Summary: Constraints on the Accuracy of Photometric Redshifts
Derived from BLAST and Herschel/SPIRE Sub­mm Surveys
Itziar Aretxaga  , David. H. Hughes  , Edward Chapin  and Enrique Gaztañaga 
 INAOE, Aptdo. Postal 51 y 216, 72000 Puebla, Mexico
Abstract. More than 150 galaxies have been detected in blank­field millimetre and sub­millimetre surveys.
However the redshift distribution of sub­mm galaxies remains uncertain due to the difficulty in identifying their
optical­IR counterparts, and subsequently obtaining their spectroscopic emission­line redshifts. In this paper
we discuss results from a Monte­Carlo analysis of the accuracy with which one can determine redshifts from
photometric measurements at sub­millimetre­FIR wavelengths. The analysis takes into account the dispersion
in colours introduced by including galaxies with a distribution of SEDs, and by including photometric and
absolute calibration errors associated with real observations. We present examples of the probability distribution
of redshifts for individual galaxies detected in the future BLAST and Herschel/SPIRE surveys. We show that the
combination of BLAST and 850µm observations constrain the photometric redshifts with sufficient accuracy to
pursue a program of spectroscopic follow­up with the 100m GBT.
DESCRIPTION OF THE TECHNIQUE AND RESULTS
Determining the density of star formation as a function of redshift is the primary science objective of the Balloon­
borne Large Aperture Submillimetre Telescope (BLAST, [1]) and other sub­mm/mm facilities. Using Monte­Carlo
simulations that take into account realistic photometric and absolute calibration errors for future BLAST surveys, we
show that it is possible to determine redshifts from BLAST data (at 250, 350 and 500µm) with a 1s average precision
of Dz 0:6. A similar level of redshift accuracy is found for simulated observations with the Herschel/SPIRE camera

Source: Aretxaga, Itziar - Instituto Nacional de Astrofísica Óptica y Electrónica

Collections: Physics