The complete catalog contains 2,866,856 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 3269 deg2 "overlap region" is defined by the area observed by all five radio surveys and covered by the SDSS photometric survey. The overlap region contains about 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.
This catalog is an updated version of the original catalog presented in Kimball & Ivezić (2008) (hereafter KI08). The first catalog was based on earlier versions of FIRST and NVSS, used Data Release 6 of the SDSS, and did not include VLSSr data. Because the new version of this catalog uses updated FIRST data and the final NVSS data, the catalog entries do not, in general, correspond to entries in version 1.1 of the catalog.
FIRST and NVSS both observed the sky at 20cm (1.4 GHz), but with very different spatial resolution. FIRST used a 5.4″ beam with astrometrical errors of 0.5-1″, while NVSS used 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 flux densities 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 20-cm radio survey. FIRST, designed to coincide with the region of sky covered by the Sloan Digital Sky Survey, covers 8500 deg2 in the north Galactic cap and a 2000 deg2 strip along the celestial equator. With a detection limit of 1 mJy, the FIRST survey contains nearly 950,000 detections. NVSS is sensitive 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.
WENSS was performed at 92 cm (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 VLSSr observed at the longest wavelength of the included surveys, 4 m (74 MHz). In this version of the VLSSr (obtained August 2013), coverage is complete north of δ = -10°, with coverage at some right ascensions (R.A. < 220° or R.A. > 320°) extending at least as far south as δ = -30°. It has a resolution of 80″ and 5σ sensitivity of about 0.5 Jy/beam.
The matched catalog includes most parameters which are available in each of the individual surveys, with some additions and modifications. We have modified the original survey parameters, where necessary, such that axis sizes and fluxes are in the same units (arcsec and mJy). 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 FIRST or NVSS neighbors found with 5″, 10″, 30″, and 120″ (matchtot parameters).
We then positionally matched to neighboring sources in GB6, WENSS, and VLSSr using a 120″ search radius. (This is different from the original version of the catalog, where we always used the FIRST position, when available, to match to the other surveys.) Each catalog entry includes the closest of each GB6, WENSS, and VLSSr neighbor within 120″. The associated matchtot parameter reports the total number of counterparts in each survey within 120″, or indicates with a value of -1 that the primary FIRST/NVSS source lies outside the region of sky covered by GB6, WENSS, or VLSSr, with a caveat for the VLSSr. See the section below on matchtot parameters for details.
We also matched the radio catalog with the SDSS Data Release 9 photometric survey: we retain photometric data, and also spectroscopic metadata when available. We used a search radius of 30″ for inclusion in the catalog, though a proximity of 2″ is generally recommended for determining "true" SDSS/FIRST counterparts.
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, we also find and report the brightest object within 3″. If the nearest object is further than 3″ but within 10″, we report the brightest object within 10″. If no photometric neighbors were found within 10″, we used the 30″ search radius. However, in over 99% 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 int | Unique catalog row identifier | ||
| 2 | ra | degree | double | Designated right ascension of entry | (FIRST position if matchflag_first=-1; NVSS position if matchflag_nvss=-1) |
| 3 | dec | degree | double | Designated declination of entry | |
| -- Matching parameters -- | |||||
| 4 | matchflag_first | int | set to -1 if FIRST is primary; otherwise equals rank of FIRST match (see note on matchflags below) | ||
| 5 | matchflag_nvss | int | set to -1 if NVSS is primary; otherwise equals rank of NVSS match (see note on matchflags below) | ||
| 6 | distance | arcsec | float | distance between NVSS and FIRST source in this row | |
| 7 | overlap | int | set to 1 if row entry falls within 3269 deg2 overlap region observed by all surveys; 0 otherwise | ||
| 8 | matchtot_5 | int | # of NVSS or FIRST neighbors within 5″ of primary source | ||
