Detection of microgauss coherent magnetic fields in a galaxy five billion years ago

Magnetic fields play a pivotal role in the physics of interstellar medium in galaxies, but there are few observational constraints on how they evolve across cosmic time. Spatially resolved synchrotron polarization maps at radio wavelengths reveal well-ordered large-scale magnetic fields in nearby galaxies that are believed to grow from a seed field via a dynamo effect. To directly test and characterize this theory requires magnetic field strength and geometry measurements in cosmologically distant galaxies, which are challenging to obtain due to the limited sensitivity and angular resolution of current radio telescopes. Here, we report the cleanest measurements yet of magnetic fields in a galaxy beyond the local volume, free of the systematics traditional techniques would encounter. By exploiting the scenario where the polarized radio emission from a background source is gravitationally lensed by a foreground galaxy at z = 0.439 using broadband radio polarization data, we detected coherent $\mu$G magnetic fields in the lensing disk galaxy as seen 4.6 Gyrs ago, with similar strength and geometry to local volume galaxies. This is the highest redshift galaxy whose observed coherent magnetic field property is compatible with a mean-field dynamo origin.Comment: 29 pages, 5 figures (including Supplementary Information). Published in Nature Astronomy on August 28, 201

Cosmic magnetic fields from velocity perturbations in the early Universe

We show, using a covariant and gauge-invariant charged multifluid perturbation scheme, that velocity perturbations of the matter-dominated dust Friedmann-Lemaitre-Robertson-Walker (FLRW) model can lead to the generation of cosmic magnetic fields. Moreover, using cosmic microwave background (CMB) constraints, it is argued that these fields can reach strengths of between 10^{-28} and 10^{-29} G at the time the dynamo mechanism sets in, making them plausible seed field candidates.Comment: 11 pages, 1 figure, IOP style, minor changes and typos correcte

Cluster Observations of Bow Shock Energetic Ion Transport Through the Magnetosheath into the Cusp

The observation of energetic particles by polar orbiting satellites in the magnetospheric cusp resulted in a controversy about their source region. It has been suggested that these cusp energetic particles (CEP) with significant fluxes from magnetosheath energies up to several hundred keV/e are accelerated locally in the cusp by the turbulence found in cusp diamagnetic cavities (CDC). As an alternative to the local acceleration region, the quasi‐parallel shock is successful as a source region for CEP events. Energetic ions accelerated at the bow shock can be transported downstream and enter the cusp along newly reconnected field lines. Composition and energy spectra of these CEP events resemble those of bow shock energetic diffuse ions. This study investigates a northern cusp pass by the Cluster satellites that encountered two CDCs with CEP ions. We use recently developed techniques to determine the location of the reconnection site at the magnetopause, draping interplanetary magnetic field lines over the magnetopause and mapping those field lines back into the solar wind to show magnetic connection of the cusp regions, Earth’s bow shock, and upstream region. Energetic ions are also observed outside the magnetopause in the boundary layer streaming from the quasi‐parallel shock toward the cusp which supports an outside source region for CEP ions

Heating Hot Atmospheres with Active Galactic Nuclei

High resolution X-ray spectroscopy of the hot gas in galaxy clusters has shown that the gas is not cooling to low temperatures at the predicted rates of hundreds to thousands of solar masses per year. X-ray images have revealed giant cavities and shock fronts in the hot gas that provide a direct and relatively reliable means of measuring the energy injected into hot atmospheres by active galactic nuclei (AGN). Average radio jet powers are near those required to offset radiative losses and to suppress cooling in isolated giant elliptical galaxies, and in larger systems up to the richest galaxy clusters. This coincidence suggests that heating and cooling are coupled by feedback, which suppresses star formation and the growth of luminous galaxies. How jet energy is converted to heat and the degree to which other heating mechanisms are contributing, eg. thermal conduction, are not well understood. Outburst energies require substantial late growth of supermassive black holes. Unless all of the approximately 10E62 erg required to suppress star formation is deposited in the cooling regions of clusters, AGN outbursts must alter large-scale properties of the intracluster medium.Comment: 60 pages, 12 figures, to appear in 1997 Annual Reviews of Astronomy and Astrophysics. This version supersedes the April 2007 version in Reviews in Advance (references and minor corrections were added), and is similar to the one scheduled to appear in Volume 45 of ARA

A mesoscopic lattice model for morphology formation in ternary mixtures with evaporation

We develop a mesoscopic lattice model to study the morphology formation in interacting ternary mixtures with the evaporation of one component. As concrete potential application of our model, we wish to capture morphologies as they are typically arising during the fabrication of organic solar cells. In this context, we consider an evaporating solvent into which two other components are dissolved, as a model for a 2-component coating solution that is drying on a substrate. We propose a 3-spins dynamics to describe the evolution of the three interacting species. As main tool, we use a Monte Carlo Metropolis-based algorithm, with the possibility of varying the system's temperature, mixture composition, interaction strengths, and evaporation kinetics. The main novelty is the structure of the mesoscopic model – a bi-dimensional lattice with periodic boundary conditions, divided into square cells to encode a mesoscopic range interaction among the units. We investigate the effect of the model parameters on the structure of the resulting morphologies. Finally, we compare the results obtained with the mesoscopic model with corresponding ones based on an analogous lattice model with a short range interaction among the units, i.e. when the mesoscopic length scale coincides with the microscopic length scale of the lattice

