On the possible generation of the young massive open clusters Stephenson 2 and BDSB 122 by ω Centauri

¹ Universidade Federal do Rio Grande do Sul, Departamento de Astronomia CP 15051, RS, Porto Alegre 91501-970, Brazil e-mail: [salerno;bica;charles]@if.ufrgs.br; irapuan@univap.br
² IP&D - Universidade do Vale do Paraíba - UNIVAP, Av. Shishima Hifumi, 2911 - Urbanova, São José dos Campos 12244-000, SP, Brazil

Received: 27 January 2009
Accepted: 10 February 2009

Abstract

Context. Passing through the disk of a galaxy, a massive object such as a globular cluster can trigger star formation.

Aims. We test the hypothesis that the most massive globular cluster in the Galaxy, ω Centauri, which crossed the disk approximately 24±2 Myr ago, may have triggered the formation of the open clusters Stephenson 2 and BDSB 122.

Methods. The orbits of ω Centauri, Stephenson 2, and BDSB 122 are computed for the three-component model of Johnston, Hernquist & Bolte, which considers the disk, spheroidal, and halo gravitational potentials.

Results. With the reconstructed orbit of ω Centauri, we show that the latest impact site is consistent, within significant uncertainties, with the birth-site of the young massive open clusters BDSB 122 and Stephenson 2. Within the uncertainties, this scenario is consistent with the timescale of their backward motion in the disk, shock propagation and delayed star formation.

Conclusions. Together with open cluster formation associated with density waves in spiral arms, the present results are consistent with massive globular clusters being additional progenitors of open clusters, the most massive ones in particular.