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Appendix A: Comparison between blind and prior catalogues

Figure A.1 presents the comparison between the blind and prior catalogues in the GOODS-N and GOODS-S fields. These comparisons are restricted to the region of the field with exposure time higher than those mentioned in the second column of Table 2. For the GOODS-S 100 and 160 μm maps, this restriction corresponds to the central deepest region of the field, i.e., GOODS-S-ultradeep. The cross-identification of PACS blind and prior sources is based on their MIPS-24 μm positions, i.e., for the blind catalogues we use the PACS/MIPS-24 μm cross-identification performed using a maximum likelihood analysis (see Sect. 4.5). For each field and passband we present the direct comparison of flux densities for sources in common to both catalogues; the distribution of unmatched sources in absolute number; and the distribution of unmatched sources in fraction relative to total in the given flux density bin.

Flux densities extracted with these two independent source extraction methods are consistent with each other. At faint flux densities, there are however few outliers, with higher flux densities in the blind catalogues than in the prior catalogues. Such outliers are expected since blind source extraction is more severely affected by blending issues leading to the overestimation of PACS flux densities.

In the GOODS-N field the absolute number of unmatched sources in the blind and prior source catalogues are very

similar. At faint flux densities, the increase of the fraction of unmatched sources is likely explained by the increase of the incompleteness of our catalogues. Indeed, because our two source extraction methods are independent, at faint flux densities their incomplete samples might not fully overlap.

The blind GOODS-S 100 and 160  μm source catalogues contain a larger number of unmatched sources than the prior source catalogues. Some sources in “excess” in the blind catalogues should correspond to sources effectively missed by our prior extraction due to the lack of MIPS-24 μm counterparts (see Sect. 4.1). However, a significant fraction of the sources in “excess” in the blind catalogue should correspond to spurious detections, as in this field the contamination of the blind catalogues is supposed to be higher than that of the prior catalogues (see Table 2). The GOODS-N 100 μm, GOODS-S 100 μm and GOODS-S 160 μm blind catalogues also contain each one a bright source (i.e., > 8  mJy) missed by the prior extraction. Examining these sources, it turns out that they are not missed because of a lack of MIPS-24 μm priors, but likely correspond to “spurious” bright sources created by the blind extraction by over-deblending very bright and crowded regions of the field. Finally, we observe that the prior GOODS-S 70 μm source catalogue contains a larger number of unmatched sources as it reaches a slightly lower 3σ detection limit than the blind catalogue.

	Fig. A.1 Comparison between blind and prior source catalogues. (Left panel) Direct comparison of flux densities for sources in common to both catalogues. (Centre panel) Distribution of unmatched sources in absolute number. (Right panel) Distribution of unmatched sources in fraction relative to total in the given flux density bin.
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© ESO, 2013