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The origin of the young stellar population in the solar neighborhood— A link to the formation of the Local Bubble?

¹ DESY Hamburg, Notkestraße 85, 22607 Hamburg, Germany
² Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstr. 1, 85740 Garching, Germany e-mail: breitsch@mpe.mpg.de

Corresponding author: T. W. Berghöfer, thomas.berghoefer@desy.de

Received: 1 May 2001
Accepted: 19 April 2002

Abstract

We have analyzed the trajectories of moving stellar groups in thesolar neighborhood in an attempt to estimate the number of supernovaexplosions in our local environment during the past 20 million years.Using Hipparcos stellar distances and the results of kinematicalanalyses by Asiain et al. ([CITE]a) on the Pleiades moving groups, weare able to show that subgroup B1, consisting of early type B starsup to, but lacking more massive objects,has passed through the local interstellar medium within less than 100 pc.Comparing the stellar content of B1 with the initial mass functionderived from the analysis of galactic OB associations, we estimate thenumber of supernova explosions and find that about 20 supernovae must have occurred during the past ~ million years, which is suggested to be the age of the Local Bubble; the age of the star cluster is about ~ million years. For the first time, this provides strong evidence that the Local Bubble must have been created and shaped bymulti-supernova explosions and presumably been reheated more than 1 million years ago, consistent with recent findings of an excess of in a deep ocean ferromanganese crust. Calculating similarity solutions of an expanding superbubble for time-dependent energy input, we show that the number of explosions is sufficient to explain the size of the Local Bubble. The present energy input rate is about erg/s, in good agreement with the estimated local soft X-ray photon output rate.It seems plausible that the origin of the LocalBubble is also linked to the formation of the Gould Belt, which originated about 30–60 Myrs ago.