CMB Lensing
The large scale
structure in the universe deflects the cosmic microwave
background photons. The typical deflection is a couple of
arcminutes, but the deflection field is coherent over a
large range angular scales, up to about a few degrees. The
deflections smooth acoustic features in the primary cmb
anisotropy, moves power from large scales in the CMB to the
damping tail and generates non-Gaussianity.
With my advisor, Professor David Spergel, I study the effect and
its implications to cosmology both analytically and
through numerical simulations.
I also intend to look for this effect in the data from the
Atacama Cosmology Telescope (ACT) project.
Statistical Gravitational Lensing
With Professor Jeremiah P. Ostriker, I have
investigated how the probability of strong lensing of
a distant source by intervening structure depends on
the cosmology. We came up with a way to analytically
generate the probability density function of the dark
matter convergence from a given input cosmology. The
results have been published in the astrophysical journal, 645, 1 (2006).
CMB Power Spectrum Estimation
With Amir Hajian and David Spergel, I have
proposed a new method for estimating the power spectrum of
high resolution CMB maps. At the resolutions of ACT and the
South Pole Telescope (SPT) the CMB maps will be
contaminated with a large number of point sources which
need to be masked. Such masking and also hard edges lead to
aliasing of power, so that the mode-coupled power spectrum
is highly biased at high multipoles. This bias leads to
large error bars on the final power spectrum when standard
decorrelation techniques are used. We came up with a real
space operation called pre-whitening which effective
reduced aliasing of power. Also, we generalized a
technique, usually used in signal processing and known as
the Adaptive Multitaper Method (AMTM) to two dimensions to
deal with aliasing due to hard edges. With these methods,
we showed that at multipoles above 2000 we were able to
reduce the error bars over the standard methods by a large
factor.