, 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 …

Two mass components

Microlenses (M) + smooth

, 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

, School of Physics

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

This is where I come in …

I can run bigger simulations with new software

, 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

10% M (# lenses = 1,133)

90% 10-5 M (# lenses = 1,020,533,131)

, 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.