CMB Anisotropy Due to Filamentary Gas: Power Spectrum and Cosmological Parameter Bias

TL;DR

This paper models the impact of filamentary gas on CMB anisotropy via the SZ effect, revealing potential biases in cosmological parameters from future CMB observations due to this extended SZ signal.

Contribution

It introduces a model for filamentary gas morphology and gas properties, quantifies its SZ-induced anisotropy power spectrum, and assesses its bias on cosmological parameter estimation.

Findings

Filamentary gas contributes significantly to CMB anisotropy at certain scales.

Filament 'noise' can bias key cosmological parameters beyond statistical uncertainties.

Future CMB experiments are highly susceptible to biases from filamentary SZ signals.

Abstract

Hot gas in filamentary structures induces CMB aniostropy through the SZ effect. Guided by results from N-body simulations, we model the morphology and gas properties of filamentary gas and determine the power spectrum of the anisotropy. Our treatment suggests that power levels can be an appreciable fraction of the cluster contribution at multipoles $\ell\lesssim 1500$. Its spatially irregular morphology and larger characteristic angular scales can help to distinguish this SZ signature from that of clusters. In addition to intrinsic interest in this most extended SZ signal as a probe of filaments, its impact on cosmological parameter estimation should also be assessed. We find that filament `noise' can potentially bias determination of $A_s$, $n_s$, and $w$ (the normalization of the primordial power spectrum, the scalar index, and the dark energy equation of state parameter, respectively) by more than the nominal statistical uncertainty in Planck SZ survey data. More generally, when inferred from future optimal cosmic-variance-limited CMB experiments, we find that virtually all parameters will be biased by more than the nominal statistical uncertainty estimated for these next generation CMB experiments.