Sunyaev-Zeldovich power spectrum measurements predictions for upcoming ground-based telescopes

Abstract

This work aimed to assess the detectability of the Sunyaev-Zeldovich (SZ) effects for upcoming highresolution ground-based telescopes such as the Simons Observatory (SO) and Fred Young Submillimeter Telescope (FYST). SZ effects describe how the energy of photons from the Comic Microwave Background (CMB), varies when they encounter galaxy clusters. The thermal Sunyaev-Zeldovich (tSZ) effect is the inverse Compton-scattering of the CMB photons on the hot electrons in the Intra-Cluster Medium (ICM). The kinematic Sunyaev-Zeldovich (kSZ) is a Doppler shift of the CMB photons due to the cluster’s motion compared to the CMB. The SZ signals are crucial for galaxy cluster detection, and measurements of cluster characteristics such as pressure, and shock events and to constrain cosmological parameters. High signal-to-noise (S/N) detection and purity of the SZ signals are essential to avoid biased measurements. SO LAT and FYST should provide unprecedented high-resolution maps of the microwave sky. This work estimates their performance on SZ power spectrum detection and purity. <br /> To predict howgood, simulations of the microwave sky had to be set up to reproduce their characteristics. Existing template maps from the Websky, SO, or Sehgal et al. (2010a) simulation were used to generate extra-galactic emissions, and the PySM Python package to generate the Galatic emissions. These maps are then brought to specific frequencies, through interpolation or the use of their Spectral Energy Distribution (SED) and processed to account for instrumental noise, beam, and atmospheric noise. This was built as an easy-to-use, versatile, and publicly available Python package to simulate high-resolution maps of the microwave sky, called the Skymodel. <br /> Using the Skymodel simulations of the microwave sky as seen by SO or FYST were generated. The goal was to make predictions of the detectability of the tSZ and purity, compared to its main contaminant, the Cosmic Infrared Background (CIB). A component separation method called Internal Linear Combination (ILC) was used to extract back the tSZ signal from the mock sky. It was found that combining SO and FYST capabilities would reduce the CIB noise residual in tSZ by ~ 35%. When applying a Constrained ILC (CILC) to null the CIB using its SED, it was found that the CIB noise could be further reduced by ~ 7% when combining SO and FYST but more importantly that the tSZ signal could be detected with an S/N above 1, on a harmonic space scales window (&ell; &isin; [1700, 3400]). <br /> To detect the weak kSZ effect signature, it is cross-correlated with the stronger tSZ effect, to form a new estimator C^yy²_kSZ_&ell;. The Skymodel is used to simulate a very simple sky approximation, containing only tSZ, kSZ, CMB, and instrumental noise. A CILC is applied, nulling CMB, to extract a tSZ map without kSZ, and another CILC deprojecting tSZ to extract a CMB map without tSZ and avoid spurious cross-correlation. A Wiener filter is used to separate the kSZ signal out of the CMB map. The result in such a simple case scenario is that a few sigma detections of the signal’s power spectrum should be possible with an experiment such as SO.