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We use Multi Unit Spectroscopic Explorer (MUSE) observations of the galaxycluster MACS J1149.5+2223 to explore the kinematics of the grand-design spiralgalaxy Sp1149 hosting the SN Refsdal. Sp1149 lies at $z\simeq1.49$, has astellar mass $M_*\simeq5\times10^9 \, \mathrm{M_\odot}$, a star-formation rate$\mathrm{SFR} \simeq1-6 \, \mathrm{M_\odot/yr}$ and represents a likelyprogenitor of a Milky-Way-like galaxy. All the four multiple images of Sp1149in our data show strong OII-line emissions pointing to a clear rotationpattern. We take advantage of the gravitational lensing magnification effect($\simeq 4 \times$) on the OII emission of the least distorted image to fit 3Dkinematic models to the MUSE data-cube and derive the rotation curve and thevelocity dispersion profile of Sp1149. We find that the rotation curve steeplyrises, peaks at $R\simeq1$ kpc and then (initially) declines and flattens to anaverage $V_\mathrm{flat} = 128^{+29}_{-19}$ km/s. The shape of the rotationcurve is well determined but the actual value of $V_\mathrm{flat}$ is quiteuncertain because of the nearly face-on configuration of the galaxy. Theintrinsic velocity dispersion due to gas turbulence is almost constant acrossthe entire disc with an average of $27\pm5$ km/s. This value is consistent with$z=0$ measurements in the ionized gas component and a factor 2-4 lower thanother estimates in different galaxies at similar redshifts. The averagestellar-to-total mass fraction is of the order of one fifth. Our kinematicanalysis returns the picture of a regular star-forming, mildly turbulent,rotation-dominated ($V / \sigma\simeq5$) spiral galaxy in a 4 Gyr old Universe.

Kinematics of the SN Refsdal host revealed by MUSE: a regularly rotating spiral galaxy at z~1.5