Impact of astrophysics on cosmology forecasts for 21 cm surveys

Abstract

We use the results of previous work building a halo model formalism for the distribution of neutral hydrogen, along with experimental parameters of future radio facilities, to place forecasts on astrophysical and cosmological parameters from next generation surveys. We consider 21 cm intensity mapping surveys conducted using the BINGO, CHIME, FAST, TianLai, MeerKAT and SKA experimental configurations. We work with the 5-parameter cosmological dataset of {${\Omega }_m,{\sigma }_8,h,n_s,{\Omega }_b$} assuming a flat $\Lambda$CDM model, and the astrophysical parameters {$v_{c,0},\beta$} which represent the cutoff and slope of the HI- halo mass relation. We explore (i) quantifying the effects of the astrophysics on the recovery of the cosmological parameters, (ii) the dependence of the cosmological forecasts on the details of the astrophysical parametrization, and (iii) the improvement of the constraints on probing smaller scales in the HI power spectrum. For an SKA I MID intensity mapping survey alone, probing scales up to ${\ell }_{\max }=1000$, we find a factor of $1.1-1.3$ broadening in the constraints on ${\Omega }_b$ and ${\Omega }_m$, and of $2.4-2.6$ on $h$, $n_s$ and ${\sigma }_8$, if we marginalize over astrophysical parameters without any priors. However, even the prior information coming from the present knowledge of the astrophysics largely alleviates this broadening. These findings do not change significantly on considering an extended HIHM relation, illustrating the robustness of the results to the choice of the astrophysical parametrization. Probing scales up to ${\ell }_{\max }=2000$ improves the constraints by factors of 1.5-1.8. The forecasts improve on increasing the number of tomographic redshift bins, saturating, in many cases, with 4 - 5 redshift bins. We also forecast constraints for intensity mapping with other experiments, and draw similar conclusions.

11 pages, 9 figures, 2 tables; version accepted for publication in MNRAS

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• Cross-correlating 21 cm and galaxy surveys: implications for cosmology and astrophysics
• Extracting HI Astrophysics from Interferometric Intensity Mapping
• Redshift space distortions of the {\rm HI} 21-cm intensity mapping signal due to the internal motions within galaxies
• Beyond $\Lambda$CDM with HI intensity mapping: robustness of cosmological constraints in the presence of astrophysics
• Modelling the post-reionization neutral hydrogen ($\mathrm{HI}$) 21-cm bispectrum
• Modeling assembly bias with machine learning and symbolic regression
• Cosmological constraints from low redshift 21 cm intensity mapping with machine learning
• Unveiling the Universe with Emerging Cosmological Probes
• Towards Optimal Foreground Mitigation Strategies for Interferometric HI Intensity Mapping in the Low-Redshift Universe
• A Multi-messenger view of Cosmic Dawn: Conquering the Final Frontier
• The effect of finite halo size on the clustering of neutral hydrogen
• 21 cm Intensity Mapping with the DSA-2000