J/MNRAS/539/1458 First Cosmic Gamma-Ray Horizon Catalogue, 1CGH (Arsioli+, 2025)
Mapping the cosmic gamma-ray horizon:
The 1CGH catalogue of Fermi-LAT detections above 10 GeV.
Arsioli B., Chang Y.-L., Ighina L.
<Mon. Not. R. Astron. Soc. 539, 1458-1470 (2025)>
=2025MNRAS.539.1458A 2025MNRAS.539.1458A (SIMBAD/NED BibCode)
ADC_Keywords: Gamma rays ; Surveys ; Galaxy catalogs ; QSOs ; BL Lac objects ;
Redshifts
Keywords: gamma-rays: galaxies - galaxies: active - catalogues -
radiation mechanisms: non-thermal
Abstract:
We present the First Cosmic Gamma-ray Horizon (1CGH) catalogue,
featuring gamma-ray detections above 10GeV based on 16 years of
observations with the Fermi Large Area Telescope (LAT) satellite.
After carefully selecting a sample of blazars and blazar candidates
from catalogues in the literature, we performed a binned likelihood
analysis and identified 2791 gamma-ray emitters above 10 GeV, at >3
sigma level, including 62 that are new gamma-ray detections. For each
source, we estimated the mean energy of the highest- energy bin and
analysed them in the context of the cosmic gamma-ray horizon. By
adopting a reference model for the Extragalactic Background Light
(EBL), we identified a subsample of 525 sources where moderate to
severe gamma-ray absorption could be detected across the redshift
range of 0 to 3. This work provides the most up-to-date compilation of
detections above 10GeV, along with their redshift information. We
condense extensive results from the literature, including reports on
observational campaigns dedicated to blazars and gamma-ray sources,
thereby delivering an unprecedented review of the redshift information
for sources detected above 10GeV. Additionally, we highlight key 1CGH
sources where redshift information remains incomplete, offering
guidance for future optical observation campaigns. The 1CGH catalogue
aims to track the most significant sources for studying the gamma-ray
transparency of the universe. Furthermore, it provides a targeted
subsample where the EBL optical depth (tau(E,z)) can be robustly
measured using Fermi-LAT data.
Description:
In this work, we use Fermi-LAT observations spanning the first 16
years of the mission (August 2008 to August 2024) to search for
gamma-ray signatures associated with a sample of blazars and blazar
candidates. By focusing on sources detectable above 10 GeV, we aim to
provide a catalogue where the EBL absorption is most pronounce and
could be effectively measured in the highest energy bins. To create a
robust gamma-ray sample suitable for studying EBL attenuation, we
calculate the mean energy of the four highest-energy photons detected
for each source. This approach offers a more stable and representative
measure of the highest energy bin (Ebin_max) detectable by Fermi-LAT,
particularly when ranking sources that experience moderate to severe
absorption, compared to using only the highest-energy photon (E_max).
The First Cosmic Gamma-ray Horizon (1CGH) catalogue represents a
significant step forward in describing the gamma-ray horizon, and will
contribute to our measurements of the EBL content and star formation
rate across cosmic history. This work builds upon and complements
existing efforts, such as the 3FHL catalogue [2017ApJS..232...18A 2017ApJS..232...18A], by
adopting a strategy with the following key aspects: an extended
observational period spanning 16 years, the targeted use of blazar
positions as seeds for gamma-ray analysis, the inclusion of sources
down to a lower detection threshold (i.e., >3 sigma), and an extensive
redshift review. These choices aim to highlight blazars that can serve
as valuable targets for investigating the transparency of the universe
to gamma- rays.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
1cgh_v1.dat 461 2791 First Cosmic Gamma-ray Horizon (1CGH) catalogue
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See also:
VII/274 : The Roma BZCAT - 5th edition (Massaro+, 2015)
IX/67 : Incremental Fermi LAT 4th source cat. (4FGL-DR3)
(Fermi-LAT col., 2022)
J/A+A/632/A77 : 3HSP blazars catalog (Chang+, 2019)
Byte-by-byte Description of file: 1cgh_v1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- 1CGH Source identifier, formatted as
1CGHJHHMM+DDMM, based on J2000
coordinates (1CGH_name) (1)
16- 24 F9.5 deg RAdeg Right Ascension (J2000) (RA_1CGH)
26- 34 F9.5 deg DEdeg Declination (J2000) (DEC_1CGH)
36- 81 A46 --- CtpName Name of the source from catalogs
such as 5BZcat, 3HSP, 4FGL-DR4,
or others (Counterpart_name)
83- 90 F8.3 10-16ph/cm2/s/MeV N0 Normalization constant of the
power-law fit at the pivot
energy (N0[1E-16])
92- 99 F8.4 10-16ph/cm2/s/MeV e_N0 Uncertainty in the normalization
constant (N0_err[1E-16])
101-104 F4.2 --- Index Photon spectral index of the
power-law model (Index)
106-109 F4.2 --- e_Index ?=- Uncertainty in the photon
spectral index (Index_err)
111-118 F8.3 10-12ph/cm2/s Flux Integrated photon flux
