What are the sensitivity limits, completeness, and reliability vs. exposure time and background level for the GALEX ERO catalogs?
The completeness and reliability of the GALEX catalogs are functions of the sensitivity limit set, the exposure time, and the background level. The local source density is of course an additional important factor. The exact relationships are still a topic of investigation by the GALEX Science Team. Some benchmark estimates have been established using the initial three months of survey data. Completeness and reliability have been investigated using multiple visits to the same fields, using MIS and DIS observations of AIS fields, and by using artificial subvisits created from MIS visits. Reliability has been studied using combined FUV and NUV catalogs, and by comparing GALEX with other catalogs such as SDSS.
The completeness and reliability of the GALEX catalogs are functions of the sensitivity limit, the exposure time, and the background level. The local source density is of course an additional important factor. The exact relationships are still a topic of investigation by the GALEX Science Team. Some estimates have been established using the initial three months of survey data: completeness and reliability have been investigated using multiple visits to the same fields, using MIS and DIS observations of AIS fields, and by using artificial subvisits created from MIS visits; reliability has been studied using combined FUV and NUV catalogs, and by comparing GALEX with other catalogs such as SDSS. The following plots give preliminary completeness results for exposure times of 400-1600 seconds in the relatively low background Groth DIS region. NUV is left and FUV is right. All GALEX magnitudes are in the AB system.
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