Triaxiality can explain the alleged dark matter deficiency in some dwarf galaxies

TL;DR

This paper demonstrates that considering the triaxial shape of dwarf galaxies can explain the observed apparent lack of dark matter, challenging previous claims of DM-deficient dwarf galaxies.

Contribution

It introduces a Monte Carlo simulation showing the importance of galaxy triaxiality in mass measurements, questioning prior evidence for DM-deficient dwarf galaxies.

Findings

Triaxiality affects dynamical mass estimates from projected shapes.

Many purported DM-deficient dwarfs may be normal galaxies viewed face-on.

Reassessment of DM deficiency claims based on shape analysis.

Abstract

Dark Matter (DM) is an ingredient essential to the current cosmological concordance model. It provides the gravitational pull needed for the baryons to form galaxies. Therefore, the existence of galaxies without DM is both disquieting and extremely interesting. Guo et al. recently presented "further evidence for a population of DM-deficient dwarf galaxies", however, their analysis bypasses the triaxiality of the dwarf galaxies. We carry out a Monte Carlo simulation showing how triaxiality must be considered to measure dynamical masses from projected axial ratios, calling into question the evidence for a population of DM-deficient dwarf galaxies. Such a population may consist of normal almost face-on HI disks with their inclination overestimated.