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

Understand

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.