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

• DOI: 10.1093/mnras/stac658
• Publication Date: 2022-03-09T12:21:33Z
• Authors: Heyang Long; Jahmour J Givans; Christopher M Hirata
• Keywords: Baryon Acoustic Oscillations; Dark Ages; Scale height

The relative velocity between baryons and dark matter in the early Universe can suppress formation of small-scale baryonic structure leave an imprint on baryon acoustic oscillation (BAO) scale at low redshifts after reionization. This "streaming velocity" affects post-reionization gas distribution by directly reducing abundance pre-existing mini-halos ($\lesssim 10^7 M_{\bigodot}$) that could be destroyed reionization indirectly modulating history via photoionization within these mini-halos. In this work, we investigate effect streaming BAO feature HI 21 cm intensity mapping reionization, with a focus $3.5\lesssim z\lesssim5.5$. We build spatially modulated halo model includes dependence filtering mass local redshift thermal intergalactic gas. our fiducial model, find isotropic bias coefficients $b_v$ ranging from $-0.0043$ $z=3.5$ to $-0.0273$ $z=5.5$, which indicates is stretched (i.e., peaks shift lower $k$). particular, shifts transverse 0.121% ($z=3.5$) 0.35% ($z=5.5$) radial 0.167% 0.505% ($z=5.5$). These exceed projected error bars more ambitious proposed hemispherical-scale surveys (0.13% $1\sigma$ per $\Delta z = 0.5$ bin).