AT20G1FGL - AT20G/Fermi 1FGL Source Catalog

Overview

The high-frequency radio sky, like the gamma-ray sky surveyed by the Fermi satellite, is dominated by flat-spectrum radio quasars and BL Lac objects at bright flux levels. To investigate the relationship between radio and gamma-ray emission in extragalactic sources, the authors have cross-matched the Australia Telescope 20-GHz survey catalog (AT20G: Murphy et al. 2010, MNRAS, 402, 2403, available as a HEASARC Browse table) with the Fermi-LAT 1-year Point Source Catalog (1FGL: Abdo et al. 2010, ApJS, 188, 405, also available as the HEASARC Browse table FERMILPSC). The 6.0 sr of sky covered by both catalogs (Declination < 0 degrees, |b| > 1.5 degrees) contains 5890 AT20G radio sources and 604 1FGL gamma-ray sources. The AT20G source positions are accurate to within ~1 arcsec and, after excluding known Galactic sources, 43% of Fermi 1FGL sources have an AT20G source within the 95% Fermi confidence ellipse. Monte Carlo tests imply that at least 95% of these matches are genuine associations. Only five gamma-ray sources (1% of the Fermi catalog) have more than one AT20G counterpart in the Fermi error box. The AT20G matches also generally support the active galactic nucleus (AGN) associations in the First LAT AGN Catalog. The authors find a trend of increasing gamma-ray flux density with 20 GHz radio flux density. The Fermi detection rate of AT20G sources is close to 100% for the brightest 20 GHz sources, decreasing to 20% at 1 Jy, and to roughly 1% at 100 mJy. Eight of the matched AT20G sources have no association listed in 1FGL and are presented here as potential gamma-ray AGNs for the first time. The authors also identify an alternative AGN counterpart to one 1FGL source. The percentage of Fermi sources with AT20G detections decreases toward the Galactic plane, suggesting that the 1FGL catalog contains at least 50 Galactic gamma-ray sources in the southern hemisphere that are yet to be identified.

This table contains the complete list of all 233 Fermi-AT20G matches.

Catalog Bibcode

2010ApJ...718..587M

References

High-frequency Radio Properties of Sources in the Fermi-LAT 1 year Point
Source Catalog
    Mahony E.K., Sadler E.M., Murphy T., Ekers R.D., Edwards P.G., Massardi M.
   <Astrophys. J. 718, 587 (2010)>
   =2010ApJ...718..587M

Provenance

This table was created by the HEASARC in August 2010 based on the electronic version of Table 4 obtained from the ApJ web site.

Parameters

Fermi_Name
The First Fermi-LAT Catalog (1FGL) gamma-ray source designation (Abdo et al. 2010, ApJS, 188, 405).

Fermi_RA
The Right Ascension of the Fermi source in the selected equinox. This was given in J2000 decimal degrees to a precision of 0.1 degrees in the original table.

Fermi_Dec
The Declination of the Fermi source in the selected equinox. This was given in J2000 decimal degrees to a precision of 0.1 degrees in the original table.

Fermi_Semi_Major_Axis_95
The semi-major axis of the error ellipse of the Fermi source at 95% confidence, in degrees.

Fermi_Semi_Minor_Axis_95
The semi-minor axis of the error ellipse of the Fermi source at 95% confidence, in degrees.

Fermi_Position_Angle_95
The position angle of the Fermi source 95%-confidence semi-major axis, from celestial North, positive toward increasing R.A. (eastward), in degrees.

Fermi_Pivot_Energy
The Fermi source energy, in MeV, at which the error in the differential photon flux is minimal (i.e., the decorrelation energy for the power-law fit). This is derived from the likelihood analysis for 100 MeV - 100 GeV.

Fermi_Flux_Density
The differential photon flux of the Fermi source at the pivot energy, in photons/cm²/MeV/s. This is derived from the likelihood analysis for 100 MeV - 100 GeV.

