Search for High-redshift Blazars with Fermi/LAT

Kreter, M.; Gokus, A.; Krauß, F.; Kadler, M.; Ojha, R.; Buson, S.; Wilms, J.; Böttcher, M.

doi:10.3847/1538-4357/abb8da

Cited by 8 publications

(9 citation statements)

References 33 publications

(23 reference statements)

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“…The transient nature of the MeV-blazar phenomenon is evidence for the presence of this population of soft FSRQs with a steep Γ (E > 100 MeV) on an approximately 1-month timescale. The month-scale variability and the pronounced increase of the emission in the keV-MeV regime are also reported by Kreter et al (2020) in their search for high-redshift blazars. The large distances of these sources and the subsequent redshifting of their emission mean that the γ-ray emission is shifted toward longer wavelengths.…”

Section: Spectral Propertiessupporting

confidence: 61%

Catalog of Long-term Transient Sources in the First 10 yr of Fermi-LAT Data

Baldini

Ballet

Bastieri

et al. 2021

ApJS

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We present the first Fermi Large Area Telescope (LAT) catalog of long-term γ-ray transient sources (1FLT). This comprises sources that were detected on monthly time intervals during the first decade of Fermi-LAT operations. The monthly timescale allows us to identify transient and variable sources that were not yet reported in other Fermi-LAT catalogs. The monthly data sets were analyzed using a wavelet-based source detection algorithm that provided the candidate new transient sources. The search was limited to the extragalactic regions of the sky to avoid the dominance of the Galactic diffuse emission at low Galactic latitudes. The transient candidates were then analyzed using the standard Fermi-LAT maximum likelihood analysis method. All sources detected with a statistical significance above 4σ in at least one monthly bin were listed in the final catalog. The 1FLT catalog contains 142 transient γ-ray sources that are not included in the 4FGL-DR2 catalog. Many of these sources (102) have been confidently associated with active galactic nuclei (AGNs): 24 are associated with flat-spectrum radio quasars, 1 with a BL Lac object, 70 with blazars of uncertain type, 3 with radio galaxies, 1 with a compact steepspectrum radio source, 1 with a steep-spectrum radio quasar, and 2 with AGNs of other types. The remaining 40 sources have no candidate counterparts at other wavelengths. The median γ-ray spectral index of the 1FLT-AGN sources is softer than that reported in the latest Fermi-LAT AGN general catalog. This result is consistent with the hypothesis that detection of the softest γ-ray emitters is less efficient when the data are integrated over year-long intervals. Unified AstronomyThesaurus concepts: High energy astrophysics (739); Active galactic nuclei (16); Gamma-ray bursts (629); Solar flares (1496); Solar gamma-ray emission (1497); Gamma-rays (637); Gamma-ray sources (633); Catalogs (205); Gamma-ray telescopes (634); Gamma-ray transient sources (1853); Blazars (164); Quasars (1319) Supporting material: figure set, machine-readable tables, FITS file 74 Funded by contract FIRB-2012-RBFR12PM1F from the Italian Ministry of Education, University and Research (MIUR).

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Section: Spectral Propertiessupporting

confidence: 61%

Catalog of Long-term Transient Sources in the First 10 yr of Fermi-LAT Data

Baldini

Ballet

Bastieri

et al. 2021

ApJS

Self Cite

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“…4, which show at least one entry with a TS ≥ 9. A more detailed background determination can be found in [15]. PKS 0537−286 (z = 3.10) in our sample.…”

Section: Background Determinationmentioning

confidence: 93%

“…The light curve is shown for the energy range of 100 MeV to 300 GeV. This source was detected in December 2016 on daily time scales during a bright flare, as indicated by the red arrow.Figure takenfrom[15].…”

mentioning

confidence: 99%

Search for high-redshift blazars with Fermi/LAT

Kreter¹,

Gokus²,

Kadler³

et al. 2020

Proceedings of 7th Annual Conference on High Energy Astrophysics in Southern Africa — PoS(HEASA2019)

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High-redshift blazars (z ≥ 2.5) are the most powerful class of persistent γ-ray sources in the Universe. These objects possess the highest jet powers and luminosities and have black hole masses often in excess of 10 9 solar masses. In addition, high-z blazars are important cosmological probes and serve as test objects for blazar evolution models. Due to their large distance and the resulting electron/positron cascading on the extragalactic background light, their high-energy emission typically peaks below the GeV range. This makes these blazars difficult to study with Fermi/LAT and only the very brightest objects are detectable. Hence, only a small number of high-z blazars could be detected with Fermi/LAT so far. In this work, we present a strategy to increase the detection statistics at redshift z ≥ 2.5 via a search for flaring events in high-z γ-ray blazars whose long-term averaged flux is just below the sensitivity limit of Fermi/LAT. Seven previously GeV undetected high-z blazars have been identified with a test statistic of TS ≥ 25 from their bright monthly outburst periods, while more detections are expected in the future.

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“…Among the many discoveries enabled by relentless efforts from the gamma-ray community, one could highlight the discovery of the gravitationally-lensed FSRQ B2 0218+35 located at z = 0.954 (d ∼ 6000 Mpc), a distance record for AGNs observed above 100 GeV, only recently superseded by the detection of an FSRQ announced at z = 0.991 [25]. For comparison, blazars observed by Fermi-LAT have been firmly detected above 100 MeV from beyond z = 3 and tentative detections have even been reported out to z > 4 [26]. Other interesting discoveries lie in the few dozen objects above 100 MeV that do not belong to the classical types of extragalactic gamma-ray sources, namely blazars and radio galaxies.…”

Section: The Extragalactic Gamma-ray Skymentioning

confidence: 99%

Gamma-Ray Cosmology and Tests of Fundamental Physics

Biteau

Meyer

2022

Galaxies

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The propagation of gamma-rays over cosmological distances is the subject of extensive theoretical and observational research at GeV and TeV energies. The mean free path of gamma-rays in the cosmic web is limited above 100 GeV due to the production of electrons and positrons on the cosmic optical and infrared backgrounds. Electrons and positrons cool in the intergalactic medium while gyrating in its magnetic fields, which could cause either its global heating or the production of lower-energy secondary gamma-rays. The energy distribution of gamma-rays surviving the cosmological journey carries observed absorption features that gauge the emissivity of baryonic matter over cosmic time, constrain the distance scale of ΛCDM cosmology, and limit the alterations of the interaction cross section. Competitive constraints are, in particular, placed on the cosmic star-formation history as well as on phenomena expected from quantum gravity and string theory, such as the coupling to hypothetical axion-like particles or the violation of Lorentz invariance. Recent theoretical and observational advances offer a glimpse of the multi-wavelength and multi-messenger path that the new generation of gamma-ray observatories is about to open.

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Search for High-redshift Blazars with Fermi/LAT

Cited by 8 publications

References 33 publications

Catalog of Long-term Transient Sources in the First 10 yr of Fermi-LAT Data

Catalog of Long-term Transient Sources in the First 10 yr of Fermi-LAT Data

Search for high-redshift blazars with Fermi/LAT

Gamma-Ray Cosmology and Tests of Fundamental Physics

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