Roman as a Dark Energy Observatory: New Frontiers with Weak Lensing
| Program ID | 19020 |
|---|---|
| Science Category | Large Scale Structure of the Universe |
| Program Type | Analysis |
| Category | Small |
| Principal Investigator | Vivian Miranda |
| PI Institution | State University of New York, Stony Brook |
| Co-Investigators |
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| Abstract | Current tensions among CMB, BAO, weak-lensing, and local measurements suggest that the agent driving cosmic acceleration may be more complex than the standard picture of smooth dark energy. In this proposal, we use Roman as a dark-energy observatory by asking a simple question with powerful consequences: Does the growth of cosmic structure follow the expansion history expected in that standard picture? If not, Roman could reveal new physics behind cosmic acceleration. Our focus is on cosmic shear, one of Roman’s strongest probes of the low-redshift Universe. Roman is especially well-suited to this test because it measures weak lensing over a broad range of redshifts and angular scales. Much of that information, however, is on scales where gravitational collapse is already becoming nonlinear. So, current analyses often discard those modes in extended dark-energy studies. Our goal is to recover that signal with a new semi-analytic weak-lensing framework for mildly nonlinear scales, carefully validated in the presence of baryonic effects and intrinsic alignments. In parallel, we will build fast surrogate models that make it practical to explore large sets of forecasts, systematic tests, and likelihood analyses without sacrificing physical realism. We will then apply our developed machinery to well-motivated dark-energy scenarios that can change the growth of structure while leaving the expansion history nearly unchanged. Roman is uniquely powerful for this problem, as its deep lensing survey places more weight on modes where improved theory is most needed. Our final proposed product will be an open, Roman-ready analysis framework that expands the usable weak-lensing signal and strengthens Roman’s ability to test the fundamental physics of dark energy. |