The complete catalog contains 2,724,343 entries in the region of the sky north of -40° declination covered by the NVSS (which completely contains the part of sky observed by FIRST). A 2955 deg2 "overlap region" is defined by the area observed by all four radio surveys and photometrically with the SDSS. The overlap region contains 178,000 FIRST-NVSS matches (within 30"), 110,000 isolated FIRST sources, and 23,000 isolated NVSS sources. The catalog includes data parameters (from the original source surveys) for the closest positional matches. In addition, the catalog has "matching parameters" which give the distance to, and total number of, positional matches found within the chosen search radii.
The catalog is available for download at the bottom of the page. A detailed description of the calibration and a preliminary science analysis is presented in Kimball & Ivezić (2008) (hereafter KI08). Individual files with high resolution figures are available here. Please see below for updates.
FIRST and NVSS both observed the sky at 20cm (1.4 GHz), but with very different spatial resolution. FIRST has a 5.4" beam with astrometrical errors of 0.5-1", while NVSS has a 45" beam with 1-7" astrometric accuracy. FIRST therefore distinguishes small-scale structures with accurate positions, but underestimates flux for extended sources. NVSS has less accurate positional measurements and cannot distinguish small-scale structures, but measures more accurate fluxes for extended sources and can find low-surface brightness objects missed by FIRST. Combining observations from the two surveys where their coverage coincides provides more information about a single source than could be gained by observations done with a single 20cm radio survey. FIRST, designed to coincide with the region of sky covered by the Sloan Digital Sky Survey, covers 9,000 deg2 in the north Galactic cap and a smaller strip along the celestial equator. With a detection limit of 1 mJy, the FIRST survey contains over 800,000 sources. NVSS is complete to 2.5 mJy, covers the entire sky north of -40°, and contains more than 1.8 million sources.
The Green Bank survey at 6cm (4.85 GHz) covers the sky in the declination region 0°<δ<75°. It has a beam size of 3.6'×3.4'. This survey is complete to 25 mJy and contains 75,000 sources.
The WENSS survey observed at the longest wavelength of the included surveys, 92cm (325 MHz). WENSS covers the entire sky north of δ=29° down to a completeness limit of approximately 18 mJy. The beam size is 54"×54"cosec(δ), and the survey contains over 200,000 sources.
The matched catalog includes most parameters which are available in each of the individual surveys, with some additions and modifications. For example, the unified radio catalog includes an integrated 6cm source flux, which can be calculated from GB6 survey parameters. We have also modified the original survey parameters, where necessary, such that axis sizes and fluxes are in the same units (arcsec and mJy). All other parameters remain the same as in the original surveys.
The first step in the catalog production was to match FIRST and NVSS. We undertook this step in two parts by first positionally matching FIRST objects to NVSS objects (using NVSS positions as search centers), then matching NVSS objects to FIRST objects (using FIRST positions as search center). For each FIRST and NVSS source, we store in the catalog the closest three neighbors from the other catalog, within 30". Most FIRST-NVSS matches show up twice in the catalog, once with the FIRST detection as the primary and once with the NVSS detection as the primary. Catalog users therefore have the option to examine matching results separately for either catalog. It is easy to distinguish between the two searches (NVSS to FIRST or FIRST to NVSS) using the catalog's matchflag parameters.
In addition to storing data for the three closest matches within 30", we also provide the total number of neighbors found with 5", 10", 30", and 120" (matchtot parameters).
We then positionally matched to neighboring sources in GB6 and WENSS using a 120" search radius. When available, we used the more accurate position of the FIRST source in each catalog row for this step. For NVSS objects with no nearby FIRST neighbor, the NVSS position was used for this step. (See note below on positions.) Each catalog entry contains data describing the closest WENSS and GB6 neighbor; the total number of GB6 and WENSS matches within 120" is stored in the respective matchtot parameter. GB6 and WENSS each cover a different portion of the sky than the 20cm surveys; for primary sources outside GB6 or WENSS survey coverage, the respective matchtot parameter is set to -1.
We also matched the radio catalog with the SDSS photometric survey: we retain photometric metadata, and also spectroscopic metadata for objects observed by the SDSS spectroscopically. Due to the very different astrometric accuracy of NVSS and FIRST, we chose two different search radii for positional matching to FIRST (where available) and NVSS (when no FIRST match available). We used a search radius of 60".
