We present spatially-resolved , rest-frame optical spectroscopy of a z \sim 3 Lyman-break galaxy ( LBG ) , Q0347-383 C5 , obtained with SINFONI on the VLT .
This galaxy , among the \sim 10 % brightest LBGs , is only the second z \sim 3 LBG observed with an integral-field spectrograph .
It was first described by Pettini et al .
( 2001 ) , who obtained WFPC2 F702W imaging and longslit spectroscopy in the K-band .
We find that the emission line morphology is dominated by two unresolved blobs at a projected distance of \sim 5 kpc with a velocity offset of \sim 33 km s ^ { -1 } .
Velocity dispersions suggest that each blob has a mass of \sim 10 ^ { 10 } M _ { \odot } .
Unlike Pettini et al .
( 2001 ) , our spectra are deep enough to detect H \beta , and we derive star-formation rates of \sim 20 - 40 M _ { \odot } yr ^ { -1 } , and use the H \beta / [ OIII ] ratio to crudely estimate an oxygen abundance 12 + [ O / H ] = 7.9 - 8.6 , which is in the range typically observed for LBGs .
We compare the properties of Q0347-383 C5 with what is found for other LBGs , including the gravitationally lensed “ arc + core ” galaxy ( Nesvadba et al .
2006 ) , and discuss possible scenarios for the nature of the source , namely disk rotation , a starburst-driven wind , disk fragmentation , and merging of two LBGs .
We favor the merging interpretation for bright , extended LBGs like Q0347-383 C5 , in broad agreement with predicted merger rates from hierarchical models .