Streaming velocity effects on the post-reionization 21-cm baryon acoustic oscillation signal

Author:

Long Heyang12ORCID,Givans Jahmour J34,Hirata Christopher M125

Affiliation:

1. Department of Physics, The Ohio State University , 191 West Woodruff Avenue, Columbus, OH 43210, USA

2. Center for Cosmology and AstroParticle Physics (CCAPP), The Ohio State University , 191 West Woodruff Avenue, Columbus, OH 43210, USA

3. Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08540, USA

4. Center for Computational Astrophysics, Flatiron Institute , 162 5th Ave, New York, NY 10010, USA

5. Department of Astronomy, The Ohio State University , 140 West 18th Avenue, Columbus, OH 43210, USA

Abstract

ABSTRACT The relative velocity between baryons and dark matter in the early Universe can suppress the formation of small-scale baryonic structure and leave an imprint on the baryon acoustic oscillation (BAO) scale at low redshifts after reionization. This ‘streaming velocity’ affects the post-reionization gas distribution by directly reducing the abundance of pre-existing mini-haloes ($\lesssim 10^7 {\rm M}_{\bigodot }$) that could be destroyed by reionization and indirectly modulating reionization history via photoionization within these mini-haloes. In this work, we investigate the effect of streaming velocity on the BAO feature in H i 21 cm intensity mapping after reionization, with a focus on redshifts 3.5 ≲ z ≲ 5.5. We build a spatially modulated halo model that includes the dependence of the filtering mass on the local reionization redshift and thermal history of the intergalactic gas. In our fiducial model, we find isotropic streaming velocity bias coefficients bv ranging from −0.0043 at z = 3.5 to −0.0273 at z = 5.5, which indicates that the BAO scale is stretched (i.e. the peaks shift to lower k). In particular, streaming velocity shifts the transverse BAO scale between 0.121 per cent (z = 3.5) and 0.35 per cent (z = 5.5) and shifts the radial BAO scale between 0.167 per cent (z = 3.5) and 0.505 per cent (z = 5.5). These shifts exceed the projected error bars from the more ambitious proposed hemispherical-scale surveys in H i (0.13 per cent at 1σ per Δz = 0.5 bin).

Funder

NASA

Publisher

Oxford University Press (OUP)

Subject

Space and Planetary Science,Astronomy and Astrophysics

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