Anisotropic Diffusion of e± in Pulsar Halos over Multiple Coherence of Magnetic Fields
The slow particle diffusion in pulsar halos, inferred from TeV gamma-ray surface brightness profiles (SBPs), is attributed to cross-field diffusion under the anisotropic diffusion model. This model assumes sub-Alfvénic interstellar turbulence in the medium surrounding the pulsar and a rough alignmen...
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IOP Publishing
2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/add6a4 |
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| author | Kai Yan Sha Wu Ruo-Yu Liu |
| author_facet | Kai Yan Sha Wu Ruo-Yu Liu |
| author_sort | Kai Yan |
| collection | DOAJ |
| description | The slow particle diffusion in pulsar halos, inferred from TeV gamma-ray surface brightness profiles (SBPs), is attributed to cross-field diffusion under the anisotropic diffusion model. This model assumes sub-Alfvénic interstellar turbulence in the medium surrounding the pulsar and a rough alignment of the line of sight of observers toward the pulsar with the local mean magnetic field direction in the halo. In this model, the expected morphology of a pulsar halo is highly dependent on the properties of the interstellar magnetic field. We investigate the anisotropic diffusion of electron–positron pairs across multiple coherence of magnetic fields in pulsar halos in this work. We focus particularly on their influence on the predicted gamma-ray SBP and the asymmetry of the halo’s morphology, as well as the observational expectations of the Large High Altitude Air Shower Observatory. Our results indicate that the requirement of a specific magnetic field geometry can be alleviated when accounting for a limited (and realistic) coherence length of the magnetic field in the model. Also, the halo’s morphology may appear less asymmetric, especially after being smoothed by the point-spread function of instruments. This largely relaxes the tension between the asymmetric morphology of halos predicted by the model and the lack of apparent asymmetric halos detected so far. Our findings demonstrate the important influence of the coherence length of the interstellar magnetic field on the distribution of particles around their accelerators, and the consequence for the measured source morphology. |
| format | Article |
| id | doaj-art-6e1983b0fe0a424580eb9efd48cba9a8 |
| institution | DOAJ |
| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
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| series | The Astrophysical Journal |
| spelling | doaj-art-6e1983b0fe0a424580eb9efd48cba9a82025-08-20T03:23:11ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198711910.3847/1538-4357/add6a4Anisotropic Diffusion of e± in Pulsar Halos over Multiple Coherence of Magnetic FieldsKai Yan0https://orcid.org/0000-0001-7542-5861Sha Wu1https://orcid.org/0000-0002-3524-1483Ruo-Yu Liu2https://orcid.org/0000-0003-1576-0961School of Astronomy and Space Science, Nanjing University , Nanjing 210023, People’s Republic of China ; ryliu@nju.edu.cn; Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University) , Ministry of Education, Nanjing 210023, People’s Republic of ChinaKey Laboratory of Particle Astrophysics & Experimental Physics Division & Computing Center, Institute of High Energy Physics, Chinese Academy of Sciences , 100049 Beijing, People’s Republic of China; Tianfu Cosmic Ray Research Center , Chengdu 610000, Sichuan, People’s Republic of ChinaSchool of Astronomy and Space Science, Nanjing University , Nanjing 210023, People’s Republic of China ; ryliu@nju.edu.cn; Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University) , Ministry of Education, Nanjing 210023, People’s Republic of China; Tianfu Cosmic Ray Research Center , Chengdu 610000, Sichuan, People’s Republic of ChinaThe slow particle diffusion in pulsar halos, inferred from TeV gamma-ray surface brightness profiles (SBPs), is attributed to cross-field diffusion under the anisotropic diffusion model. This model assumes sub-Alfvénic interstellar turbulence in the medium surrounding the pulsar and a rough alignment of the line of sight of observers toward the pulsar with the local mean magnetic field direction in the halo. In this model, the expected morphology of a pulsar halo is highly dependent on the properties of the interstellar magnetic field. We investigate the anisotropic diffusion of electron–positron pairs across multiple coherence of magnetic fields in pulsar halos in this work. We focus particularly on their influence on the predicted gamma-ray SBP and the asymmetry of the halo’s morphology, as well as the observational expectations of the Large High Altitude Air Shower Observatory. Our results indicate that the requirement of a specific magnetic field geometry can be alleviated when accounting for a limited (and realistic) coherence length of the magnetic field in the model. Also, the halo’s morphology may appear less asymmetric, especially after being smoothed by the point-spread function of instruments. This largely relaxes the tension between the asymmetric morphology of halos predicted by the model and the lack of apparent asymmetric halos detected so far. Our findings demonstrate the important influence of the coherence length of the interstellar magnetic field on the distribution of particles around their accelerators, and the consequence for the measured source morphology.https://doi.org/10.3847/1538-4357/add6a4Pulsar wind nebulaeGamma-ray sourcesNon-thermal radiation sources |
| spellingShingle | Kai Yan Sha Wu Ruo-Yu Liu Anisotropic Diffusion of e± in Pulsar Halos over Multiple Coherence of Magnetic Fields The Astrophysical Journal Pulsar wind nebulae Gamma-ray sources Non-thermal radiation sources |
| title | Anisotropic Diffusion of e± in Pulsar Halos over Multiple Coherence of Magnetic Fields |
| title_full | Anisotropic Diffusion of e± in Pulsar Halos over Multiple Coherence of Magnetic Fields |
| title_fullStr | Anisotropic Diffusion of e± in Pulsar Halos over Multiple Coherence of Magnetic Fields |
| title_full_unstemmed | Anisotropic Diffusion of e± in Pulsar Halos over Multiple Coherence of Magnetic Fields |
| title_short | Anisotropic Diffusion of e± in Pulsar Halos over Multiple Coherence of Magnetic Fields |
| title_sort | anisotropic diffusion of e in pulsar halos over multiple coherence of magnetic fields |
| topic | Pulsar wind nebulae Gamma-ray sources Non-thermal radiation sources |
| url | https://doi.org/10.3847/1538-4357/add6a4 |
| work_keys_str_mv | AT kaiyan anisotropicdiffusionofeinpulsarhalosovermultiplecoherenceofmagneticfields AT shawu anisotropicdiffusionofeinpulsarhalosovermultiplecoherenceofmagneticfields AT ruoyuliu anisotropicdiffusionofeinpulsarhalosovermultiplecoherenceofmagneticfields |