CATALOGS OF UNIQUE GALEX SOURCES FROM GALEX fifth data release (GR5)
The catalogs of unique GALEX sources
from data release GR5, for the AIS and MIS surveys separately, were constructed by Bianchi et al. (2011, MNRAS) with the following criteria (see paper for more details):
1) only observations when both FOV and NUV detectors were turned on are included. This is useful for science analyses where the fraction of sources
with a given FUV-NUV color is of interest, or to estimate the fraction of sources with significant detection in both FUV and NUV over the total number of sources with NUV-only
More observations exist in the GALEX archive taken with one detector off (mostly FUV); those can be found in the galex.stsci.edu MAST page. Inclusion of
observations where one detector was not exposed would bias the statistics of # FUV detections or # of sources in a given FUV-NUV color range, as the FUV magnitude
may appear as a non-detection (FUV=-999)
both because the FUV detector was off, or the FUV detector was on but the FUV flux of that source was actually below detection.
2) only sources within the central 0.5
degrees radius of the field-of-view are included, to avoid sources with poor photometry/astrometry near the edge, and rim artifacts.
This makes the catalogs useful for statistical analysis of sources with homogeneous quality, without great loss of area coverage (also
considering that overlap exist among several fields).
Users interested in a particular source that happens to fall on a galex field edge, should obtain the measurements from the main catalog and examine the quality.
3) we retained sources with NUV magnitude errors less or equal 0.5mag (see column 4 of Table 2 in Bianchi et al. 2011, MNRAS, 411, 2770
paper, and Figure 4 of Bianchi et al. 2011 MNRAS, and Figures 2--4 of Bianchi et al. 2011, ApSS,
for effects of error cuts on the resulting sample statistics).
4) The general GALEX database contains all measurements for sources with repeated observations.
In each catalog (AIS and MIS), we removed duplicate measurements to produce a unique source catalog
GALEX sources within
2.5" of each other, but from different observations, were considered
duplicates. In such cases the object from the observation with the
longest NUV exposure time was retained, and - in cases of equal exposure times - the object closest to the
center of the field of view.
Catalogs were constructed in this way for the two GALEX surveys with the largest sky coverge (excluding the Nearby Galaxy Survey), shown below in Galactic coordinates:
MIS (Medium Imaging Survey, depth about 22.7 ABmag in FUV/NUV) and AIS (All-Sky Imaging Survey, depth about 19.9/20.8 FUV/NUV ABmag). See e.g. reviews
by Bianchi 2009, 320, 11 ( DOI: 10.1007/s10509-008-9761-3 )
and 2011 ApSS DOI: 10.1007/s10509-011-0612-2, for details). Note that a source observed in both surveys may appear in the separate catalogs
with different object-id and slightly differing position and magnitudes.
GR5 AIS and MIS coverage
For estimating density of sources in the sky from extracted subcatalogs, it is useful to have the area coverage.
Table 1 of Bianchi et al. (2011) provides the area coverage for each catalog, both
total area and divided by latitude ranges.
AIS :Catalogs of unique GALEX sources from the AIS survey (65.3 million sources)
The catalog is divided in 180 gzipped files, each
containing sources for a 1 degree band of Galactic latitude). These are grouped in four tar files for download,
covering different Galactic latitude ranges: latitude 0 - 45 N (2.3G) latitude 45 -90 N (1.5G) latitude 45 - 90 S(1.6G) latitude 0 - 45 S (2.0G)
The files within each .tar have the following naming convention, e.g.:
GR5_70_65N.ais.csv.gz, GR5_65_70S.ais.csv.gz, where
70_65N means it contains sources with b between 65 and 70 North
65_70S sources with b between -65 and -70 degrees South
Comma-separated columns contained in the catalog files are listed below.
Detailed field descriptions can be found at the
MAST GALEX site.