Simon Samuroff’s research and participation on Dark Energy Survey (DES), presented in his Ph.D. thesis titled “Systematic Biases in Weak Lensing Cosmology with the Dark Energy Survey,” won him the 2017 URA Thesis Award, presented annually for outstanding work by a graduate student working at or in collaboration with Fermilab.
“Samuroff’s thesis is a truly outstanding example of the original and innovative research of a young physicist, enabled by Fermilab, honored by the URA Thesis Award,” said URA Executive Director Marta Cehelsky.
Samuroff built computer simulations to model the shapes of galaxies captured by the Dark Energy Camera (DECam), which was built by Fermilab is mounted on the Victor M. Blanco also known as the Blanco 4m, telescope at the Cerro Tololo Inter-American Observatory (CTIO) in north central Chile. Samuroff closely compared thousands of the simulations to actual images to determine the amount by which scientists’ initial estimates of these distortions are incorrect. He singled out miscues so the Dark Energy Camera could make improved measurements and be more sensitive to subtle effects of phenomena such as dark matter.
“The committee was impressed by both the quality of writing and the magnitude of his study — cataloging millions of galaxies or clusters and taking very small effects into account,” said Fermilab scientist Lenny Spiegel, chair of the URA Thesis Award Committee. “His work is invaluable to scientists studying mysteries regarding astrophysics, which may ultimately point the direction for future progress in particle physics.”
One of Samuroff’s major results showed that interactions between the images of neighboring galaxies that overlapped affected scientists’ measurements more severely than they realized. By identifying where and to what degree distortions like this cause inaccuracies, Samuroff helps scientists create a more reliable system of measurement.
His final product is one of two catalogs based on the first year of DES data. The catalogs contain painstaking measurements of the size, shape and relative distance of over 20 million galaxies, calibrated and tested according to Samuroff’s simulated images. Applying methods described in his thesis enables scientists to account for the skew created by specific types of image distortions — some of which introduce extra stretching of galaxies’ apparent shapes by as little as 1 percent. But when the distance is measured in light-years, galaxies produce a minuscule cosmic signal, and a 1 percent error is not to be ignored. Scientists have already begun referencing his catalog and will continue to use it in the future, improving their image analysis methods to make cosmological discoveries.
Samuroff earned his Ph.D. in 2017 at the University of Manchester under Professor Sarah Bridle, and is currently a postdoctoral research associate at Carnegie Mellon University specialising in cosmological weak lensing, or the deflection of light by large scale structure. Simon is an active member of the Dark Energy Survey (DES) and a member of the LSST Dark Energy Science Collaboration (DESC).
Samuroff will present his research and accept the URA Thesis Award June 20, during the two-day 51st Annual Users Meeting at Fermilab.
Source: Fermilab at Work, June 5, 2018