Matthew Hasselfield

Research Associate

520 Davey Lab
University Park, PA 16802

Phone: +1 814-863-9342
Fax: +1 814-863-2842


matthew hasselfield

I am a cosmologist specializing in observations of the Cosmic Microwave Background (CMB). I work primarily with the Atacama Cosmology Telescope (ACT), contributing to its daily operation, data pipeline, and the cosmological interpretation of its maps and other data products. While CMB measurements from WMAP and the Planck satellite are a cornerstone of our current cosmological model, observatories such as ACT deepen this understanding by mapping the sky with increased sensitivity, higher resolution, and particular attention to the polarized component of the CMB. In combination with other cosmological probes, high resolution CMB observations help to understand the nature of Dark Matter and Dark Energy, to measure the energy density in cosmic neutrinos (and thus the neutrino masses), and to trace how structure in the Universe has evolved since the Big Bang.

I am also involved in using galaxy cluster counts to constrain cosmological parameters. As a result of the Sunyaev-Zeldovich effect (SZE), the gaseous envelopes of galaxy clusters leave an imprint on the CMB. The signature makes high-redshift, massive clusters clearly visible to ACT, and provides a signal that constrains each cluster’s mass. The distribution of clusters in mass and redshift is tied to very basic cosmological parameters (especially the matter density and the amplitude of scalar fluctuations), and the broad redshift coverage of SZE samples as well as the high fidelity of their mass measurements make them an especially interesting cosmological probe. As the statistical power of the SZE galaxy cluster samples increases, my attention has turned to securing accurate calibration of the galaxy cluster masses, and the development of analysis techniques for the reliable extraction of cosmological information.