arXiv subjects

Eric I. Barnes

Publications and source records attributed to Eric I. Barnes.

21 records · Page 2Linked to original sources

arXiv2002

Uncertainties in Spiral Galaxy Projection Parameters

We investigate the impact of nonaxisymmetric structure on estimates of galaxy inclinations and position angles. A new minimization technique is used to obtain estimates of inclination and position angle from a global fit to either photometric or kinematic data. We discuss possible systematic uncertainties which are much larger than statistical uncertainties. Our investigation reveals that systematic uncertainties associated with fitting photometric data dominate the formal statistical uncertainties. For our sample of inclined galaxies, we estimate that nonaxisymmetric features introduce inclination and position angle uncertainties of approximately 5 degrees, on average. The magnitudes of these uncertainties weaken the arguments for intrinsically elliptical galaxy disks.

astro-ph↗

arXiv2001

Alternative Fourier Expansions for Inverse Square Law Forces

Few-body problems involving Coulomb or gravitational interactions between pairs of particles, whether in classical or quantum physics, are generally handled through a standard multipole expansion of the two-body potentials. We discuss an alternative based on a compact, cylindrical Green's function expansion that should have wide applicability throughout physics. Two-electron "direct" and "exchange" integrals in many-electron quantum systems are evaluated to illustrate the procedure which is more compact than the standard one using Wigner coefficients and Slater integrals.

physics.atom-ph↗

arXiv2001

Using Correlation Integrals to Characterize 3D Stellar Orbits

In an effort to more fully understand the variety of stellar distribution functions that can be used to construct models of realistic galaxies, the correlation integral method for orbit characterization that previously has been introduced by Grassberger & Procaccia (1983) and Carnevali & Santangelo (1984) is examined in considerable detail. The broad utility of the method is validated and demonstrated by applying it to orbits in a number of different, previously studied test cases (1D, 2D, and 3D; nonrotating and rotating). At the same time, the correlation integral method is compared and contrasted with other more traditional characterization tools such as Lyapunov exponents and surfaces of section. The method is then extended to orbits in a previously unexamined rotating, 3D bar potential. The correlation integral method is found to be a simple and reliable way to quantitatively categorize orbits in virtually any potential. It is recommended that it be broadly adopted as a tool for characterizing the properties of orbits and, by extension, stellar distribution functions, in all Hamiltonian dynamical systems.

astro-ph↗