Resolving the Origin of the Unidentified TeV Source HESS J1626-490 as a Relic of the Ancient Cosmic-Ray Factory SNR G335.2+0.1
While decades of observations in the TeV gamma-ray band have revealed more than 200 sources with radio or X-ray counterparts, there remain dozens of unidentified TeV sources, which may provide crucial information of cosmic-ray (CR) accelerators. HESS J1626−490 is an unidentified TeV gamma-ray source...
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IOP Publishing
2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/adec80 |
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| author | Tomohiko Oka Wataru Ishizaki Masaki Mori Hidetoshi Sano Hiromasa Suzuki Takaaki Tanaka |
| author_facet | Tomohiko Oka Wataru Ishizaki Masaki Mori Hidetoshi Sano Hiromasa Suzuki Takaaki Tanaka |
| author_sort | Tomohiko Oka |
| collection | DOAJ |
| description | While decades of observations in the TeV gamma-ray band have revealed more than 200 sources with radio or X-ray counterparts, there remain dozens of unidentified TeV sources, which may provide crucial information of cosmic-ray (CR) accelerators. HESS J1626−490 is an unidentified TeV gamma-ray source but is expected to originate from CRs that escaped from the nearby supernova remnant (SNR) G335.2+0.1 and are interacting with dense interstellar clouds. To test this scenario, we scrutinize the properties of the SNR and search for nonthermal counterparts by analyzing observational data in the radio, X-ray, and GeV gamma-ray bands. From analysis of the H i and ^12 CO ( J = 1–0) line data, we identify the cloud associated with the SNR and compare the morphologies of the cloud and the gamma-ray emission. The distance and age of the SNR are estimated to be 3.3 ± 0.6 kpc and ∼5 kyr, respectively. From X-ray and GeV gamma-ray data analyses, we find an extended GeV gamma-ray emission overlapping with the SNR and H.E.S.S. source regions but no X-ray emission. The location of the peak of the extended GeV emission changes from near the SNR at ≲1 GeV to the H.E.S.S. source at >10 GeV. We find a spectral hardening at ∼50 GeV, which is consistent with the existence of two components in the gamma-ray emission. We find that a combination of emission from the escaped CRs and the SNR itself can reproduce the observed broadband spectrum, on the assumption that the SNR has accelerated protons to ≳100 TeV in the past. |
| format | Article |
| id | doaj-art-b8e11c0539cc40ae8d59273e64d7deaa |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal |
| spelling | doaj-art-b8e11c0539cc40ae8d59273e64d7deaa2025-08-20T02:58:11ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01989213710.3847/1538-4357/adec80Resolving the Origin of the Unidentified TeV Source HESS J1626-490 as a Relic of the Ancient Cosmic-Ray Factory SNR G335.2+0.1Tomohiko Oka0https://orcid.org/0000-0002-9924-9978Wataru Ishizaki1https://orcid.org/0000-0002-7005-7139Masaki Mori2https://orcid.org/0000-0003-2921-1592Hidetoshi Sano3https://orcid.org/0000-0003-2062-5692Hiromasa Suzuki4https://orcid.org/0000-0002-8152-6172Takaaki Tanaka5https://orcid.org/0000-0002-4383-0368Department of Physical Sciences, Ritsumeikan University , Kusatsu, Shiga 525-8577, Japan ; toka@fc.ritsumei.ac.jp; Research Organization of Science and Technology, Ritsumeikan University , Kusatsu, Shiga 525-8577, JapanCenter for Gravitational Physics, Yukawa Institute for Theoretical Physics, Kyoto University , Kyoto 606-8502, Japan; Astronomical Institute, Graduate School of Science, Tohoku University , Sendai 980-8578, JapanDepartment of Physical Sciences, Ritsumeikan University , Kusatsu, Shiga 525-8577, Japan ; toka@fc.ritsumei.ac.jpFaculty of Engineering, Gifu University , 1-1 Yanagido, Gifu 501-1193, JapanFaculty of Engineering, University of Miyazaki , Miyazaki 889-2192, JapanDepartment of Physics, Konan University , 8-9-1 Okamoto, Higashinada, Kobe, Hyogo 658-8501, JapanWhile decades of observations in the TeV gamma-ray band have revealed more than 200 sources with radio or X-ray counterparts, there remain dozens of unidentified TeV sources, which may provide crucial information of cosmic-ray (CR) accelerators. HESS J1626−490 is an unidentified TeV gamma-ray source but is expected to originate from CRs that escaped from the nearby supernova remnant (SNR) G335.2+0.1 and are interacting with dense interstellar clouds. To test this scenario, we scrutinize the properties of the SNR and search for nonthermal counterparts by analyzing observational data in the radio, X-ray, and GeV gamma-ray bands. From analysis of the H i and ^12 CO ( J = 1–0) line data, we identify the cloud associated with the SNR and compare the morphologies of the cloud and the gamma-ray emission. The distance and age of the SNR are estimated to be 3.3 ± 0.6 kpc and ∼5 kyr, respectively. From X-ray and GeV gamma-ray data analyses, we find an extended GeV gamma-ray emission overlapping with the SNR and H.E.S.S. source regions but no X-ray emission. The location of the peak of the extended GeV emission changes from near the SNR at ≲1 GeV to the H.E.S.S. source at >10 GeV. We find a spectral hardening at ∼50 GeV, which is consistent with the existence of two components in the gamma-ray emission. We find that a combination of emission from the escaped CRs and the SNR itself can reproduce the observed broadband spectrum, on the assumption that the SNR has accelerated protons to ≳100 TeV in the past.https://doi.org/10.3847/1538-4357/adec80Cosmic raysGalactic cosmic raysCosmic ray sourcesGamma-ray astronomySupernova remnantsInterstellar medium |
| spellingShingle | Tomohiko Oka Wataru Ishizaki Masaki Mori Hidetoshi Sano Hiromasa Suzuki Takaaki Tanaka Resolving the Origin of the Unidentified TeV Source HESS J1626-490 as a Relic of the Ancient Cosmic-Ray Factory SNR G335.2+0.1 The Astrophysical Journal Cosmic rays Galactic cosmic rays Cosmic ray sources Gamma-ray astronomy Supernova remnants Interstellar medium |
| title | Resolving the Origin of the Unidentified TeV Source HESS J1626-490 as a Relic of the Ancient Cosmic-Ray Factory SNR G335.2+0.1 |
| title_full | Resolving the Origin of the Unidentified TeV Source HESS J1626-490 as a Relic of the Ancient Cosmic-Ray Factory SNR G335.2+0.1 |
| title_fullStr | Resolving the Origin of the Unidentified TeV Source HESS J1626-490 as a Relic of the Ancient Cosmic-Ray Factory SNR G335.2+0.1 |
| title_full_unstemmed | Resolving the Origin of the Unidentified TeV Source HESS J1626-490 as a Relic of the Ancient Cosmic-Ray Factory SNR G335.2+0.1 |
| title_short | Resolving the Origin of the Unidentified TeV Source HESS J1626-490 as a Relic of the Ancient Cosmic-Ray Factory SNR G335.2+0.1 |
| title_sort | resolving the origin of the unidentified tev source hess j1626 490 as a relic of the ancient cosmic ray factory snr g335 2 0 1 |
| topic | Cosmic rays Galactic cosmic rays Cosmic ray sources Gamma-ray astronomy Supernova remnants Interstellar medium |
| url | https://doi.org/10.3847/1538-4357/adec80 |
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