HerMES: Herschel-SPIRE observations of Lyman Break Galaxies
  We present first results of a study of the submillimetre (rest frame
far-infrared) properties of z~3 Lyman Break Galaxies (LBGs) and their
lower-redshift counterparts BX/BM galaxies, based on Herschel-SPIRE
observations of the Northern field of the Great Observatories Origins Deep
Survey (GOODS-N). We use stacking analysis to determine the properties of LBGs
well below the current limit of the survey. Although LBGs are not detected
individually, stacking the infrared luminous LBGs (those detected with Spitzer
at 24 microns yields a statistically significant submm detection with mean flux
<S_{250}>= 5.9+/-1.4 mJy confirming the power of SPIRE in detecting UV-selected
high-redshift galaxies at submillimetre wavelengths. In comparison, the Spitzer
24 microns detected BX/BM galaxies appear fainter with a stacked value of
<S_{250}> = 2.7 +/-0.8 mJy. By fitting the Spectral Energy Distributions (SEDs)
we derive median infrared luminosities, L_{IR}, of 2.8x10^{12} Lsun and
1.5x10^{11} Lsun for z~3 LBGs and BX/BMs, respectively. We find that $L_{IR}
estimates derived from present measurements are in good agreement with those
based on UV data for z~2 BX/BM galaxies, unlike the case for z~3 infrared
luminous LBGs where the UV underestimates the true $L_{IR}. Although sample
selection effects may influence this result we suggest that differences in
physical properties (such as morphologies, dust distribution and extent of
star-forming regions) between z ~3 LBGs and z~2 BX/BMs may also play a
significant role.
