1,672 research outputs found

    Diurnal and annual variations of meteor rates at the arctic circle

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    Meteors are an important source for (a) the metal atoms of the upper atmosphere metal layers and (b) for condensation nuclei, the existence of which are a prerequisite for the formation of noctilucent cloud particles in the polar mesopause region. For a better understanding of these phenomena, it would be helpful to know accurately the annual and diurnal variations of meteor rates. So far, these rates have been little studied at polar latitudes. Therefore we have used the 33 MHz meteor radar of the ALOMAR observatory at 69&deg; N to measure the meteor rates at this location for two full annual cycles. This site, being within 3&deg; of the Arctic circle, offers in addition an interesting capability: The axis of its antenna field points (almost) towards the North ecliptic pole once each day of the year. In this particular viewing direction, the radar monitors the meteoroid influx from (almost) the entire ecliptic Northern hemisphere. <P style='line-height: 20px;'> We report on the observed diurnal variations (averaged over one month) of meteor rates and their significant alterations throughout the year. The ratio of maximum over minimum meteor rates throughout one diurnal cycle is in January and February about 5, from April through December 2.3&plusmn;0.3. If compared with similar measurements at mid-latitudes, our expectation, that the amplitude of the diurnal variation is to decrease towards the North pole, is not really borne out. <P style='line-height: 20px;'> Observations with the antenna axis pointing towards the North ecliptic pole showed that the rate of deposition of meteoric dust is substantially larger during the Arctic NLC season than the annual mean deposition rate. The daylight meteor showers of the Arietids, Zeta Perseids, and Beta Taurids supposedly contribute considerably to the June maximum of meteor rates. We note, though, that with the radar antenna pointing as described above, all three meteor radiants are close to the local horizon but all three radiants were detected

    Molecular gas heating in Arp 299

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    Understanding the heating and cooling mechanisms in nearby (Ultra) luminous infrared galaxies can give us insight into the driving mechanisms in their more distant counterparts. Molecular emission lines play a crucial role in cooling excited gas, and recently, with Herschel Space Observatory we have been able to observe the rich molecular spectrum. CO is the most abundant and one of the brightest molecules in the Herschel wavelength range. CO transitions are observed with Herschel, and together, these lines trace the excitation of CO. We study Arp 299, a colliding galaxy group, with one component harboring an AGN and two more undergoing intense star formation. For Arp 299 A, we present PACS spectrometer observations of high-J CO lines up to J=20-19 and JCMT observations of 13^{13}CO and HCN to discern between UV heating and alternative heating mechanisms. There is an immediately noticeable difference in the spectra of Arp 299 A and Arp 299 B+C, with source A having brighter high-J CO transitions. This is reflected in their respective spectral energy line distributions. We find that photon-dominated regions (PDRs) are unlikely to heat all the gas since a very extreme PDR is necessary to fit the high-J CO lines. In addition, this extreme PDR does not fit the HCN observations, and the dust spectral energy distribution shows that there is not enough hot dust to match the amount expected from such an extreme PDR. Therefore, we determine that the high-J CO and HCN transitions are heated by an additional mechanism, namely cosmic ray heating, mechanical heating, or X-ray heating. We find that mechanical heating, in combination with UV heating, is the only mechanism that fits all molecular transitions. We also constrain the molecular gas mass of Arp 299 A to 3e9 Msun and find that we need 4% of the total heating to be mechanical heating, with the rest UV heating

    The neutron time-of-flight facility n-TOF at CERN: Phase II

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    Neutron-induced reactions are studied at the neutron time-of-flight facility n-TOF at CERN. The facility uses 6∼ns wide pulses of 20 GeV/c protons impinging on a lead spallation target. The large neutron energy range and the high instantaneous neutron flux combined with high resolution are among the key characteristics of the facility. After a first phase of data taking during the period 2001-2004, the facility has been refurbished with an upgraded spallation target and cooling system for a second phase of data taking which started in 2009. Since 2010, the experimental area at 185 m where the neutron beam arrives, has been modified into a worksector of type A, allowing the extension of the physics program to include neutron-induced reactions on radioactive isotopes

    "Zum reichen Jüngling" Mk 10, 13–27.

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    Resolving the molecular gas around the lensed quasar RXJ0911.4+0551

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    We report on high angular resolution observations of the CO(7-6) line and millimeter continuum in the host galaxy of the gravitationally lensed (z~2.8) quasar RXJ0911.4+0551 using the Plateau de Bure Interferometer. Our CO observations resolve the molecular disk of the source. Using a lens model based on HST observations we fit source models to the observed visibilities. We estimate a molecular disk radius of 1±\pm0.2 kpc and an inclination of 69±\pm6\deg, the continuum is more compact and is only marginally resolved by our observations. The relatively low molecular gas mass, Mgas=(2.3±0.5)×109Mgas=(2.3\pm 0.5)\times 10^{9} Msolar, and far infrared luminosity, LFIR=(7.2±1.5)×1011LFIR=(7.2\pm 1.5) \times 10^{11} Lsolar, of this quasar could be explained by its relatively low dynamical mass, Mdyn=(3.9±0.9)×109Mdyn=(3.9\pm 0.9)\times 10^9 Msolar. It would be a scaled-down version the QSOs usually found at high-z. The FIR and CO luminosities lie on the correlation found for QSOs from low to high redshifts and the gas-to-dust ratio (45±1745\pm 17) is similar to the one measured in the z=6.4 QSO, SDSS J1148+5251. Differential magnification affects the continuum-to-line luminosity ratio, the line profile and possibly the spectral energy distribution.Comment: Accepted for publication in A&A, revised after language editin

