Southern eROSITA bubble as a forward shock and the low-metallicity CGM. South-east side story
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| Format: | Preprint |
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2026
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| _version_ | 1866908905183903744 |
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| author | Churazov, E. Khabibullin, I. I. Bykov, A. M. Chugai, N. N. Sunyaev, R. A. Utrobin, V. P. Zinchenko, I. I. |
| author_facet | Churazov, E. Khabibullin, I. I. Bykov, A. M. Chugai, N. N. Sunyaev, R. A. Utrobin, V. P. Zinchenko, I. I. |
| contents | Unlike the complicated X-ray and radio structure observed in the North Polar Spur area, the South-Eastern part of the eROSITA bubbles can be reasonably well described as a propagating forward shock, plausibly created by the transient energy release at the Galactic Center. In this model, the physical radius of the bubble is $R_{\rm b}\sim 7-8\,{\rm kpc}$ and the age of the outburst is $t_{\rm age}\sim 5-8\,{\rm Myr}$. The visible segment of the shock front (located at a distance of $\sim 10-12\,{\rm kpc}$ above the Galactic Disk and at a similar distance from the Sun) is currently expanding with the velocity $\sim 700\,{\rm km\,s^{-1}}$ through the gas with density $n_e\sim 3\times 10^{-4}\,{\rm cm^{-3}}$, and the abundance of heavy elements in this gas is $Z\lesssim 0.1 \times Z_\odot$. Unlike constraints derived from the line-of-sight-integrated quantities, these are effectively in situ measurements of the circumgalactic medium (CGM) properties. Given the simplifying assumptions used in deriving the density, we assign a factor of 2 systematic uncertainty to the final estimate. An eventual decisive test for the shock properties can be provided by the velocity measurements of the X-ray-emitting gas with soft X-ray bolometers. The extended forward shock propagating through low-metallicity gas is a favorable site to accelerate very high-energy cosmic rays, which might contribute to the observed proton-rich galactic cosmic ray component at PeV energies. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2603_20740 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Southern eROSITA bubble as a forward shock and the low-metallicity CGM. South-east side story Churazov, E. Khabibullin, I. I. Bykov, A. M. Chugai, N. N. Sunyaev, R. A. Utrobin, V. P. Zinchenko, I. I. High Energy Astrophysical Phenomena Astrophysics of Galaxies Unlike the complicated X-ray and radio structure observed in the North Polar Spur area, the South-Eastern part of the eROSITA bubbles can be reasonably well described as a propagating forward shock, plausibly created by the transient energy release at the Galactic Center. In this model, the physical radius of the bubble is $R_{\rm b}\sim 7-8\,{\rm kpc}$ and the age of the outburst is $t_{\rm age}\sim 5-8\,{\rm Myr}$. The visible segment of the shock front (located at a distance of $\sim 10-12\,{\rm kpc}$ above the Galactic Disk and at a similar distance from the Sun) is currently expanding with the velocity $\sim 700\,{\rm km\,s^{-1}}$ through the gas with density $n_e\sim 3\times 10^{-4}\,{\rm cm^{-3}}$, and the abundance of heavy elements in this gas is $Z\lesssim 0.1 \times Z_\odot$. Unlike constraints derived from the line-of-sight-integrated quantities, these are effectively in situ measurements of the circumgalactic medium (CGM) properties. Given the simplifying assumptions used in deriving the density, we assign a factor of 2 systematic uncertainty to the final estimate. An eventual decisive test for the shock properties can be provided by the velocity measurements of the X-ray-emitting gas with soft X-ray bolometers. The extended forward shock propagating through low-metallicity gas is a favorable site to accelerate very high-energy cosmic rays, which might contribute to the observed proton-rich galactic cosmic ray component at PeV energies. |
| title | Southern eROSITA bubble as a forward shock and the low-metallicity CGM. South-east side story |
| topic | High Energy Astrophysical Phenomena Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2603.20740 |