We present optical and near-IR imaging and spectroscopy of SGAS J105039.6 + 001730 , a strongly lensed galaxy at z = 3.6252 magnified by > 30 \times , and derive its physical properties .
We measure a stellar mass of log ( M _ { * } /M _ { \odot } ) = 9.5 \pm 0.35 , star formation rates from [ O II ] \lambda \lambda 3727 and H- \beta of 55 \pm 25 and 84 \pm 24 M _ { \odot } yr ^ { -1 } , respectively , an electron density of n _ { e } \leq 10 ^ { 3 } cm ^ { -2 } , an electron temperature of T _ { e } \leq 14000 K , and a metallicity of 12 + log ( O/H ) = 8.3 \pm 0.1 .
The strong C III ] \lambda \lambda 1907,1909 emission and abundance ratios of C , N , O and Si are consistent with well-studied starbursts at z \sim 0 with similar metallicities .
Strong P Cygni lines and He II \lambda 1640 emission indicate a significant population of Wolf-Rayet stars , but synthetic spectra of individual populations of young , hot stars do not reproduce the observed integrated P Cygni absorption features .
The rest-frame UV spectral features are indicative of a young starburst with high ionization , implying either 1 ) an ionization parameter significantly higher than suggested by rest-frame optical nebular lines , or 2 ) differences in one or both of the initial mass function and the properties of ionizing spectra of massive stars .
We argue that the observed features are likely the result of a superposition of star forming regions with different physical properties .
These results demonstrate the complexity of star formation on scales smaller than individual galaxies , and highlight the importance of systematic effects that result from smearing together the signatures of individual star forming regions within galaxies .