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Javiera Parada: Relaxing in NGC 362*

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Two-Body Relaxation in NGC 362 as measured by white dwarfs

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Javiera Parada: Relaxing in NGC 362*

  1. 1. Relaxation in NGC 362 Javiera Parada May 8th 2019 A Richer Universe In collaboration with: I. Caiazzo, J. Heyl, H. Richer (UBC), J. Kalirai, P.Tremblay, M. Correnti, J. Cummings, B. Hansen, L. Watkins,A. Bellini, J.Anderson
  2. 2. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Introduction Determine the relaxation time in the core of the globular cluster NGC 362 by tracking the positions of the youngest white dwarfs.
  3. 3. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Observations in the UV HST/WFC3 UV filters F225W and F275W.
  4. 4. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Observations in the UV White dwarfs
  5. 5. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Colour-magnitude diagram
  6. 6. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Colour-magnitude diagram White dwarfs are bright in the UV
  7. 7. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Colour-magnitude diagram White dwarfs Small Magellanic Cloud stars
  8. 8. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Colour-magnitude diagram White dwarfs Small Magellanic Cloud stars Other stars we don’t like
  9. 9. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Proper Motion Cleaning
  10. 10. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Proper Motion Cleaning
  11. 11. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Completeness corrections – SMC background stars
  12. 12. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Colour-magnitude diagram
  13. 13. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Selecting stars • Select stars based on their position in the CMD. • Clear white dwarf sequence.
  14. 14. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Tracking positions - Distributions of stars
  15. 15. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Tracking positions - Distributions of stars • Young white dwarfs have recently lost close to half their mass and are just beginning to migrate outwards due to relaxation. • Older white dwarfs are already further out.
  16. 16. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions The relaxation time • As defined in Heyl et at. 2015 (ApJ, 804:43) 𝑡"#$%& = 𝑎* + 𝜅
  17. 17. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Time dependent core radius • As defined in Heyl et at. 2015 (ApJ, 804:43) • Time dependent core radius 𝑡"#$%& = 𝑎* + 𝜅
  18. 18. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Modelling the distributions • As defined in Heyl et at. 2015 (ApJ, 804:43) • Time dependent core radius • King model 𝑡"#$%& = 𝑎* + 𝜅
  19. 19. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Modelling the distributions • As defined in Heyl et at. 2015 (ApJ, 804:43) • Time dependent core radius • King model 𝑡"#$%& = 𝑎* + 𝜅
  20. 20. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Modelling the distributions
  21. 21. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Modelling the distributions
  22. 22. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Estimating 𝑎* and 𝜅 Binning Unbinned likelihood estimation White dwarfs ages Dividing WDs into faint and bright WDs
  23. 23. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions White dwarfs ages White dwarfs ages WD birth rate (Counting stars) WD cooling models 𝑡- = 1 𝑁̇ 1 1 𝐶3 35- Ages from F225W magnitude
  24. 24. • Introduction • Proper motion cleaning • Modelling • Results • Conclusions Isochrone & cooling models • 11 Gyr isochrone built using MESA models. • Initial mass of main sequence stars currently becoming WDs is 0.81 M⦿ • Cooling curve for the 0.54 M⦿ white dwarf generated from a 0.81 M⦿ main- sequence star.

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