Dark matter fraction in disk-like galaxies over the past 10 Gyr

We present an observational study of the dark matter fraction in star-forming disk-like galaxies up to redshift z ∼ 2.5 selected from publicly available integral field spectroscopic surveys: KMOS3D, KGES, and KROSS. To model the Hα kinematics of these galaxies, we employed 3D forward modeling, which incorporates beam-smearing and inclination corrections and yields rotation curves. Subsequently, we corrected these rotation curves for gas pressure gradients, resulting in circular velocity curves or ‘intrinsic’ rotation curves. Our final sample comprises 263 rotationally supported galaxies with redshifts ranging from 0.6 ≤ z < 2.5, stellar masses within the range 9.0 ≤ log(Mstar [M⊙]) < 11.5, and star formation rates between 0.49 ≤ log(SFR [M⊙ yr−1]) ≤ 2.5. We estimated the dark matter fraction of these galaxies by subtracting the baryonic mass from the total mass, where the total mass is derived from the intrinsic rotation curves. We provide novel observational evidence suggesting that at a fixed redshift, the dark matter fraction gradually increases with radius such that the outskirts of galaxies are dark matter dominated, similarly to local star-forming disk galaxies. This observed dark matter fraction exhibits a decreasing trend with increasing redshift, and on average, the fraction within the effective radius (up to the outskirts) remains above 50%, similar to the galaxies in the local Universe. We investigated the relationships between dark matter, baryon surface density, and the circular velocity of galaxies. We observed that low stellar mass galaxies, with log(Mstar [M⊙]) ≤ 10.0, undergo a higher degree of evolution, which may be attributed to the hierarchical merging of galaxies. We discuss several sources of uncertainties and current limitations in the field as well as their impact on the measurements of the dark matter fraction and its trend across galactic scales and cosmic time.