(10-800GeV), estimated with a
power-law fit (Flux[1E-12])
120-127 F8.4 10-12ph/cm2/s e_Flux Uncertainty in the integrated
photon flux (Flux_err[1E-12])
129-135 F7.1 --- TS Test Statistic value for the
source detection (TS)
137-142 F6.2 --- sigma The significance for the source
detection (sigma)
144-149 F6.4 --- z ?=- Redshift of the source (z)
151 I1 --- f_z [1/3]? Redshift reliability flag
(zflag) (2)
153-215 A63 --- r_z Reference for the redshift, as
described in the text
(z_origin) (3)
217-220 I4 --- Nph128 Number of photons associated
(Source_type events,
evclass=128) (Nph_128)
222-229 F8.3 GeV Emax128 Maximum photon energy detected
(evclass=128) (Emax_128[GeV])
231-234 I4 --- Nph512 Number of photons associated
(UltraClean_type events,
evclass=512) (Nph_512)
236-242 F7.3 GeV Emax512 Maximum photon energy detected
(evclass=512) (Emax_512[GeV])
244-251 F8.3 GeV Ebinmax Mean energy of the four
highest-energy photons
(evclass=128) (Ebin_max[GeV])
253-262 F10.8 --- TransEbin ?=- Flux transmission factor at
Ebin_max. (TransmissionEbin)
264-273 F10.8 --- AbsEbin ?=- Flux absorption factor at
Ebin_max, calculated as
(1 - Transmission) (AbsEbin)
275-282 F8.6 --- tauEbin ?=- EBL optical depth at Ebin_max
(tauEbin)
284 I1 --- Absflag [0/1]? Absorption flag
(Abs_flag) (4)
286-294 F9.5 deg GLAT Galactic latitude (GAL_LAT)
296-309 A14 --- BZcat Identifier in the 5BZcat
catalogue, if available. (BZcat)
311-316 F6.4 --- z3HSP ?=- Redshift from the 3HSP
catalogue, if available (z_3HSP)
318 I1 --- f_z3HSP [1/5]?=- Redshift flag from the
3HSP catalogue (zflag_3HSP) (5)
322-339 A18 --- 4FGL Counterpart name in 4FGL-DR4
(4FGLcountername)
341 A1 --- f_4FGL Flag for TeVCat association, as
per 4FGL-DR4
(TEVCATFLAG4FGLdr4)
343-363 A21 --- Ass4FGL4 TeV association in 4FGL-DR4
(ASSOCTEV4FGLdr4)
365-369 A5 --- Class4FGL4 Classification in 4FGL-DR4
(CLASS1_4FGLdr4)
371-398 A28 --- Asso4FGL4 Counterpart name in 4FGL-DR4
(ASSOC1_4FGLdr4)
400-416 A17 --- 4LACdr3 Counterpart name in 4LAC-DR3
(Name_4LACdr3)
418-425 F8.6 --- z4LACdr3 ?=- Redshift as reported in
4LAC-DR3. (z4LACdr31)
427-443 A17 --- 3FHL Counterpart name in 3FHL
(Name_3FHL)
445-452 F8.6 --- z3FHL ?=- Redshift as reported in 3FHL
(z_3FHL)
454-461 F8.6 --- Curv3FHL ?=- Detectable spectral curvature
in 3FHL (Curvature_3FHL) (6)
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Note (1): Includes four digits each for R.A. and Dec. For associated sources,
the coordinates are from the counterpart; for unassociated sources,
we follow 4FGL-DR4 astrometry
Note (2): Redshift reliability flag as follows:
1 = spectroscopic
2 = photometric/uncertain
3 = lower limit
Note (3): For cases with no corresponding redshift value, it tracks sources
where spectroscopic observation has been attempted.
Note (4): Absorption flag as follows:
1 = tau > 0.1 (moderate to severe absorption)
0 = tau<0.1 (nearly no absorption)
Note (5): Redshift flag from the 3HSP catalogue as follows:
1 = spectroscopic
2 = uncertain
3 = lower limit redshift
4 = photometric, with featureless optical spectrum
5 = photometric, without optical spectrum
Note (6): (1)yes, (2)no, (-) unknown. Sources marked as "unknown" are out of
the 3FHL catalogue.
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History:
From Bruno Arsioli, bsarsioli(at)ciencias.ulisboa.pt
Acknowledgements:
The authors thank the anonymous Referee for the careful review and
helpful comments that improved the quality -and impact- of our work.
BA thanks the Institute of Astrophysics and Space Sciences (IA) at the
University of Lisbon for their ongoing support. BA is currently a
Marie Skodowska-Curie Postdoctoral Fellow at IA, funded by the
European Union's Horizon 2020 research and innovation program under
the MSCA agreement No. 101066981. BA also acknowledges the support
from 'Fundacao para a Ciencia e a Tecnologia' (FCT) through the
research grant UIDP/04434/2020 (DOI: 10.54499/UIDP/04434/2020) in
support of general IA activities. This work was produced with the
support of the "National Distributed Computing Infrastructure" (INCD),
Portugal (https://www.incd.pt), funded by FCT and FEDER under project
01/SAICT/2016 No. 022153. We acknowledge FCT's support through the A1
Computation Call (project's doi: 10.54499/2023.09549.CPCA.A1) for the
allocation of HPC resources at INCD. We are grateful to the entire
Fermi-LAT collaboration for maintaining a publicly accessible
mission database, enabling discoveries across the entire gamma-ray
community. We also used archival data and bibliographic information
from the NASA-IPAC Extragalactic Database (NED), and data/software
facilities maintained by the Space Science Data Center (SSDC) from the
Italian Space Agency. We extend our thanks to the TeVCat team,
especially Deirdre Horan and Scott Wakely, for their continuous work
on VHE detections, as well as NASA and NSF for their support of these
follow-up efforts.
(End) Patricia Vannier [CDS] 25-Feb-2025