Fermi Gamma-ray Space Telescope

Preliminary LAT 8-year Point Source List (FL8Y)

This page provides a preliminary Fermi Large Area Telescope (LAT) list of sources (FL8Y) initially meant to help in writing 2018 NASA Fermi Guest Investigator proposals. Based on the first eight years of science data from the Fermi Gamma-ray Space Telescope mission and the 100 MeV-1 TeV range, it is the deepest yet in this energy range. Relative to the 3FGL catalog, the FL8Y source list has twice as much exposure as well as a number of analysis improvements, but is lacking an updated model for Galactic diffuse gamma-ray emission. The FL8Y source list includes 5523 sources above 4-sigma significance, with source location regions and spectral properties. Fifty-eight sources are modeled explicitly as spatially extended, and overall 300 sources are considered as identified based on angular extent or correlated variability (periodic or otherwise) observed at other wavelengths. For 2131 sources we have not found plausible counterparts at other wavelengths. More than 2900 of the identified or associated sources are active galaxies of the blazar class, 218 are pulsars. This source list is meant to be replaced within a few months by the official 4FGL catalog which will benefit from an improved model of diffuse emission.


The FL8Y list is meant to provide researchers analyzing Fermi data with an updated description of the gamma-ray sky with respect to 3FGL. It contains nearly 2500 new sources which can be used as a starting point for new works. It can also be used for modelling the source background in a region of interest.

Being a courtesy effort, FL8Y is neither published nor posted on the arXiv. We request the community users to refrain from publishing works (in particular population studies) using directly material from FL8Y, and wait for the future 4FGL catalog that will supersede FL8Y.

FL8Y Source List Data Products

The 8-year Source List is currently available as a FITS file. Supporting tools and documentation have been provided and are linked below.

Using the FL8Y Point Source List in Xamin

You can use the HEASARC Xamin interface to upload, query and cross-correlate the FL8Y point source catalog. To do this:
  1. Download the comma-separated values (.csv) version of the FL8Y point source catalog.
  2. Go to the Xamin home page.
  3. In the "Query Pane" window, click the "Select File" button (note: if the Query Pane is not visible, click on the magnifying glass icon at the top left of the main Xamin window).
  4. Choose the comma-separated version (.csv) of the FL8Y point source catalog that you downloaded to upload into Xamin (upload should take 2-3 seconds if your upload speed is 1MB/s).
The FL8Y point source catalog will now appear as a table labelled "Upload" in the "Selected Tables" box in the Xamin Query Pane. You can now do all the things with this table that you can do with internal tables in Xamin: display the table and search by parameter, use Xamin to make plots of one parameter versus another, make a sky plot of sources, and cross-correlate the uploaded FL8Y point source table with other Xamin catalogs (both positional cross-correlations and parameter cross-correlations are supported, and anti-correlations are allowed as well). You can view the Xamin User Upload video for details on file uploads in Xamin, if necessary, which also gives examples of performing positional cross-correlations and anti-correlations.

FL8Y Source List Change Log

Rev Date Filename Change Description
v6 03 May 2018 gll_psc_8year_v6.fit Corrects a mistake in the solar flare screening. Three sources (FL8Y J2229.7-0832 = PKS 2227-08, PSR J2310-0555 and FL8Y J2319.5-0458) were seriously affected in the previous version (brighter than they should have been). One faint source (FL8Y J2306.9-0333) was entirely spurious and has gone away. Five other nearby sources have changed a little. The FITS file now contains the Flags column.
v5 26 Jan 2018 gll_psc_8year_v5.fit Corrects association names. One point source was mistakenly associated to the SMC and is now considered unassociated.
v4 10 Jan 2018 gll_psc_8year_v4.fit Corrected mistake in LP_Index column. Other spectral columns have changed slightly, 16 positive flags are now 0 and three 0FGL sources are reported in ASSOC_GAM.
v3 03 Jan 2018 gll_psc_8year_v3.fit Initial Release