Observational Cosmology Seminar

The Large Scale Structure (LSS) of the late-time universe contains information about primordial curvature perturbations. Of particular interest is the degree of non-Gaussianity of these early perturbations, parameterized by fNL, whose measurement would constrain models of inflation. This particular measurement is complicated by the fact that it is easiest to detect on the largest scales, which are also the scales most susceptible to observational systematics. The Spherical Fourier-Bessel (SFB) basis, in separating the angular and radial modes of the power spectrum, permits a targeted identification and mitigation of systematics in clustering surveys while retaining more cosmological signal than traditional Cartesian power spectrum analyses. I demonstrate this principle on the eBOSS DR16 LRG and QSO samples, identifying modes which may be contaminated by systematics. Using the SFB basis, I vary the selection of angular and radial modes to search for inconsistencies in the inferred value of fNL, an indicator of underlying systematics. In the QSO sample, I find evidence of a systematic afflicting large angular scales which is consistent with residual stellar contamination; I also find evidence for an unknown systematic in the QSO and LRG samples at the approximate angular plate and imaging scale of eBOSS. I will end with a forward look to doing blinded systematic discovery in DESI and SPHEREx with SFB.