6,410 research outputs found

    Determination of the stability and control derivatives of the F/A-18 HARV from flight data using the maximum likelihood method

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    The research being conducted pertains to the determination of the stability and control derivatives of the F/A-18 High Alpha Research Vehicle (HARV) from flight data using the Maximum Likelihood Method. The document outlines the approach used in the parameter estimation (PID) process and briefly describes the mathematical modeling of the F/A-18 HARV and the maneuvers designed to generate a sufficient data base for the PID research

    Certified quantum non-demolition measurement of material systems

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    An extensive debate on quantum non-demolition (QND) measurement, reviewed in Grangier et al. [Nature, {\bf 396}, 537 (1998)], finds that true QND measurements must have both non-classical state-preparation capability and non-classical information-damage tradeoff. Existing figures of merit for these non-classicality criteria require direct measurement of the signal variable and are thus difficult to apply to optically-probed material systems. Here we describe a method to demonstrate both criteria without need for to direct signal measurements. Using a covariance matrix formalism and a general noise model, we compute meter observables for QND measurement triples, which suffice to compute all QND figures of merit. The result will allow certified QND measurement of atomic spin ensembles using existing techniques.Comment: 11 pages, zero figure

    Colour and stellar population gradients in galaxies

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    We discuss the colour, age and metallicity gradients in a wide sample of local SDSS early- and late-type galaxies. From the fitting of stellar population models we find that metallicity is the main driver of colour gradients and the age in the central regions is a dominant parameter which rules the scatter in both metallicity and age gradients. We find a consistency with independent observations and a set of simulations. From the comparison with simulations and theoretical considerations we are able to depict a general picture of a formation scenario.Comment: 4 pages, 4 figures. Proceedings of 54th Congresso Nazionale della SAIt, Napoli 4-7 May 201

    Evolution of central dark matter of early-type galaxies up to z ~ 0.8

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    We investigate the evolution of dark and luminous matter in the central regions of early-type galaxies (ETGs) up to z ~ 0.8. We use a spectroscopically selected sample of 154 cluster and field galaxies from the EDisCS survey, covering a wide range in redshifts (z ~ 0.4-0.8), stellar masses (logM/M\log M_{\star}/ M_{\odot} ~ 10.5-11.5 dex) and velocity dispersions (σ\sigma_{\star} ~ 100-300 \, km/s). We obtain central dark matter (DM) fractions by determining the dynamical masses from Jeans modelling of galaxy aperture velocity dispersions and the MM_{\star} from galaxy colours, and compare the results with local samples. We discuss how the correlations of central DM with galaxy size (i.e. the effective radius, ReR_{\rm e}), MM_{\star} and σ\sigma_{\star} evolve as a function of redshift, finding clear indications that local galaxies are, on average, more DM dominated than their counterparts at larger redshift. This DM fraction evolution with zz can be only partially interpreted as a consequence of the size-redshift evolution. We discuss our results within galaxy formation scenarios, and conclude that the growth in size and DM content which we measure within the last 7 Gyr is incompatible with passive evolution, while it is well reproduced in the multiple minor merger scenario. We also discuss the impact of the IMF on our DM inferences and argue that this can be non-universal with the lookback time. In particular, we find the Salpeter IMF can be better accommodated by low redshift systems, while producing stellar masses at high-zz which are unphysically larger than the estimated dynamical masses (particularly for lower-σ\sigma_{\star} systems).Comment: 14 pages, 6 figures, 3 tables, MNRAS in pres

    Mass-to-light ratios in early-type galaxies and the dark matter content

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    The distribution of the radial trends of the mass-to-light ratios (M/L) within an assorted sample of early-type galaxies is discussed. Three classes of galaxies are identified according to their M/L gradients. Two such classes are characterized by the presence or by the absence of a radial gradient of the dark-matter (DM) distribution. A third class contains objects which are likely undergoing interaction; they exhibit steep M/L gradients which are possibly the result of a wrong assumption on their equilibrium conditions. Finally, a possible correlation between DM content and morphological types is briefly discussed.Comment: 10 pages, 2 ps figures. To appear in the proceedings for the Sakharov Conference of Physics (Moskow, June 2002

    Results from the LSND Neutrino Oscillation Search

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    The Liquid Scintillator Neutrino Detector (LSND) at the Los Alamos Meson Physics Facility sets bounds on neutrino oscillations in the appearance channel nu_mu_bar --> nu_e_bar by searching for the signature of the reaction nu_e_bar p --> e^+ n: an e+^+ followed by a 2.2MeV gamma ray from neutron capture. Five e^{+/-} -- gamma coincidences are observed in time with the LAMPF beam, with an estimated background of 6.2 events. The 90\% confidence limits obtained are: Delta (m^2) < 0.07eV^2 for sin^2 (2theta) = 1, and sin^2(2theta) < 6 10^{-3} for Delta (m^2) > 20 eV^2.Comment: 10 pages, uses REVTeX and epsf macro
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