Observation of Galactic center in the sub-MeV gamma-ray band with electron-tracking Compton camera
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arXiv
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| Format: | Preprint |
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2025
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| author | Ikeda, Tomonori Tanimori, Toru Takada, Atsushi Takemura, Taito Yoshikawa, Kei Nakamura, Yuta Onozaka, Ken Abe, Mitsuru Mizumura, Yoshitaka |
| author_facet | Ikeda, Tomonori Tanimori, Toru Takada, Atsushi Takemura, Taito Yoshikawa, Kei Nakamura, Yuta Onozaka, Ken Abe, Mitsuru Mizumura, Yoshitaka |
| contents | We report the direct detection of gamma-ray emission from the Galactic center in the 150-600 keV band using the electron-tracking Compton camera (ETCC), which has a wide field of view of 3.1 sr. This represents the first application of this linear, imaging-spectroscopy method to observations of the Galactic center. Measurements in a one-day flight over Australia yielded significant gamma-ray detection in the light curve and revealed a $7.9σ$ excess over the background in the image map from the Galactic center region. These results, obtained through a simple and unambiguous analysis, demonstrate the high reliability and sensitivity of the ETCC and establish its potential for future high-precision MeV gamma-ray observations. The measured intensity and spatial distribution were tested against three emission models: a single point-like source, a multi-component structure, and a symmetric two-dimensional Gaussian. All three were found to be statistically consistent with the data. The positronium-related flux provided by the multi-component model is $(3.2~\pm~1.4) \times 10^{-2}$ photons cm$^{-2}$s$^{-1}$, consistent with the value reported by INTEGRAL within $1σ$. These results establish the potential of the ETCC for future high-precision MeV gamma-ray surveys. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2509_15851 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Observation of Galactic center in the sub-MeV gamma-ray band with electron-tracking Compton camera Ikeda, Tomonori Tanimori, Toru Takada, Atsushi Takemura, Taito Yoshikawa, Kei Nakamura, Yuta Onozaka, Ken Abe, Mitsuru Mizumura, Yoshitaka High Energy Astrophysical Phenomena High Energy Physics - Experiment We report the direct detection of gamma-ray emission from the Galactic center in the 150-600 keV band using the electron-tracking Compton camera (ETCC), which has a wide field of view of 3.1 sr. This represents the first application of this linear, imaging-spectroscopy method to observations of the Galactic center. Measurements in a one-day flight over Australia yielded significant gamma-ray detection in the light curve and revealed a $7.9σ$ excess over the background in the image map from the Galactic center region. These results, obtained through a simple and unambiguous analysis, demonstrate the high reliability and sensitivity of the ETCC and establish its potential for future high-precision MeV gamma-ray observations. The measured intensity and spatial distribution were tested against three emission models: a single point-like source, a multi-component structure, and a symmetric two-dimensional Gaussian. All three were found to be statistically consistent with the data. The positronium-related flux provided by the multi-component model is $(3.2~\pm~1.4) \times 10^{-2}$ photons cm$^{-2}$s$^{-1}$, consistent with the value reported by INTEGRAL within $1σ$. These results establish the potential of the ETCC for future high-precision MeV gamma-ray surveys. |
| title | Observation of Galactic center in the sub-MeV gamma-ray band with electron-tracking Compton camera |
| topic | High Energy Astrophysical Phenomena High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2509.15851 |