A Quantitative Schlieren System for Measuring Radial Density Profiles of Reduced Density Channels in Gases

1981 ◽  
Author(s):  
M. Raleigh ◽  
J. R. Greig
Keyword(s):  
Radial Density ◽  
Density Profiles ◽  
Schlieren System ◽  
Reduced Density

scholarly journals Mapping dark matter and finding filaments: calibration of lensing analysis techniques on simulated data

2020 ◽  
Vol 496 (3) ◽  
pp. 3973-3990
Author(s):  
Sut-Ieng Tam ◽  
Richard Massey ◽  
Mathilde Jauzac ◽  
Andrew Robertson
Keyword(s):  
Gravitational Lensing ◽  
Simulated Data ◽  
Line Of Sight ◽  
Radial Density ◽  
Density Profiles ◽  
Analysis Techniques ◽  
Scientific Goal ◽  
Mass Mapping ◽  
Mapping Techniques ◽  
Suppress Noise

ABSTRACT We quantify the performance of mass mapping techniques on mock imaging and gravitational lensing data of galaxy clusters. The optimum method depends upon the scientific goal. We assess measurements of clusters’ radial density profiles, departures from sphericity, and their filamentary attachment to the cosmic web. We find that mass maps produced by direct (KS93) inversion of shear measurements are unbiased, and that their noise can be suppressed via filtering with mrlens. Forward-fitting techniques, such as lenstool, suppress noise further, but at a cost of biased ellipticity in the cluster core and overestimation of mass at large radii. Interestingly, current searches for filaments are noise-limited by the intrinsic shapes of weakly lensed galaxies, rather than by the projection of line-of-sight structures. Therefore, space-based or balloon-based imaging surveys that resolve a high density of lensed galaxies could soon detect one or two filaments around most clusters.

Properties of a Dense Hard-Sphere Gas Near the Walls of a Microchannel

2004 ◽  
Author(s):  
S. V. Nedea ◽  
A. J. H. Frijns ◽  
A. A. van Steenhoven ◽  
A. P. J. Jansen
Keyword(s):  
Particle Size ◽  
Hard Sphere ◽  
Md Simulation ◽  
Analytical Techniques ◽  
Dense Gas ◽  
Density Profiles ◽  
Dilute Gas ◽  
System L ◽  
Density Oscillation ◽  
Reduced Density

A mathematical model has been developed to characterize the effect of packing of molecules of a hard-sphere dense gas near the hard walls of a microchannel. Analytical techniques, Monte Carlo (MC) methods and Molecular Dynamics (MD) simulation methods have been used to characterize the influence of the characteristic parameters such as number density, reduced density, length of the system and molecular diameter on the equilibrium properties of the gas near the hard walls of the microchannel. The height and the position of the density oscillation peaks near the wall are characterized. Comparisons between MD and MC results for particles having different diameter are presented. For the same size of the particles and moderately dense gas, MC and MD results are similar, differences in the density profiles being limited only to the oscillatory region. For different particle sizes, MD and MC results are limited to a short distance near the wall for long size systems and moderately dense fluids. The effect of the boundary (particle size) on the simulation results is increasing with η (reduced density) and it is very small in case of a dilute gas. For small η and small particle size (R) relative to length of the system L, the height of the oscillations peaks is slowly increasing with R/L, and for high densities is always decreasing with R/L. The position of these peaks depends only on the size of the particles and when R is much smaller than L, it shows a small dependence on L.

Radial density profiles of highly charged carbon ions in TEXTOR

1990 ◽  
Vol 176-177 ◽  
pp. 398-403 ◽  
Author(s):  
H.A. Claassen ◽  
R.P. Schorn ◽  
H. Gerhauser ◽  
E. Hintz
Keyword(s):  
Carbon Ions ◽  
Radial Density ◽  
Density Profiles

scholarly journals X-Ray Constraints on Dark Matter in Galaxy Clusters and Elliptical Galaxies: A View from Chandra and XMM

