The protogalaxy cB58 was discovered in the Canadian Network of Observational Cosmology (CNOC) survey of cluster redshifts. Absorption features reveal that this system is at a redshift of z = 2.72, implying an absolute magnitude of Mv∼ -26, and has a star formation rate of 4700 M⊙ yr-1, making it the most 'active' star-forming galaxy. This protogalaxy is observed to lie close (∼ 6 arcsec) to a central cluster galaxy at z = 0.373. The X-ray properties of the cluster suggest that its mass, and therefore its lensing potential, could be greater than that found using a virial analysis. In this Letter we argue that the phenomenal properties of this protogalaxy are due to the gravitational lensing effect of the foreground cluster, and the unlensed properties of the source are typical of high-redshift star-forming systems.
- Galaxies: clusters: general
- Galaxies: fundamental parameters
- Gravitational lensing