The HI content of dark matter halos at $z\approx 0$ from ALFALFA

TL;DR

This study combines galaxy clustering data and HI content measurements to constrain the relation between dark matter halo mass and its neutral hydrogen content at redshift zero, providing insights into galaxy formation and the distribution of HI in the universe.

Contribution

It introduces a halo-model-based approach to jointly analyze clustering and HI content, constraining the $M_{HI}(M_h)$ relation with new parameters and comparing results with simulations.

Findings

Power-law index for $M_{HI}(M_h)$ is $0.44\u00b1 0.08$.

Minimum halo mass for HI content is $\, ext{log}_{10} M_{min} \,= 11.27^{+0.24}_{-0.30}$.

HI bias at $z=0$ is $0.875\u00b1 0.022$.

Abstract

We combine information from the clustering of HI galaxies in the 100% data release of the Arecibo Legacy Fast ALFA survey (ALFALFA), and from the HI content of optically-selected galaxy groups found in the Sloan Digital Sky Survey (SDSS) to constrain the relation between halo mass $M_h$ and its average total HI mass content $M_{\rm HI}$. We model the abundance and clustering of neutral hydrogen through a halo-model-based approach, parametrizing the $M_{\rm HI}(M_h)$ relation as a power law with an exponential mass cutoff. To break the degeneracy between the amplitude and low-mass cutoff of the $M_{\rm HI}(M_h)$ relation, we also include a recent measurement of the cosmic HI abundance from the $\alpha$.100 sample. We find that all datasets are consistent with a power-law index $\alpha=0.44\pm 0.08$ and a cutoff halo mass $\log_{10}M_{\rm min}/(h^{-1}M_\odot)=11.27^{+0.24}_{-0.30}$. We compare these results with predictions from state-of-the-art magneto-hydrodynamical simulations, and find both to be in good qualitative agreement, although the data favours a significantly larger cutoff mass that is consistent with the higher cosmic HI abundance found in simulations. Both data and simulations seem to predict a similar value for the HI bias ($b_{\rm HI}=0.875\pm0.022$) and shot-noise power ($P_{\rm SN}=92^{+20}_{-18}\,[h^{-1}{\rm Mpc}]^3$) at redshift $z=0$.