Search in
Xamin or Browse...

FERMILPSC - Fermi LAT 14-Year Point Source Catalog (4FGL-DR4)

 HEASARC
Archive

Overview

The Fermi Point Source Catalog (4FGL) is a catalog of high-energy gamma-ray sources detected by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope. The 14-year catalog is an incremental version (4FGL-DR4, for Data Release 4) of the fourth Fermi-LAT catalog of gamma-ray sources. Based on the first fourteen years of science data in the energy range from 50 MeV to 1 TeV, it uses the same analysis methods as the 4FGL- DR3 catalog did for 12 years of data. The spectral parameters, spectral energy distributions, light curves and associations are updated for all sources.

Catalog Bibcode

2023arXiv230712546B

Bulletin

The FERMILPSC database table was last updated on 22 February 2024.

Caveats

We emphasize several important points and caveats regarding use of the 4FGL-DR4 catalog:

  • This work is a summary of the LAT results covering the time period August 4, 2008, to August 2, 2022.
  • The analysis is based on data in the 50 MeV to 1 TeV energy range.
  • Source detection is based on the integrated data set, i.e., sources are detected according to their average fluxes.
  • The catalog adopted multiple spectral shapes, depending on the observed source properties. Pulsars are modeled by an exponentially cutoff Power Law. Others are modeled as a LogParabola if statistically significant curvature (according to Signif_Curve) is detected, or as a simple Power Law otherwise.
  • After computing the maximum likelihood, the threshold for inclusion of new sources is likelihood Test Statistic TS > 25, corresponding to somewhat more than 4 sigma significance. The catalog has 7194 sources. All previous 4FGL sources (except for a few discussed in the paper) are retained in the 4FGL-DR4 even if TS < 25.
  • The corresponding energy flux limit varies according to the hardness of the source spectrum and the brightness of the background Galactic diffuse emission.
  • Catalog entries include quality flags that indicate potential issues: any non-zero entry in the "Flags" column indicates that the source is affected by systematic errors (see the table in the preprint for details). Sources with these indicators should be used with great care. They correspond to significant excesses of photons, but such excesses can result from residual extended emission or confused source pile-up.
  • The catalog analysis assumed point source emission for all but 82 extended sources, which were modeled using spatial templates and are indicated by an "e" following the name. Results for extended sources such as the LMC and Cen A lobes are likely to not be representative of the total emission, and additional catalog point sources may appear near such objects.
  • The Crab pulsar and PWN are represented by a total of three entries, two of which (designated "i" for inverse compton and "s" for synchrotron) represent spectral components of the PWN. We consider these three entries to represent two sources.
  • Associations listed in the catalog are not in general to be taken as firm identifications. Associations are positional coincidences that are statistically unlikely to be due to chance alignment between known and candidate gamma-ray producing objects with 4FGL-DR4 sources. Upper case in the CLASS1 column means identified. Except for those cases with correlated variability or spatial extent, a physical relationship is not established. The designators for some associated sources may be updated in a future release to use more common or more complete names.
  • The DR4 catalog was developed using a smooth spatial and spectral rescaling of the 4FGL Galactic diffuse model gll_iem_v07, as explained in Sect 2.2 of the document. The adjustment is largely equivalent to modulating the gll_iem_v07 model with a LogParabola spectral shape in each region of interest. It is not recommended as an all-purpose replacement for gll_iem_v07 because its behavior above 10 GeV was not carefully controlled, but it can be used in the GeV domain following the DR4 prescription (modulated by a power law and associated with the fixed isotropic spectrum and the DR4 background of sources). When using it, please quote "the rescaled gll_iem_v07 interstellar emission model associated to the 4FGL-DR4 catalog" and cite the DR4 document (link to document). This rescaled diffuse model has the same limitations as gll_iem_v07, and comparing results obtained with this rescaled model and with gll_iem_v07 cannot quantify systematic errors due to the model of the diffuse emission.

References

A full description of the LAT Fourth Point Source Catalog is given in the "Fermi Large Area Telescope Fourth Source Catalog" by the Fermi LAT team.

The 4FGL-DR2 update is described in Fermi Large Area Telescope Fourth Source Catalog Data Release 2.

The 4FGL-DR3 update is described in Fermi Large Area Telescope Fourth Source Catalog Data Release 3.

The 4FGL-DR4 update is described in Fermi Large Area Telescope Fourth Source Catalog Data Release 4.

Additional information is available at http://fermi.gsfc.nasa.gov/ssc/data/access/lat/14yr_catalog/.

Provenance

This database table was last updated by the HEASARC in February 2024, using the latest electronic data obtained from the Fermi Science Support Center (FSSC) available at http://fermi.gsfc.nasa.gov/ssc/data/access/lat/14yr_catalog/.

Parameters

Name
The source designation, 4FGL JHHMM.m+DDMM[c], constructed according to the IAU Specifications for Nomenclature, in which the Right Ascension and Declination have been truncated to 0.1 decimal minutes and 1', respectively. The '4' refers to the eight-year catalog (the first-year catalog was '1'; the second-year catalog was '2'; the four-year catalog was '3') and 'FGL' represents Fermi Gamma-ray LAT. The letter at the end can be "c" (coincident with interstellar clump), "e" (extended source), "i" (for Crab nebula inverse Compton) or "s" (for Crab nebula synchrotron).

