The dark galaxy problem and compound gravitational lensing
Ben Metcalf (IofA Cambridge) - 10 Oct at 12:00 noon
I will show how observations of multiply--imaged quasars at high redshift
can be used to probe dark matter clumps within the lensing halos.
A large abundance of such satellites with masses greater than 10^7 solar
masses is predicted by numerical simulations of galaxy formation in cold
dark matter (CDM) cosmologies, but not in warm dark matter or interacting
dark matter models. In addition, I argue, CDM substructures
with masses below the resolution of these simulations are likely to be
even more numerous within galactic halos and contain no visible matter.
Numerical lensing simulations are used to show that this substructure
has important implications for the magnification ratios of quasar images
and the morphology of multiply imaged radio jets. The strength of these
effects will depend on the angular size of the QSO and thus
the wavelength of the observations.
The seminar will be held in 501 Campbell Hall.
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