1. Introduction  
2. Observations  
2.1. Sample and ancillary data  
2.2. ALMA observations and data reduction  
2.3. FIR continuum measurements and detection fractions  
3. Analysis  
3.1. $L_{\mathrm{IR}}$ estimation from ALMA observations  
3.2. Stacking analysis  
4. Results  
4.1. IRX $\cdot\beta$ relation  
4.2. IRX $M_{\star}$ relation  
4.3. The obscured fraction of star formation  
5. Summary and conclusions