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Arnold, William S.

doi:10.1023/a:1014596909319

Cited by 30 publications

(3 citation statements)

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“…Attempts have been made to find the attractive Abel character of this simple model in more complex geometries and dynamical states. Some models do indeed possess this interesting property, allowing a possible determination of the distribution function (Merritt 1985;Dejonghe 1987;Arnold 1990;de Zeeuw & Hunter 1990;Dejonghe & Laurent 1991, hereafter DL91).…”

Section: Introductionmentioning

confidence: 99%

Triaxial dynamical models of elliptical galaxies using Stackel potentials

Mathieu

Dejonghe

1999

Monthly Notices of the Royal Astronomical Society

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A new development for components of collisionless stellar systems in a triaxial Sta Èckel potential is presented. The non-rotating Abel components introduced by Dejonghe & Laurent are generalized. Two families of components with internal net rotation about the long or short axis of the ellipsoidal ®gure are described. The simple Abel character of the non-rotating components is no longer conserved when rotation is included. The rotating components can be used to build realistic three-integral dynamical models of elliptical galaxies with rotation. A triaxial dynamical model is proposed for the E2 galaxy Centaurus A. A good ®t to the photometry and to planetary nebulae kinematical data (rotation and velocity dispersion on the photometric major and minor axes) is obtained. The total mass for our model of Cen A amounts to ,41´1010 M ( , half of which is dark mass.Key words: galaxies: elliptical and lenticular, cD ± galaxies: individual: Centaurus A ± galaxies: kinematics and dynamics ± galaxies: structure. I N T R O D U C T I O NThe dynamical state of a stellar system is entirely determined by its phase-space distribution function. The recovery of the underlying distribution function of a system from observational data is very complicated due to the equations involved. By assuming simple geometries for stellar systems, one can ®nd interesting relations between the distribution function and other physical characteristics of the system. This may help investigate the dynamical properties of more complex stellar systems. An important equation relates the distribution function Fr; v to the mass density distribution rr through integration over all the velocities. For a spherical mass density in a spherical potential, the integral equation turns out to be of Abel form, for which the analytical inversion is known (Eddington 1916). Attempts have been made to ®nd the attractive Abel character of this simple model in more complex geometries and dynamical states. Some models do indeed possess this interesting property, allowing a possible determination of the distribution function (Merritt 1985;Dejonghe 1987;Arnold 1990;de Zeeuw & Hunter 1990; Dejonghe & Laurent 1991, hereafter DL91). In the framework of triaxial Sta Èckel potentials, the Abel components described by DL can be used as basis functions to build dynamical models of triaxial stellar systems without rotation. Here a generalization taking into account net internal rotation is proposed. These components allow the construction of models using the photometry and kinematics (rotation and velocity dispersion) of a stellar system in a triaxial Sta Èckel potential.In this study we do not consider ®gure rotation, but only internal streaming around the long and short axes of the ellipsoidal ®gure. The expression relating the mass density distribution to the distribution function is no longer an Abel integral when rotation is included, although the distribution function has the same form. The difference comes from a change in the integration volume for the moments of the distri...

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Section: Introductionmentioning

confidence: 99%

Triaxial dynamical models of elliptical galaxies using Stackel potentials

Mathieu

Dejonghe

1999

Monthly Notices of the Royal Astronomical Society

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“…The technique of artificially producing seedlings and releasing them into fishing grounds is an effective method of aquaculture enhancement. This technique has been implemented with a variety of fishery species (e.g., finfish [1,2], flounder [3], shellfish [4][5][6][7]). In artificial seed production, large numbers of seedlings are often produced by a few broodstocks and released into natural seawater, which reduces the genetic diversity of wild populations in the field.…”

Section: Introductionmentioning

confidence: 99%

Genetic diversity and population structure of razor clamSinonovacula constrictain Ariake Bay, Japan, revealed using RAD-Seq SNP markers

