Constraining the Thickness of the Galactic Halo through Cosmic-Ray Anisotropy Using the Spatial-Dependent-Propagation Model
The spatial-dependent-propagation (SDP) model with a nearby source works well to reproduce the coevolving features of both cosmic-ray (CR)-nuclei spectra and anisotropy. However, it is well known that the Sun is actually deviating from the galactic disk. This will lead to a dominating anisotropy in...
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MDPI AG
2023-08-01
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| Online Access: | https://www.mdpi.com/2218-1997/9/8/363 |
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| author | Bing-Qiang Qiao Yu-Hua Yao Wei Liu Qiang Yuan Xiao-Jun Bi Hong-Bo Hu Yi-Qing Guo |
| author_facet | Bing-Qiang Qiao Yu-Hua Yao Wei Liu Qiang Yuan Xiao-Jun Bi Hong-Bo Hu Yi-Qing Guo |
| author_sort | Bing-Qiang Qiao |
| collection | DOAJ |
| description | The spatial-dependent-propagation (SDP) model with a nearby source works well to reproduce the coevolving features of both cosmic-ray (CR)-nuclei spectra and anisotropy. However, it is well known that the Sun is actually deviating from the galactic disk. This will lead to a dominating anisotropy in the direction perpendicular to the galactic disk, which is discrepant with current observations. Thus, it is necessary to further investigate the effect of the solar offset on anisotropy. In this work, to the best of our knowledge, this is the first time that the combined studies of the solar offset, nuclei spectra, and anisotropy have been performed based on the SDP model. As a result, to reproduce CR spectra and anisotropy, the thickness of the inner halo <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>(</mo><msub><mi>Z</mi><mrow><mi>I</mi><mi>H</mi></mrow></msub><mo>)</mo></mrow></semantics></math></inline-formula> needs to increase linearly with the displacement of the Sun. We also know that the PeV anisotropy could be used to estimate the value of the diffusion coefficient, thus breaking the degeneracy between the diffusion coefficient and halo thickness. Therefore, it is a good approach to constrain the halo thickness. Moreover, the anisotropy in the PeV energy region, as a new probe, might also shed new light on constraining the solar offset. It is hoped that the anisotropy of the energies from ∼TeV to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>PeV</mi></semantics></math></inline-formula> can be finely measured with the LHAASO experiment, leading to a better understanding of the thick halo. |
| first_indexed | 2024-03-10T23:31:27Z |
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| issn | 2218-1997 |
| language | English |
| last_indexed | 2024-03-10T23:31:27Z |
| publishDate | 2023-08-01 |
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| record_format | Article |
| series | Universe |
| spelling | doaj.art-3b690498f2d64e2ca79cbff6b8fa72502023-11-19T03:16:36ZengMDPI AGUniverse2218-19972023-08-019836310.3390/universe9080363Constraining the Thickness of the Galactic Halo through Cosmic-Ray Anisotropy Using the Spatial-Dependent-Propagation ModelBing-Qiang Qiao0Yu-Hua Yao1Wei Liu2Qiang Yuan3Xiao-Jun Bi4Hong-Bo Hu5Yi-Qing Guo6Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, ChinaCollege of Physics, Chongqing University, Chongqing 401331, ChinaKey Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, ChinaKey Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, ChinaKey Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, ChinaKey Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, ChinaKey Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, ChinaThe spatial-dependent-propagation (SDP) model with a nearby source works well to reproduce the coevolving features of both cosmic-ray (CR)-nuclei spectra and anisotropy. However, it is well known that the Sun is actually deviating from the galactic disk. This will lead to a dominating anisotropy in the direction perpendicular to the galactic disk, which is discrepant with current observations. Thus, it is necessary to further investigate the effect of the solar offset on anisotropy. In this work, to the best of our knowledge, this is the first time that the combined studies of the solar offset, nuclei spectra, and anisotropy have been performed based on the SDP model. As a result, to reproduce CR spectra and anisotropy, the thickness of the inner halo <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>(</mo><msub><mi>Z</mi><mrow><mi>I</mi><mi>H</mi></mrow></msub><mo>)</mo></mrow></semantics></math></inline-formula> needs to increase linearly with the displacement of the Sun. We also know that the PeV anisotropy could be used to estimate the value of the diffusion coefficient, thus breaking the degeneracy between the diffusion coefficient and halo thickness. Therefore, it is a good approach to constrain the halo thickness. Moreover, the anisotropy in the PeV energy region, as a new probe, might also shed new light on constraining the solar offset. It is hoped that the anisotropy of the energies from ∼TeV to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>PeV</mi></semantics></math></inline-formula> can be finely measured with the LHAASO experiment, leading to a better understanding of the thick halo.https://www.mdpi.com/2218-1997/9/8/363spatial-dependent propagationcosmic-ray anisotropynearby sourcesolar offsetthick halo |
| spellingShingle | Bing-Qiang Qiao Yu-Hua Yao Wei Liu Qiang Yuan Xiao-Jun Bi Hong-Bo Hu Yi-Qing Guo Constraining the Thickness of the Galactic Halo through Cosmic-Ray Anisotropy Using the Spatial-Dependent-Propagation Model Universe spatial-dependent propagation cosmic-ray anisotropy nearby source solar offset thick halo |
| title | Constraining the Thickness of the Galactic Halo through Cosmic-Ray Anisotropy Using the Spatial-Dependent-Propagation Model |
| title_full | Constraining the Thickness of the Galactic Halo through Cosmic-Ray Anisotropy Using the Spatial-Dependent-Propagation Model |
| title_fullStr | Constraining the Thickness of the Galactic Halo through Cosmic-Ray Anisotropy Using the Spatial-Dependent-Propagation Model |
| title_full_unstemmed | Constraining the Thickness of the Galactic Halo through Cosmic-Ray Anisotropy Using the Spatial-Dependent-Propagation Model |
| title_short | Constraining the Thickness of the Galactic Halo through Cosmic-Ray Anisotropy Using the Spatial-Dependent-Propagation Model |
| title_sort | constraining the thickness of the galactic halo through cosmic ray anisotropy using the spatial dependent propagation model |
| topic | spatial-dependent propagation cosmic-ray anisotropy nearby source solar offset thick halo |
| url | https://www.mdpi.com/2218-1997/9/8/363 |
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