Dark matter fraction in z ~1 star-forming galaxies

We present a observational study of the dark matter fraction in 225 rotation supported star-forming galaxies at z≈0.9 having stellar mass range: 9.0≤log(M∗ M⊙)≤11.0 and star formation rate: 0.49≤log(SFR [M⊙ yr−1])≤1.77. This is a sub sample of KMOS redshift one spectroscopic survey (KROSS) previously studied by \citet{GS20}. The stellar masses (M∗) of these objects were previously estimated using mass-to-light ratios derived from fitting the spectral energy distribution of the galaxies. Star formation rates were derived from the Hα luminosities. The total gas masses (Mgas) are determined by scaling relations of molecular and atomic gas \citep[][respectively] {Tacconi2018, Lagos2011}. The dynamical masses (Mdyn) are directly derived from the rotation curves (RCs) at different scale lengths (effective radius: Re, ∼2 Re and ∼3 Re) and then the dark matter fractions (fDM=1−Mbar/Mdyn) at these radii are calculated. We report that at z∼1 only a small fraction (∼5%) of our sample has a low (<20%) DM fraction within ∼ 2-3 Re. The majority (>72%) of SFGs in our sample have dark matter dominated outer disks (∼5−10 kpc) in agreement with local SFGs. Moreover, we find a large scatter in the fraction of dark matter at a given stellar mass (or circular velocity) with respect to local SFGs, suggesting that galaxies at z∼1, a) span a wide range of stages in the formation of stellar disks, b) have diverse DM halo properties coupled with baryons