| 9 | matchtot_10 | int | # of NVSS or FIRST neighbors within 10″ of primary source | ||
| 10 | matchtot_30 | int | # of NVSS or FIRST neighbors within 30″ of primary source | ||
| 11 | matchtot_120 | int | # of NVSS or FIRST neighbors within 120″ of primary source | ||
| 12 | gb6_matchtot_120 | int | # of GB6 neighbors within 120″ of primary source | ||
| 13 | gb6_distance | arcsec | float | distance to nearest GB6 source within 120″ | |
| 14 | wenss_matchtot_120 | int | # of WENSS neighbors within 120″ of primary source | ||
| 15 | wenss_distance | arcsec | float | distance to nearest WENSS source within 120″ | |
| 16 | vlss_matchtot_120 | int | # of WENSS neighbors within 120″ of primary source | ||
| 17 | vlss_distance | arcsec | float | distance to nearest WENSS source within 120″ | |
| 18 | sdss_matchtot | int | # of photometric neighbors within 3″, 10″, or 30″ of primary (see note on SDSS photometry) | ||
| 19 | near_distance | arcsec | float | distance tonearest SDSS photometric source within 30″ | |
| 20 | bright_distance | arcsec | float | distance to brightest nearby SDSS photometric source within 3″, 10″, or 30″ (see note on SDSS photometry) | |
| -- FIRST data -- | |||||
| 21 | first_id | long int | unique FIRST identifier | ||
| 22 | first_ra | degree | double | right ascension (J2000) | values from FIRST survey; for details see the FIRST website |
| 23 | first_dec | degree | double | declination (J2000) | |
| 24 | first_sideprob | float | probability that detection is a sidelobe of nearby bright source | ||
| 25 | first_fpeak | mJy/beam | float | peak flux density at 20cm | |
| 26 | first_fint | mJy | float | integrated flux density at 20cm | |
| 27 | first_rms | mJy/beam | float | local noise estimate at source position | |
| 28 | first_major | arcsec | float | FWHM of major axis (after PSF deconvolution) | |
| 29 | first_minor | arcsec | float | FWHM of minor axis (after PSF deconvolution) | |
| 30 | first_posang | degree | float | position angle east of north (after PSF deconvolution) | |
| 31 | first_ntmass | int | # of 2MASS sources within 8″ | ||
| 32 | first_tmass_sep | arcsec | float | distance to nearest 2MASS source within 8″ of FIRST source | |
| 33 | first_tmass_mag | Vega magnitudes | float | K-band magnitude of nearest 2MASS source | |
| -- NVSS data -- | |||||
| 34 | nvss_id | long int | unique NVSS identifier | ||
| 35 | nvss_ra | degree | double | right ascension (J2000) | values from NVSS survey; for details see the NVSS website |
| 36 | nvss_dec | degree | double | declination (J2000) | |
| 37 | nvss_peak | mJy/beam | float | peak intensity at 20cm (Stokes I) | |
| 38 | nvss_flux | mJy | float | integrated flux density at 20cm (Stokes I) | |
| 39 | nvss_flux_err | mJy | float | error on integrated flux density | |
| 40 | nvss_major | arcsec | float | FWHM major axis after deconvolution | |
| 41 | nvss_major_err | arcsec | float | error on major axis | |
| 42 | nvss_minor | arcsec | float | FWHM minor axis after deconvolution | |
| 43 | nvss_minor_err | arcsec | float | error on minor axis | |
| 44 | nvss_posangle | degree | float | position angle east of north | |
| 45 | nvss_posangle_err | degree | float | error on position angle | |
| 46 | nvss_q | mJy/beam | float | interpolated Stokes Q value at position of I peak | |
| 47 | nvss_u | mJy/beam | float | interpolated Stokes U value at position of I peak | |
| 48 | nvss_pol_flux | mJy | float | integrated linear polarized flux | |
| 49 | nvss_pol_flux_err | mJy | float | integrated linear polarized flux | |
| 50 | nvss_pol_angle | degree | float | polarization angle | |
| 51 | nvss_pol_angle_err | degree | float | error on polarization angle | |
| -- GB6 Data -- | |||||
| 52 | gb6_id | long int | unique GB6 identifier | ||
| 53 | gb6_ra | degree | double | right ascension (J2000) | values from GB6 survey; for details see the GB6 catalog paper |
| 54 | gb6_ra_err | degree | float | error on right ascension | |
| 55 | gb6_dec | degree | double | declination (J2000) | |
| 56 | gb6_dec_err | degree | float | error on declination | |
| 57 | gb6_peak_flux | mJy | float | peak flux density at 6cm | |
| 58 | gb6_peak_flux_err | mJy | float | error on peak flux density | |
| 59 | gb6_major | arcsec | float | FWHM major axis | |
| 60 | gb6_minor | arcsec | float | FWHM minor axis | |
| 61 | gb6_posangle | degree | float | fitted major axis position east of north | |
| 62 | gb6_sky | mJy | float | local sky level | |
| 63 | gb6_eflag | char | flag indicating significantly extended source | ||
