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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 detection. 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 as follows. 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.

Catalogs:

MIS :Catalog of unique GALEX sources from the MIS survey (12.6 million sources, 1.5GB tar file, contains 26 gzipped files, each file containing sources for a 5 degree band of Galactic latitude)

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.

#objid, ra, dec, glon, glat, tilenum, img, subvisit, fov_radius, type, band, e_bv, istherespectrum, objtype, quality, fuv_mag, fuv_magerr, nuv_mag, nuv_magerr, fuv_mag_best, fuv_magerr_best, nuv_mag_best, nuv_magerr_best, fuv_mag_auto, fuv_magerr_auto, nuv_mag_auto, nuv_magerr_auto, fuv_mag_aper_4, fuv_magerr_aper_4, nuv_mag_aper_4, nuv_magerr_aper_4, fuv_mag_aper_6, fuv_magerr_aper_6, nuv_mag_aper_6, nuv_magerr_aper_6, fuv_artifact, nuv_artifact, fuv_flags, nuv_flags, fuv_flux, fuv_fluxerr, nuv_flux, nuv_fluxerr, fuv_x_image, fuv_y_image, nuv_x_image, nuv_y_image, fuv_fwhm_image, nuv_fwhm_image, fuv_fwhm_world, nuv_fwhm_world, photoextractid, mpstype, avaspra, avaspdec

Many of these fields will not be of interest to most users. The columns of probable interest are in bold::

1 objid: The GALEX objid
2 ra: (in degrees)
3 dec: (in degrees)
4 glon: Galactic Longitude (in degrees)
5 glat: Galactic Latitude (in degrees)
6 tilenum: tile number
7 img: image number (exposure# for _visits)
8 subvisit: sub-visit number for ais
9 fov_radius: distance from center of field-of-view in degrees
10 type: obs.type (0single,1multi)
11 band: band number (1nuv,2fuv,3both)
12 e_bv: e(B-V) Galactic reddening inferred from 100um dust emission maps
13 istherespectrum: Does this object have a (GALEX) spectrum? Yes (1), No (0)
14 objtype: 0=galaxy, 1=star, -1=unknown
15 quality: quality flag (undefined)
16 fuv_mag: same as fuv_mag_best
17 fuv_magerr
18 nuv_mag
19 nuv_magerr
20 fuv_mag_best: pipeline-chosen "best" magnitude (either mag_auto or mag_isocor)
21 fuv_magerr_best
22 nuv_mag_best
23 nuv_magerr_best
24 fuv_mag_auto: kron-like elliptical aperture magnitude
25 fuv_magerr_auto
26 nuv_mag_auto
27 nuv_magerr_auto
28 fuv_mag_aper_4: flux aperture (8.000)
29 fuv_magerr_aper_4
30 nuv_mag_aper_4
31 nuv_magerr_aper_4
32 fuv_mag_aper_6: flux aperture (17.000)
33 fuv_magerr_aper_6
34 nuv_mag_aper_6
35 nuv_magerr_aper_6
36 fuv_artifact: fuv artifact flag (logical or near source)
37 nuv_artifact
38 fuv_flags: extraction flags
39 nuv_flags
40 fuv_flux: fuv calibrated flux (micro jansky)
41 fuv_fluxerr
42 nuv_flux
43 nuv_fluxerr
44 fuv_x_image: object position along x
45 fuv_y_image: object position along y
46 nuv_x_image
47 nuv_y_image
48 fuv_fwhm_image: fwhm assuming a gaussian core
49 nuv_fwhm_image
50 fuv_fwhm_world: fwhm assuming a gaussian core
51 nuv_fwhm_world
52 photoextractid: Pointer to photoExtract Table
53 mpstype: survey type (e.g, "MIS")
54 avaspra: field center RA
55 avaspdec: field center Dec.