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941.
The probabilistic nature of the IMF in stellar systems implies that clusters of the same mass and age do not present the same
unique values of their observed parameters. Instead they follow a distribution. We address the study of such distributions
in terms of their confidence limits that can be obtained by evolutionary synthesis models. These confidence limits can be
understood as the inherent uncertainties of synthesis models. We will compare such confidence limits arising from the discreteness
of the number of stars obtained with Monte Carlo simulations with the dispersion resulting from an analytical formalism. We
give some examples of the effects on the kinetic energy, V–K, EW(Hβ) and multiwavelength continuum.
This revised version was published online in September 2006 with corrections to the Cover Date. 相似文献
942.
João Medeiros Carlo R. Contaldi 《Monthly notices of the Royal Astronomical Society》2006,367(1):39-45
We investigate the effect of foreground residuals in the WMAP ( Wilkinson Microwave Anisotropy Probe ) data by adding foreground contamination to Gaussian ensembles of cosmic microwave background (CMB) signal and noise maps. We evaluate a set of non-Gaussian estimators on the contaminated ensembles to determine with what accuracy any residual in the data can be constrained using higher-order statistics. We apply the estimators to the raw and cleaned Q -, V - and W -band first-year maps. The foreground subtraction method applied to clean the data in Bennett et al. appears to have induced a correlation between the power spectra and normalized bispectra of the maps which is absent in Gaussian simulations. It also appears to increase the correlation between the Δℓ= 1 inter-ℓ bispectrum of the cleaned maps and the foreground templates. In a number of cases the significance of the effect is above the 98 per cent confidence level. 相似文献
943.
Aurora Sicilia-Aguilar Lee Hartmann César Briceño María Eugenia Contreras James Muzerolle Nuria Calvet 《Astrophysics and Space Science》2004,292(1-4):457-463
We are studying the young clusters Tr37 and NGC7160 in the Cep OB2 region as part of a program to understand the evolution of accretion disks at the ages of disk dissipation and planet formation. Here, we present the first identifications of low mass (spectral types K-M) members of the clusters and study the presence and characteristics of their accretion disks, finding evidences of disk evolution. Using optical photometry and spectroscopy, we have identified ~70 members in Tr37 and ~20 in NGC7160, confirming age estimates of 3 and 10 Myr respectively. Accretion rates are ~10?8 M ⊙yr?1 in Tr37. We have not found any accreting members in NGC7160, suggesting that disk accretion generally ends before the age of 10 Myr, which is consistent with the results from other populations. 相似文献
944.
945.
We have calibrated self-consistent simulations of isolated disc galaxies including star, gas and star formation with the spectro-photometric
evolutionary model GISSEL2000 (Bruzual and Charlot, 1993). With this approach we can compare morphologies studying mass and
luminous distributions. We present an example about the evolution of bar ellipticity, which is simultaneously governed by
dynamic and spectro-photometric evolution.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
946.
We have studied the evolution of isolated galaxies over several Gyr using a self-consistent N-body code including stars, gas
and star formation. The results of our simulations are calibrated using spectrophotometric evolution models. We thus simultaneously
analyse kinematical and photometrical evolution of the various stellar populations born during the successive bursts of star
formation. Our calibrated simulations show that the properties of stellar velocity dispersion drops observed in the centre
of three barred active galaxies by Emsellem et al. (2001) could depend on the observational wavelength.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
947.
948.
Results of observations of the Galilean satellites during the week of the impact of comet Shoemaker-Levy 9 on Jupiter are reported. These observations have been carried out at the Pico dos Dias observatory, at Brasópolis, Brazil. The satellites's light flux was monitored with a photometer during the time of the predicted impact of fragments B, F, J and L. No conclusive flash was observed in any of the data adquired. This non-detection imposes an upper limit to the energy released during the impact of these fragments.Observations carried out at the Observatório do Pico dos Dias, operated by the Laboratório Nacional de Astrofísica/CNPq/MCT, Brazil 相似文献
949.
The shape of meteorites is one of the major factors influencing the production of cosmogenic nuclides. Numerical simulations using the Los Alamos Code System (LCS) particle production and transport codes were done to investigate particle fluxes and production rates of cosmogenic nuclides 10Be, 26Al, and 60Co in meteoroids of spherical, ellipsoidal, and cylindrical shapes. The calculations show that fluxes of nuclear active particles and also production rates of cosmogenic nuclides are sensitive to the shape of the irradiated parent body. 相似文献
950.