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Redshift space distortions of the {\rm HI} 21-cm intensity mapping signal due to the internal motions within galaxies

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arxiv 1906.07032 v1 pith:ITEG54MC submitted 2019-06-17 astro-ph.CO

classification astro-ph.CO
keywords galaxiesmotionsredshiftlinesigmasignaldistortionseffect
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abstract

The {\rm HI} 21-cm intensity mapping signal experiences redshift space distortions due to the motion of the galaxies which contain the {\rm HI} as well as the motions of the {\rm HI} gas within the galaxies. A detailed modelling is essential if this signal is to be used for precision cosmology. Considering dark matter only simulations where the {\rm HI} is assumed to reside in galaxies which are associated with haloes, in this work we introduce a technique to incorporate the {\rm HI} motions within the galaxies. This is achieved through a line profile which accounts for both the rotational and random (thermal and turbulent) motions of the {\rm HI} within galaxies. The functional form of the double horned line profiles used here is motivated by observations of $z=0$ spiral galaxies. Analyzing the simulated 21-cm power spectrum over the redshift range $1 \le z \le 6$ we find that the {\rm HI} motions within galaxies makes a significant contribution that is manifested as an enhancement in the Finger of God (FoG) effect which can be modelled reasonably well through a Lorentzian damping profile with a single free parameter $\sigma_p$. The value of $\sigma_p$ is significantly enhanced if motions within the galaxies are included. This is particularly important at $z>3$ where $\sigma_p$ is dominated by the internal motions and a measurement of the FoG effect here could provide a handle on the line profiles of high redshift galaxies.

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Forward citations

Cited by 5 Pith papers

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. OpenAlex reports about 19 citations worldwide. Full citation record

  1. Simulation-Based Priors for HI Bias from Halo Occupation Physics

    astro-ph.CO 2026-07 conditional novelty 6.0 of 10

    A conditional normalizing flow learned from two simulation suites maps HI halo-occupation parameters to EFT bias parameters, producing correlated non-Gaussian priors that are much tighter than flat priors for 21 cm analyses.

  2. Tracing Signatures of Modified Gravity in Redshift-Space Galaxy Bispectrum Multipoles: Prospects for Euclid

    astro-ph.CO 2025-08 unverdicted novelty 6.0 of 10

    In Hu-Sawicki f(R) gravity the redshift-space bispectrum monopole and quadrupole show 2-8% deviations from GR at z=0.7 and k~0.3 h/Mpc with forecasted SNR of 30 and 15 for Euclid.

  3. Modeling the HI-Halo Connection: Evolution, Scatter, and a Halo-based Prescription for 21-cm Mock Catalogs

    astro-ph.CO 2026-07 accept novelty 5.0 of 10

    A prescription fitted to GAEA2023 reproduces the median HI-halo mass relation and its scatter using halo spin and concentration, enabling realistic 21-cm mock catalogs.

  4. Cosmology with Multi-Wavelength Line Intensity Mapping Synergies in the SKAO Era

    astro-ph.CO 2026-06 unverdicted novelty 2.0 of 10

    Reviews how cross-correlating SKAO 21-cm LIM with other lines like [CII], CO, and Ly-alpha can mitigate systematics, enhance sensitivity, and disentangle cosmological from astrophysical parameters.

  5. Cosmology with Intensity Mapping via Statistics Beyond the Power Spectrum in the SKAO Era

    astro-ph.CO 2026-06 unverdicted novelty 2.0 of 10

    Reviews multiple higher-order statistics for 21-cm intensity mapping and forecasts their detectability with SKAO, incorporating noise and foreground effects.

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