Polarized thermal emission from dust in a galaxy at redshift 2.6

Geach, J. E.; Lopez-Rodriguez, E.; Doherty, M. J.; Chen, Jianhang; Ivison, R. J.; Bendo, G. J.; Dye, S.; Coppin, K. E. K.

doi:10.1038/s41586-023-06346-4

Cited by 17 publications

(1 citation statement)

References 35 publications

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“…Theoretical and observational studies predict that the magnetic energy budget is comparable to that of the thermal and turbulent components in the ISM (Beck 2007;Bernet et al 2008;Mao et al 2017;Pakmor et al 2017;Martin-Alvarez et al 2020;Lopez-Rodriguez et al 2021;Geach et al 2023;Lopez-Rodriguez 2023), and dominates over the thermal component in cold molecular clouds (Crutcher 1999). Magnetic fields impact the ISM, due to their significant strengths, with typical values in the ∼3-7 μG range for the large-scale ordered component and are typically on the order of ∼17 μG for the total field strength (Fletcher 2010;Beck et al 2019).…”

Section: Introductionmentioning

confidence: 99%

Extragalactic Magnetism with SOFIA (SALSA Legacy Program). VII. A Tomographic View of Far-infrared and Radio Polarimetric Observations through MHD Simulations of Galaxies

Martin-Alvarez,

Lopez-Rodriguez,

Dacunha

et al. 2024

ApJ

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The structure of magnetic fields in galaxies remains poorly constrained, despite the importance of magnetism in the evolution of galaxies. Radio synchrotron and far-infrared (FIR) polarization and polarimetric observations are the best methods to measure galactic scale properties of magnetic fields in galaxies beyond the Milky Way. We use synthetic polarimetric observations of a simulated galaxy to identify and quantify the regions, scales, and interstellar medium (ISM) phases probed at FIR and radio wavelengths. Our studied suite of magnetohydrodynamical cosmological zoom-in simulations features high-resolutions (10 pc full-cell size) and multiple magnetization models. Our synthetic observations have a striking resemblance to those of observed galaxies. We find that the total and polarized radio emission extends to approximately double the altitude above the galactic disk (half-intensity disk thickness of h I radio ∼ h PI radio = 0.23 ± 0.03 kpc) relative to the total FIR and polarized emission that are concentrated in the disk midplane (h I FIR ∼ h PI FIR = 0.11 ± 0.01 kpc). Radio emission traces magnetic fields at scales of ≳300 pc, whereas FIR emission probes magnetic fields at the smallest scales of our simulations. These scales are comparable to our spatial resolution and well below the spatial resolution (<300 pc) of existing FIR polarimetric measurements. Finally, we confirm that synchrotron emission traces a combination of the warm neutral and cold neutral gas phases, whereas FIR emission follows the densest gas in the cold neutral phase in the simulation. These results are independent of the ISM magnetic field strength. The complementarity we measure between radio and FIR wavelengths motivates future multiwavelength polarimetric observations to advance our knowledge of extragalactic magnetism.

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Section: Introductionmentioning

confidence: 99%

Extragalactic Magnetism with SOFIA (SALSA Legacy Program). VII. A Tomographic View of Far-infrared and Radio Polarimetric Observations through MHD Simulations of Galaxies

Martin-Alvarez,

Lopez-Rodriguez,

Dacunha

et al. 2024

ApJ

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Computational approaches to modeling dynamos in galaxies

Korpi-Lagg,

Mac Low,

Gent

2024

Living Rev Comput Astrophys

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Galaxies are observed to host magnetic fields with a typical total strength of around 15 $$\upmu $$ μ G. A coherent large-scale field constitutes up to a few microgauss of the total, while the rest is built from strong magnetic fluctuations over a wide range of spatial scales. This represents sufficient magnetic energy for it to be dynamically significant. Several questions immediately arise: What is the physical mechanism that gives rise to such magnetic fields? How do these magnetic fields affect the formation and evolution of galaxies? In which physical processes do magnetic fields play a role, and how can that role be characterized? Numerical modelling of magnetized flows in galaxies is playing an ever-increasing role in finding those answers. We review major techniques used for these models. Current results strongly support the conclusion that field growth occurs during the formation of the first galaxies on timescales shorter than their accretion timescales due to small-scale turbulent dynamos. The saturated small-scale dynamo maintains field strengths at only a few percent of equipartition with turbulence. This is in contradiction with the observed magnitude of turbulent fields, but may be reconciled by the further contribution to the turbulent field of the large-scale dynamo. The subsequent action of large-scale dynamos in differentially rotating discs produces field strengths observed in low redshift galaxies, where it reaches equipartition with the turbulence and has substantial power at large scales. The field structure resulting appears consistent with observations including Faraday rotation and polarisation from synchrotron and dust thermal emission. Major remaining challenges include scaling numerical models toward realistic scale separations and Prandtl and Reynolds numbers.

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