Data_Release
The data release in which the source was added to the catalog: '1' for the original 8-year catalog, '2' for the 10-year catalog, '3' for the 12-year catalog, '4' for the 14-year catalog.

RA
The Right Ascension of the gamma-ray source in the selected equinox. This was given in J2000 decimal degree coordinates in the original table.

Dec
The Declination of the gamma-ray source in the selected equinox. This was given in J2000 decimal degree coordinates in the original table.

LII
The Galactic Longitude of the gamma-ray source, as derived from the J2000 position in the original table.

BII
The Galactic Latitude of the gamma-ray source, as derived from the J2000 position in the original table.

Semi_Major_Axis_68
The semi-major axis of the error ellipse at 68% confidence, in degrees.

Semi_Minor_Axis_68
The semi-minor axis of the error ellipse at 68% confidence, in degrees.

Position_Angle_68
The position angle of the 68%-confidence semi-major axis, from celestial North, positive toward increasing R.A. (eastward), in degrees.

Semi_Major_Axis_95
The semi-major axis of the error ellipse at 95% confidence, in degrees.

Semi_Minor_Axis_95
The semi-minor axis of the error ellipse at 95% confidence, in degrees.

Position_Angle_95
The position angle of the 95%-confidence semi-major axis, from celestial North, positive toward increasing R.A. (eastward), in degrees.

Detection_Significance
The source detection significance, in Gaussian sigma units, over the 100 MeV to 1 TeV band.

Pivot_Energy
The 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 - 1 TeV.

Flux_1_100_GeV
The integral photon flux for 1 - 100 GeV, in photons/cm2/s.

Flux_1_100_GeV_Error
The 1-sigma uncertainty in the integral photon flux for 1 - 100 GeV, in photons/cm2/s.

Energy_Flux
The energy flux, in erg/cm2/s, in the 100 MeV to 100 GeV range obtained by spectral fitting from 100 MeV to 100 GeV.

Energy_Flux_Error
The 1-sigma error on energy flux from 100 MeV to 100 GeV.

Spectrum_Type
The spectral type in the global model (PowerLaw, LogParabola, PLSuperExpCutoff).

PL_Flux_Density
The differential flux at pivot_energy for the PowerLaw fit, in photons/cm2/MeV/s.

PL_Flux_Density_Error
The 1-sigma uncertainty in differential flux at pivot_energy in PowerLaw fit, in photons/cm2/MeV/s.

PL_Index
The photon index for the PowerLaw fit.

PL_Index_Error
The 1-sigma uncertainty on the photon index for PowerLaw fit.

LP_Flux_Density
The differential flux at pivot_energy for the LogParabola fit, in photons/cm2/MeV/s.

LP_Flux_Density_Error
The 1-sigma uncertainty in differential flux at pivot_energy in LogParabola fit, in photons/cm2/MeV/s. lp_index The 1-sigma uncertainty on the photon index for LogParabola fit.

LP_Index
Photon Index at Pivot Energy for LogParabola Fit

LP_Index_Error
The 1-sigma uncertainty on the photon index for LogParabola fit.

LP_Beta
The curvature parameter (beta) for LogParabola spectrum types.

LP_Beta_Error
The 1-sigma uncertainty on lp_beta for LogParabola spectrum types.

LP_Curve_Significance
The significance in sigma of the fit improvement between PowerLaw and LogParabola fits.

LP_Epeak
Peak energy in nuFnu estimated from LogParabola model.

LP_Epeak_Error
The 1-sigma uncertainty on peak energy for LogParabola model.

PLEC_Flux_Density
The differential flux at pivot_energy for the PLSuperExpCutoff fit, in photons/cm2/MeV/s.

PLEC_Flux_Density_Error
The 1-sigma uncertainty in differential flux at pivot_energy in PLSuperExpCutoff fit, in photons/cm2/MeV/s.

PLEC_Index_S
The best fit local photon index at pivot_energy in the PLSuperExpCutoff model.

PLEC_Index_S_Error
The 1-sigma uncertainty on plec_index_s for PLSuperExpCutoff fit.

PLEC_Exp_Factor_S
The best fit local spectral curvature at pivot_energy in the PLSuperExpCutoff model.

PLEC_Exp_Factor_S_Error
The 1-sigma uncertainty on plec_exp_factor_s for PLSuperExpCutoff fit.

PLEC_Exp_Index
The exponential index for PLSuperExpCutoff fit.

PLEC_Exp_Index_Error
The 1-sigma uncertainty on exponential index for the PLSuperExpCutoff fit.

PLEC_Curve_Significance
The significance in sigma of the fit improvement between PowerLaw and PLEC fits.

PLEC_Epeak
Peak energy in nuFnu estimated from PLSuperExpCutoff model.

PLEC_Epeak_Error
The 1-sigma uncertainty on peak energy for PLSuperExpCutoff model.

Npred
The number of predicted events in the model.

