Cosmology with the Roman High Latitude Imaging Survey
PI: Olivier Doré / Jet Propulsion Laboratory
The most surprising cosmological discovery of the last decades has been the demonstration that the expansion of the universe is accelerating rather than decelerating. We have since measured the cosmic expansion history by multiple methods with much greater precision over a wide range of redshift, but understanding the origin of cosmic acceleration remains one of the most pressing unsolved problems in fundamental physics.
Alongside the expansion history, one can probe the physics of cosmic acceleration by measuring the growth of matter clustering from primordial fluctuations measured in the cosmic microwave background (CMB) to low redshift structure measured through weak gravitational lensing or redshift-space distortions of the galaxy distribution.
Measurements of structure growth are especially important for distinguishing theories that explain cosmic acceleration with an exotic energy component (a cosmological constant or more general “dark energy”) from theories that modify general relativity itself.
The Nancy Grace Roman Space Telescope (hereafter Roman) will be one of the most powerful facilities for weak lensing cosmology ever built; compared to the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (hereafter LSST), Roman measures a similar number of galaxy shapes per unit observing time with the high angular resolution and stability afforded by space-based observations. Forecasts imply that cosmological weak lensing in a 2000 square degree high-latitude imaging survey (HLIS) with Roman could lead to an order of magnitude improvement in precision over current measurements. Cross-correlations with galaxies and the masses and abundance of galaxy clusters will provide valuable additional cosmological information. To realize Roman’s cosmological goals, it is critical to control sources of systematic uncertainty and extract information from small scales and non-Gaussian statistics that are enabled by the gains in redshift coverage, galaxy number density and the quality of space based imaging with Roman. These measurements have the potential to revolutionize our understanding of cosmology, gravity, and fundamental physics.
We propose a program of infrastructure development that will enable the Roman high-latitude imaging survey to achieve its extraordinary cosmological potential, while simultaneously providing unprecedented volumes of exquisite data for an enormous range of astrophysical investigations. We have structured this proposal tightly around a list of deliverables, grouped under the broad categories of survey strategy, weak lensing measurements, cosmological inference, and community engagement. Our team is composed of leading experts on these topics, many of whom have been heavily involved with the Roman mission for a decade or more. The infrastructure proposed here will build heavily on the work that we have done over the past six years as members of the Science Investigation Team for cosmology with the HLIS. We look forward to working with the mission team and with scientists from the Science Operations Center (SOC), the Roman community, and the astronomy and cosmology community at large. Our program will build the infrastructure required to meet the relevant Roman cosmological science goals and will lay the foundations for future powerful joint analysis between Roman and other cosmological surveys such as DESI, Rubin, Euclid, SO and CMB-S4, which will greatly enhance the scientific impact of the Roman HLIS.