Modeling the neutral hydrogen distribution in the post-reionization Universe: intensity mapping

Abstract

We model the distribution of neutral hydrogen (HI) in the post-reionization era and investigate its detectability in 21 cm intensity mapping with the future SKA radio telescope. We rely on high resolution hydrodynamical N-body simulations. The HI is assigned a-posteriori to the gas particles following two different approaches: a halo-based method in which HI is assigned only to gas particles residing within dark matter halos; a particle-based method that assigns HI to all gas particles using a prescription based on the physical properties of the particles. The HI statistical properties are then compared to the observational properties of Damped Lyman-$\alpha$ Absorbers (DLAs) and of lower column density systems and reasonable good agreement is found for all the cases. Among the halo-based method, we further consider two different schemes that aim at reproducing the observed properties of DLAs by distributing HI inside halos: one of this results in a much higher bias for DLAs, in agreement with recent observations, which boosts the 21 cm power spectrum by a factor $\sim 4$ with respect to the other recipe. We compute the 21 cm power spectrum from the simulated HI distribution and calculate the expected signal for both SKA1-mid and SKA1-low configurations at $2.4\le z\le 4$. We find that SKA will be able to detect the 21 cm power spectrum, in the non-linear regime, up to $k\sim 1h$/Mpc for SKA1-mid and $k\sim 5h$/Mpc for SKA1-low with 100 hours of observations. We also investigate the perspective of imaging the HI distribution. Our findings indicate that SKA1-low could detect the most massive HI peaks with a signal to noise ratio (SNR) higher than 5 for an observation time of about 1000 hours at $z=4$, for a synthesized beam width of $2^{\prime }$. Detection at redshifts $z⩾2.4$ with SKA1-mid would instead require a much longer observation time to achieve a comparable SNR level.

46 pages, 21 figures; published on JCAP

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Cited by in corpus (12)

• General Relativity and Cosmology: Unsolved Questions and Future Directions
• Baryonic acoustic oscillations from 21cm intensity mapping: the Square Kilometre Array case
• Imaging the redshifted 21-cm pattern around the first sources during the cosmic dawn using the SKA
• Theoretical and observational constraints on the HI intensity power spectrum
• Modelling redshift-space distortion in the post-reionization $\mathrm{HI}$ 21-cm power spectrum
• Multi-wavelength mock galaxy catalogs of the low-redshift Universe
• Redshift space distortions of the {\rm HI} 21-cm intensity mapping signal due to the internal motions within galaxies
• Probing Compensated Isocurvature with the 21-cm Signal during Cosmic Dawn
• The redshifted HI 21 cm signal from the post-reionization epoch: Cross-correlations with other cosmological probes
• Probing Quintessence using BAO imprint on the cross-correlation of weak lensing and post-reionization HI 21 cm signal
• Prospects of detecting HI using redshifted 21 cm radiation at z ~ 3
• Combined lensed estimator to probe the post reionization H I power spectrum