CHANG-ES XXXIX. Magnetic field structure in edge-on galaxies: Stacking Stokes parameters
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arXiv
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| Autori principali: | , , , , , , , , , , , , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2026
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| _version_ | 1866909011571376128 |
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| author | Stein, M. Beck, R. Adebahr, B. Dettmar, R. -J. Mele, C. Taziaux, S. Kamphuis, P. English, J. Wiegert, T. Stil, J. Heesen, V. Riseley, C. Irwin, J. Skeggs, N. B. Henriksen, R. |
| author_facet | Stein, M. Beck, R. Adebahr, B. Dettmar, R. -J. Mele, C. Taziaux, S. Kamphuis, P. English, J. Wiegert, T. Stil, J. Heesen, V. Riseley, C. Irwin, J. Skeggs, N. B. Henriksen, R. |
| contents | Galactic magnetic fields regulate star formation and cosmic-ray (CR) transport, and understanding their three-dimensional structure, particularly in star-forming late-type galaxies, is key to constraining galactic CR transport. We explore the validity of stacking Stokes $Q$ and $U$ spectra, to infer about the intrinsic polarisation characteristics of star-forming galaxies. To prepare the stacking experiment, we align, scale, convolve, and reproject $C$-band (6 GHz) Stokes $Q$ and Stokes $U$ cubes of 27 star-forming late-type edge-on galaxies. On the stacked cubes, we perform RM-synthesis and discuss the derived polarised intensity (PI), polarisation angle ($χ_0$), and RM maps. Synthetic data tests demonstrate that stacking Stokes $Q$ and $U$ spectra is valid for tightly constrained underlying distributions of PI, $χ_0$, and RM. For underlying PI, $χ_0$, and RM distributions that represent star-forming galaxies, stacking introduces a systematic uncertainty of $δ_\mathrm{RM}^\mathrm{sys}=90 \mathrm{rad m^{-2}}$ and significantly underestimates the recovered PI. Stacking results reveal a clear X-shaped pattern in the polarisation plane, consistent with prior findings, detecting polarised emission up to 9 kpc above the galactic disc. We find stronger PI on the approaching side of galaxies. Furthermore, we find a decrease in PI in the galactic halo of $\sim 60$% near the galaxy's minor axis. A global RM pattern, as reported in a previous study, cannot be confirmed. Based on our analysis, we present stacking of Stokes $Q$ and Stokes $U$ cubes as an effective tool to recover faint polarised emission in the halo of nearby galaxies, if the underlying distributions of PI, $χ_0$, and RM are tightly constrained. Our findings motivate future studies using broader-band data to increase the resolution in Faraday depth. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_02053 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | CHANG-ES XXXIX. Magnetic field structure in edge-on galaxies: Stacking Stokes parameters Stein, M. Beck, R. Adebahr, B. Dettmar, R. -J. Mele, C. Taziaux, S. Kamphuis, P. English, J. Wiegert, T. Stil, J. Heesen, V. Riseley, C. Irwin, J. Skeggs, N. B. Henriksen, R. Astrophysics of Galaxies Galactic magnetic fields regulate star formation and cosmic-ray (CR) transport, and understanding their three-dimensional structure, particularly in star-forming late-type galaxies, is key to constraining galactic CR transport. We explore the validity of stacking Stokes $Q$ and $U$ spectra, to infer about the intrinsic polarisation characteristics of star-forming galaxies. To prepare the stacking experiment, we align, scale, convolve, and reproject $C$-band (6 GHz) Stokes $Q$ and Stokes $U$ cubes of 27 star-forming late-type edge-on galaxies. On the stacked cubes, we perform RM-synthesis and discuss the derived polarised intensity (PI), polarisation angle ($χ_0$), and RM maps. Synthetic data tests demonstrate that stacking Stokes $Q$ and $U$ spectra is valid for tightly constrained underlying distributions of PI, $χ_0$, and RM. For underlying PI, $χ_0$, and RM distributions that represent star-forming galaxies, stacking introduces a systematic uncertainty of $δ_\mathrm{RM}^\mathrm{sys}=90 \mathrm{rad m^{-2}}$ and significantly underestimates the recovered PI. Stacking results reveal a clear X-shaped pattern in the polarisation plane, consistent with prior findings, detecting polarised emission up to 9 kpc above the galactic disc. We find stronger PI on the approaching side of galaxies. Furthermore, we find a decrease in PI in the galactic halo of $\sim 60$% near the galaxy's minor axis. A global RM pattern, as reported in a previous study, cannot be confirmed. Based on our analysis, we present stacking of Stokes $Q$ and Stokes $U$ cubes as an effective tool to recover faint polarised emission in the halo of nearby galaxies, if the underlying distributions of PI, $χ_0$, and RM are tightly constrained. Our findings motivate future studies using broader-band data to increase the resolution in Faraday depth. |
| title | CHANG-ES XXXIX. Magnetic field structure in edge-on galaxies: Stacking Stokes parameters |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2605.02053 |