394 research outputs found
A scaling-relation for disc galaxies: circular-velocity gradient versus central surface brightness
No full textFor disc galaxies, a close relation exists between the distribution of light and the
shape of the rotation curve. We quantify this relation by measuring the inner circular-
velocity gradient dRV (0) for spiral and irregular galaxies with high-quality rotation
curves. We find that dRV (0) correlates with the central surface brightness μ0 over
more than two orders of magnitude in dRV (0) and four orders of magnitudes in μ0.
This is a scaling-relation for disc galaxies. It shows that the central stellar density of a
galaxy closely relates to the inner shape of the potential well, also for low-luminosity
and low-surface-brightness galaxies that are expected to be dominated by dark matter.
Key words: dark matter – galaxies: kinematics and dynamics – galaxies: structure
Rembrandt en de Broederschap der Schilderkunst; een nieuwe hypothese voor de Pallas Athene in Museu Calouste Gulbenkian
No full textAbstractThe purchaser of a colour slide of the painting with the inventory number I488 in the Museu Gulbenkian in Lisbon will see that the work is entitled 'Palas Atcneia ou Alexandre'. This ambiguous designation is typical of the doubts surrounding this unsigned and undated painting, which is usually attributed to Rembrandt (fig. I). For some decades now, art-historical literature has put forward varying opinions about the painting, and it continues to give rise to questions. Its subject, date, backgrounds and attribution to Rembrandt are all controversial issues. The purpose of this article is to contribute to the forming of opinion regarding the Lisbon painting. The author presents a new hypothesis as to what prompted the work. On October 2I I654, painters, sculptors and their patrons gathered in the St. Joris Doelen in Amsterdam to celebrate the Feast of St. Luke. The occasion was marked by the publication of an anthology: 'Broederschap Der Schildcrkunst, INGEWYDT Door SCHILDERS, BEELDTHOUWERS En des Zelfs BEGUNSTIGERS; Op den zI van Wynmaent I654, op St. Joris Doelen, in ANISTER-DAM'. The book contains three texts, the third of which is by Asselijn. It seems to be a play that was performed during the festivities. Towards the end an election of a painter and a sculptor from among those present is described. Both must make a work of art. The painter has to paint a Minerva; the sculptor is asked to carve an Apollo from stone. Unfortunately Asselijn does not say who was the winner, although he does refer to the candidates as the foremost representatives of their profession. Jan Vos' well-known poem Strydt tusscben de Doodt en Natuur, of Zeege der Schilderkunst, also written in I654, may have been connected with the celebrations held that year. A passage in the text lists the names of a number of artists. The fact that Rembrandt comes first and the context in which this happens could suggest that Vos regarded Rembrandt as Amsterdam's leading painter at that time. Various indications support the author's assumption that this opinion was probably shared by members of Vos' circle such as Kretzer and Meures, both of whom participated in the I654 festivities, and Six and Soop, with whom Vos, Kretzer and Meures were well acquainted. All this suggests that Rembrandt was very likely a candidate for election and that he was invited to paint a Minerva at the time of the celebration. Assuming that the invitation really was issued, Rembrandt must have painted this subject in I654 or thereabouts. It could be the work which is now in Lisbon and whose subject might well be identified as Minerva.
