We use Multi Unit Spectroscopic Explorer ( MUSE ) observations of the galaxy cluster MACS J1149.5+2223 to explore the kinematics of the grand-design spiral galaxy ( Sp1149 ) hosting the SN ‘ ‘ Refsdal ’ ’ .
Sp1149 lies at z \simeq 1.49 , has a stellar mass M _ { * } \simeq 5 \times 10 ^ { 9 } { M } _ { \odot } , a star-formation rate \mathrm { SFR } \simeq 1 - 6 { M _ { \odot } yr } ^ { -1 } and represents a likely progenitor of a Milky-Way-like galaxy .
All the four multiple images of Sp1149 in our data show strong \mathrm { [ O \textsc { ii } ] } -line emissions pointing to a clear rotation pattern .
We take advantage of the gravitational lensing magnification effect ( \simeq 4 \times ) on the \mathrm { [ O \textsc { ii } ] } emission of the least distorted image to fit 3D kinematic models to the MUSE data-cube and derive the rotation curve and the velocity dispersion profile of Sp1149 .
We find that the rotation curve steeply rises , peaks at R \simeq 1 kpc and then ( initially ) declines and flattens to an average { V _ { \mathrm { flat } } } = 128 ^ { +29 } _ { -19 } km/s .
The shape of the rotation curve is well determined but the actual value of { V _ { \mathrm { flat } } } is quite uncertain because of the nearly face-on configuration of the galaxy .
The intrinsic velocity dispersion due to gas turbulence is almost constant across the entire disc with an average of 27 \pm 5 km/s .
This value is consistent with z = 0 measurements in the ionized gas component and a factor 2-4 lower than other estimates in different galaxies at similar redshifts .
The average stellar-to-total mass fraction is of the order of one fifth .
Our kinematic analysis returns the picture of a regular star-forming , mildly turbulent , rotation-dominated ( V / \sigma \simeq 5 ) spiral galaxy in a 4 Gyr old Universe .