Kinematic scaling relations of disc galaxies from ionised gas at

We derive the Tully-Fisher (TFR; M* − Vcirc, f) and Fall (FR; j* − M*) relations at redshift z = 0.9 using a sample of 43 main-sequence disc galaxies with Hα IFU data and JWST/HST imaging. The strength of our analysis lies in the use of state-of-the-art 3D kinematic models to infer galaxy rotation curves, the inclusion of near-IR bands and their morphological modelling, and the application of homogeneous spectral energy distribution modelling to our photometry measurements to estimate stellar masses. After correcting the inferred Hα velocities for asymmetric drift, we find a TFR of the form log(M*/M⊙) = a log(Vcirc,f/ 150 km s−1 + b, with $ a = 3.82^{+0.55}_{-0.40} $ and $ b = 10.27^{+0.06}_{-0.07} $, as well as a FR of the form log(j*/kpc km s−1) = alog(M*/1010.5 M⊙)+b, with $ a = 0.44^{+0.06}_{-0.06} $ and $ b = 2.86^{+0.02}_{-0.02} $. Compared with their z = 0 counterparts, we found moderate evolution in the TFR and strong evolution in the FR over the past 8 Gyr. We interpreted our findings in the context of the galaxy-to-halo scaling parameters fM = M*/Mvir and fj = j*/jvir. We inferred that fj shows little redshift evolution and depends very weakly on M*, with typical values around fj ∼ 0.8. As for fM, we find it to be higher and less dependent on M* at z = 0.9 than at z = 0. We discuss how interpreting our observed fM − M* relations within the cold dark matter framework implies necessarily that the galaxy populations at z = 0.9 and z = 0 are not the progenitor nor descendant of one another. The alternative scenario is that the z = 0.9 scaling relations are incorrect due to strong selection effects, unidentified systematics, or the possibility that Hα kinematics may not be a reliable dynamical tracer. Such problems would affect not only our work but also previous studies on the same subject.