Angular momentum content in gas-rich dwarf galaxies

Abstract

We derive the specific baryonic angular momentum of five gas-rich dwarf galaxies from H i kinematics complemented by stellar mass profiles. Since the gas mass of these galaxies is much larger than the stellar mass, the angular momentum can be determined with relatively little uncertainty arising from the uncertainties in the stellar mass-to-light ratio. We compare the relation between the specific baryonic angular momentum (j) and the total baryonic mass (M) for these galaxies with that found for spiral galaxies. Our combined sample explores the j–M plane over three orders of magnitude in baryon mass. We find that our sample dwarf has significantly higher specific angular momentum than expected from the relation found for spiral galaxies. The probability that these gas-rich dwarf galaxies follow the same relation as spirals is found to be <10−6. This implies a difference in the evolution of angular momentum in these galaxies compared to larger ones. We suggest that this difference could arise due to one or more of the following: a lower baryon fraction in dwarf galaxies, particularly that arising from preferential outflows low angular momentum gas as found in high-resolution simulations that include baryonic feedback; ‘cold mode’ anisotropic accretion from cosmic filaments. Our work reinforces the importance of the j–M plane in understanding the evolution of galaxies.