Cosmic Microwave Background and Polarized Foregrounds
Supervisors: Angela Taylor, Mike Jones
A major goal in observational cosmology is to try to detect the 'B-mode' of the polarization of the cosmic microwave background, which is linked to the fundamental physics of inflation and the Big Bang. There is a huge experimental effort around the world both to build the telescopes that will detect the B-mode, and to understand the instrumental and confusing systematic effects that could either mask the polarization signal or give rise to false detections.
The Oxford team are involved in both primary B-mode CMB observaitions via the Simons Observatory, and in understanding the low-frequency foregrounds, concentrating on one of the key potential contaminants to the B-mode signal, polarized emission from synchrotron radiation in our own Galaxy. We also have a unique data set, from the C-Band All-Sky Survey (C-BASS), and close collaborations with other groups in Europe with similar experiments. In this project the student will use these data and other observations to improve our understanding of synchrotron contamination of the CMB, apply this to observations from the Simons Observatory, and predict the impact of foreground contamination on CMB experiments currently being developed.
Type Ia Supernova cosmology with the Rubin Observatory’s Legacy of Space and Time
Supervisors: Maria Vincenzi, Stephen Smartt
It's an exciting time for cosmology. Over the past 12 months, numerous independent cosmological studies have been published, each employing very different techniques (Type Ia Supernovae, Baryonic Acoustic Oscillations, Cosmic Microwave Background). Remarkably, all these findings seem to point to the same conclusion: the properties of Dark Energy are more complex than what we have previously understood.
Type Ia supernovae (SNe Ia) are among the most well-established tools in modern cosmology, with dozens of successful cosmological experiments conducted over the past three decades. The Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST), set to begin in January 2025, is expected to significantly transform the field. In just the first few months of observations, LSST will discover more SNe Ia than observed since the field began, thus revolutionizing SN Ia cosmological measurements and transient astronomy as a whole.
Our team is leading the preparation for the beginning of LSST and will be heavily involved in the analysis of the first LSST transient data. We work on a wide range of projects (both observations oriented and simulations oriented), revolving around the development and testing of transient discovery and classification pipelines, optimisation of LSST spectroscopic follow-up programs, and the design of new strategies to compile cosmological samples using LSST supernova data.
In collaboration with UK scientists, we are also leading the TiDES spectroscopic follow-up program, which will use the 4MOST spectrograph to follow up on tens of thousands of LSST transients and their host galaxies, providing crucial insights into their properties and redshifts.
The DPhil project will focus on preparing for future SN Ia cosmological measurements using LSST and TiDES data, with an emphasis on addressing key sources of uncertainty that impact these measurements.