Unveiling radio halos in galaxy clusters in the LOFAR era

Giant radio halos are mega-parsec scale synchrotron sources detected in a fraction of massive and merging galaxy clusters. Radio halos provide one of the most important pieces of evidence for non-thermal components in large scale structure. Statistics of their properties can be used to discriminate among various models for their origin. Therefore, theoretical predictions of the occurrence of radio halos are important as several new radio telescopes are about to begin to survey the sky at low frequencies with unprecedented sensitivity. In this paper we carry out Monte Carlo simulations to model the formation and evolution of radio halos in a cosmological framework. We extend previous works on the statistical properties of radio halos in the context of the turbulent re-acceleration model. First we compute the fraction of galaxy clusters that show radio halos and derive the luminosity function of radio halos. Then, we derive differential and integrated number count distributions of radio halos at low radio frequencies with the main goal to explore the potential of the upcoming LOFAR surveys. By restricting to the case of clusters at redshifts <0.6, we find that the planned LOFAR all sky survey at 120 MHz is expected to detect about 350 giant radio halos. About half of these halos have spectral indices larger than 1.9 and substantially brighten at lower frequencies. If detected they will allow for a confirmation that turbulence accelerates the emitting particles. We expect that also commissioning surveys, such as MSSS, have the potential to detect about 60 radio halos in clusters of the ROSAT Brightest Cluster Sample and its extension (eBCS). These surveys will allow us to constrain how the rate of formation of radio halos in these clusters depends on cluster mass.Comment: 12 pages, 12 figures, accepted for publication in Astronomy and Astrophysic

Space charge effects in a vacuum thermionic diode

Temperature effects on thermionic diode with space charge model including emitter and accumulator electrode emission

Pressure measuring systems for closed cycle liquid metal facilities Ninth quarterly report, Mar. 1 - May 31, 1966

Thermionic diode pressure transducer for liquid metal application

Pressure measuring systems for closed cycle liquid metal facilities fifth quarterly report, 1 mar. - 31 may 1965

Pressure transducer system with thermionic diode sensor for closed cycle liquid metal applicatio

Pressure measuring systems for closed cycle liquid metal facilities Eighth quarterly report, 1 Dec. 1965 - 28 Feb. 1966

Thermionic diode pressure transducer for liquid metal applications and thermionic sensor desig

Pressure measuring systems for closed cycle liquid metal facilities Final report

Thermionic diode pressure sensor for liquid, vapor, and two phase potassium flow measurements at high temperature

Pressure measuring systems for closed cycle liquid metal facilities Seventh quarterly report, 1 Sep. - 30 Nov. 1965

Thermionic diode pressure transducer for closed cycle liquid metal application

Pressure measuring systems for closed cycle liquid metal facilities fourth quarterly report, 1 dec. 1964 - 28 feb. 1965

Pressure transducer system for liquid metal applications - fabrication of test pressure capsules, and deflection tests using optical measurement techniqu

Anxious to see you: Neuroendocrine mechanisms of social vigilance and anxiety during adolescence.

Social vigilance is a behavioral strategy commonly used in adverse or changing social environments. In animals, a combination of avoidance and vigilance allows an individual to evade potentially dangerous confrontations while monitoring the social environment to identify favorable changes. However, prolonged use of this behavioral strategy in humans is associated with increased risk of anxiety disorders, a major burden for human health. Elucidating the mechanisms of social vigilance in animals could provide important clues for new treatment strategies for social anxiety. Importantly, during adolescence the prevalence of social anxiety increases significantly. We hypothesize that many of the actions typically characterized as anxiety behaviors begin to emerge during this time as strategies for navigating more complex social structures. Here, we consider how the social environment and the pubertal transition shape neural circuits that modulate social vigilance, focusing on the bed nucleus of the stria terminalis and prefrontal cortex. The emergence of gonadal hormone secretion during adolescence has important effects on the function and structure of these circuits, and may play a role in the emergence of a notable sex difference in anxiety rates across adolescence. However, the significance of these changes in the context of anxiety is still uncertain, as not enough studies are sufficiently powered to evaluate sex as a biological variable. We conclude that greater integration between human and animal models will aid the development of more effective strategies for treating social anxiety

Pressure measuring systems for closed cycle liquid metal facilities Sixth quarterly report, Jun. 1 - Aug. 31, 1965

Pressure transducers for closed cycle power systems using liquid metal