Variability_Index
The sum of the log(likelihood) difference between the flux fitted in each time interval and the average flux over the full catalog interval; a value greater than 27.69 over 12 intervals indicates <1% chance of being a steady source. See the accompanying paper for details.

Frac_Variability
The fractional variability computed from the fluxes in each year.

Frac_Variability_Error
The 1-sigma uncertainty on exponential index on the fractional variability.

Significance_Peak
The source significance in peak interval in sigma units.

Flux_Peak
The peak integral photon flux from 100 MeV to 100 GeV, in photon/cm2/s.

Flux_Peak_Error
The 1-sigma error on peak integral photon flux, in photon/cm2/s

Time_Peak
Time of center of interval in which peak flux was measured, in MJD.

Time_Peak_Interval
Length of interval in which peak flux was measured, in seconds.

Alt_GammaRay_Name_1
Most recent correspondence to previous FGL source catalogs, if any.

Alt_GammaRay_Name_2
Most recent correspondence to previous FHL source catalogs, if any.

Alt_GammaRay_Name_3
Name of likely corresponding source from AGL source catalogs, if any.

Alt_GammaRay_Name_4
Name of likely corresponding 3EG source, if any.

Alt_GammaRay_Name_5
Name of likely corresponding EGR source, if any.

Alt_GammaRay_Name_6
Name of corresponding 4FGL-DR2 source, if any.

Extended_Source_Name
The extended source identification, if any.

TeVCat_Flag
This flag parameter indicates a possible association with the TeVCat. The flag values have the following meanings: 

             N = No TeV association
             P = Small TeV source
             E = Extended TeV source (diameter > 40 arcminutes)

TeVCat_Assoc
The designation of the likely corresponding source from the TeVCat catalog, if any.

Source_Type
The primary class designation of the identification or likely associated source. Refer to the accompanying 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. The following abbreviations are used: 

            agn   = other non-blazar active galaxy
            bcu   = active galaxy of uncertain type
            bin   = binary
            bll   = BL Lac type of blazar
            css   = compact steep spectrum quasar
            fsrq  = FSRQ type of blazar
            gal   = normal galaxy (or part)
            glc   = globular cluster
            hmb   = high-mass binary
            mc    = molecular cloud
            nlsy1 = narrow line Seyfert 1
            nov   = nova
            PSR   = pulsar, identified by pulsations
            psr   = pulsar, no pulsations seen in LAT yet
            pwn   = pulsar wind nebula
            rdg   = radio galaxy
            sbg   = starburst galaxy
            sey   = Seyfert galaxy
            sfr   = star-forming region
            snr   = supernova remnant
            spp   = special case - potential association with SNR or PWN
            ssrq  = soft spectrum radio quasar
            unk   = unknown

Source_Type_Alt
Class designation for an alternative, low-confidence association.

Assoc_Name
The designation of the identified or likely associated source.

Assoc_Name_Alt
The alternate designation or an indicator as to whether the source is inside an extended source.

Assoc_Prob_Bay
The probability of association according to the Bayesian method. It is set to NULL for extended sources (which do not enter that calculation) and to 0 for point sources that did not reach 0.8, the threshold for declaring associations.

Assoc_Prob_LR
The probability of association according to the Likelihood Ratio method. It is set to NULL for extended sources (which do not enter that calculation) and to 0 for point sources that did not reach 0.8, the threshold for declaring associations.

Assoc_RA
The Right Ascension of assoc_name counterpart, in degrees.

Assoc_Dec
The Declination of assoc_name counterpart, in degrees.

Assoc_Error_Radius
The position uncertainty at 68% confidence level of the counterpart localization for assoc_name, in degrees.

Analysis_Flags
These analysis flags indicate possible issues noted in the detection or characterization of the source. A value of 0 indicates no known problem. Each condition present raises a unique bit flag. The flag values are bit-encoded into a single integer, with flag N contributing 2N-1 to the value, where N is given as: 

      N=1: Source with TS > 35 which went to TS < 25 when changing the diffuse
           model. Note that sources with TS < 35 are not flagged with this bit
           because normal statistical fluctuations can push them to TS < 25.

      N=2: Not used.

      N=3: Flux (> 1 GeV) or energy flux (> 100 MeV) changed by more than 3
           sigma when changing the diffuse model or the analysis method. Requires
           also that the flux change by more than 35% (to not flag strong
           sources).

      N=4: Not used.

      N=5: Not used.

      N=6: Not used.

      N=7: Not used.

      N=8: Not used.

      N=9: Localization Quality > 8 in pointlike (see Section 3.1 in catalog
           paper) or long axis of 95% ellipse > 0.25.

      N=10: Spectral Fit Quality > 30 in pointlike.

      N=11: Not used.

      N=12: Highly curved spectrum; LogParabola beta fixed to 1 or PLEC_Index
            fixed to 0 (see Section 3.3 in catalog paper).

Contact Person

Questions regarding the FERMILPSC database table can be addressed to the HEASARC Help Desk.
Page Author: Browse Software Development Team
Last Modified: Monday, 16-Sep-2024 17:27:36 EDT