Fletcher et al. 2011 M51 Almost 100 nearby galaxies observed @ GHz (Beck & Wielebinsky 2013) Most recently these studies are extended to very low frequencies with LOFAR Adding a piece to the puzzle Dust polarization measurements in nearby galaxies to investigate magnetic fields in cold gas Rosita Paladino INAF IRA Bologna Italy Annie Hughes, Maud Galametz et al. host magnetic field whose structure has mostly been probed through polarimetric radio continuum observations @ cm wavelengths (synchrotron radiation and its polarization) Magnetic fields directly affect the mean gas density, which impacts significantly the star formation rate (Birnboim et al. 2015) They regulate Star Formation, both on the scale of individual stars and filaments and through the collapse and fragmentation of molecular clouds (Mac Low 2009; Crutcher 2012) Magnetic fields play an important role in launching galactic winds and outflows (Heesen et al. 2011) Nearby Galaxies To date, magnetic fields in external galaxies have been studied through synchrotron emission which do not probe the field’s properties in the cold gas component. ALMA’s unprecedented resolution and sensitivity in full polarization mode allows for the first time observations of dust polarization in Observations of magnetic fields in Nearby Galaxies are the most useful tool to provide constraints on the models, since unlike the Milky Way, the galactic environment and gas kinematic of star-forming regions can be well-characterized! In blue LOFAR emission Mulcahy et al 2018 NGC891 NGC 253 Magnetic fields influence structure and evolution of galaxies In the Milky Way, Planck polarization results show a poor correspondence between the polarization fraction and direction obtained from radio synchrotron and dust polarization measurements In regions where the effects of local structures dominate (Planck XIX, 2015) Dust Polarization data are important complement to radio observations. Both synchrotron and dust polarization trace the magnetic field component projected into the plane of the sky, but NGC253 is a nearby (3.5 Mpc) highly inclined (78°) starburst galaxy. Observed @ different wavelengths 0 An ideal target for pioneering extragalactic dust polarization observations. ALMA Band 7 data probe spatial scales between 5 and 50 pc, never accessed so far! Questions to possibly answer: What is the magnetic field direction at the foot of a galactic wind? How ordered is the magnetic field in the starburst region? Does the magnetic field at the disk-halo interface have a preferred orientation? Do GHz radio and dust polarization observations yield a consistent picture of the magnetic structure? Spatial resolution 6 pc Hughes et al. in prep Its prominent wind is powered by the intense star formation within a central zone of 300 pc diameter. Lobes and filamentary structures of Hα, radio synchrotron, X-ray and UV emission are observed up to several Kpc from the disk plane. Dust continuum at 353 GHz is extremely bright. On large scales radio polarization observations reveal a magnetic field in the disk that is parallel to the midplane and an X-shaped halo field centered on the nucleus. On the smallest scales (~150 pc), the magnetic field shows a vertical component aligned with the non-thermal radio filaments. Chyzy & Beck 2004 Antennae First dust polarization image of an external galaxy Heesen et al. 2011 Spatial resolution 150 pc their emissivities have different dependencies on the magnetic field strength. Planck XIX, 2015 Spatial resolution 3 pc Band 7 rms 15 μJy Very ongoing work!