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IceCube-Gen2: A Vision for the Future of Neutrino Astronomy in Antarctica
No full text20 pages, 12 figures. Address correspondence to: E. Blaufuss, F. Halzen, C. Kopper (Changed to add one missing author, no other changes from initial version.)20 pages, 12 figures. Address correspondence to: E. Blaufuss, F. Halzen, C. Kopper (Changed to add one missing author, no other changes from initial version.)20 pages, 12 figures. Address correspondence to: E. Blaufuss, F. Halzen, C. Kopper (Changed to add one missing author, no other changes from initial version.)The recent observation by the IceCube neutrino observatory of an astrophysical flux of neutrinos represents the "first light" in the nascent field of neutrino astronomy. The observed diffuse neutrino flux seems to suggest a much larger level of hadronic activity in the non-thermal universe than previously thought and suggests a rich discovery potential for a larger neutrino observatory. This document presents a vision for an substantial expansion of the current IceCube detector, IceCube-Gen2, including the aim of instrumenting a volume of clear glacial ice at the South Pole to deliver substantial increases in the astrophysical neutrino sample for all flavors. A detector of this size would have a rich physics program with the goal to resolve the sources of these astrophysical neutrinos, discover GZK neutrinos, and be a leading observatory in future multi-messenger astronomy programs
Probing primordial non-gaussianity with SKA galaxy redshift surveys:a fully relativistic analysis
No full textModelo de previsão da demanda para as indústrias atuantes no setor de infra-estrutura brasileiro dos segmentos de energia elétrica e telecomunicações
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenhara de Produção.Proposição de um modelo de processo de previsão da demanda - combinando métodos quantitativos e qualitativos - para as indústrias atuantes no setor de infra-estrutura brasileiro dos segmentos de Energia Elétrica e Telecomunicações, baseando-se em recentes pesquisas e bibliografia sobre o tema e no estudo de caso do processo de previsão em empresas destes segmentos. O modelo consiste em um processo que combina métodos quantitativos e qualitativos de julgamento, ressaltando a necessidade de se utilizar os primeiros sempre que as séries temporais permitirem - preferencialmente os mais simples - e sistematizando o emprego das técnicas qualitativas de modo a minimizar a introdução de viés por julgamento
Lateral distribution of muons in IceCube cosmic ray events
No full textIn cosmic ray air showers, the muon lateral separation from the center of the shower is a measure of the transverse momentum that the muon parent acquired in the cosmic ray interaction. IceCube has observed cosmic ray interactions that produce muons laterally separated by up to 400 m from the shower core, a factor of 6 larger distance than previous measurements. These muons originate in high p(T) (>2 GeV/c) interactions from the incident cosmic ray, or high-energy secondary interactions. The separation distribution shows a transition to a power law at large values, indicating the presence of a hard p(T) component that can be described by perturbative quantum chromodynamics. However, the rates and the zenith angle distributions of these events are not well reproduced with the cosmic ray models tested here, even those that include charm interactions. This discrepancy may be explained by a larger fraction of kaons and charmed particles than is currently incorporated in the simulations.R. Abbasi ... G. C. Hill ... et al. (IceCube Collaboration
Coherent radar reflections from an electron-beam induced particle cascade
No full textExperiment T-576 ran at SLAC in 2018, in development of a new radar-based detection scheme for ultra-high energy neutrinos. In this experiment, the electron beam (N∼109e−
at ∼10
GeV) was directed into a plastic target to simulate a 1019
eV neutrino-induced shower in ice. This shower was interrogated with radio frequency (RF) radiation, in an attempt to measure a radar-like reflection from the ionization produced in the target during the particle shower. This technique could be employed to detect the rare interactions of ultra-high-energy neutrinos in dense material, such as polar ice sheets, extending the extant energy range of detected neutrinos up to EeV and beyond. In this proceeding, we detail the experiment and present results from the analysis and the observation of a signal consistent with a radar signal
IceCube-Gen2 - The Next Generation Neutrino Observatory at the South Pole: Contributions to ICRC 2015
No full text85 pages, 52 figures, Papers submitted to the 34th International Cosmic Ray Conference, The Hague 2015, v2 has a corrected author list85 pages, 52 figures, Papers submitted to the 34th International Cosmic Ray Conference, The Hague 2015, v2 has a corrected author listPapers submitted to the 34th International Cosmic Ray Conference (ICRC 2015, The Hague) by the IceCube-Gen2 Collaboration
Camera design and performance of the prototype schwarzschild-couder telescope for the Cherenkov Telescope Array
No full textThe Schwarzschild-Couder Telescope (SCT) is a candidate technology for a medium-sized telescope within the Cherenkov Telescope Array, the next generation ground based observatory for very high energy gamma ray astronomy. The SCT uses a novel two-mirror design and is expected to yield improvements in field of view and image resolution compared to traditional Cherenkov telescopes based on single-mirror-dish optics. To match the improved optical resolution, challenging requirements of high channel count and density at low power consumption must be overcome by the camera. The prototype camera, currently commissioned and tested on the prototype SCT, has been developed based on millimeter scale SiPM pixels and a custom high density digitizer ASIC, TARGET, to provide 1600 pixels spanning a 2.7 degree field of view while being able to sample nanosecond photon pulses. It is mechanically designed to allow for an upgrade to 11,328 pixels covering a field of view of 8 degrees and demonstrating the full potential of the technology. The camera was installed on the telescope in 2018. We will present its design and performance including first light data
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