We present deep SINFONI K band integral field spectra of two submillimeter ( SMG ) galaxy systems : BR 1202-0725 and J1000+0234 , at z = 4.69 and 4.55 respectively .
Spectra extracted for each object in the two systems do not show any signature of the [ O ii ] \lambda \lambda 3726,29Å emission-lines , placing upper flux limits of 3.9 and 2.5 \times 10 ^ { -18 } erg s ^ { -1 } cm ^ { -2 } for BR 1202-0725 and J1000+0234 , respectively .
Using the relation between the star formation rate ( SFR ) and the luminosity of the [ O ii ] doublet from \citet kennicutt98 , we estimate unobscured SFR upper limits of \sim 10 - 15 M _ { \odot } yr ^ { -1 } and \sim 30 - 40 M _ { \odot } yr ^ { -1 } for the objects of the two systems , respectively .
For the SMGs , these values are at least two orders of magnitude lower than those derived from SED and IR luminosities .
The differences on the SFR values would correspond to internal extinction of , at least , 3.4 - 4.9 and 2.1 - 3.6 mag in the visual for BR 1202-0725 and J1000+0234 SMGs , respectively .
The upper limit for the [ O ii ] -derived SFR in one of the LAEs ( Ly \alpha 2 ) in the BR1202-0725 system is at least one order of magnitude lower than the previous SFR derived from infrared tracers , while both estimates are in good agreement for Ly \alpha 1 .
The lower limits to the internal extinction in these two Lyman-alpha emitters ( LAEs ) are 0.6 mag and 1.3 mag , respectively .
No evidence for the previously claimed \citep ohta00 [ O ii ] emission associated with Ly \alpha 1 is identified in our data , implying that residuals of the K-band sky emission lines after subtraction in medium-band imaging data could provide the adequate flux .