We present a comprehensive analysis of the rest-frame UV to near-IR spectral energy distributions and rest-frame optical spectra of four of the brightest gravitationally lensed galaxies in the literature : RCSGA 032727-132609 at z = 1.70 , MS1512-cB58 at z = 2.73 , SGAS J152745.1+065219 at z = 2.76 and SGAS J122651.3+215220 at z = 2.92 .
This includes new Spitzer imaging for RCSGA0327 as well as new spectra , near-IR imaging and Spitzer imaging for SGAS1527 and SGAS1226 .
Lensing magnifications of 3-4 magnitudes allow a detailed study of the stellar populations and physical conditions .
We compare star formation rates as measured from the SED fit , the H \alpha and [ O II ] \lambda 3727 emission lines , and the UV+IR bolometric luminosity where 24 \mu m photometry is available .
The SFR estimate from the SED fit is consistently higher than the other indicators , which suggests that the Calzetti dust extinction law used in the SED fitting is too flat for young star-forming galaxies at z \sim 2 .
Our analysis finds similar stellar population parameters for all four lensed galaxies : stellar masses 3 - 7 \times 10 ^ { 9 } M _ { \odot } , young ages \sim 100 Myr , little dust content E ( B - V ) =0.10-0.25 , and star formation rates around 20-100 M _ { \odot } yr ^ { -1 } .
Compared to typical values for the galaxy population at z \sim 2 , this suggests we are looking at newly formed , starbursting systems that have only recently started the build-up of stellar mass .
These results constitute the first detailed , uniform analysis of a sample of the growing number of strongly lensed galaxies known at z \sim 2 .