Cosmic-ray electron propagation in the peculiar barred spiral galaxy NGC 2442

@misc{wang2026cosmicray,
  title = {{Cosmic-ray electron propagation in the peculiar barred spiral galaxy NGC 2442}},
  author = {Shengtao Wang and Xiaohui Sun and Volker Heesen and George Heald and Jiangtao Li and Chao-Wei Tsai and Stefan W. Duchesne and Andrew J. Battisti and Yik Ki Ma and Amit Seta and Jun Xu and Naomi McClure-Griffiths and Christopher J. Riseley and Sam Taziaux and Jacco Th. van Loon and Tayyaba Zafar},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.10270},
  eprint = {2609.10270},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.10270},
}

TY  - UNPB
TI  - Cosmic-ray electron propagation in the peculiar barred spiral galaxy NGC 2442
AU  - Shengtao Wang
AU  - Xiaohui Sun
AU  - Volker Heesen
AU  - George Heald
AU  - Jiangtao Li
AU  - Chao-Wei Tsai
AU  - Stefan W. Duchesne
AU  - Andrew J. Battisti
AU  - Yik Ki Ma
AU  - Amit Seta
AU  - Jun Xu
AU  - Naomi McClure-Griffiths
AU  - Christopher J. Riseley
AU  - Sam Taziaux
AU  - Jacco Th. van Loon
AU  - Tayyaba Zafar
PY  - 2026
DA  - 2026/09/09
PB  - arXiv
DO  - 10.48550/arxiv.2609.10270
UR  - https://arxiv.org/abs/2609.10270
AB  - Face-on spiral galaxies offer a favorable geometry for studying magnetic-field structures and cosmic-ray (CR) propagation because projection effects and structural overlap are reduced. We investigate cosmic-ray electron (CRE) transport in the nearby face-on spiral galaxy NGC 2442 and assess how its environment and magnetic-field structure influence propagation. We combine radio continuum (RC) observations from ASKAP at 943 MHz, MeerKAT at 1.28 and 1.7 GHz, and ATCA at 5 GHz with optical Hα and infrared data, and compare them with 2D CRE transport simulations. NGC 2442 has a steep integrated RC spectrum, with α=−0.96±0.04 for the total emission and α_nt=−1.21±0.04 for the synchrotron emission over 408 MHz-5 GHz. A break near 1 GHz indicates substantial radiative aging. Under equipartition, we derive a mean magnetic-field strength of 10.8 μG. RC-SFR smoothing gives effective CRE propagation lengths of ∼0.65-$0.89$ kpc at 943-1700 MHz and ∼0.44 kpc at 5 GHz, corresponding to diffusion coefficients of order 10^28 cm^2 s^−1. We identify a steep-spectrum synchrotron ``island'' in the southeast, with α∼−1.09 and no clear Hα, infrared, FUV, or NUV counterpart, indicating that CREs are unlikely to be injected in situ. Our 2D CRPropa simulations show that anisotropic diffusion along ordered magnetic fields enables CREs to reach the island more efficiently than isotropic diffusion. NGC 2442 therefore shows that environmental disturbances and ordered magnetic fields can strongly regulate CRE propagation in disturbed spiral galaxies.
ER  -