We propose to address these questions about the astrophysics focused telescope assets (afta) implementation of the wide- field infra-red survey telescope (wfirst): (1) what constraints does…

This is a $149,967 grant awarded by the National Aeronautics and Space Administration (NASA) to The Johns Hopkins University to develop simulation tools to evaluate the impact of mission design parameters on the ability of the Wide-Field Infrared Survey Telescope (WFIRST) Astrophysics Focused Telescope Assets (AFTA) to constrain cosmological parameters related to inflation and dark energy. The grant is focused on assessing how variations in factors like sky area, observing duration, sensitivity, and astrophysical assumptions would affect WFIRST/AFTA's ability to provide insights into the early and late-time accelerated expansion of the universe. This work is intended to provide the WFIRST/AFTA study office with detailed analysis to inform the mission design. The grant does not have a set-aside designation and is scheduled to be completed by April 23, 2018.

We propose to address these questions about the astrophysics focused telescope assets (afta) implementation of the wide- field infra-red survey telescope (wfirst): (1) what constraints does wfirst/afta place on inflationary and dark energy cosmological parameters for a given set of nominal instrument design and observing parameters? (2) how do these constraints change with variations in mission parameters (sky area, observing duration, sensitivity, purity, astrophysical assumptions, etc.)? And (3) how should requirements or capabilities be included in the design to ensure the dark energy and inflation parameter estimates can be met? To answer these questions we propose to develop a set of simulation tools to better understand the dependencies of the cosmological results on the mission design. We emphasize that IT is not our intent to argue for particular changes to the mission, but rather to provide the wfirst/afta study office with insights, specific numbers, and functional dependencies so that the study office can make informed decisions. Early time accelerated expansion (inflation) and late time accelerated expansion (from dark energy) have physical similarities and differences. They are both, in their simplest form, exponential expansions with the equation of state parameter w = -1, yet they appear unrelated in the sense that they occur on vastly different energy scales. Neither is well understood, hence the strong desire for improved measurements. In a practical sense, the interpretation of future measurements are interdependent. Flatness (omega_k=0) is often assumed to deduce limits on w, or alternatively w = -1 is assumed to deduce limits on flatness. Baryon acoustic oscillations (BAO) are effectively differential and hence approximately independent of the detailed shape of the power spectrum, p(k), but if the afta galaxy redshift survey is used to deduce p(k), then there is a strong interaction between the interpretation of p(k) and inflation, including its assumptions and parameters. We propose to explore this interaction, and the mission's ability to place constraints for a range of instrumental, astrophysical, and observational conditions. The science definition team's afta report (spergel ET AL. 2013) states, "the broad-band shape of the galaxy power spectrum p(k) provides a second 'standard ruler' for geometrical measurements via the turnover scale imprinted by the transition from radiation to matter domination in the early universe, as well as a diagnostic for neutrino masses, extra radiation components, and the physics of inflation." IT further notes that to constrain dark energy IT is necessary to also constrain other cosmological parameters such as the hubble constant and the matter density (both values were recently reported by bennett ET AL. (2014)), as well as "the curvature omega_k, and the amplitude and spectral index of the inflationary fluctuation spectrum." rather than only treating these latter parameters as uncertainties to marginalize over to get dark energy constraints, we seek to study the constraints afta places on these inflationary parameters, both separately and jointly with dark energy constraints. Fortunately the afta survey design does not require a strong trade-off between achieving dark energy and inflation constraints; both tend to be strengthened or weakened together by varying survey parameters. We begin with tools we have already developed and propose to build increasingly detailed simulation and analysis tools to evaluate the afta galaxy redshift survey cosmological results as a function of mission specific input parameters.