CMB-HD Foregrounds: Simulations, Source Detection, and Foreground Removal

Abstract

We present simulations of the microwave sky at 2.5 arcsecond resolution over 100 square degrees, generated from existing full-sky, lower-resolution simulations, and use them to demonstrate extragalactic foreground removal for a CMB-HD survey. Our cleaning method detects and removes the cosmic infrared background and radio galaxies, yielding source catalogs that are 95% complete down to flux limits of 0.008 and 0.04 mJy at 90 and 148 GHz, respectively. It also identifies and removes galaxy clusters via the thermal Sunyaev-Zel'dovich effect, producing a cluster sample that is nearly complete above $M_{500c}=5\times 10^{13}{M}_{\odot }$. After cleaning, the residual foreground-plus-noise power spectrum of the coadded 90 and 148 GHz temperature map is 50% higher than previous idealized estimates, increasing cosmological parameter uncertainties for an 11-parameter $\Lambda$CDM + $N_{\mathrm{eff}}$ + $\sum m_{\nu }$ + $T_{\mathrm{AGN}}$ + $A_{\mathrm{kSZ}}$ + $n_{\mathrm{kSZ}}$ model by less than 7%. The small impact on cosmological parameters reflects the strong constraining power of CMB polarization, the temperature-polarization cross spectra, and CMB lensing spectra reconstructed from polarization-only estimators, all of which are minimally affected by extragalactic foregrounds. In particular, the survey remains a sensitive probe of light thermal relic particles, achieving $\sigma (N_{\mathrm{eff}})=0.0154$, which can exclude any new species ($\Delta N_{\mathrm{eff}}\ge 0.027$) with at least 90% confidence. Our simulation and foreground-removal codes are publicly available and should aid the development of analysis pipelines for ultradeep, ultrahigh-resolution microwave surveys.

35 pages, 19 figures, 8 tables. The simulations are available at https://lambda.gsfc.nasa.gov/simulation/ultrahigh_resolution_sims.html , the simulation code is available at https://github.com/CMB-HD/hdsims , and the foreground cleaning code is available at https://github.com/CMB-HD/hdfgclean