Rebecca Levinson

I am a sixth year graduate student at MIT. I am working with Paul Schechter on weak gravitational lensing in galaxy clusters and formerly telescope aberrations. This means that day to day, I create, implement in code, and fine-tune analytic models in order to better describe physical phenomena such as the deflecions of light due to gravitational lenses or telescope optics. I curve fit, to test models against real data. Most of my time is spent at a computer, but some of it is spent at a telescope, collecting data.

Research

Gravitational Flexion

My gravitational flexion work is ongoing. I am primarily concerned with measuring halo truncation of galaxies in galaxy clusters.

• For those unfamiliar with the lingo, this means that I am trying to see how the dark matter (invisible mass) of galaxies in groups changes depending on where the galaxies are in the groups. We expect the innermost galaxies to be skinnier because their mass is stolen away.
• For those who speak jive, I am using galaxy-galaxy lensing to measure halo truncation for galaxies within clusters. We expect tidal stripping to leave the innermost galaxies with narrower dark matter profiles than the outermost galaxies.

I observe at the Magellan telescopes using MegaCam. My primary lensing tool is gravitational flexion, which produces an apparent bending in lensed galaxy images. This bending (a combination of induced lopsidedness and triangularity), is detectable further away from lensing masses than the strong lensing signal. And while flexion is a more subtle effect than shear (the image stretching due to gravitational mass), galaxies are usually innately unflexed whereas they are often physically elliptical. Therefore flexion can be a less noisy signal than shear for measuring halo truncation.

The following two posters explain my work in slightly more detail. They are identical, except one used only the 'ten hundred' most common words in the English language. Feel free to click to view in more detail.

Optics

My optics work is detailed in Generic Misalignment Aberration Patterns in Wide Field Telescopes , and in the shorter paper the Generic Misalignment Aberration Patterns and the Subspace of Benign Misalignment . However the very short version is effectively this poster below.

DoPHOT in C

If you're into photometry, or just want a nice, stand-alone program to find and fit objects in your minimally cleaned fits images, check out DoPHOT . I rewrote in C and added some upgrades to Schechter, Mateo, and Saha 's 1990's curvefitting photometry program. It iteratively finds, fits to a PseudoGaussian (or function of your choosing), and subtracts objects from images, allowing for automated photometry and neighbor subtraction in fields.