Lyman Break Galaxies (LBGs) form a substantial fracti...

We present 1.2 mm MAMBO-2 observations of a field which is over-dense in Lyman Break Galaxies (LBGs) at z ∼ 5. The field includes seven spectroscopically-confirmed LBGs contained within a narrow (z = 4.95 ± 0.08) redshift range and an eighth at z = 5.2. We do not detect any individual source to a limit of 1.6 mJy/beam (2 × rms). When stacking the flux from the positions of all eight galaxies, we obtain a limit to the average 1.2 mm flux of these sources of 0.6 mJy/beam. This limit is consistent with FIR imaging in other fields which are over-dense in UV-bright galaxies at z ∼ 5. Independently and combined, these limits constrain the FIR luminosity (8-1000µm) to a typical z ∼ 5 LBG of LFIR. 3 × 1011 L, implying a dust mass of Mdust. 108 M (both assuming a grey body at 30K). This LFIR limit is an order of magnitude fainter than the LFIR of lower redshift sub-mm sources (z ∼ 1 − 3). We see no emission from any other sources within the field at the above level. While this is not unexpected given millimetre source counts, the clustered LBGs trace significantly over-dense large scale structure in the field at z = 4.95. The lack of any such detection in either thi