The role of stellar radial motions in shaping galaxy surface brightness profiles

Aims. The physics driving features such as breaks observed in galaxy surface brightness (SB) profiles remains contentious. Here, we assess the importance of stellar radial motions in shaping their characteristics. Methods. We use the simulated Milky Way-mass cosmological discs from the Ramses Disc Environment Study (RaDES) to characterise the radial redistribution of stars in galaxies displaying type-I (pure exponentials), II (downbending), and III (upbending) SB profiles. We compare radial profiles of the mass fractions and the velocity dispersions of different sub-populations of stars according to their birth and current location. Results. Radial redistribution of stars is important in all galaxies regardless of their light profiles. Type-II breaks seem to be a consequence of the combined effects of outward-moving and accreted stars. The former produce shallower inner profiles (lack of stars in the inner disc) and accumulate material around the break radius and beyond, strengthening the break; the latter can weaken or even convert the break into a pure exponential. Further accretion from satellites can concentrate material in the outermost parts, leading to type-III breaks that can coexist with type-II breaks, but situated further out. Type-III galaxies would be the result of an important radial redistribution of material throughout the entire disc, as well as a concentration of accreted material in the outskirts. In addition, type-III galaxies display the most efficient radial redistribution and the largest number of accreted stars, followed by type-I and II systems, suggesting that type-I galaxies may be an intermediate case between types-II and III. In general, the velocity dispersion profiles of all galaxies tend to flatten or even increase around the locations where the breaks are found. The age and metallicity profiles are also affected, exhibiting different inner gradients depending on their SB profile, being steeper in the case of type-II systems (as found observationally). The steep type-II profiles might be inherent to their formation rather than acquired via radial redistribution

Large-Scale Magnetic Fields, Dark Energy and QCD

Cosmological magnetic fields are being observed with ever increasing correlation lengths, possibly reaching the size of superclusters, therefore disfavouring the conventional picture of generation through primordial seeds later amplified by galaxy-bound dynamo mechanisms. In this paper we put forward a fundamentally different approach that links such large-scale magnetic fields to the cosmological vacuum energy. In our scenario the dark energy is due to the Veneziano ghost (which solves the $U(1)_A$ problem in QCD). The Veneziano ghost couples through the triangle anomaly to the electromagnetic field with a constant which is unambiguously fixed in the standard model. While this interaction does not produce any physical effects in Minkowski space, it triggers the generation of a magnetic field in an expanding universe at every epoch. The induced energy of the magnetic field is thus proportional to cosmological vacuum energy: $\rho_{EM}\simeq B^2 \simeq (\frac{\alpha}{4\pi})^2 \rho_{DE}$, $\rho_{DE}$ hence acting as a source for the magnetic energy $\rho_{EM}$. The corresponding numerical estimate leads to a magnitude in the nG range. There are two unique and distinctive predictions of our proposal: an uninterrupted active generation of Hubble size correlated magnetic fields throughout the evolution of the universe; the presence of parity violation on the enormous scales $1/H$, which apparently has been already observed in CMB. These predictions are entirely rooted into the standard model of particle physics.Comment: jhep style, 22 pages, v2 with updated estimates and extended discussion on parity violation, v3 as published (references updated

Efectos de un sistema integrado de recolección para pequeños productores en la calidad de la aceituna recogida

Small producers confront specific challenges when they opt to produce high-quality olive fruit. Limited resources for investing in harvest machinery and manpower are the main reasons for continuing a traditional harvest method that puts the final product and its economic value at risk. This paper discusses the efficiency of an integrated harvest system as a possible solution to these specific challenges. The system is formed by a newly designed manual harvesting device and the use of a cooling room near the olive grove. Both systems were evaluated to assess their feasibility for optimum conditions before processing. The combined effect of the harvesting method and cold storage on the fruit characteristics (incidence of decay, skin color, weight loss, firmness, respiration, and ethylene production) was evaluated on three different varieties (‘Arbequina’, ‘Picual’ and ‘Verdial’) and four different storage times (0, 4, 8, and 14 days). The results indicate that the proposed harvesting method in combination with an appropriate cooling system offers an affordable alternative for obtaining fruit with the best physiological characteristics.Los pequeños productores se enfrentan a retos específicos, cuando optan por producir aceitunas de alta calidad. La imposibilidad económica de invertir, tanto en maquinaria de cosecha, como en mano de obra es la razón principal que obliga a continuar una recolección tradicional que pone en riesgo el producto final y su valor económico. Este estudio analiza la eficiencia de un sistema de recolección integrado como una posible solución a estos desafíos específicos. El sistema está formado por un dispositivo de recogida manual de nuevo diseño y el uso de una cámara de frío en la finca. El efecto combinado del método de recolección presentado y el almacenamiento en frío sobre las características de la fruta (incidencia de podredumbre, color de piel, pérdida de peso, firmeza, respiración y producción de etileno) se evaluó en tres variedades diferentes (‘Arbequina’, ‘Picual’ y ‘Verdial’) y diferentes tiempos de almacenamiento (0, 4, 8, 14 días). Los resultados indican que la combinación de un método de recolección mecánica y un sistema de enfriamiento adecuado ofrece una alternativa económicamente asequible para obtener frutos con las mejores características fisiológicas