1. Solar System Science with Subaru and HSC
Matthew Lehner
ASIAA

2. 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…

3. 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

4. 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

5. 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

6. Position uncertainty <1” over 4 years

7. 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

8. 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

9. 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

10. 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…

11. 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…

12. Size Distribution

13. 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

14. Near resonant TNOs

15. Near resonant TNOs
High q

16. Distant high-q TNOs

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

18. Distant high-q TNOs

19. 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!