ESO Science Archive facility and reduced them with the publicly available CRUSH (version 2.12–2) pipeline [@Kovacs2006; @Kovacs2008]. We used the algorithm settings optimized for deep field observations[^4]. The output of CRUSH includes an intensity map and a noise map. The mapped area extends over approximately 1.4 square degrees with a non-uniform noise that increases toward the edges of the field. In this work we use the inner $\sim$0.7deg$^2$ of the map where a fairly uniform sensitivity of $\sim$4.3 mJy/beam is reached (Pannella et al. in prep.) with a smoothed beam size of $\sim$27.6". Contrary to SPIRE data, which are confusion limited, LABOCA data are noise limited and the maps are thus beam-smoothed to minimize their RMS.

AzTEC data
----------

An area of 0.72deg$^2$ was scanned by the AzTEC bolometer camera mounted on the Atacama submillimeter telescope experiment (ASTE). The sensitivity in the center of the field is 1.23mJy RMS and the PSF FWHM after beam-smoothing is 34" [@Aretxaga2011].\

Methods {#stackfit}
=======

Sample selection
----------------

![\[fig:massdistr\] Stellar mass distribution of our samples of star-forming galaxies in the various redshift bins we used. Only galaxies more massive than our cut of $3\times 10^{10}\,\rm M_\odot$ are represented. The first bin contain fewer objects 