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arXiv · 2311.01904

ViCTORIA project: The LOFAR-view of environmental effects in Virgo Cluster star-forming galaxies

H. W. Edler·I. D. Roberts·A. Boselli·F. de Gasperin·V. Heesen·M. Brüggen·A. Ignesti·L. Gajović
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Abstract

Environmental effects such as ram-pressure stripping (RPS) shape the evolution of galaxies in dense regions. We use the nearby Virgo cluster as a laboratory to study environmental effects on the non-thermal components of star-forming galaxies. We constructed a sample of 17 RPS galaxies in the Virgo cluster and a statistical control sample of 119 nearby galaxies from the Herschel Reference Survey. All objects in these samples are detected in LOFAR 144 MHz observations and come with H$\alpha$ and/or far-UV star formation rate (SFR) estimates. We derived the radio-SFR relations, confirming a clearly super-linear slope of $\approx1.4$. We found that Virgo cluster RPS galaxies have radio luminosities that are a factor of 2-3 larger than galaxies in our control sample. We also investigated the total mass-spectral index relation, where we found a relation for the Virgo cluster RPS galaxies that is shifted to steeper spectral index values by $0.17\pm0.06$. Analyzing the spatially resolved ratio between the observed and the expected radio emission based on the hybrid near-UV + 100$\,\mu$m SFR surface density, we generally observe excess radio emission all across the disk with the exception of a few leading-edge radio-deficient regions. The radio excess and the spectral steepening for the RPS sample could be explained by an increased magnetic field strength if the disk-wide radio enhancement is due to projection effects. For the galaxies that show the strongest radio excesses (NGC 4330, NGC 4396, NGC 4522), a rapid decline of the SFR ($t_\mathrm{quench} \leq 100$ Myr) could be an alternative explanation. We disfavor shock acceleration of electrons as cause for the radio excess since it cannot easily explain the spectral steepening and radio morphology.

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H. W. Edler, I. D. Roberts, A. Boselli, F. de Gasperin, V. Heesen, M. Brüggen, A. Ignesti, L. Gajović. 2023-11-03. ViCTORIA project: The LOFAR-view of environmental effects in Virgo Cluster star-forming galaxies. https://arxiv.org/abs/2311.01904

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