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arXiv · 1801.06546

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

E. M. Di Teodoro·C. Grillo·F. Fraternali·R. Gobat·W. Karman·A. Mercurio·P. Rosati·I. Balestra·G. B. Caminha·K. I. Caputi·M. Lombardi·S. H. Suyu·T. Treu·E. Vanzella
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Abstract

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 $z\simeq1.49$, has a stellar mass $M_*\simeq5\times10^9 \, \mathrm{M_\odot}$, a star-formation rate $\mathrm{SFR} \simeq1-6 \, \mathrm{M_\odot/yr}$ and represents a likely progenitor of a Milky-Way-like galaxy. All the four multiple images of Sp1149 in our data show strong OII-line emissions pointing to a clear rotation pattern. We take advantage of the gravitational lensing magnification effect ($\simeq 4 \times$) on the OII 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 $R\simeq1$ 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 $27\pm5$ 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 ($V / \sigma\simeq5$) spiral galaxy in a 4 Gyr old Universe.

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E. M. Di Teodoro, C. Grillo, F. Fraternali, R. Gobat, W. Karman, A. Mercurio, P. Rosati, I. Balestra, G. B. Caminha, K. I. Caputi, M. Lombardi, S. H. Suyu, T. Treu, E. Vanzella. 2018-01-19. Kinematics of the SN Refsdal host revealed by MUSE: a regularly rotating spiral galaxy at z~1.5. https://doi.org/10.1093/mnras%2Fsty175

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