SearcharxivSearch

arXiv subjects

Jacques Lépine

Publications and source records attributed to Jacques Lépine.

2 recordsLinked to original sources

Comparing dynamical effects of the central bar and the spiral arms in the solar neighborhood

The dynamical effects on the stellar motion produced by the Galactic central bar and the spiral arms perturbations are investigated separately and compared. The stars from the Gaia DR3 catalog are selected in the region of observable completeness, which we estimate as $\sim$1 kpc from the Sun. We apply the 2D model of the Galactic potential consisting of three axisymmetric components, the disk, the bulge, and the dark matter halo, and two non-axisymmetric components, the central bar and the spiral arms. The stellar dynamics is studied using analytical and numerical techniques, such as Hamiltonian topology analysis, the construction of dynamical maps on the representative planes, dynamic spectra, and Poincaré sections. We identify the main dynamical features in the solar neighborhood (SNd), the corotation (CR) and Lindblad resonances (LRs). By assuming that the main moving groups (MGs) in the SNd originate from the resonances, we compare their locations, structures, and intensities with the theoretical predictions and provide a description of the process involved in the formation of the MGs. In addition, we explore parametric planes by adjusting the values of the pattern rotation speed $Ω_{p}$ with the positions of the MGs, for both the spiral arms and bar models, and conclude that the spiral arms model shows better results when compared to those of the bar, under the hypothesis of the dynamical origin of MGs.

astro-ph.GA

A Galaxy Model from 2MASS Star Counts in the Whole Sky Including the Plane

We use the star counts model of Ortiz & Lépine (1993) to perform an unprecedented exploration of the most important galactic parameters comparing the predicted counts with the 2MASS observed star counts in the J, H and K_S bands for a grid of positions covering the whole sky. The comparison is made using a grid of lines-of-sight given by the HEALPix pixelization scheme. The resulting best fit values for the parameters are: (2120 +- 200) pc for the radial scale length and (205 +- 40) pc for the scale height of the thin disk, with a central hole of (2070_{-800}^{+2000}) pc for the same disk; (3050 +- 500) pc for the radial scale length and (640 +- 70) pc for the scale height of the thick disk; (400 +- 100) pc for the central dimension of the spheroid, (0.0082 +- 0.0030) for the spheroid to disk density ratio, and (0.57 +- 0.05) for the oblate spheroid parameter.

astro-ph.GA