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We present new radio continuum images of the edge-on starburst galaxy NGC 5775, from LOFAR (140 MHz) and the Karl G. Jansky Very Large Array CHANG-ES survey (1500 MHz). We trace the non-thermal radio halo up to 13 kpc from the disc, measuring the non-thermal spectral index and estimating the total equipartition magnetic field strength (≈13 μG in the disc and ≈7 μG above the plane). The radio halo has a similar extent at both frequencies, displays evidence for localized cosmic ray streaming coinciding with prominent H α filaments and vertical extensions of the regular magnetic field, and exhibits a boxy morphology especially at 140 MHz. In order to understand the nature of the disc–halo flow, we extend our previous model of cosmic ray propagation by implementing an iso-thermal wind with a tunable 'flux tube' (approximately hyperboloidal) geometry. This updated model is successful in matching the vertical distribution of non-thermal radio emission, and the vertical steepening of the associated spectral index, in a consistent conceptual framework with few free parameters. Our new model provides the opportunity to estimate the mass outflow driven by the star formation process, and we find an implied rate of M˙≈3–6M⊙yr−1 (≈40–80 per cent of the star formation rate) if the escape velocity is reached, with substantial uncertainty arising from the poorly understood distribution of interstellar medium material entrained in the vertical flow. The wind may play a role in influencing the vertical gradient in rotational velocity. © 2021 The Author(s). ; This paper is based (in part) on data obtained with the International LOFAR Telescope (ILT) under project code LC1_046. LOFAR (van Haarlem et al. 2013) is the Low Frequency Array designed and constructed by ASTRON. It has observing, data processing, and data storage facilities in several countries, that are owned by various parties (each with their own funding sources), and that are collectively operated by the ILT foundation under a joint scientific policy. The ILT resources have benefitted from the following recent major funding sources: CNRS-INSU, Observatoire de Paris and Université d'Orléans, France; BMBF, MIWF-NRW, MPG, Germany; Science Foundation Ireland (SFI), Department of Business, Enterprise and Innovation (DBEI), Ireland; NWO, The Netherlands; The Science and Technology Facilities Council, UK; Ministry of Science and Higher Education, Poland. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. GH thanks Phil Edwards for useful feedback after a critical reading of the manuscript, and Tim Galvin for advice and help with tricky plotting issues. We would like to thank B. P. Brian Yu, for kindly providing us with their computer code of the cosmic ray-driven wind model. We thank the anonymous referee for a comprehensive review and for comments that led to substantial improvements to the paper. MB acknowledges support from the Deutsche Forschungsgemeinschaft under Germany's Excellence Strategy - EXC 2121 'Quantum Universe' - 390833306. This research was undertaken as an activity organized by the LOFAR Magnetism Key Science Project (MKSP; https://lofar-mksp.org/). ; With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709. ; Peer reviewed

We identify stellar structures in the PHANGS sample of 74 nearby galaxies and construct morphological masks of sub-galactic environments based on Spitzer 3.6 mu m images. At the simplest level, we distinguish five environments: centres, bars, spiral arms, interarm regions, and discs without strong spirals. Slightly more sophisticated masks include rings and lenses, which are publicly released but not explicitly used in this paper. We examine trends with environment in the molecular gas content, star formation rate, and depletion time using PHANGS-ALMA CO(2-1) intensity maps and tracers of star formation. The interarm regions and discs without strong spirals clearly dominate in area, whereas molecular gas and star formation are quite evenly distributed among the five basic environments. We reproduce the molecular Kennicutt-Schmidt relation with a slope compatible with unity within the uncertainties and without significant slope differences among environments. In contrast to what has been suggested by early studies, we find that bars are not always deserts devoid of gas and star formation, but instead they show large diversity. Similarly, spiral arms do not account for most of the gas and star formation in disc galaxies, and they do not have shorter depletion times than the interarm regions. Spiral arms accumulate gas and star formation, without systematically boosting the star formation efficiency. Centres harbour remarkably high surface densities and on average shorter depletion times than other environments. Centres of barred galaxies show higher surface densities and wider distributions compared to the outer disc; yet, depletion times are similar to unbarred galaxies, suggesting highly intermittent periods of star formation when bars episodically drive gas inflow, without enhancing the central star formation efficiency permanently. In conclusion, we provide quantitative evidence that stellar structures in galaxies strongly affect the organisation of molecular gas and star formation, but their impact on star formation efficiency is more subtle. ; Instituto de Salud Carlos III Spanish Government PID2019-106027GA-C44 European Research Council (ERC) 694343 National Science Foundation (NSF) National Research Foundation of Korea 1615105 1615109 1653300 National Aeronautics and Space Administration (NASA) under ADAP grants NNX16AF48G NNX17AF39G German Research Foundation (DFG) SFB 881 138713538 Heidelberg Cluster of Excellence "STRUCTURES" in the framework of Germany's Excellence Strategy EXC-2181/1 390900948 European Research Council via the ERC Synergy Grant "ECOGAL" 855130 SKA South Africa 694343 721463 726384/Empire Academy of Finland 297738 German Research Foundation (DFG) KR4801/1-1 KR4598/2-1 KR4801/2-1 BI1546/3-1 European Research Council (ERC) 714907 National Science Foundation (NSF) 1903946 Spanish Government AYA2016-79006-P Spanish Government European Commission PID2019-108765GB-I00 Programme National Cosmology et Galaxies (PNCG) of CNRS/INSU INP IN2P3 French Atomic Energy Commission Centre National D'etudes Spatiales Programme National 'Physique et Chimie du Milieu Interstellaire' (PCMI) of CNRS/INSU INC/INP - CEA Natural Sciences and Engineering Research Council of Canada (NSERC) RGPIN-2017-03987 Spanish funding grant (MINECO/FEDER) AYA2016-79006-P Spanish funding grant (MCIU/AEI/FEDER) PGC2018-094671-B-I00 Spanish funding grant (MICINN) PID2019-108765GB-I00 German Research Foundation (DFG) 138713538 - SFB 881 ; Versión sometida a revisión - Preprint