Due to the high density of photometric SDSS sources (about 7.5 arcmin-2), it is easy to find serendipitous line-of-sight matches between intrinsically unrelated objects. We therefore provide data separately for both the nearest and the brightest SDSS photometric matches. If the nearest source is within 3" of the primary object (see Matchflags below), we also find the brightest object within 3". If the nearest object is further than 3" but within 10", we find the brightest object within 10". If no photometric neighbors were found within 10", we used a 30" search radius. If that failed, we used a 60" search radius. In 98.8% of cases where an SDSS match was found within 3", the nearest object and the brightest object are the same source.
Data Field | Units | Format | Description | ||
---|---|---|---|---|---|
-- Row Identifiers -- | |||||
1 | uniq_id | long integer | Unique catalog row identifier | ||
2 | ra | degree | double | Designated right ascension of entry | (see note on positions) |
3 | dec | degree | double | Designated declination of entry | |
-- FIRST data -- | |||||
4 | first_id | long integer | unique FIRST identifier | ||
5 | first_ra | degree | double | right ascension (J2000) | values from FIRST survey; for details see the FIRST website |
6 | first_dec | degree | double | declination (J2000) | |
7 | first_wflag | char | warning: possible sidelobe of nearby bright source | ||
8 | first_peak_flux | mJy/beam | float | peak flux at 20cm | |
9 | first_flux | mJy | float | integrated flux density at 20cm | |
10 | first_sky | mJy/beam | float | local noise estimate at source position | |
11 | first_major | arcsec | float | FWHM of major axis (after PSF deconvolution) | |
12 | first_minor | arcsec | float | FWHM of minor axis (after PSF deconvolution) | |
13 | first_posangle | degree | float | position angle east of north (after PSF deconvolution) | |
14 | first_fmajor | arsec | float | fitted major axis (before PSF deconvolution) | |
15 | first_fminor | arsec | float | fitted minor axis (before PSF deconvolution) | |
16 | first_fposangle | degree | float | fitted position angle east of north (before PSF deconvolution) | |
17 | first_field | char | name of source field | ||
-- NVSS data -- | |||||
18 | nvss_id | long integer | unique NVSS identifier | ||
19 | nvss_ra | degree | double | right ascension (J2000) | values from NVSS survey; for details see the NVSS website. Also, please see note on NVSS corrections. |
20 | nvss_dec | degree | double | declination (J2000) | |
21 | nvss_peak_int | mJy/beam | float | peak intensity at 20cm (Stokes I) | |
22 | nvss_flux | mJy | float | integrated flux at 20cm | |
23 | nvss_major | arcsec | float | FWHM major axis after deconvolution (please see note on NVSS corrections) | |
24 | nvss_minor | arcsec | float | FWHM minor axis after deconvolution (please see note on NVSS corrections) | |
25 | nvss_posangle | degree | float | position angle east of north | |
26 | nvss_q | mJy/beam | float | interpolated Stokes Q value at position of I peak | |
27 | nvss_u | mJy/beam | float | interpolated Stokes U value at position of I peak | |
28 | nvss_p_flux | mJy | float | integrated linear polarized flux | |
29 | nvss_i_rms | mJy/beam | float | RMS noise in Stokes I image | |
30 | nvss_pol_rms | mJy/beam | float | RMS noise in Stokes Q,U images | |
31 | nvss_res_rms | mJy/beam | float | RMS Stokes I residual | |
32 | nvss_res_peak | mJy/beam | float | peak Stokes I residual | |
33 | nvss_res_flux | mJy/beam | float | integrated Stokes I residual | |
34 | nvss_xpixel | pixel | float | "X" pixel of source center | |
35 | nvss_ypixel | pixel | float | "Y" pixel of source center | |
36 | nvss_field | char | name of (4x4 deg) field | ||
37 | nvss_jd_processed | day | long integer | Julian date of processing | |
-- WENSS data -- | |||||
38 | wenss_id | long integer | unique WENSS identifier | ||
39 | wenss_ra | degree | double | right ascension | values from the WENSS survey; for details see the WENSS paper |
40 | wenss_dec | degree | double | declination | |