2004 ◽  
Vol 220 ◽  
pp. 149-158 ◽  
Author(s):  
David A. Buote
Keyword(s):  
Dark Matter ◽  
Galaxy Clusters ◽  
Elliptical Galaxies ◽  
Matter Content ◽  
The Self ◽  
Radial Density ◽  
Density Profiles ◽  
X Ray ◽  
Matter Model ◽  
Dark Matter Model

X-ray observations with Chandra and XMM are providing valuable new measurements of the dark matter content of elliptical galaxies and galaxy clusters. I review constraints on the radial density profiles and ellipticities of the dark matter in these systems (with an emphasis on clusters) obtained from recent X-ray observations and discuss their implications, especially for the self-interacting dark matter model.

scholarly journals Recent developments in supernova research with VLBI

2013 ◽  
Vol 9 (S296) ◽  
pp. 53-57 ◽  
Author(s):  
Norbert Bartel ◽  
Michael F. Bietenholz
Keyword(s):  
Very Long Baseline Interferometry ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Expansion Velocity ◽  
Radial Density ◽  
Density Profiles ◽  
Long Baseline ◽  
Vlbi Observations ◽  
Recent Developments ◽  
Circumstellar Medium

AbstractVery long baseline interferometry (VLBI) observations during the last 30 years have resolved many supernovae and provided detailed measurements of the expansion velocity and deceleration. Such measurements are useful for estimating the radial density profiles of both the ejecta and the circumstellar medium left over from the progenitor. VLBI measurements are also the most direct way of confirming the relativistic expansion velocities thought to occur in supernovae associated with gamma-ray bursts. Well-resolved images of a few supernovae have been obtained, and the interaction of the ejecta as it expands into the circumstellar medium could be monitored in detail. We discuss recent results, for SN 1979C, SN 1986J, and SN 1993J, and note that updated movies of the latter two of the supernovae from soon after the explosion to the present are available from the first author's personal website.

scholarly journals Recovering galaxy cluster gas density profiles with XMM-Newton and Chandra

2017 ◽  
Vol 608 ◽  
pp. A88 ◽  
Author(s):  
I. Bartalucci ◽  
M. Arnaud ◽  
G. W. Pratt ◽  
A. Vikhlinin ◽  
E. Pointecouteau ◽  
...  
Keyword(s):  
Galaxy Cluster ◽  
Correction Method ◽  
Parametric Models ◽  
Quality Data ◽  
Gas Temperature ◽  
Radial Density ◽  
Density Profiles ◽  
X Ray ◽  
Cross Calibration ◽  
The Impact

We examined the reconstruction of galaxy cluster radial density profiles obtained from Chandra and XMM-Newton X-ray observations, using high quality data for a sample of twelve objects covering a range of morphologies and redshifts. By comparing the results obtained from the two observatories and by varying key aspects of the analysis procedure, we examined the impact of instrumental effects and of differences in the methodology used in the recovery of the density profiles. We find that the final density profile shape is particularly robust. We adapted the photon weighting vignetting correction method developed for XMM-Newton for use with Chandra data, and confirm that the resulting Chandra profiles are consistent with those corrected a posteriori for vignetting effects. Profiles obtained from direct deprojection and those derived using parametric models are consistent at the 1% level. At radii larger than ~6″, the agreement between Chandra and XMM-Newton is better than 1%, confirming an excellent understanding of the XMM-Newton PSF. Furthermore, we find no significant energy dependence. The impact of the well-known offset between Chandra and XMM-Newton gas temperature determinations on the density profiles is found to be negligible. However, we find an overall normalisation offset in density profiles of the order of ~2.5%, which is linked to absolute flux cross-calibration issues. As a final result, the weighted ratios of Chandra to XMM-Newton gas masses computed at R2500 and R500 are r = 1.03 ± 0.01 and r = 1.03 ± 0.03, respectively. Our study confirms that the radial density profiles are robustly recovered, and that any differences between Chandra and XMM-Newton can be constrained to the ~2.5% level, regardless of the exact data analysis details. These encouraging results open the way for the true combination of X-ray observations of galaxy clusters, fully leveraging the high resolution of Chandra and the high throughput of XMM-Newton.

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