The fundamental properties of the postulated dark matter (DM) affect the internal structure of gravitationally bound structures. In the cold dark matter paradigm, DM particles interact only via... Show moreThe fundamental properties of the postulated dark matter (DM) affect the internal structure of gravitationally bound structures. In the cold dark matter paradigm, DM particles interact only via gravity. Their distribution is well represented by an Einasto profile with shape parameter alpha approximate to 0.18 in the smallest dwarf galaxies or the most massive galaxy clusters alike. Conversely, if DM particles self-interact via additional forces, we expect the mass density profiles of DM halos to flatten in their central regions, thereby increasing the Einasto shape parameter. We measured the structural properties of 12 massive galaxy clusters from observations of their hot gaseous atmosphere, using the X-ray observatory XMM-Newton, and of the Sunyaev-Zel'dovich effect using the Planck all-sky survey. After removing morphologically disturbed systems, we measured Einasto shape parameters with mean =0.19 +/- 0.03 and intrinsic scatter sigma(alpha)=0.06, which is in close agreement with the prediction of the cold dark matter paradigm. We used cosmological hydrodynamical simulations of cluster formation with self-interacting DM (BAHAMAS-SIDM) to determine how the Einasto shape parameter depends on the self-interaction cross section. We used the fitted relation to turn our measurements of alpha into constraints on the self-interaction cross section, which imply sigma/m< 0.19 cm(2) g(-1) (95% confidence level) at collision velocity v(DM - DM)similar to 1000 km s(-1). This is lower than the interaction cross section required for DM self-interactions to solve the core-cusp problem in dwarf spheroidal galaxies, unless the cross section is a strong function of velocity. Show less
Context. The evolution of galaxies is influenced by many physical processes, which may vary depending on their environment.Aims. We combine Hubble Space Telescope (HST) and Multi-Unit Spectroscopic... Show moreContext. The evolution of galaxies is influenced by many physical processes, which may vary depending on their environment.Aims. We combine Hubble Space Telescope (HST) and Multi-Unit Spectroscopic Explorer (MUSE) data of galaxies at 0.25 less than or similar to z less than or similar to 1.5 to probe the impact of environment on the size-mass relation, the main sequence (MS) relation, and the Tully-Fisher relation (TFR).Methods. We perform a morpho-kinematics modelling of 593 [O II] emitters in various environments in the COSMOS area from the MUSE-gAlaxy Groups In Cosmos survey. The HST F814W images are modelled with a bulge-disk decomposition to estimate their bulge-disk ratio, effective radius, and disk inclination. We use the [O II] lambda lambda 3727, 3729 doublet to extract the galaxies' ionised gas kinematics maps from the MUSE cubes, and we model those maps for a sample of 146 [O II] emitters, including bulge and disk components constrained from morphology and a dark matter halo.Results. We find an offset of 0.03 dex (1 sigma - significant) on the size-mass relation zero point between the field and the large structure sub-samples, with a richness threshold of N = 10 to separate between small and large structures, and of 0.06 dex (2 sigma) with N = 20. Similarly, we find a 0.1 dex (2 sigma) difference on the MS relation with N = 10 and 0.15 dex (3 sigma) with N = 20. These results suggest that galaxies in massive structures are smaller by 14% and have star formation rates reduced by a factor of 1.3-1.5 with respect to field galaxies at z approximate to 0.7. Finally, we do not find any impact of the environment on the TFR, except when using N = 20 with an offset of 0.04 dex (1 sigma). We discard the effect of quenching for the largest structures, which would lead to an offset in the opposite direction. We find that, at z approximate to 0.7, if quenching impacts the mass budget of galaxies in structures, these galaxies would have been affected quite recently and for roughly 0.7-1.5 Gyr. This result holds when including the gas mass but vanishes once we include the asymmetric drift correction. Show less
Aims. Intergalactic magnetic fields in the voids of the large-scale structure can be probed via measurements of secondary gamma-ray emission from gamma-ray interactions with extragalactic... Show moreAims. Intergalactic magnetic fields in the voids of the large-scale structure can be probed via measurements of secondary gamma-ray emission from gamma-ray interactions with extragalactic background light. Lower bounds on the magnetic field in the voids were derived from the nondetection of this emission. It is not clear a priori what kind of magnetic field is responsible for the suppression of the secondary gamma-ray flux: a cosmological magnetic field that might be filling the voids, or the field spread by galactic winds driven by star formation and active galactic nuclei. Methods. We used IllustrisTNG cosmological simulations to study the effect of magnetized galactic wind bubbles on the secondary gamma-ray flux. Results. We show that within the IllustrisTNG model of baryonic feedback, galactic wind bubbles typically provide energy-independent secondary flux suppression at a level of about 10%. The observed flux suppression effect has to be due to the cosmological magnetic field in the voids. This might not be the case for the special case when the primary gamma-ray source has a hard intrinsic gamma-ray spectrum that peaks in the energy range above 50 TeV. In this case, the observational data may be strongly affected by the magnetized bubble that is blown by the source host galaxy. Show less