41 | wenss_type | char | label: Single, Component, Multiple, or Extended | ||
42 | wenss_flag | char | set to "*" when source-finding algorithm failed | ||
43 | wenss_peak_flux | mJy/beam | float | peak flux density at 92cm | |
44 | wenss_flux | mJy | float | integrated source flux at 92cm | |
45 | wenss_major | arcsec | float | source major axis size | |
46 | wenss_minor | arcsec | float | source minor axis size | |
47 | wenss_posangle | degree | float | source angle on sky east of north | |
48 | wenss_sky | mJy/beam | float | local rms noise level | |
49 | wenss_frame | char | name of WENSS frame | ||
-- GB6 Data -- | |||||
50 | gb6_id | long integer | unique GB6 identifier | ||
51 | gb6_ra | degree | double | right ascension (J2000) | values from GB6 survey; for details see the GB6 catalog paper |
52 | gb6_dec | degree | double | declination (J2000) | |
53 | gb6_ra_err | degree | float | error in right ascension | |
54 | gb6_dec_err | degree | float | error in declination | |
55 | gb6_peak_flux | mJy/beam | float | peak flux at 6cm | |
56 | gb6_peak_flux_err | mJy/beam | float | error in peak flux | |
57 | gb6_major | arcsec | float | FWHM major axis | |
58 | gb6_minor | arcsec | float | FWHM minor axis | |
59 | gb6_flux | mJy | float | integrated source flux | |
60 | gb6_posangle | degree | float | fitted major axis position east of north | |
61 | gb6_sky | mJy | float | local sky level | |
62 | gb6_xpixel | pixel | float | "X" pixel of object center | |
63 | gb6_ypixel | pixel | float | "Y" pixel of object center | |
64 | gb6_eflag | char | flag indicating significantly extended source | ||
65 | gb6_wflag | char | warning flag | ||
66 | gb6_cflag | char | flag indicating confusion | ||
-- SDSS photometric data (nearest) -- | |||||
67 | near_ra | degree | double | right ascension | values from SDSS photometric survey; for details see www.sdss.org |
68 | near_dec | degree | double | declination | |
69 | near_type | integer | indicates source photometric type | ||
70 | near_flags | char | SDSS quality flags | ||
71 | near_modelmag_u | magnitude | float | u,g,r,i,z magnitudes | |
72 | near_modelmag_g | magnitude | float | ||
73 | near_modelmag_r | magnitude | float | ||
74 | near_modelmag_i | magnitude | float | ||
75 | near_modelmag_z | magnitude | float | ||
76 | near_modelmagerr_u | magnitude | float | u,g,r,i,z magnitude errors | |
77 | near_modelmagerr_g | magnitude | float | ||
78 | near_modelmagerr_r | magnitude | float | ||
79 | near_modelmagerr_i | magnitude | float | ||
80 | near_modelmagerr_z | magnitude | float | ||
-- SDSS photometric data (brightest) -- | |||||
81 | bright_ra | degree | double | right ascension | values from SDSS photometric survey; for details see www.sdss.org |
82 | bright_dec | degree | double | declination | |
83 | bright_type | integer | indicates source photometric type | ||
84 | bright_flags | char | SDSS quality flags | ||
85 | bright_modelmag_u | magnitude | float | u,g,r,i,z magnitudes | |
86 | bright_modelmag_g | magnitude | float | ||
87 | bright_modelmag_r | magnitude | float | ||
88 | bright_modelmag_i | magnitude | float | ||
89 | bright_modelmag_z | magnitude | float | ||
90 | bright_modelmagerr_u | magnitude | float | u,g,r,i,z magnitude errors | |
91 | bright_modelmagerr_g | magnitude | float | ||
92 | bright_modelmagerr_r | magnitude | float | ||
93 | bright_modelmagerr_i | magnitude | float | ||
94 | bright_modelmagerr_z | magnitude | float | ||
-- SDSS data (spectroscopic) -- | |||||
95 | spec_type | integer | indicates source spectroscopic type | values from SDSS spectroscopic survey; for details see www.sdss.org | |
96 | spec_mjd | day | long integer | Julian date of observation | |
97 | spec_plate | integer | SDSS plate # | ||
98 | spec_fiber | integer | SDSS fiber # | ||
99 | spec_redshift | double | spectroscopic redshift | ||
100 | spec_redshifterr | double | error in spectroscopic redshift | ||
101 | spec_redshift_warning | long integer | warning flag for redshift calculation | ||
-- Matching parameters -- | |||||
