Search results for "Spatial Distribution"
showing 10 items of 180 documents
Reconstruction of an Accretion Disk Image in AU Mon from CoRoT Photometry
2011
AbstractThe long-period binary system AU Mon was photometrically observed on-board the CoRoT satellite in a continuous run of almost 60 days long which has covered almost 5 complete cycles. Unprecedented sub milimag precision of CoRoT photometry reveals all complexity of its light variations in this, still active mass-transfer binary system. We present images of an accretion disk reconstructed by eclipse mapping, and an optimization of intensity distribution along disk surface. Time resolution and accurate CoRoT photometric measurements allow precise location of spatial distribution of ‘hot’ spots on the disk, and tracing temporal changes in their activity. Clumpy disk structure is similar …
Correlation between the spatial distribution of circumstellar disks and massive stars in the young open cluster NGC 6611
2009
Context: the observations of the proplyds in the Orion Nebula Cluster, showing clear evidence of ongoing photoevaporation, have provided a clear proof about the role of the externally induced photoevaporation in the evolution of circumstellar disks. NGC 6611 is an open cluster suitable to study disk photoevaporation, thanks to its large population of massive members and of stars with disk. In a previous work, we obtained evidence of the influence of the strong UV field generated by the massive cluster members on the evolution of disks around low-mass Pre-Main Sequence members. That work was based on a multi-band BVIJHK and X-ray catalog purposely compiled to select the cluster members with …
Physical and Chemical Inhomogeneities Inside the Vela SNR Shell: Indications of Ejecta Shrapnels
2007
We present the results of the combined analysis of three XMM-Newton EPIC observations of the northern rim of the Vela SNR. The three pointings cover an area of ~10 pc^2 (at 250 pc) behind the main shock front and we aim at studying with high resolution the spatial distribution of the physical and chemical properties of the X-ray emitting plasma on this large scale. We produce count-rate images and equivalent width maps of the Ne IX and Mg XI emission blends. We also perform a spatially resolved spectral analysis of a set of physically homogeneous regions. We reveal physical and chemical inhomogeneities in the X-ray emitting plasma. In particular, we find large variations of the O, Ne, Mg, a…
On the accretion history of galaxy clusters: temporal and spatial distribution
2020
We analyse the results of an Eulerian AMR cosmological simulation in order to quantify the mass growth of galaxy clusters, exploring the differences between dark matter and baryons. We have determined the mass assembly histories (MAHs) of each of the mass components and computed several proxies for the instantaneous mass accretion rate (MAR). The mass growth of both components is clearly dominated by the contribution of major mergers, but high MARs can also occur during smooth accretion periods. We explored the correlations between MARs, merger events and clusters' environments, finding the mean densities in $1 \leq r/R_{200m} \leq 1.5$ to correlate strongly with $\Gamma_{200m}$ in massive …
Spatial distribution and statistical properties of small-scale convective vortex-like motions in a quiet-Sun region
2011
High-resolution observations of a quiet Sun internetwork region taken with the Solar 1-m Swedish Telescope in La Palma are analyzed. We determine the location of small-scale vortex motions in the solar photospheric region by computing the horizontal proper motions of small-scale structures on time series of images. These plasma convectively-driven swirl motions are associated to: (1) downdrafts (that have been commonly explained as corresponding to sites where the plasma is cooled down and hence returned to the interior below the visible photospheric level), and (2) horizontal velocity vectors converging into a central point. The sink cores are proved to be the final destination of passive …
Moment Equations for a Spatially Extended System of Two Competing Species
2005
The dynamics of a spatially extended system of two competing species in the presence of two noise sources is studied. A correlated dichotomous noise acts on the interaction parameter and a multiplicative white noise affects directly the dynamics of the two species. To describe the spatial distribution of the species we use a model based on Lotka-Volterra (LV) equations. By writing them in a mean field form, the corresponding moment equations for the species concentrations are obtained in Gaussian approximation. In this formalism the system dynamics is analyzed for different values of the multiplicative noise intensity. Finally by comparing these results with those obtained by direct simulat…
Spatial correlation of laser-generated electrons and holes in quantum wells
1995
The spatial correlation of hot electrons and holes generated by light in a semiconductor quantum well (QW) is studied. For hot electron-hole pairs in a polar material, this correlation is determined by the interaction with LO-phonons. We analyze the distribution F N (r, K) of electrons and holes which are created in a given light absorption process, with respect to their relative separation r and total quasimomentum ħK, after the emission of a number N of LO-phonons. The relationship between the spatial distribution of electrons and holes in these intermediate states and the cross-section of multi-phonon resonant Raman scattering (MPRRS) is established. Spatial correlation effects are stron…
Mass Segregation in the Open Cluster NGC 2422
2003
UBVRI photometry of the open cluster NGC2422 (age ~10 8 yr) down to a limiting magnitude V ≃ 19 is used to study the cluster spatial distribution and the luminosity and mass functions. From the Color-Magnitude Diagram (CMD), we obtained a list of candidate cluster members based on a photometric criterion. Using a comparison field region and an iterative procedure, a correction for contaminating field stars has been inferred in order to obtain the luminosity and the mass functions in the M=0.4 -3.5 M ⊙ range. By analyzing the spatial distribution, we infer that a non-negligible number of cluster stars lie outside our investigated region. We estimate a correction to the mass function of the …
A Preliminary Analysis of a New Chandra Observation (ObsID 6148) of Cir X-1
2008
We present the preliminary spectral analysis of a 25 ks long Chandra observation of the peculiar source Cir X–1 near the periastron passage. We estimate more precise coordinates of the source compatible with the optical and radio counterpart coordinates. We detect emission lines associated to Mg XII, Si XIII, Si XIV, S XV, S XVI Ar XVII, Ar XVIII, Ca XIX, Ca XX, Fe XXV, Fe XXVI showing a redshift of 470 km s−1. The more intense emission features at 6.6 keV show a double‐peaked shape that can be modelled with two or three Gaussian lines.
Macroecological properties of ammonites : spatial distribution, phylogeny, and faunal similarity
2016
The present work, which lies between macroecology and macroevolution, focuses on the spatio-temporal dynamics of early Pliensbachian ammonites of the western Tethys. Two main questions are addressed: how does inter-assemblage compositional similarity decrease with geographical distance? What is the relationship between species range size and phylogeny, species duration and latitudinal position?Ammonite dispersal dynamics are studied through a multi-scale Similarity Distance Decay analysis. We show that their long-distance dispersal is facilitated when the environment is more homogeneous and that it is not related to their morphology. This suggests that their long-distance dispersal occurred…