Orita

Nagano

Kawamura

et al. 2020

Preprint

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The razor clam Sinonovacula constricta is a commercially important bivalve in Japan. The current distribution of this species in Japan is limited to Ariake Bay, where the fishery stock is declining. It is necessary to understand the genetic population structure of this species in order to restore the fishery stock while preserving the genetic diversity of the clam. Here, we report for the first time the genetic population structure of S. constricta in Ariake Bay, Japan. Paired-end restriction site-associated DNA sequencing (RAD-Seq) analyzed samples of S. constricta collected from seven mudflats located along Ariake Bay. Two different genetic populations exist in Ariake Bay, one inhabiting wild habitats and the other inhabiting the transplanted area of artificial seedlings. Our results suggest that genetic differentiation occurred between these two populations (Fst value = 0.052), and a high level of genetic differentiation is maintained between the two groups. In the future, the two genetically distinct populations need to be available as fishery resources, while taking into account their conservation and hybridization status.

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“…For example, on the basis of results on TMAE-based gases from the DELPHI prototype (see Table 1), Arnold et.al. [12] report the following behavior of the θ parameter as a function of the visible gain G : θ =1.8x10 -6 G-0.095 for G>5.3x10 4 (i.e. θ >0) and θ =0 for G<5.3x10 4 (to get the total gain, multiply by a factor ~5).…”

Section: The Quantification Of Avalanche Quenchingmentioning

confidence: 99%

Photon Detectors

Field Guide to Radiometry

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This paper compares the photon detectors used to date in high energy physics and astrophysics experiments, with particular emphasis on design features, problems and mistakes. The paper also describes a new direction in the area of photon detection. Invited talk presented at the International Workshop on RICH Detectors (RICH 95)Uppsala, Sweden, June 12-16, 1995 * Work supported by the Royal Swedish Academy of Sciences through its Nobel Institute for Physics, and Department of Energy contract DE-AC03-765SF00515. J. Seguinot and T. Ypsilantis have recently described the theory and history of Ring Imaging Cherenkov (RICH) detectors [1,2]. In this paper, I will expand on these excellent review papers, by covering the various photon detector designs in greater detail, and by including discussion of mistakes made, and detector problems encountered, along the way. However, I will not consider overall system geometries, radiators, optics, gas systems, etc. As a result, there will be no discussion of angular resolution or the value of N o achieved in the various experiments.Photon detectors are among the most difficult devices used in physics experiments, because they must achieve high efficiency for photon transport and for the detection of single photo-electrons. For gaseous devices, this requires the correct choice of gas gain in order to prevent breakdown and wire aging, together with the use of low noise electronics having the maximum possible amplification. In addition, the detector must be constructed of materials which resist corrosion due to photosensitive materials such as TMAE, the detector enclosure must be tightly sealed in order to prevent oxygen leaks, etc.The most critical step is the selection of the photocathode material. Typically, a choice must be made between a solid (CsI) or gaseous photocathode (TMAE, TEA). A conservative approach favors a gaseous photocathode, since it is continuously being replaced by flushing, and permits the photon detectors to be easily serviced (the air sensitive photocathode can be removed at any time). In addition, it can be argued that we now know how to handle TMAE, which, as is generally accepted, is the best photocathode material available as far as quantum efficiency is concerned (see Fig.1 and ref.3).However, it is a very fragile molecule, and therefore its use may result in relatively fast wire aging. A possible alternative is TEA, which, in the early days, was rejected because it requires expensive CaF 2 windows, which could be contaminated easily in the region of 8.3 eV and thus lose their UV transmission; there was also a suspicion that it had low quantum efficiency. Although the CaF 2 windows are still expensive to use, the contamination problem appears to be manageable, and the results of several tests presented in this paper remove the second concern by confirming the high quantum efficiency reported in ref. 1. The TEA molecule is also not as fragile as the TMAE molecule, so that its wire aging effects should be less severe. This would certainly be helped by cond...

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Cited by 30 publications

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Triaxial dynamical models of elliptical galaxies using Stackel potentials

Triaxial dynamical models of elliptical galaxies using Stackel potentials

Genetic diversity and population structure of razor clamSinonovacula constrictain Ariake Bay, Japan, revealed using RAD-Seq SNP markers

Photon Detectors

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