ALMA Lensing Cluster Survey: a strongly lensed multiply imaged dusty system at <i>z</i> ≥ 6

We report the discovery of an intrinsically faint, quintuply-imaged, dusty galaxy MACS0600-z6 at a redshift $z=$6.07 viewed through cluster MACSJ0600.1-2008 ($z$=0.46). A $\simeq4\sigma$ dust detection is seen 1.2mm as part ALMA Lensing Cluster Survey (ALCS), on-going Large program, and secured via [C II] 158 $\mu$m emission described in companion paper. In addition, spectroscopic follow-up with GMOS/Gemini-North shows break galaxy's spectrum, consistent Lyman that redshift. use detailed mass model infer magnification $\mu\gtrsim$30 for most magnified image this galaxy, which provides unprecedented opportunity to probe physical properties sub-luminous end cosmic reionisation. Based on spectral energy distribution, we lensing-corrected stellar masses $\rm{2.9^{+11.5}_{-2.3}\times10^9}$ $\rm{4.8^{+4.5}_{-3.4}\times10^6}$ $\rm{M_{\odot}}$ respectively, star formation rate $\rm{9.7^{+22.0}_{-6.6} M_{\odot} yr^{-1}}$, intrinsic size $\rm{0.54^{+0.26}_{-0.14}}$ kpc, luminosity-weighted age 200$\pm$100 Myr. Strikingly, production relatively young appears be larger than observed equivalent, lower sources. discuss if implies early supernovae are more efficient producers consequences using earlier formation.