Wide-field photometry of the Galactic globular cluster M22     

L. Monaco  E. Pancino  F. R. Ferraro  M. Bellazzini 《Monthly notices of the Royal Astronomical Society》2004,349(4):1278-1290

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The many manifestations of downsizing: hierarchical galaxy formation models confront observations     

Fabio Fontanot  Gabriella De Lucia  Pierluigi Monaco  Rachel S. Somerville  Paola Santini 《Monthly notices of the Royal Astronomical Society》2009,397(4):1776-1790

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Faint Lyman-break galaxies as a crucial test for galaxy formation models     

Barbara Lo Faro  Pierluigi Monaco  Eros Vanzella  Fabio Fontanot  Laura Silva  Stefano Cristiani 《Monthly notices of the Royal Astronomical Society》2009,399(2):827-841

It has recently been shown that galaxy formation models within the Λ cold dark matter cosmology predict that, compared to the observed population, small galaxies (with stellar masses  <10¹¹ M_⊙  ) form too early, are too passive since   z ∼ 3  and host too old stellar populations at   z = 0  . We then expect an overproduction of small galaxies at   z ≳ 4  that should be visible as an excess of faint Lyman-break galaxies. To check whether this excess is present, we use the morgana galaxy formation model and grasil spectrophotometric  +  radiative transfer code to generate mock catalogues of deep fields observed with Hubble Space Telescope Advanced Camera for Surveys. We add observational noise and the effect of Lyman α emission, and perform colour–colour selections to identify Lyman-break galaxies. The resulting mock candidates have plausible properties that closely resemble those of observed galaxies. We are able to reproduce the evolution of the bright tail of the luminosity function of Lyman-break galaxies (with a possible underestimate of the number of the brightest i -dropouts), but uncertainties and degeneracies in dust absorption parameters do not allow to give strong constraints to the model. Besides, our model shows a clear excess with respect to observations of faint Lyman-break galaxies, especially of   z ₈₅₀∼ 27 V   -dropouts at   z ∼ 5  . We quantify the properties of these 'excess' galaxies and discuss the implications: these galaxies are hosted in dark matter haloes with circular velocities in excess of 100 km s⁻¹, and their suppression may require a deep rethinking of stellar feedback processes taking place in galaxy formation.  相似文献   

Effects of turbulence development in solar surges     

Vincenzo Carbone  Giorgio Einaudi  Pierluigi Veltri 《Solar physics》1987,111(1):31-41

Several authors have claimed for correlations between surges (dark features) and various kinds of solar emissions (radio, microwave, X-ray). In this paper we propose a model to explain such correlations, in particular presenting the properties of the instabilities resulting from the coupling between material flow, connected to the appearance of a surge, and magnetic field topology. As a consequence of such instability a turbulent energy cascade to small characteristic lengths grows up. Depending of the relevant parameters of the surge (dark feature), different regimes can be found, producing different levels of electrons acceleration and mass motion deceleration. We try then to correlate the different developments of the instability with the behavior observed in type I and type III radio bursts related to surges.Proceedings of the Second CERSA Workshop on Particle Acceleration and Trapping in Solar Flares, held at Aubigny-sur-Nère (France), 23–26 June, 1986.  相似文献   

Magnetic Field Line Transport in Anisotropic Magnetic Turbulence: Anomalous, Quasilinear, and Percolative Regimes Versus the Kubo Number     

Gaetano Zimbardo  Pierluigi Veltri  Pierre Pommois 《Astrophysics and Space Science》2001,277(1-2):101-102

The transport of plasma and of energetic particles because of magnetic turbulence is relevant to many space plasmas, ranging from the planetary magnetospheres to the solar corona and to the heliosphere. Various transport regimes for magnetic field lines can be obtained depending on the Kubo number. Here we show, by means of a numerical simulation, that the Kubo number also determines the level of chaos of the field lines. Weak chaos, closed magnetic surfaces, and anomalous transport regimes are obtained for R≪ 1; widespread chaos, destroyed magnetic surfaces, and quasilinear scaling of the diffusion coefficient for R ≳ 0.3; and global stochasticity as well as percolation scaling of the diffusion coefficient for R≫ 1. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

Soil morphology and organic matter dynamics under cheatgrass and sagebrush-steppe plant communities     

Jay B. Norton  Thomas A. Monaco  Jeanette M. Norton  Douglas A. Johnson  Thomas A. Jones 《Journal of Arid Environments》2004,57(4):445

Widespread cheatgrass (Bromus tectorum L.) invasion represents a major shift in species dominance that may alter ecosystem processes across much of the western US. To investigate differences following such conversion, soil morphology and organic matter under cheatgrass-dominated and native shrub-steppe vegetation were compared by standard soil analysis procedures at seven paired sites in Idaho and Utah. Results suggest that, following conversion to cheatgrass dominance, increased porosity and labile organic inputs enhance microbial decomposition in near-surface horizons beneath cheatgrass compared to adjacent soils under native vegetation. Enhanced decomposition could result in depletion of long-term SOM, leading to impoverished sites difficult to restore to native perennial vegetation.  相似文献   

