نتایج جستجو برای: dust density
تعداد نتایج: 448715 فیلتر نتایج به سال:
Gravitational lensing of an optical QSO by a spiral galaxy is often counteracted by dust obscuration, since the line-of-sight to the QSO passes close to the center of the galactic disk. The dust in the lens is likely to be correlated with neutral hydrogen, which in turn should leave a Lyα absorption signature on the QSO spectrum. We use the estimated dust-to-gas ratio of the Milky–Way galaxy as...
The analysis of dust hazard studies in southwest region of Iran in 22 years (1996-2017) Dust storms are natural hazards that mostly occur in arid and semi-arid regions and there are many harmful consequences. According to the topographic-climatic conditions in Iran and the significant increase in the number and severity of dust storms occurrence in recent decades, especially in the West and So...
Dust particles consist of important aerosols and resulting in blowing strong winds on the surface of desert areas. These particles enter the atmosphere under the influence of different factors including: weather condition (wind, precipitation and temperature), land surface (topography, humidity level, roughness and vegetation), soil features (texture, density, composition and land use (agricult...
2D finite dust clusters are systems of small number of charged grains immersed in the plasma. The particle-in-cell (PIC) simulations are used to study the plasma structure, potential field and distributions of ion, electron and charge density within a dust cluster consisting of 19 grains in the absence and presence of a directed ion flow. In the isotropic plasma, an energetically stable configu...
We investigate the apparent discrepancy between gas and dust outer radii derived from millimeter observations of protoplanetary disks. Using 230 and 345 GHz continuum and CO J=3-2 data from the Submillimeter Array for four nearby disk systems (HD 163296, TW Hydrae, GM Aurigae, and MWC 480), we examine models of circumstellar disk structure and the effects of their treatment of the outer disk ed...
Aims. To understand the origin of the Lyα line profile of the prototypical Lyman break galaxy (LBG) MS 1512–cB58 and other similar objects. To attempt a consistent fit of Lyα and other UV properties of this galaxy. To understand the main physical parameter(s) responsible for the large variation of Lyα line strengths and profiles observed in LBGs. Methods. Using our 3D Lyα radiation transfer cod...
Starting from the exact microscopic equations for an unmagnetized dusty plasma, where the dust charge is regarded as a new degree of freedom of the system, we present a self-consistent set of equations that is suitable for weak turbulence analyses, where we have considered that the dust is electrically charged by absorption of plasma particles through inelastic collisions. In the quasilinear li...
Narrow dust rings observed around some young stars (e.g., HR 4796A) need to be confined. We present a possible explanation for the formation and confinement of such rings in optically thin circumstellar disks, without invoking shepherding planets. If an enhancement of dust grains (e.g., due to a catastrophic collision) occurs somewhere in the disk, photoelectric emission from the grains can hea...
We used 3.6, 8.0, 70, 160 μm Spitzer Space Telescope data, James Clerk Maxwell Telescope HARP-B CO J=(3-2) data, National Radio Astronomy Observatory 12 meter telescope CO J=(1-0) data, and Very Large Array HI data to investigate the relations among PAHs, cold (∼ 20 K) dust, molecular gas, and atomic gas within NGC 2403, an SABcd galaxy at a distance of 3.13 Mpc. The dust surface density is mai...
Repeated, self-excited dust acoustic shock waves (DASWs) have been observed in a dc glow discharge dusty plasma using high-speed video imaging. Two major observations are reported: (1) The self-steepening of a nonlinear dust acoustic wave (DAW) into a saw-tooth wave with sharp gradient in dust density, very similar to those found in numerical solutions of the fully nonlinear fluid equations for...
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