Intensity Mapping Foreground Cleaning with Generalized Needlet Internal Linear Combination

Abstract

Intensity mapping (IM) is a new observational technique to survey the large-scale structure of matter using spectral emission lines. IM observations are contaminated by instrumental noise and astrophysical foregrounds. The foregrounds are at least three orders of magnitude larger than the searched signals. In this work, we apply the Generalized Needlet Internal Linear Combination (GNILC) method to subtract radio foregrounds and to recover the cosmological HI and CO signals within the IM context. For the HI IM case, we find that GNILC can reconstruct the HI plus noise power spectra with 7.0% accuracy forz= 0.13 − 0.48 (960 − 1260 MHz) and ℓ ≲ 400, while for the CO IM case, we find that it can reconstruct the CO plus noise power spectra with 6.7% accuracy forz= 2.4 − 3.4 (26 − 34 GHz) and ℓ ≲ 3000.

The Dark Sector Cosmology

“…Different techniques exploring different characteristics about foregrounds or about 21cm signal are available or under development to disentangle the signals. As an example we cite GNILC [40][41][42] and GMCA 43 that are also used in case of the CMB. 44 Other lines and atoms or molecules can also be used in IM such as CO(1-0) b , CO(2-1), CO(3-2) among others.…”