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Register a new userRecovery of the internal orbital structure of galaxies
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G. van de Ven
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We construct axisymmetric and triaxial galaxy models with a phase-space distribution function that depends on linear combinations of the three exact integrals of motion for a separable potential. These Abel models, first introduced by Dejonghe & Laurent and subsequently extended by Mathieu & Dejonghe, are the axisymmetric and triaxial generalisations of the well-known spherical Osipkov-Merritt models. We show that the density and higher order velocity moments, as well as the line-of-sight velocity distribution (LOSVD) of these models can be calculated efficiently and that they capture much of the rich internal dynamics of early-type galaxies. We build a triaxial and oblate axisymmetric galaxy model with projected kinematics that mimic the two-dimensional kinematic observations that are obtained with integral-field spectrographs such as SAURON. We fit the simulated observations with axisymmetric and triaxial dynamical models constructed with our numerical implementation of Schwarzschilds orbit-superposition method. We find that Schwarzschilds method is able to recover the internal dynamics and three-integral distribution function of realistic models of early-type galaxies.
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The Large-Scale Structure (LSS) of the Universe is a homogeneous network of galaxies separated in dense complexes, the superclusters of galaxies, and almost empty voids. The superclusters are young structures that did not have time to evolve into dynamically relaxed systems through the age of the Universe. Internally, they are very irregular, with dense cores, filaments and peripheral systems of galaxies. We propose a methodology to map the internal structure of superclusters of galaxies using pattern recognition techniques. Our approach allows to: i) identify groups and clusters in the LSS distribution of galaxies; ii) correct for the fingers of God projection effect, caused by the partial knowledge of the third space coordinate; iii) detect filaments of galaxies and trace their skeletons. In this paper, we present the algorithms, discuss the optimization of the free parameters and evaluate the results of its application. With this methodology, we have mapped the internal structure of 42 superclusters in the nearby universe (up to $z=0.15$).
We investigate the scatter in the fundamental plane (FP) of early-type galaxies (ETGs) and its dependence on age and internal structure of ETGs, using $16,283$ ETGs with $M_rle-19.5$ and $0.025le z<0.055$ in Sloan Digital Sky Survey data. We use the relation between the age of ETGs and photometric parameters such as color, absolute magnitude, and central velocity dispersion of ETGs and find that the scatter in the FP depends on age. The FP of old ETGs with age $gtrsim9$ Gyrs has a smaller scatter of $sim0.06$ dex ($sim14%$) while that of young ETGs with age $lesssim6$ Gyrs has a larger scatter of $sim0.075$ dex ($sim17%$). In the case of young ETGs, less compact ETGs have a smaller scatter in the FP ($sim0.065$ dex; $sim15%$) than more compact ones ($sim0.10$ dex; $sim23%$). On the other hand, the scatter in the FP of old ETGs does not depend on the compactness of galaxy structure. Thus, among the subpopulations of ETGs, compact young ETGs have the largest scatter in the FP. This large scatter in compact young ETGs is caused by ETGs that have low dynamical mass-to-light ratio ($M_mathrm{dyn}/L$) and blue color in the central regions. By comparing with a simple model of the galaxy that has experienced a gas-rich major merger, we find that the scenario of recent gas-rich major merger can reasonably explain the properties of the compact young ETGs with excessive light for a given mass (low $M_mathrm{dyn}/L$) and blue central color.
Plasmons are usually described in terms of macroscopic quantities such as electric fields and currents. However as fundamental excitations of metals they are also quantum objects with internal structure. We demonstrate that this can induce an intrinsic dipole moment which is tied to the quantum geometry of the Hilbert space of plasmon states. This {it quantum geometric dipole} offers a unique handle for manipulation of plasmon dynamics, via density modulations and electric fields. As a concrete example we demonstrate that scattering of plasmons with non-vanishing quantum geometric dipole from impurities is non-reciprocal, skewing in different directions in a valley-dependent fashion. This internal structure can be used to control plasmon trajectories in two dimensional materials.
The status of kinematic observations in Local Group dwarf spheroidal galaxies (dSphs) is reviewed. Various approaches to the dynamical modelling of these data are discussed and some general features of dSph dark matter haloes based on simple mass models are presented.
It is known that internal energy flow in a light beam can be divided into the orbital flow, associated with the macroscopic energy redistribution within the beam, and the spin flow originating from instantaneous rotation of the field vectors inherent in circular or elliptic polarization. In contrast to the orbital one, experimental observation of the spin flow constituent seemed problematic because (i) it does not manifest itself in the visible transformation of the beam profile and (ii) it converts into the orbital flow upon tight focusing of the beam, usually employed for the energy flow detection by the mechanical action on probe particles. We propose a two-beam interference technique that permits to obtain appreciable level of the spin flow in moderately focused beams and to detect the orbital motion of probe particles within a field where the transverse energy circulation is associated exclusively with the spin flow. This result can be treated as the first demonstration of mechanical action of the spin flow of a light field.
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