An ALMA view of the Jet-Arc CO clouds toward the TeV $γ$-ray source HESS J1023-575 and Westerlund 2; Evidence for the footprints of microquasar jets, the very powerful cosmic-ray accelerator in the Galactic disk

[2608.14988] An ALMA view of the Jet-Arc CO clouds toward the TeV $γ$-ray source HESS J1023-575 and Westerlund 2; Evidence for the footprints of microquasar jets, the very powerful cosmic-ray accelerator in the Galactic disk Skip to main content Search Submit Donate Log in Search arXiv Press Enter to search · Advanced search Astrophysics > High Energy Astrophysical Phenomena arXiv:2608.14988 (astro-ph) [Submitted on 15 Aug 2026 ( v1 ), last revised 14 Sep 2026 (this version, v2)] Title: An ALMA view of the Jet-Arc CO clouds toward the TeV $γ$-ray source HESS J1023-575 and Westerlund 2; Evidence for the footprints of microquasar jets, the very powerful cosmic-ray accelerator in the Galactic disk Authors: Yasuo Fukui , Kisetsu Tsuge , Hidetoshi Sano , G. R. Bhuvana , Rin I. Yamada , Ryoji Matsumoto , Yuta Asahina , Tsuyoshi Inoue , Tim Lukas Holch , Emma de Oña Wilhelmi View a PDF of the paper titled An ALMA view of the Jet-Arc CO clouds toward the TeV $\gamma$-ray source HESS J1023-575 and Westerlund 2; Evidence for the footprints of microquasar jets, the very powerful cosmic-ray accelerator in the Galactic disk, by Yasuo Fukui and 9 other authors View PDF Abstract: The TeV $\gamma$-ray source HESS J1023-575 (HESSJ 1023 hereafter) is one of the brightest H.E.S.S. sources near the young massive cluster Westerlund 2. HESS J1023 shows a remarkable positional alignment with the Jet and Arc CO clouds on its eastern and western sides over 170 pc length. We have carried out sub-pc scale observations of the CO clouds with ALMA and have discovered that the clouds consist of numerous thin filamentary features of $\sim$0.5 pc width and 10--20 pc length at distance of 7.5 kpc, which are well aligned with the Jet-Arc axis. Based on the magneto-hydrodynamical model of microquasar jets launched from {the center of the $\gamma$-ray source} HESS J1023-575, we present an interpretation that the thin filamentary clouds are the footprints of the microquasar jets on the HI gas. The model also explains the dissimilar Jet vs. Arc clouds in terms of HI density difference on each side. By using the density of the CO and HI gas and the $\gamma$-ray luminosity, we have calculated the cosmic ray proton energy $W_{\rm p}$ to be 7$\times$10$^{48}$ erg under the hadronic scheme, which is ten times larger than those derived in the TeV $\gamma$-ray SNRs RX J1713.7-3946 and RX J0852.0-4622. It is likely that HESS~J1023 has been active over 1-10 Myr, which is significantly longer than the duration of cosmic ray acceleration of the SNRs. HESS~J1023 is therefore an outstanding source of cosmic rays equivalent to at least 1000 SNRs, and is possibly the most powerful CR accelerator in the Galactic disk. A high energy compact source in HESS~J1023, which is likely a Myr-old black hole or neutron star, remains veiled due to heavy extinction. Comments: 6 pages, 3 figures, 1 table. Accepted for publication in PASJ as a Letter Subjects: High Energy Astrophysical Phenomena (astro-ph.HE) ; Astrophysics of Galaxies (astro-ph.GA) Cite as: arXiv:2608.14988 [astro-ph.HE] (or arXiv:2608.14988v2 [astro-ph.HE] for this version) https://doi.org/10.48550/arXiv.2608.14988 Focus to learn more arXiv-issued DOI via DataCite Submission history From: Kisetsu Tsuge [ view email ] [v1] Sat, 15 Aug 2026 02:31:19 UTC (23,174 KB) [v2] Mon, 14 Sep 2026 02:22:29 UTC (23,174 KB) Full-text links: Access Paper: View a PDF of the paper titled An ALMA view of the Jet-Arc CO clouds toward the TeV $\gamma$-ray source HESS J1023-575 and Westerlund 2; Evidence for the footprints of microquasar jets, the very powerful cosmic-ray accelerator in the Galactic disk, by Yasuo Fukui and 9 other authors View PDF TeX Source view license Additional Features Audio Summary Current browse context: astro-ph.HE < prev | next > new | recent | 2026-08 Change to browse by: astro-ph astro-ph.GA References & Citations INSPIRE HEP NASA ADS Google Scholar Semantic Scholar export BibTeX citation Loading... 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