CRRfast: An emulator for the Cosmological Recombination Radiation with effects from inhomogeneous recombination

Understand

The Cosmological Recombination Radiation (CRR) is one of the guaranteed $\Lambda$CDM Spectral Distortion (SD) signals.

• Even if very small in amplitude, it provides a direct probe of the three recombination eras, opening the path for testing one of the key pillars in our cosmological interpretation of the measured CMB anisotropies.
• Here we develop a new emulator, CRRfast, to quickly and accurately represent the CRR for a wide range of cosmologies, using the state-of-the-art CosmoSpec code as a reference.
• CRRfast has been made publicly available both as stand-alone code and as part of CLASS, thereby completing the set of $\Lambda$CDM sources of SDs that can be modeled with CLASS.