    Excitation of the molecular gas in the nuclear region of M82

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    We present high resolution HIFI spectroscopy of the nucleus of the archetypical starburst galaxy M82. Six 12CO lines, 2 13CO lines and 4 fine-structure lines are detected. Besides showing the effects of the overall velocity structure of the nuclear region, the line profiles also indicate the presence of multiple components with different optical depths, temperatures and densities in the observing beam. The data have been interpreted using a grid of PDR models. It is found that the majority of the molecular gas is in low density (n=10^3.5 cm^-3) clouds, with column densities of N_H=10^21.5 cm^-2 and a relatively low UV radiation field (GO = 10^2). The remaining gas is predominantly found in clouds with higher densities (n=10^5 cm^-3) and radiation fields (GO = 10^2.75), but somewhat lower column densities (N_H=10^21.2 cm^-2). The highest J CO lines are dominated by a small (1% relative surface filling) component, with an even higher density (n=10^6 cm^-3) and UV field (GO = 10^3.25). These results show the strength of multi-component modeling for the interpretation of the integrated properties of galaxies.Comment: Accepted for publication in A&A Letter

    Effects of Diversity on Multi-agent Systems: Minority Games

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    We consider a version of large population games whose agents compete for resources using strategies with adaptable preferences. The games can be used to model economic markets, ecosystems or distributed control. Diversity of initial preferences of strategies is introduced by randomly assigning biases to the strategies of different agents. We find that diversity among the agents reduces their maladaptive behavior. We find interesting scaling relations with diversity for the variance and other parameters such as the convergence time, the fraction of fickle agents, and the variance of wealth, illustrating their dynamical origin. When diversity increases, the scaling dynamics is modified by kinetic sampling and waiting effects. Analyses yield excellent agreement with simulations.Comment: 41 pages, 16 figures; minor improvements in content, added references; to be published in Physical Review

    Das exemte Bistum Bamberg 3. Die Bischofsreihe von 1522 bis 1693

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    Dieter J. Weiss, Das exemte Bistum Bamberg 3: Die Bischofsreihe von 1522 bis 1693 (Germania Sacra N. F. 38,1), Berlin/New York 2000

    Das exemte Bistum Bamberg 4. Die Bamberger Bischöfe von 1693 bis 1802

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    Mit den Bischofsviten von 1693 bis 1802 liegt nun die vollständige Bischofsreihe des Bistums Bamberg vor. Der Band reicht vom Beginn des Pontifikats des Lothar Franz von Schönborn bis zur Säkularisation unter Christoph Franz von Buseck. Damit fallen der Barockkatholizismus, Ansätze zur absolutistischen Herrschaft und die Aufklärung in den Untersuchungszeitraum. Mit Lothar Franz und Friedrich Karl von Schönborn, Adam Friedrich von Seinsheim und Franz Ludwig von Erthal werden Fürstbischöfe erfasst, die weit über den Bamberger Raum hinaus Bedeutung hatten. Die ebenso umfassenden wie markanten Bischofsporträts berücksichtigen auch literar- und kunstgeschichtliche Fragestellungen. Ein eigener Abschnitt enthält Kurzbiographien der Weihbischöfe, Generalvikare, Fiskale und Kanzler und stellt damit die eigentlichen Träger der geistlichen Verwaltung vor. Über die individuellen Biographien hinaus werden auch längerfristige Entwicklungen wie die Herausbildung absolutistischer Regierungsformen oder der Wandel des Bischofsideals im Zuge der Aufklärung deutlich.2018-10Dieter J. Weiß, Das exemte Bistum Bamberg 4: Die Bamberger Bischöfe von 1693 bis 1802 (Germania Sacra. Dritte Folge 12), Berlin/Boston 2015

    Ammonia (J,K) = (1,1) to (4,4) and (6,6) inversion lines detected in the Seyfert 2 galaxy NGC 1068

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    We present the detection of the ammonia (NH3) (J,K) = (1,1) to (4,4) and (6,6) inversion lines toward the prototypical Seyfert 2 galaxy NGC 1068, made with the Green Bank Telescope (GBT). This is the first detection of ammonia in a Seyfert galaxy. The ortho-to-para-NH3 abundance ratio suggests that the molecule was formed in a warm medium of at least 20 K. For the NH3 column density and fractional abundance, we find (1.09\pm0.23)\times10^14 cm^-2 and (2.9\pm0.6)\times10^-8, respectively, from the inner 1.2 kpc of NGC 1068. The kinetic temperature can be constrained to 80\pm20 K for the bulk of the molecular gas, while some fraction has an even higher temperature of 140\pm30 K.Comment: 5 pages, 3 figures, accepted by A&
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