The low mass end of the neutral gas mass and velocity width functions of galaxies in $\Lambda$CDM

TL;DR

This study uses high-resolution simulations and semi-analytic models to examine the low-mass end of galaxy neutral gas and velocity functions, finding good agreement with observations and supporting the $ m f ext{Lambda} CDM$ model.

Contribution

It demonstrates that $ m f ext{Lambda} CDM$ predictions align with observed low-mass galaxy properties without fine-tuning, clarifying previous tensions from abundance matching methods.

Findings

Good agreement between simulations and ALFALFA survey data.

Dark matter halo properties match observational inferences.

No discrepancy with $ m f ext{Lambda} CDM$ predictions at low masses.

Abstract

We use the high-resolution Aquarius cosmological dark matter simulations coupled to the semi-analytic model by Starkenburg et al. (2013) to study the HI content and velocity width properties of field galaxies at the low mass end in the context of $\Lambda$CDM. We compare our predictions to the observed ALFALFA survey HI mass and velocity width functions, and find very good agreement without fine-tuning, when considering central galaxies. Furthermore, the properties of the dark matter halos hosting galaxies, characterised by their peak velocity and circular velocity at 2 radial disk scalelengths overlap perfectly with the inferred values from observations. This suggests that our galaxies are placed in the right dark matter halos, and consequently at face value, we do not find any discrepancy with the predictions from the $\Lambda$CDM model. Our analysis indicates that previous tensions, apparent when using abundance matching models, arise because this technique cannot be straightforwardly applied for objects with masses $M_{vir} < 10^{10} M_{\odot}$.