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Adrian Price-Whelan
October 30, 2014
Science
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87
Rewinder
Presented at the Gaia Challenge 2 at the MPIA in Heidelberg.
Adrian Price-Whelan
October 30, 2014
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Transcript
REWINDER Adrian Price-Whelan (Columbia University) Kathryn Johnston, David Hogg, Sarah
Pearson, Andreas Küpper, Allyson Sheffield
Internal dynamics / disruption Underlying potential Streams encode info. about:
How to “fit” stream data? Need a generative model!
GRAVITY Progenitor Lagrange points
Stars Progenitor
Present Past Rewinder
None
Stripped star Progenitor
(Star orbit) - (Progenitor orbit)
x1 = ri · ˆ r prog ( t )
L prog (t), r prog (t), x3 = ri · ˆ L prog ( t ) x2 = ri · ˆ x2
Instantaneous orbital plane
Normalized by tidal radius
None
Incorrect potential
✓ The disruption is simple?
✓ At the (unknown) unbinding time for each star…
“The Pal 5 Challenge” with 4 stars: 3 leading arm
1 trailing arm
None
Previously… Price-Whelan et al. (2014) Nparams / 6Nstars Bug: Computationally
can only use a few stars Feature: We can infer the potential with a few stars!
Price-Whelan et al. (2014)
Now Use importance sampling to marginalize over “true” phase-space positions
of the stars Only params. of marginal likelihood are potential params., progenitor position, nuisance params. Price-Whelan et al. (in prep.)
Price-Whelan et al. (in prep.)
SMHASH Spitzer Merger History And Shape of the Halo RR
Lyrae stars: intrinsic 2% scatter in P-L relation in IR Johnston, Madore, Majewski, Besla, Bono, Clementini, Cioni, Cohen, Freedman, Grillmair, Kallivayalil, Kollmeier, Law, Marengo, Mondon, Nidever, Pietrzynski, Persson, Price-Whelan, Rich, Scowcroft, Seibert, Smith, Sesar, Soszynski, Thompson, Udalski, van der Marel (Madore & Freedman 2012) (+ Spitzer Cycle 9 work)
SMHASH Debris targets: ~30 stars in Orphan stream ~100 stars
in Sagittarius (Sgr) stream 2 Sgr globular clusters 20 Sgr core fields
None