A joint analysis of BLAST 250--500um and LABOCA 870um observations in
  the Extended Chandra Deep Field South
  We present a joint analysis of the overlapping BLAST 250, 350, 500um, and
LABOCA 870um observations (from the LESS survey) of the ECDF-S. Out to z~3, the
BLAST filters sample near the peak wavelength of far-infrared (FIR) emission
from galaxies (rest-frame wavelengths ~60--200um), primarily produced by dust
heated through absorption in star-forming clouds. However, identifying
counterparts to individual BLAST peaks is very challenging, given the large
beams (FWHM 36--60"). In contrast, the 870um observations have a significantly
smaller 19" FWHM beam, and are sensitive to higher redshifts (z~1--5, and
potentially beyond) due to the more favourable negative K-correction. We use
the LESS data, as well as deep Spitzer and VLA imaging, to identify 118
individual sources that produce significant emission in the BLAST bands. We
characterize the temperatures and FIR luminosities for a subset of 69 sources
which have well-measured submm SEDs and redshift measurements out to z~3. For
flux-limited sub-samples in each BLAST band, and a dust emissivity index
\beta=2.0, we find a median temperature T=30K (all bands) as well as median
redshifts: z=1.1 (interquartile range 0.2--1.9) for S250 > 40mJy; z=1.3
(interquartile range 0.6--2.1) for S350 > 30mJy; and z=1.6 (interquartile range
1.3--2.3) for S500 > 20mJy. Taking into account selection effects for our
survey (a bias toward detecting lower-temperature galaxies), we find no
evidence for evolution in the local FIR-temperature correlation out to z~2.5.
Comparing with star-forming galaxy SED templates, about 8% of our sample
appears to exhibit significant excesses in the radio and/or mid-IR, consistent
with those sources harbouring an AGN. We describe the following techniques in
two appendices: our `matched filter' for identifying sources in the presence of
point-source confusion; and our approach for identifying counterparts using
likelihood ratios.
