MIGHTEE-HI: Mass Models and Dark Matter properties

MIGHTEE-HI: Mass Models and Dark Matter properties
Anastasia A. Ponomareva, P. E. Mancera Pi~na, A. A. Vu{a}ru{a}c{s}teanu, M. Glowacki, H. Desmond, M. J. Jarvis, T. Yasin, I. Heywood, N. Maddox, E. A. K. Adams, M. Baes, A. Gebek, S. Kurapati, M. Maksymowicz-Maciata, K. A. Oman, H. Pan, I. Prandoni, S. H. A. Rajohnson, I. Ruffa, K. Spekkens
arXiv:2603.16992v1 Announce Type: new
Abstract: Measuring galaxy rotation curves is critical for inferring the properties of dark-matter haloes in the Lambda Cold Dark Matter ($Lambda$CDM) paradigm. We present HI rotation curves and mass models for 20 galaxies from the MIGHTEE survey. Using extended HI kinematics, we construct resolved mass models that include stellar, gaseous, and dark-matter components. Stellar masses are derived using 3.6 $mu$m imaging under fixed mass-to-light ratio ($Upsilon_{*} = M/L$) assumptions and are complemented, for the first time for a HI-selected sample, by spatially resolved $M/L$, obtained from multi-wavelength SED fitting. We examine the ratio of baryonic to observed rotation velocity ($V_{rm bar}/V_{rm obs}$) at the characteristic radius $R_{2.2}$. Adopting a fixed $Upsilon_star = 0.5,M_odot/L_odot$ yields a clear dependence of $V_{2.2}/V_{rm obs}$ on galaxy luminosity, while adopting $Upsilon_star = 0.2,M_odot/L_odot$ substantially weakens this trend. In contrast, the resolved $M/L$ analysis preserves the luminosity dependence while modifying the stellar contribution on a galaxy-by-galaxy basis, providing a more accurate representation of the underlying relation. We model the dark-matter haloes using Navarro-Frenk-White profiles and find that the different assumptions for a fixed a $M/L$ systematically shift galaxies relative to the theoretical stellar-to-halo mass and baryonic-to-halo mass relations, while the spatially varying $M/L$ yields the closest agreement with theoretical benchmarks within $Lambda$CDM. We therefore demonstrate that future investigations of the dark matter properties of galaxies using rotation curves need to account for varying $M/L$ across individual galaxy profiles and between galaxies in order to obtain accurate measurements of the dark matter, and therefore test $Lambda$CDM.arXiv:2603.16992v1 Announce Type: new
Abstract: Measuring galaxy rotation curves is critical for inferring the properties of dark-matter haloes in the Lambda Cold Dark Matter ($Lambda$CDM) paradigm. We present HI rotation curves and mass models for 20 galaxies from the MIGHTEE survey. Using extended HI kinematics, we construct resolved mass models that include stellar, gaseous, and dark-matter components. Stellar masses are derived using 3.6 $mu$m imaging under fixed mass-to-light ratio ($Upsilon_{*} = M/L$) assumptions and are complemented, for the first time for a HI-selected sample, by spatially resolved $M/L$, obtained from multi-wavelength SED fitting. We examine the ratio of baryonic to observed rotation velocity ($V_{rm bar}/V_{rm obs}$) at the characteristic radius $R_{2.2}$. Adopting a fixed $Upsilon_star = 0.5,M_odot/L_odot$ yields a clear dependence of $V_{2.2}/V_{rm obs}$ on galaxy luminosity, while adopting $Upsilon_star = 0.2,M_odot/L_odot$ substantially weakens this trend. In contrast, the resolved $M/L$ analysis preserves the luminosity dependence while modifying the stellar contribution on a galaxy-by-galaxy basis, providing a more accurate representation of the underlying relation. We model the dark-matter haloes using Navarro-Frenk-White profiles and find that the different assumptions for a fixed a $M/L$ systematically shift galaxies relative to the theoretical stellar-to-halo mass and baryonic-to-halo mass relations, while the spatially varying $M/L$ yields the closest agreement with theoretical benchmarks within $Lambda$CDM. We therefore demonstrate that future investigations of the dark matter properties of galaxies using rotation curves need to account for varying $M/L$ across individual galaxy profiles and between galaxies in order to obtain accurate measurements of the dark matter, and therefore test $Lambda$CDM.