Impact of Dust on Spectral Distortion Measurements of the Cosmic Microwave Background

Spectral distortions of the cosmic microwave background (CMB) are sensitive to energy injection by exotic physics in early universe. The proposed Primordial Inflation Explorer (PIXIE) mission has raw sensitivity provide meaningful limits on new physics, but only if foreground emission can be adequately modeled. We quantify impact interstellar dust Compton $y$ and $\mu$ measurements considering a range grain size distributions compositions constrained theoretical observational priors (Zelko & Finkbeiner 2020). find that PIXIE marginalize over modest number parameters still recover estimates, though with increased uncertainty. As more components included (synchrotron, free-free), estimates degrade, measurement sometimes considered for standard $\Lambda$CDM $2\times10^{-8}$ becomes infeasible without ancillary low-frequency information. An additional concern is absorption CMB monopole, subtle effect must included. one form model discrepancy error, finding error introduced fitting our medium modified blackbody too large spectral detectable. greatest challenge may infrared (CIB). extremely modeling choices CIB, biases expected assumptions.