Polarization-shape alignment of IllustrisTNG star-forming galaxies
Rui Zhou, Liang Dai, Junwu Huang, Weichen Winston Yin, and Simone Ferraro

TL;DR
This study investigates the alignment between radio polarization and galaxy shape in star-forming galaxies across redshifts using simulations, revealing redshift-dependent degradation and potential for cosmological measurements.
Contribution
It provides the first simulation-based analysis of polarization-shape misalignment evolution up to z=2, with analytic fits and implications for cosmic birefringence detection.
Findings
Alignment at z=0 matches local spiral data.
Alignment deteriorates with increasing redshift.
Higher frequency observations mitigate depolarization effects.
Abstract
In star-forming disk galaxies, the radio continuum emission (-GHz) powered by star formation has an integrated polarization direction imperfectly aligned with the apparent disk minor axis. This polarization-shape alignment effect was previously observed in a small sample of local spirals. If this is prevalent for disk galaxies out to cosmological redshifts, novel measurements of cosmic birefringence and cosmic shear will be enabled by leveraging radio continuum surveys synergized with galaxy shape measurements. We calculate the polarization-shape misalignment angle for star-forming galaxies in the \texttt{IllustrisTNG50} simulation at , assuming that additional polarized radio emission from an AGN is negligible. The alignment found for is consistent with local spiral data, but significantly deteriorates as redshift increases. Moreover, it degrades toward lower…
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Taxonomy
TopicsAstronomy and Astrophysical Research · Stellar, planetary, and galactic studies · Astronomical Observations and Instrumentation
