per deg.2 for HSC SSP 5 objects per deg.2 for OSSOS Subaru > 5× aperture of CFHT Expect 50 to 200 objects deg.2 for well designed survey using HSC Limiting magnitude of r’ = 26.5 2 magnitudes fainter than OSSOS

Science TNO size distribution Trojans Resonant TNOs Near-resonant TNOs Different dynamical classes Trojans Size distribution, rotation, colors… Jupiter, Saturn, Neptune Resonant TNOs Near-resonant TNOs Kozai plutinos Distant high-q TNOs High-i TNOs Hildas Size distribution, rotation, colors…

Solar System Science TNO size distribution Trojans Resonant TNOs Different dynamical classes Trojans Size distribution, rotation, colors… Jupiter, Saturn, Neptune Resonant TNOs Near-resonant TNOs Kozai plutinos Distant high-q TNOs High-i TNOs Hildas Size distribution, rotation, colors…

Size Distribution

Size Distribution OSSOS HSC Break in size distribution near r’ = 23 Classical Belt Plutinos Break in size distribution near r’ = 23 Much interesting TNO physics beyond break Collisional history Internal strength Constraints on Neptune’s migration Difference between different dynamical classes Need more objects beyond OSSOS detection limit Need well characterized survey Debias measurements

Near resonant TNOs

Near resonant TNOs High q

Distant high-q TNOs

Distant high-q TNOs Planet 9??? Apparent clustering

Distant high-q TNOs

Conclusion Much incredible science there for the taking Challenging to get this approved Large program Many dark nights per semester EAO shared time is a great opportunity Needs support from EAO Solar System community Please join us! Need more people Especially South Korea and China!