There are no requirements on the completeness for the 3-band data release. The goal of the testing done on the 3-band data was to characterize the completeness.
To determine the completeness we have carried out two kinds of tests with the 3-band WISE data. First, a comparison was made for a field within the area covered by the 3-band release which also was observed by Spitzer with IRAC. There is one large extragalactic field, Elias N2 from the SWIRE project, covering about 2 square degrees, which was used for this purpose. Second, a comparison was made of the sources extracted from the 3-band WDB with the sources in the All-Sky catalog in this same Elias N2 field. These two tests are described more fully below.
The IRAC catalog made by SWIRE for the Elias N2 field is available from IRSA. This catalog has a 10 sigma limit of approximately 10/10/40 microJy in the IRAC ch1/ch2/ch4 bands, significantly deeper than the WISE 3-band data in the vast majority of the area covered by the WISE 3-band release. The W1/ch1 and W2/ch2 bandpasses are similar, while W3 is different from IRAC ch3, which should be kept in mind when assessing the completeness results. We extracted sources from the IRSA IRAC catalog in Elias N2 (centered at RA = 16:36:48, Dec=+41:01:45) down to an SNR = 10. Sources in the same area were extracted from the 3-band WDB with SNR > 5, and ccflag!=DHOP, separately in each band. These two criteria are the ones most important to completeness. Sources were positionally matched between the two catalogs (IRAC and 3-band) with a matching radius of 3 arcsec. The resulting fraction of matches of WISE sources to all sources in the selected IRAC catalog is the completeness fraction. We show the results for W1, W2, and W3 in the Elias N2 field in the following plots. As expected, the completeness is very similar in W1 and W2 to that found in the external comparisons of WISE data from the All-Sky release with IRAC data. The W3 completeness is lower at the same flux density compared to the completeness found in the All-Sky release completeness testing, although still high at the flux density corresponding to SNR=20.
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| Figure 1a - (left) Completeness in W1 as a function of IRAC ch1 flux density in the Elias N2 field. The vertical black dashed line represents an SNR=20. | Figure 1b - (center) Completeness in W2 as a function of IRAC ch2 flux density in the Elias N2 field. The vertical black dashed line represents an SNR=20. | Figure 1c - (right) Completeness in W3 as a function of IRAC ch4 flux density in the Elias N2 field. The vertical black dashed line represents an SNR=20. |
| Band | Flux Density (milli-Jy) |
|---|---|
| W1 | 0.100 |
| W2 | 0.120 |
| W3 | 3.0 |
In the same Elias N2 field, we obtained all of the sources in the All-Sky release catalog, and compared withsources selected from the WISE 3-band WDB again using the criteria w?snr > 5 and ccflags!=DHOP. The positional matching was done with a radius of 3 arcsec. The fraction of sources in the 3-band catalog to all of the sources in the All-Sky release is plotted in the following figures for W1, W2, and W3. These plots illustrate the relative completeness of the 3-band data vs the 4-band data in the All-Sky release and most useful for assesing the completeness in the W3 data in the 3-band release.
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| Figure 2a - (left) Completeness in W1 as a function of W1 All-Sky flux density in the Elias N2 field. The vertical black dashed line represents an SNR=20. | Figure 2b - (center) Completeness in W2 as a function of W2 All-Sky flux density in the Elias N2 field. The vertical black dashed line represents an SNR=20. | Figure 2c - (right) Completeness in W3 as a function of W3 All-Sky flux density in the Elias N2 field. The vertical black dashed line represents an SNR=20. |
Last update: 2011 June 12