| 64 | gb6_wflag | char | warning flag | ||
| 65 | gb6_cflag | char | flag indicating confusion | ||
| -- WENSS data -- | |||||
| 66 | wenss_id | long int | unique WENSS identifier | ||
| 67 | wenss_ra | degree | double | right ascension | values from the WENSS survey; for details see the WENSS paper |
| 68 | wenss_dec | degree | double | declination | |
| 69 | wenss_type | char | label: Single, Component, Multiple, or Extended | ||
| 70 | wenss_errflag | char | set to "*" when source-finding algorithm failed | ||
| 71 | wenss_peak_flux | mJy/beam | float | peak flux density at 92cm | |
| 72 | wenss_flux | mJy | float | integrated source flux at 92cm | |
| 73 | wenss_major | arcsec | float | source major axis size | |
| 74 | wenss_minor | arcsec | float | source minor axis size | |
| 75 | wenss_posangle | degree | float | source angle on sky east of north | |
| 76 | wenss_sky | mJy/beam | float | local rms noise level | |
| -- VLSSr data -- | |||||
| 77 | vlss_id | long int | unique VLSSr identifier | ||
| 78 | vlss_ra | degree | double | right ascension (J2000) | values from VLSSr survey; for details see the VLSSr website |
| 79 | vlss_dec | degree | double | declination (J2000) | |
| 80 | vlss_flux | mJy | float | integrated flux density at 20cm (Stokes I) | |
| 81 | vlss_flux_err | mJy | float | error on integrated flux density | |
| 82 | vlss_major | arcsec | float | FWHM major axis after deconvolution | |
| 83 | vlss_major_err | arcsec | float | error on major axis | |
| 84 | vlss_minor | arcsec | float | FWHM minor axis after deconvolution | |
| 85 | vlss_minor_err | arcsec | float | error on minor axis | |
| 86 | vlss_posangle | degree | float | position angle east of north | |
| 87 | vlss_posangle_err | degree | float | error on position angle | |
| -- SDSS photometric data (nearest) -- | |||||
| 88 | near_ra | degree | double | right ascension | values from SDSS photometric survey; for details see www.sdss.org |
| 89 | near_dec | degree | double | declination | |
| 90 | near_type | int | indicates source photometric type | ||
| 91 | near_flags | char | SDSS quality flags | ||
| 92 | near_modelmag_u | magnitude | float | u,g,r,i,z magnitudes | |
| 93 | near_modelmag_g | magnitude | float | ||
| 94 | near_modelmag_r | magnitude | float | ||
| 95 | near_modelmag_i | magnitude | float | ||
| 96 | near_modelmag_z | magnitude | float | ||
| 97 | near_modelmagerr_u | magnitude | float | u,g,r,i,z magnitude errors | |
| 98 | near_modelmagerr_g | magnitude | float | ||
| 99 | near_modelmagerr_r | magnitude | float | ||
| 100 | near_modelmagerr_i | magnitude | float | ||
| 101 | near_modelmagerr_z | magnitude | float | ||
| -- SDSS photometric data (brightest) -- | |||||
| 102 | bright_ra | degree | double | right ascension | values from SDSS photometric survey; for details see www.sdss.org |
| 103 | bright_dec | degree | double | declination | |
| 104 | bright_type | int | indicates source photometric type | ||
| 105 | bright_flags | char | SDSS quality flags | ||
| 106 | bright_modelmag_u | magnitude | float | u,g,r,i,z magnitudes | |
| 107 | bright_modelmag_g | magnitude | float | ||
| 108 | bright_modelmag_r | magnitude | float | ||
| 109 | bright_modelmag_i | magnitude | float | ||
| 110 | bright_modelmag_z | magnitude | float | ||
| 111 | bright_modelmagerr_u | magnitude | float | u,g,r,i,z magnitude errors | |
| 112 | bright_modelmagerr_g | magnitude | float | ||
| 113 | bright_modelmagerr_r | magnitude | float | ||
| 114 | bright_modelmagerr_i | magnitude | float | ||
| 115 | bright_modelmagerr_z | magnitude | float | ||
| -- SDSS spectroscopic data (nearest) -- | |||||
| 116 | spec_class | char | indicates source spectroscopic type | values from SDSS spectroscopic survey; for details see www.sdss.org | |
| 117 | spec_subclass | char | indicates source spectroscopic type | ||
| 118 | spec_mjd | day | long int | Julian date of observation | |
| 119 | spec_plate | int | SDSS plate # | ||
| 120 | spec_fiberid | int | SDSS fiber # | ||
| 121 | spec_redshift | float | spectroscopic redshift | ||
| 122 | spec_redshift_warning | int | warning flag for redshift calculation | ||
| 123 | spec_veldisp | km/s | float | spectroscopic redshift | |
| 124 | spec_veldisperr | km/s | float | warning flag for redshift calculation | |
For rows with a FIRST detection as primary, we set matchflag_first = -1, and the values of matchflag_nvss are determined similarly to what was described in the previous paragraph.
