The Lynx arc , with a redshift of 3.357 , was discovered during spectroscopic follow-up of the z = 0.570 cluster ( catalog ) from the ROSAT Deep Cluster Survey .
The arc is characterized by a very red R - K color and strong , narrow emission lines .
Analysis of HST WFPC 2 imaging and Keck optical and infrared spectroscopy shows that the arc is an H ii galaxy magnified by a factor of \sim 10 by a complex cluster environment .
The high intrinsic luminosity , the emission line spectrum , the absorption components seen in Ly \alpha and C iv , and the restframe ultraviolet continuum are all consistent with a simple H ii region model containing \sim 10 ^ { 6 } hot O stars .
The best fit parameters for this model imply a very hot ionizing continuum ( T _ { BB } \simeq 80 , 000 K ) , high ionization parameter ( \log U \simeq - 1 ) , and low nebular metallicity ( Z / Z _ { \odot } \simeq 0.05 ) .
The narrowness of the emission lines requires a low mass-to-light ratio for the ionizing stars , suggestive of an extremely low metallicity stellar cluster .
The apparent overabundance of silicon in the nebula could indicate enrichment by past pair instability supernovæ , requiring stars more massive than \sim 140 M _ { \odot } .