{
  "id": "2502.15235",
  "version": "v2",
  "published": "2025-02-21T06:19:04.000Z",
  "updated": "2025-05-16T13:47:04.000Z",
  "title": "A Stacked Analysis of GeV Gamma-Ray Emission from SPT-SZ Galaxy Clusters with 16 Years of Fermi-LAT Data",
  "authors": [
    "Siddhant Manna",
    "Shantanu Desai"
  ],
  "comment": "14 pages, 9 figures. Some additional tests done. Accepted for publication in Physics of Dark Universe",
  "categories": [
    "astro-ph.HE",
    "astro-ph.CO"
  ],
  "abstract": "We report a statistically significant detection of cumulative $\\gamma$-ray emission from a stacked sample of SPT-SZ selected galaxy clusters using 16.4 years of data from the Fermi Gamma-Ray Space Telescope's Large Area Telescope (LAT). By analyzing a population of clusters with individual Test Statistic (TS) values $<$ 9.0, we identify a robust cumulative signal with a TS of 75.2, which corresponds to approximately $8.4\\sigma$ significance. In contrast, clusters with TS $<$ 4.0 yield a weaker cumulative signal of TS equal to 9.65 (2.65$\\sigma$), consistent with background fluctuations. The derived $\\gamma$-ray spectrum is well characterized by a power law model with a best-fit spectral index of $-2.59 \\pm 0.20$ and an integrated flux of $1.67^{+1.35}_{-1.07} \\times 10^{-11}$ ph cm$^{-2}$ s$^{-1}$. The high TS values in the full sample are likely driven by AGN-dominated clusters. However, when clusters with TS between 4 and 9 are excluded, the remaining low-TS population shows a stacked signal consistent with hadronic emission.",
  "revisions": [
    {
      "version": "v2",
      "updated": "2025-05-16T13:47:04.000Z"
    }
  ],
  "analyses": {
    "keywords": [
      "gev gamma-ray emission",
      "spt-sz galaxy clusters",
      "telescopes large area telescope",
      "gamma-ray space telescopes large",
      "space telescopes large area"
    ],
    "note": {
      "typesetting": "TeX",
      "pages": 14,
      "language": "en",
      "license": "arXiv",
      "status": "editable"
    }
  }
}