A SIMPLE FORMULA FOR THE THIRD INTEGRAL OF MOTION OF DISK-CROSSING STARS IN THE GALAXY

Autor(es)

Vieira, Ronaldo S. S. ^{[1, 2]} ; Ramos-Caro, Javier ^[3]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083859 Campinas, SP - Brazil

^[2] Nicholaus Copernicus Astron Ctr, PL-00716 Warsaw - Poland

^[3] Univ Fed Sao Carlos, Dept Fis, BR-13565905 Sao Carlos, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: ASTROPHYSICAL JOURNAL; v. 786, n. 1 MAY 1 2014.
• Citações Web of Science: 3

Resumo

We present a simple analytical formula for an approximated third integral of motion associated with nearly equatorial orbits in the Galaxy: I-3 = Z Sigma(1/3)(I) I, where Z(R) is the vertical amplitude of the orbit at galactocentric distance R and Sigma(I)(R) is the integrated dynamical surface mass density of the disk, a quantity which has recently become measurable. We also suggest that this relation is valid for disk-crossing orbits in a wide variety of axially symmetric galactic models, which range from razor-thin disks to disks with non-negligible thickness, whether or not the system includes bulges and halos. We apply our formalism to a Miyamoto-Nagai model and to a realistic model for the Milky Way. In both cases, the results provide fits for the shape of nearly equatorial orbits which are better than the corresponding curves obtained by the usual adiabatic approximation when the orbits have vertical amplitudes comparable to the disk's scale height. We also discuss the role of this approximate third integral of motion in modified theories of gravity. (AU)

• Processo FAPESP: 10/00487-9 - Estudo dinâmico de sistemas autogravitantes newtonianos e pós-newtonianos com matéria escura
• Beneficiário: Ronaldo Savioli Sumé Vieira
• Modalidade de apoio: Bolsas no Brasil - Doutorado