The roussillon continental margin (Gulf of Lions): Plio-Quaternary paleogeographic interpretation     

AndrA. Monaco 《Sedimentary Geology》1973,10(4):261-284

The paleographic evolution of the Roussillon continental margin during the Plio-Quaternary has been reconstructed on the basis of indirect methods of investigation (continuous seismic reflexion) and of analysis of core samples. Interpretation of the first group is based on the character of the reflectors, their position, morphology, and their correlation with outcrop equivalents. Evolution in this area can be integrated in the more general history of the Gulf of Lions and the western Mediterranean. A remarkable factor is the morphotectonic control played by the Paleozoic substratum until recently. The Quaternary origin of the canyon seems to be characteristic of submarine valleys in this part of the Mediterranean. The different studies confirm the importance of submarine phenomena in the shaping and maintaining their morphology.

The following are defined in the Quaternary complex: alluvial deposits and the fossil channel of the early and mid-Quaternary; the major Tyrrhenian phase of filling; the recent eustatic oscillations. The latter have been defined in the light of analytical data. The oldest sequence reached by drilling for core samples is the transgressive neo-Tyrrhenian. The recent Würm is figured by two regressive phases (Würm III and Würm IV) and one positive interstadial. The Holocene facies enable us to measure the rise of Flandrian sea level at a rate of 10 m per 1,000 years.  相似文献   

Geotechnical properties of shelf and slope deposits off the Rhône Delta     

B. Chassefière  J. C. Aloisi  A. Monaco 《Geo-Marine Letters》1985,5(2):121-126

Some geotechnical parameters, such as water content, bulk density, shear strength, and Atterberg limits, result directly from sedimentation mechanisms. The results of geotechnical tests for each physiographic zone of the Rhône Delta system—continental shelf, continental slope, and upper rise (base of slope)—are presented in this paper. These geotechnical parameters are correlated with the hydrodynamic, morphologic, and structural environmental conditions. They are also used to explain and forecast the instability of superficial deposits.  相似文献   

Dealing with uncertainties in angles-only initial orbit determination     

Roberto Armellin  Pierluigi Di Lizia  Renato Zanetti 《Celestial Mechanics and Dynamical Astronomy》2016,125(4):435-450

A method to deal with uncertainties in initial orbit determination (IOD) is presented. This is based on the use of Taylor differential algebra (DA) to nonlinearly map uncertainties from the observation space to the state space. When a minimum set of observations is available, DA is used to expand the solution of the IOD problem in Taylor series with respect to measurement errors. When more observations are available, high order inversion tools are exploited to obtain full state pseudo-observations at a common epoch. The mean and covariance of these pseudo-observations are nonlinearly computed by evaluating the expectation of high order Taylor polynomials. Finally, a linear scheme is employed to update the current knowledge of the orbit. Angles-only observations are considered and simplified Keplerian dynamics adopted to ease the explanation. Three test cases of orbit determination of artificial satellites in different orbital regimes are presented to discuss the feature and performances of the proposed methodology.  相似文献   

A common feeding system of the NE and S rifts as revealed by the bilateral 2002/2003 eruptive event at Mt. Etna (Sicily, Italy)     

P. P. Giacomoni  C. Ferlito  G. Alesci  M. Coltorti  C. Monaco  M. Viccaro  R. Cristofolini 《Bulletin of Volcanology》2012,74(10):2415-2433

Mount Etna volcano is often characterized by bilateral eruptive events, involving both the south (S) and the north east (NE) rifts. The last event occurred in 2002?C2003 from October 27 to January 28. A detailed, stratigraphically time-controlled sampling of lavas and tephra of the southern eruptive fissure was performed in order to (1) track the petrological features of products during the eruption and (2) integrate the results with those previously obtained on the NE rift. Whole-rock composition and textural observations were implemented by major and minor element analyses of plagioclases in lavas and tephra from both sides of the volcano. Fractionation models constrained by mass balance (major and trace elements) and Rayleigh calculations suggest that magmas are linked by the same liquid line of descent by fractionating 9.11?% of a mineral assemblage of Cpx (52.69?%), Plg (21.41), and Ol (7.46?%). These new data allowed us to identify at least two feeding episodes through the southern fissure and infer that high-K₂O porphyritic magmas, emitted on both the S and NE rifts, derives by fractionation from the same parent magma. However, lavas and tephra from the southern flank were slightly more primitive. Textural and petrological study of plagioclase moreover indicates that chemical?Cphysical conditions in the deep feeding system were similar for magmas erupting from both rifts as suggested by the presence of dissolved rounded cores in both lavas. Magmas evolved differently on the S and the NE rifts only at shallow levels. Comparison with published seismotectonic data supports the idea that the main magma feeding the eruption on October 27 ascended along the same pathway at depth and was intercepted by the fracture system of the S and NE rifts at shallow depth, between 6 and 3?km b.s.l.  相似文献