Polarization Leakage and the IXPE PSF
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arXiv
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| Auteurs principaux: | , |
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| Format: | Preprint |
| Publié: |
2024
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| _version_ | 1866912040607547392 |
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| author | Dinsmore, Jack T. Romani, Roger W. |
| author_facet | Dinsmore, Jack T. Romani, Roger W. |
| contents | By measuring photoelectron tracks, the gas pixel detectors of the Imaging X-ray Polarimetry Explorer satellite provide estimates of the photon detection location and its electric vector position angle (EVPA). However, imperfections in reconstructing event positions blur the image and EVPA-position correlations result in artificial polarized halos around bright sources. We introduce a new model describing this "polarization leakage" and use it to recover the on-orbit telescope point-spread functions, useful for faint source detection and image reconstruction. These point spread functions are more accurate than previous approximations or ground-calibrated products ($Δχ^2\approx 3\times 10^{4}$ and $4 \times 10^4$ respectively for a bright $10^6$-count source). We also define an algorithm for polarization leakage correction substantially more accurate than existing prescriptions ($Δχ^2\approx 1\times 10^{3}$). These corrections depend on the reconstruction method, and we supply prescriptions for the mission-standard "Moments" methods as well as for "Neural Net" event reconstruction. Finally, we present a method to isolate leakage contributions to polarization observations of extended sources and show that an accurate PSF allows the extraction of sub-PSF-scale polarization patterns. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2401_10231 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Polarization Leakage and the IXPE PSF Dinsmore, Jack T. Romani, Roger W. Instrumentation and Methods for Astrophysics High Energy Astrophysical Phenomena By measuring photoelectron tracks, the gas pixel detectors of the Imaging X-ray Polarimetry Explorer satellite provide estimates of the photon detection location and its electric vector position angle (EVPA). However, imperfections in reconstructing event positions blur the image and EVPA-position correlations result in artificial polarized halos around bright sources. We introduce a new model describing this "polarization leakage" and use it to recover the on-orbit telescope point-spread functions, useful for faint source detection and image reconstruction. These point spread functions are more accurate than previous approximations or ground-calibrated products ($Δχ^2\approx 3\times 10^{4}$ and $4 \times 10^4$ respectively for a bright $10^6$-count source). We also define an algorithm for polarization leakage correction substantially more accurate than existing prescriptions ($Δχ^2\approx 1\times 10^{3}$). These corrections depend on the reconstruction method, and we supply prescriptions for the mission-standard "Moments" methods as well as for "Neural Net" event reconstruction. Finally, we present a method to isolate leakage contributions to polarization observations of extended sources and show that an accurate PSF allows the extraction of sub-PSF-scale polarization patterns. |
| title | Polarization Leakage and the IXPE PSF |
| topic | Instrumentation and Methods for Astrophysics High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2401.10231 |