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, School of Physics
A billion points of lightA billion points of light
Hugh Garsden, PhD StudentSupervisor: Geraint Lewis
OzLens 2008
, School of Physics
Area of Research …
• Anomalous flux ratios– Don’t fit theory/models
• Simulations show– due to microlensing– if add smooth matter– produces high demagnifications
Quasar Microlensing at High Magnification and the Role of Dark Matter: Enhanced Fluctuations and Suppressed Saddle Points. Schechter and Wambsganss, Ap. J. 2002.
Quasar MG 0414+0534
, School of Physics
Area of Research …
• Suggests magnification distributions are dependant on mass function
• Further simulations where smooth matter is “broken up” into compact matter objects– Compact objects all the same mass, but vary that
Qualitative Aspects of Quasar Microlensing with Two Mass Components: Magnification Patterns and Probability Distributions. Schechter, Wambsganss, Lewis, Ap. J. 2004.
, School of Physics
Area of Research …Two mass components x Two scenarios
Microlenses (M)+ smooth Microlenses (M)+ compact
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10% M (# lenses = 1,133)
90% smooth10% M (# lenses = 1,133)
90% 10-3 M (# lenses = 10,205,331)
There are large scale similarities
, School of Physics
Area of Research …• Compact matter can appear as smooth
matter. Size of source is important.Quasar Microlensing: When Compact Masses Mimic Smooth Matter.Lewis and Gil-Merino, Ap. J., 2006.
Smooth Matter and Source Size in Microlensing Simulations ofGravitationally Lensed Quasars. Bate, Webster, Wyithe, Mon. Not.R. Astron. Soc., 2008.
• Scale at which dark matter can be detected?– Suppose compact masses are dark matter candidates– Might appear as smooth matter
, School of Physics
Area of Research• Ongoing area of research
– Microlensing Simulations– Bi-modal mass distributions – Source size
• Reached an impasse“… significant numerical challengessignificant numerical challenges due to thenumber of microlensing massesnumber of microlensing masses that are needed[in simulations]”
Probing the Nature of Dark Matter With Gravitational Lensing.Lewis, Manchester Microlensing Conference, 2008.
, School of Physics
Software• microlens by Joachim Wambsganss• Gold standard for microlensing simulations• Sims limited to ~107 lenses due to memory• Modify
– Put lenses on disk– Parallelize
• One billion lenses in 3-4 days on supercomputer
, School of Physics
Why one billion?
• “Because it’s there”• “Because I can”• Really – needed for further simulations,
up to 1.3 billion
, School of Physics
Continuing work
• Developing the software• Probe the parameter space with more
simulations• More science coming!!! Watch this space.
Acknowledgement:Thanks to The Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Melbourne, for use of their supercomputer.