Galaxy-cluster-stacked Fermi-LAT III: substructure and radio-relic counterparts
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arXiv
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| Natura: | Preprint |
| Pubblicazione: |
2025
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| _version_ | 1866917954621276160 |
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| author | Keshet, Uri |
| author_facet | Keshet, Uri |
| contents | Faint $γ$-ray signatures emerge in Fermi-LAT data stacked scaled to the characteristic $R_{500}$ radii of MCXC galaxy clusters. This third paper in a series shows a $4.3σ$ excess of discrete 4FGL-DR4 catalog $γ$-ray sources at the $r<1.5R_{500}$ radii of 205 clusters, coincident with an $r\sim R_{500}$ diffuse $2.6σ$ excess of 1-100 GeV emission from 75 high-latitude clusters. The source excess becomes highly ($>5σ$) significant when considering the substantial ($3.4σ$) and unexpectedly rapid quenching of $γ$-ray sources just inside the virial shock. The excess sources show radial, spectral, and luminosity distributions better matching radio-relic counterparts or substructure than present tentative classifications as blazar-candidates. Their spectral distribution is bimodal: flat-spectrum sources are consistent with enhanced hadronic emission behind weak, Mach $\sim2$ shocks, while softer sources may be phoenix counterparts. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2503_09687 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Galaxy-cluster-stacked Fermi-LAT III: substructure and radio-relic counterparts Keshet, Uri High Energy Astrophysical Phenomena Faint $γ$-ray signatures emerge in Fermi-LAT data stacked scaled to the characteristic $R_{500}$ radii of MCXC galaxy clusters. This third paper in a series shows a $4.3σ$ excess of discrete 4FGL-DR4 catalog $γ$-ray sources at the $r<1.5R_{500}$ radii of 205 clusters, coincident with an $r\sim R_{500}$ diffuse $2.6σ$ excess of 1-100 GeV emission from 75 high-latitude clusters. The source excess becomes highly ($>5σ$) significant when considering the substantial ($3.4σ$) and unexpectedly rapid quenching of $γ$-ray sources just inside the virial shock. The excess sources show radial, spectral, and luminosity distributions better matching radio-relic counterparts or substructure than present tentative classifications as blazar-candidates. Their spectral distribution is bimodal: flat-spectrum sources are consistent with enhanced hadronic emission behind weak, Mach $\sim2$ shocks, while softer sources may be phoenix counterparts. |
| title | Galaxy-cluster-stacked Fermi-LAT III: substructure and radio-relic counterparts |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2503.09687 |