Photometric redshifts in the SWIRE Survey

We present the SWIRE Photometric Redshift Catalogue 1 025 119 redshifts of unprecedented reliability and of accuracy comparable with or better than previous work. Our methodology is based on fixed galaxy and quasi-stellar object templates applied to data at 0.36¿4.5 µm, and on a set of four infrared emission templates fitted to infrared excess data at 3.6¿170 µm. The galaxy templates are initially empirical, but are given greater physical validity by fitting star formation histories to them, which also allows us to estimate stellar masses. The code involves two passes through the data, to try to optimize recognition of active galactic nucleus (AGN) dust tori. A few carefully justified priors are used and are the key to supression of outliers. Extinction, AV, is allowed as a free parameter. The full reduced ¿2¿ (z) distribution is given for each source, so the full error distribution can be used, and aliases investigated.