The sdss_matchtot parameter indicates the total number of SDSS photometric neighbors within 3″, 10″, or 30″ (see note below on SDSS photometry). If no SDSS counterpart was found, it is set to a value of 0, even for sources outside of the SDSS sky coverage area. However, note that the SDSS photometric survey is so dense that nearly all FIRST/NVSS sources within the SDSS footprint are within 30″ of at least one SDSS source.
The subclass of an SDSS spectroscopic source contains a more specific classification. Galaxies and QSOs have optional subclasses of "AGN", "BROADLINE", "STARBURST", or "STARFORMING".
To unzip a g-zipped file filename.gz, type "gunzip filename.gz" at the command line (exclude quotation marks).
The complete catalog (version 2.0) is available as a compressed, tarred archive of files each with a 5° width in right ascension. There are 2,866,856 rows. File names have the format complete_version2.0_0.RA.5 (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 individual files from the unzipped archive, type "tar -xvf <file>.tar" at the command line (exclude quotation marks).
Download the fits archive (255M compressed; 1.5G uncompressed).
This small subset of the catalog may be useful for familiarizing yourself with the catalog format and for testing code. It covers a 106 deg2 region of the sky in the range 150° ≤ R.A. ≤ 165°, 40° ≤ dec. ≤ 50°. It contains 16,469 rows, with the format given above.
Download the fits file (1.9M compressed; 8.8M uncompressed).
The set of components detected by FIRST and NVSS:
580,846 (including up to 3 duplicate FIRST components matched to a single
NVSS source, and vice-versa; see rules above
for Matchflags). Matching radius is 30″.
Parameters include: uniq_id, ra, dec, matchflag_nvss, matchflag_first,
distance, overlap, first_fpeak, first_fint, nvss_flux, gb6_flag, gb6_flux, gb6_distance,
wenss_flag, wenss_flux, wenss_distance, vlss_flux, vlss_distance.
Download the fits file (15M compressed; 34M uncompressed).
The set of galaxies with optical spectra from SDSS DR9 and a counterpart
in FIRST. Matching radius 2″ between FIRST and SDSS results in 54,165
rows, including ≤ 3 NVSS counterparts within 30″ of the FIRST
source. Select those with matchflag_nvss ≤ 1 to obtain the 54,075
unique FIRST/SDSS rows.
Parameters are: uniq_id, ra, dec, matchflag_first, matchflag_nvss,
distance, overlap, first_fpeak, first_fint, nvss_flux, gb6_flag, gb6_flux,
gb6_distance, wenss_flag, wenss_flux, wenss_distance, vlss_flux, vlss_distance,
sdss_matchtot, near_distance, near_type, near_flags,
the near_modelmags and their errors, and the SDSS spectroscopic
parameters.
Download the fits file (4.6M compressed; 8.7M uncompressed).
The set of broad-line QSOs with optical spectra from SDSS DR9 and a
counterpart in FIRST. Matching radius 2″ between FIRST and SDSS results
in 14,467 rows, including ≤ 3 NVSS counterparts within 30″ of the
FIRST source. Select those with matchflag_nvss ≤ 1 to obtain the
14,430 unique FIRST/SDSS rows.
Parameters are: uniq_id, ra, dec, matchflag_first, matchflag_nvss,
distance, overlap, first_fpeak, first_fint, nvss_flux, gb6_flag, gb6_flux,
gb6_distance, wenss_flag, wenss_flux, wenss_distance, vlss_flux, vlss_distance,
sdss_matchtot, near_distance, near_type, near_flags,
the near_modelmags and their errors, and the SDSS spectroscopic
parameters.
Download the fits file (14K compressed; 2.3M uncompressed).
The set of isolated FIRST-NVSS sources. It comprises 368,441 objects observed
in both FIRST and NVSS (matched within 15") with no other FIRST or NVSS
counterpart within 30" of the NVSS source.
Parameters include: uniq_id, ra, dec, distance, overlap, first_fpeak, first_fint,
nvss_flux, gb6_flag, gb6_flux, gb6_distance, wenss_flag, wenss_flux, vlss_flux,
vlss_distance.
Download the fits file (11M compressed; 20M uncompressed).
The set of isolated FIRST-NVSS sources (as described above in item 6) with a photometric SDSS match within 2″ of the FIRST position: 167,404 rows. It includes all data parameters described in item 6 above, as well as SDSS data (near_ra, near_dec, near_distance, near_type, near_flags, near_modelmags, and their errors).
Download the fits file (12M compressed; 26M uncompressed).
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
I am happy to discuss or help compile subsamples to help in your
research.
Please send your questions, comments, or suggestions to: kimball
.dot. amy .dot. e @at@ gmail .dot. com .