102 | matchflag_first | integer | set to -1 if FIRST is primary; otherwise equals rank of FIRST match (see matchflag note below) | ||
103 | matchflag_nvss | integer | set to -1 if NVSS is primary; otherwise equals rank of NVSS match (see matchflag note below) | ||
104 | distance | arcsec | double | distance between NVSS and FIRST source in this row. | |
105 | overlap | integer | set to 1 if row entry falls within overlap region; 0 otherwise (see note on positions) | ||
106 | spec_overlap | integer | set to 1 if row entry falls within SDSS spectroscopic overlap region; 0 otherwise (see note on positions) | ||
107 | matchtot5 | integer | # of NVSS or FIRST neighbors within 5" of primary source | ||
108 | matchtot10 | integer | # of NVSS or FIRST neighbors within 10" of primary source | ||
109 | matchtot30 | integer | # of NVSS or FIRST neighbors within 30" of primary source | ||
110 | matchtot120 | integer | # of NVSS or FIRST neighbors within 120" of primary source | ||
111 | wenss_distance | arcsec | double | distance between primary and nearest WENSS source within 120" (see note on positions) | |
112 | wenss_matchtot120 | integer | # of WENSS neighbors within 120" of primary source (see note on positions) | ||
113 | gb6_distance | arcsec | double | distance between primary and nearest GB6 source within 120" (see note on positions) | |
114 | gb6_matchtot120 | integer | # of GB6 neighbors within 120" of primary source (see note on positions) | ||
115 | near_distance | arcsec | double | distance between primary and nearest SDSS photometric source within 60" (see note on positions) | |
116 | bright_distance | arcsec | double | distance between primary and nearest bright SDSS photometric source within 3", 10", 30", or 60" (see notes on positions and SDSS photometry) | |
117 | sdss_matchtot | integer | # of photometric neighbors within 60" of primary (see notes on positions and updates) |
Version 1.1 of the catalog is available below. See the note above on NVSS corrections for a discussion of the changes.
For details regarding the selection of sources for each file, see KI08. The file extension .csv refers to a comma-separated-variable text file. To unzip a .gz file, type "gunzip filename" at the command line (exclude quotation marks).
The complete catalog (version 1.1) is available as a compressed, tarred archive of files each with a 5° width in right ascension. There are 2,724,343 rows. File names have the format Complete_0RA5 (containing sources between 0° and 5° in right ascension). The data have the format described in the above table. To unzip the compressed archives, type "bunzip2 file.tar.bz2" at the command line (exclude quotation marks). To extract files from the unzipped archive, type "tar -xvf file.tar" at the command line (exclude quotation marks).
Download the fits archive (271M compressed; 1.4G uncompressed) or the csv archive (227M compressed; 1.3G uncompressed).
A small subset of the catalog could be useful for familiarizing yourself with the catalog format and for testing code. It covers a region of the sky about 106 deg2 in the range 150° < R.A. < 165°, 40° < dec. < 50°. It contains 16,453 rows, with the format given above.
Download the fits file (2.1M compressed; 8.7M uncompressed) or the csv file (9.5M).
The set of sources detected by FIRST and NVSS in the 2955 deg2 overlap region containing 141,881 sources. Matching radius is 25". Parameters include: uniq_id, ra, dec, first_peak_flux, first_flux, nvss_flux, gb6_flux, wenss_flux, distance, wenss_distance, gb6_distance.
Download the fits file (5.5M compressed; 8.7M uncompressed) or the csv file (9.2M).
The set of sources detected by all four radio catalogs and the SDSS in the 2955 deg2 overlap region containing 4732 sources. Matching radii are: (FIRST-NVSS) 25", (FIRST-WENSS) 30", (FIRST-GB6) 70", (FIRST-SDSS) 2". In addition to those listed in item 3 above, parameters include: near_type, near_flags, the near model magnitudes and their errors.
Download the fits file (470K compressed; 625K uncompressed) or the csv file (837 K).