Fermi_Flux_Density_Error
The 1-sigma uncertainty in the differential flux of the Fermi source at the pivot energy, in photons/cm²/MeV/s.

Fermi_Variability_Index
The result of a chi-squared test of deviations of the Fermi source flux in 11 time segments from a flat lightcurve over the full 11-month catalog interval. A value greater than 23.21 indicates less than a 1% chance of being a steady source. See the 1FGL paper (Abdo et al. 2010, ApJS, 188, 405) for more details.

Alt_GammaRay_Name
The corresponding name of the 1FGL source in the Fermi Bright Gamma-Ray Source List (0FGL: Abdo et al. 2009, ApJS, 183, 46).

Alt_Name
The designation of the identified or likely associated source to the Fermi source, as given in the 1FGL Catalog.

Fermi_Source_Type
The primary class designation of the identification or likely associated source as given in the 1FGL Catalog (Abdo et al. 2010, ApJS, 188, 405). Refer to that paper for details of class designations and the association method. Note that designations shown in capital letters are firm identifications; lower case letters indicate associations. In the case of AGN, many of the associations have high confidence (Abdo et al. 2010, ApJ, 715, 429).The following abbreviations are used:

            agn = other non-blazar agn
            agu = active galaxy of uncertain type
            bzb = BL Lac type of blazar
            bzq = FSRQ type of blazar
            glc = globular cluster
            gal = normal galaxy
            mqo = micro-quasar object = X-ray binary (black hole or neutron star)
                  with radio jet
            sbg = starburst galaxy
            snr = supernova remnant
            spp = special case - potential association with SNR or PWN
            PSR = pulsar, identified by pulsations
            psr = pulsar, spatial association
            pwn = pulsar wind nebula
            xrb = other X-ray binary

Table 7 in the 1FGL Catalog (Abdo et al. 2010, ApJS, 188, 405) lists possible associations for sources near supernova remnants, designated 'spp' herein.

Name
The AT20G radio source designation (AT20G JHHMMSS-DDMMSS).

RA
The Right Ascension of the AT20G radio source in the selected equinox. This was given in J2000 equatorial coordinates to a precision of 0.01 seconds of time in the original table.

Dec
The Declination of the AT20G radio source in the selected equinox. This was given in J2000 equatorial coordinates to a precision of 0.1 arcseconds in the original table.

LII
The Galactic Longitude of the AT20G radio source.

BII
The Galactic Latitude of the AT20G radio source.

Offset
The offset between the Fermi and AT20G source positions, in degrees.

Flux_1p5_cm
The radio source integrated flux density at 20 GHz, in mJy.

Flux_3p5_cm
The radio source integrated flux density at 8.4 GHz, in mJy.

Flux_6_cm
The radio source integrated flux density at 4.8 GHz, in mJy.

Radio_Spectral_Index
The radio source spectral index between 4.8 and 20 GHz.

At20g_Quality_Flag
The AT20G radio source flux quality flag, where 'p' denotes a poor flux measurement for a variety of reasons as explained in Murphy et al. (2010, MNRAS, 402, 2403), and 'g' refers to a good flux measurement.

Flux_30_cm
The radio source integrated flux density at ~ 1 GHz, in mJy, based on the NVSS 1.4-GHz or SUMSS 843-MHz cataloged values for the source.

Optical_RA
The Right Ascension of the optical source counterpart, when available, in the selected equinox. This was given in J2000 equatorial coordinates to a precision of 0.01 seconds of time in the original table.

Optical_Dec
The Declination of the optical source counterpart, when available, in the selected equinox. This was given in J2000 equatorial coordinates to a precision of 0.1 arcseconds in the original table.

BJ_Mag
The SuperCOSMOS B_J band magnitude of the optical source counterpart, when available.

Redshift
The redshift of the source.

Ref_Redshift
The reference or bibliographical reference code for the source of the quoted redshift.

Contact Person

Questions regarding the AT20G1FGL database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: Thursday, 26-Aug-2010 13:33:27 EDT