Tracing the Local Volume galaxy halo-to-stellar mass ratio with satellite kinematics

TL;DR

This study estimates the halo-to-stellar mass ratio of nearby galaxies using satellite kinematics, revealing variations with galaxy type and luminosity, and highlighting a subset of galaxies with declining rotation curves and low dark matter content.

Contribution

It provides new measurements of halo-to-stellar mass ratios for a large sample of nearby galaxies, including distinctions based on galaxy morphology and rotation curve behavior.

Findings

Average mass-to-light ratio for luminous galaxies is 31±6 M_sun/L_sun.

Dwarf galaxies have a mass-to-light ratio up to ~200 M_sun/L_sun.

Luminous spiral galaxies with declining rotation curves have a low mass-to-light ratio of 5.5±1.1 M_sun/L_sun.

Abstract

Rapid advance has been made recently in accurate distance measurements for nearby ($D < 11$ Mpc) galaxies based on the magnitude of the tip of red giant branch stars resolved with the Hubble Space Telescope. We use observational properties of galaxies presented in the last version of Updated Nearby Galaxy Catalog to derive a halo mass of luminous galaxies via orbital motion of their companions. Our sample contains 298 assumed satellites with known radial velocities around 25 Milky Way-like massive galaxies and 65 assumed satellites around 47 fainter dominant galaxies. The average total mass-to-$K$-band luminosity ratio is $31\pm6 M_\odot/L_\odot$ for the luminous galaxies, increasing up to $\sim200 M_\odot/L_\odot$ toward dwarfs. The bulge-dominated luminous galaxies are characterized with $\langle{}M_T/L_K\rangle = 73\pm15 M_\odot/L_\odot$, while the disc-dominated spirals have $\langle{}M_T/L_K\rangle = 17.4\pm2.8 M_\odot/L_\odot$. We draw attention to a particular subsample of luminous spiral galaxies with signs of declining rotation curve, which have a radial velocity dispersion of satellites less than 55 km/s and a poor dark matter halo with $\langle{}M_T/L_K\rangle = 5.5\pm1.1 M_\odot/L_\odot$. We note that a fraction of quenched (dSph, dE) companions around Milky Way-like galaxies decreases with their linear projected separation as $0.75 \exp(-R_p/350\,\mathrm{kpc})$.