paper

MSA-3D: Rotation Curves and Dark Matter Fractions at z~0.5-1.7 with JWST/NIRSpec

arXiv:2606.27853

Abstract

We present rotation curves and inner mass distributions for 30 star-forming galaxies at $0.5 < z < 1.7$ , observed with JWST/NIRSpec as part of the MSA-3D Cycle 1 survey. Combining spatially resolved ionised-gas kinematics with JWST/NIRCam imaging, we constrain baryonic and dark matter contributions through forward dynamical modelling for galaxies extending down to stellar masses of $\sim 1 0^{9} M_{⊙}$ . For the 23 galaxies in our primary statistical sample, we find predominantly rotationally supported disks with intrinsic dispersions $I ¨ _{0} \sim 31$ -65 km s $^{- 1}$ and a wide range of dark matter fractions, $f_{D M} (R_{e}) \sim 0.1$ -0.9, with a median of 0.63 and substantial galaxy-to-galaxy scatter of $\sim 0.2$ dex. These results are supported by a complementary consistency check using stellar mass maps and SFR-derived gas profiles. Among the 19 galaxies reaching $≳ 2 R_{e}$ , we identify six rising, six flat, and seven falling rotation curves. These classes define an observed ordering from rotationally dominated, dark-matter-rich disks ( $V_{r o t} / I ¨ _{0} \approx 4$ , $f_{D M} ≳ 0.7$ ) to more dispersion-supported systems with centrally concentrated baryonic mass distributions ( $V_{r o t} / I ¨ _{0} \approx 2$ , $f_{D M} ≲ 0.55$ ). The stellar Tully-Fisher relation lies close to the local relation evolved under the adopted self-similar $I^$ CDM scaling. A simplified seeing-degradation test shifts the inferred normalisation by ~0.2 dex at fixed $V_{c}$ , suggesting that spatial resolution contributes to, but does not fully explain, differences among high-redshift Tully-Fisher measurements. Overall, MSA-3D provides a high-resolution extension of previous surveys toward lower stellar masses, spanning $9.0 < lo g (M_{⋆} / M_{⊙}) < 11.2$ , and reinforces that star-forming disks near $z \sim 1$ span a broad range of dynamical states and inner mass distributions.

21 pages + 8 appendix + 15 supplementary material, 14 figures, submitted to A&A