Optimización de la producción de biomasa usando glicerol crudo, de una cepa mutante de Yarrowia lipolytica con actividad incrementada de lipasa

218-225The yeast Yarrowia lipolytica accumulates oils and is able to produce extracellular lipases when growing in different carbon sources including glycerol, the principal by-product of the biodiesel industry. In this study, biomass production of a novel mutant strain of Y. lipolytica was statistically optimized by Response Surface Methodology in media containing biodiesel-derived glycerol as main carbon source. This strain exhibited distinctive morphological and fatty acid profile characteristics, and showed an increased extracellular lipase activity. An organic source of nitrogen and the addition of 1.0 g/l olive oil were necessary for significant lipase production. Plackett-Burman and Central Composite Statistical Designs were employed for screening and optimization of fermentation in shaken flasks cultures, and the maximum values obtained were 16.1 g/l for biomass and 12.2 Units/ml for lipase, respectively. Optimized batch bioprocess was thereafter scaled in aerated bioreactors and the values reached for lipase specific activity after 95 percent of the glycerol had been consumed, were three-fold higher than those obtained in shaken flasks cultures. A sustainable bioprocess to obtain biomass and extracellular lipase activity was attained by maximizing the use of the by-products of biodiesel industry

A Faraday Rotation Search for Magnetic Fields in Large Scale Structure

Faraday rotation of radio source polarization provides a measure of the integrated magnetic field along the observational lines of sight. We compare a new, large sample of Faraday rotation measures (RMs) of polarized extragalactic sources with galaxy counts in Hercules and Perseus-Pisces, two nearby superclusters. We find that the average of RMs in these two supercluster areas are larger than in control areas in the same galactic latitude range. This is the first RM detection of magnetic fields that pervade a supercluster volume, in which case the fields are at least partially coherent over several megaparsecs. Even the most conservative interpretation of our observations, according to which Milky Way RM variations mimic the background supercluster galaxy overdensities, puts constraints on the IGM magneto-ionic ``strength'' in these two superclusters. We obtain an approximate typical upper limit on the field strength of about 0.3 microGauss l/(500 kpc), when we combine our RM data with fiducial estimates of electron density from the environments of giant radio galaxies, and of the warm-hot intergalactic medium (WHIM).Comment: 8 pages, 3 figures, 1 table, to appear in the Astrophysical Journa

Intense Current Structures Observed at Electron Kinetic Scales in the Near‐Earth Magnetotail During Dipolarization and Substorm Current Wedge Formation

We use data from the 2013–2014 Cluster Inner Magnetosphere Campaign, with its uniquely small spacecraft separations (less than or equal to electron inertia length, λe), to study multiscale magnetic structures in 14 substorm‐related prolonged dipolarizations in the near‐Earth magnetotail. Three time scales of dipolarization are identified: (i) a prolonged growth of the BZ component with duration ≤20 min; (ii) BZ pulses with durations ≤1 min during the BZ growth; and (iii) strong magnetic field gradients with durations ≤2 s during the dipolarization growth. The values of these gradients observed at electron scales are several dozen times larger than the corresponding values of magnetic gradients simultaneously detected at ion scales. These nonlinear features in magnetic field gradients denote the formation of intense and localized (approximately a few λe) current structures during the dipolarization and substorm current wedge formation. These observations highlight the importance of electron scale processes in the formation of a 3‐D substorm current system.Key PointsMultiscale current structure formed during dipolarization growthIntense current structures are transiently (≤2 s) observed at the leading and trailing edges of BZ pulses during dipolarization growthSpatial scales of the intense current structures are ~100–200 km ~(2.5–5.0)λePeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142547/1/grl56899_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142547/2/grl56899.pd

A Magnetized Local Supercluster and the Origin of the Highest Energy Cosmic Rays

A sufficiently magnetized Local Supercluster can explain the spectrum and angular distribution of ultra-high energy cosmic rays. We show that the spectrum of extragalactic cosmic rays with energies below $\sim 10^{20}$ eV may be due to the diffusive propagation in the Local Supercluster with fields of $\sim 10^{-8} - 10^{-7}$ Gauss. Above $\sim 10^{20}$ eV, cosmic rays propagate in an almost rectilinear way which is evidenced by the change in shape of the spectrum at the highest energies. The fit to the spectrum requires that at least one source be located relatively nearby at $\sim 10-15$ Mpc away from the Milky Way. We discuss the origin of magnetic fields in the Local Supercluster and the observable predictions of this model.Comment: 11 pages, 2 figures, submitted to PR

Statistics of clustering of ultra-high energy cosmic rays and the number of their sources

Observation of clustering of ultra-high energy cosmic rays (UHECR) suggests that they are emitted by compact sources. Assuming small deflection of UHECR during the propagation, the statistical analysis of clustering allows to estimate the spatial density of the sources, h, including those which have not yet been observed directly. When applied to astrophysical models involving extra-galactic sources, the estimate based on 14 events with energy E>10^{20} eV gives h ~ 6 X 10^{-3} Mps^{-3}. With increasing statistics, this estimate may lead to exclusion of the models which associate the production of UHECR with exceptional galaxies such as AGN, powerful radio-galaxies, dead quasars, and models based on gamma ray bursts.Comment: The version accepted for publication in Phys. Rev. Lett. Notations changed to conventional ones. The estimate of the effective GZK radius replaced by the result of numerical simulatio