Low frequency measurements of synchrotron absorbing HII regions and modeling of observed synchrotron emissivity

Cosmic rays (CRs) and magnetic fields are dynamically important components in the Galaxy, and their energy densities are comparable to that of the turbulent interstellar gas. The interaction of CRs and Galactic magnetic fields produces synchrotron radiation clearly visible in the radio regime. Detailed measurements of synchrotron radiation averaged over the line-of-sight (LOS), so-called synchrotron emissivities, can be used as a tracer of the CR density and Galactic magnetic field (GMF) strength. Our aim is to model the synchrotron emissivity in the Milky Way using a 3 dimensional dataset instead of LOS-integrated intensity maps on the sky. Using absorbed HII regions we can measure the synchrotron emissivity over a part of the LOS through the Galaxy, changing from a 2 dimensional to a 3 dimensional view. Performing these measurements on a large scale is one of the new applications of the window opened by current low frequency arrays. Using various simple axisymmetric emissivity models and a number of GMF-based emissivity models we can simulate the synchrotron emissivities and compare them to the observed values in the catalog. We present a catalog of low-frequency absorption measurements of HII regions, their distances and electron temperatures, compiled from literature. These data show that the axisymmetric emissivity models are not complex enough, but the GMF-based emissivity models deliver a reasonable fit. These models suggest that the fit can be improved by either an enhanced synchrotron emissivity in the outer reaches of the Milky Way, or an emissivity drop near the Galactic center. State-of-the-art GMF models plus a constant CR density model cannot explain low-frequency absorption measurements, but the fits improved with slight (ad-hoc) adaptations. It is clear that more detailed models are needed, but the current results are very promising.Comment: 14 pages, 9 figures, accepted for publication in A&

Twisted partial actions of Hopf algebras

In this work, the notion of a twisted partial Hopf action is introduced as a unified approach for twisted partial group actions, partial Hopf actions and twisted actions of Hopf algebras. The conditions on partial cocycles are established in order to construct partial crossed products, which are also related to partially cleft extensions of algebras. Examples are elaborated using algebraic groups

Substituição de copa do cupuaçuzeiro - método alternativo para controle da vassoura-de-bruxa.

bitstream/item/72694/1/Oriental-ComTec236.pd

Gravitational collapse of the OMC-1 region

We have investigated the global dynamical state of the Integral Shaped Filament in the Orion A cloud using new N$_2$H$^+$ (1-0) large-scale, IRAM30m observations. Our analysis of its internal gas dynamics reveals the presence of accelerated motions towards the Orion Nebula Cluster, showing a characteristic blue-shifted profile centred at the position of the OMC-1 South region. The properties of these observed gas motions (profile, extension, and magnitude) are consistent with the expected accelerations for the gravitational collapse of the OMC-1 region and explain both the physical and kinematic structure of this cloud.Comment: 5 pages, 2 figures; Accepted by A&

Compatibilidade entre genótipos de cupuaçuzeiro (Theobroma grandiflorum (Willd. ex Spreng.) Schum.

bitstream/item/37386/1/ORIENTAL-BPD53.pdfVersão eletrônica. 1ª impressão: 2009