The set of galaxies with optical spectra detected by NVSS, FIRST, WENSS, and SDSS in the 2955 deg2 overlap region containing 2885 sources. Matching radii are: (FIRST-NVSS) 25", (FIRST-WENSS) 30", (FIRST-SDSS) 2". Parameters include: uniq_id, ra, dec, first_peak_flux, first_flux, nvss_flux, wenss_flux, near_type, near_flags, distance, wenss_distance, near_distance, the near_modelmags and their errors, and the SDSS spectroscopic parameters.
Download the fits file (298K compressed; 439K uncompressed) or the csv file (570K).
The set of quasars with optical spectra detected by NVSS, FIRST, WENSS, and SDSS in the 2955 deg2 overlap region containing 1288 sources. Matching radii are: (FIRST-NVSS) 25", (FIRST-WENSS) 30", (FIRST-SDSS) 2". For each source, the file includes all 74 parameters originally provided in the Schneider et al. (2007, AJ, 134, 102) SDSS DR5 known quasar catalog. Additionally, parameters from the unified catalog include: uniq_id, ra, dec, first_peak_flux, first_flux, nvss_flux, wenss_flux, the near_modelmags and their errors. The file includes a header describing each of the columns.
Download the text file (755K).
The set of isolated FIRST-NVSS sources. It is comprised of objects observed in both FIRST and NVSS (matched within 15") with no other FIRST detection within 30" of the NVSS source. The file contains all 109,825 such sources within the 2955 deg2 overlap region. Parameters include: uniq_id, ra, dec, first_peak_flux, first_flux, nvss_flux, wenss_flux, gb6_flux, distance, wenss_distance, gb6_distance described above. The two FIRST fluxes and the NVSS flux are necessary and sufficient to divide the data into the three morphological classes described in KI08.
Download the fits file (4.1M compressed; 6.8M uncompressed) or the csv file (7.0M).
The set of isolated FIRST-NVSS sources with a photometric SDSS match containing 42,144 sources. This file is a subset of sources from item 7 above. FIRST-SDSS matching radius is 2". It includes all data parameters described in items 7 above, as well as SDSS data (near_ra, near_dec, near_distance, near_type, near_flags, model magnitudes, and model magnitude errors).
Download the fits file (3.7M compressed; 5.7M uncompressed) or the csv file (6.9M).
The set of 9337 high-redshift (z > 1) galaxy candidates detected by FIRST, NVSS, WENSS (and not SDSS). These objects were selected based on their lack of an optical counterpart, and their steep radio spectra (α 9220 < -0.5). (See notes on updates.) The selection of these sources is described in Section 5.2 of KI08. These objects: are detected by FIRST, NVSS, and WENSS, have no SDSS match within 3", have compact radio morphology, and have steep radio spectra (α 9220 < -0.5). (Please note: these objects are a subset of sample D in table 8, not of sample E as is stated in that table. I.e.: GB6 criteria were not used in their selection.)
Download the fits file (2.5M compressed; 5.0M uncompressed) or the csv file (5.8M).
An auxiliary text file containing NVSS angular sizes in agreement with the NVSS catalog browser. See the note above on NVSS corrections for details. The file contains one row for each NVSS source in the Unified Catalog. Parameters include: NVSS id, major axis [arcsec], major axis flag, minor axis [arcsec], minor axis flag. Flags are 0 for unresolved (upper limit only), 1 for resolved (actual angular size).
Download the csv file (12M compressed; 38M uncompressed).
(Posted 11 Oct 2008) Correction: The original set of high-redshift (z > 1) galaxy candidates for download mistakenly included sources with flat spectra and uncorrected NVSS fluxes. The version currently posted here is correct. Note that the corrected version is smaller than the dataset referred to in KI08.
(Posted 9 March 2009) Now available: version 1.1 of the catalog contains corrected NVSS fluxes and major/minor axis sizes. See the note above on NVSS corrections for details. We thank Dr Haida Liang, Dr Hui Shi, and Dr Jess Broderick for bringing this issue to our attention.
Amy E Kimball National Radio Astronomy Observatory PO Box O Socorro, NM 87801 USA Željko Ivezić Department of Astronomy Box 351580, U.W. Seattle, WA 98195-1580 USA
Please send your questions, comments, or suggestions to: akimball@nrao.edu