EDP Sciences
Free access
Volume 390, Number 1, July IV 2002
Page(s) 299 - 306
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20020627

A&A 390, 299-306 (2002)
DOI: 10.1051/0004-6361:20020627

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

T. W. Berghöfer1 and D. Breitschwerdt2

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

(Received 1 May 2001 / Accepted 19 April 2002 )

We have analyzed the trajectories of moving stellar groups in the solar neighborhood in an attempt to estimate the number of supernova explosions in our local environment during the past 20 million years. Using Hipparcos stellar distances and the results of kinematical analyses by Asiain et al. (1999a) on the Pleiades moving groups, we are able to show that subgroup B1, consisting of early type B stars up to $10\, {M}_\odot$, 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 function derived from the analysis of galactic OB associations, we estimate the number of supernova explosions and find that about 20 supernovae must have occurred during the past ~ 10 - 20 million years, which is suggested to be the age of the Local Bubble; the age of the star cluster is about ~ 20 - 30 million years. For the first time, this provides strong evidence that the Local Bubble must have been created and shaped by multi-supernova explosions and presumably been reheated more than 1 million years ago, consistent with recent findings of an excess of ${}^{60}{\rm Fe}$ 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 $\dot E_{\rm SN} \sim 5 \times 10^{36}$ erg/s, in good agreement with the estimated local soft X-ray photon output rate. It seems plausible that the origin of the Local Bubble is also linked to the formation of the Gould Belt, which originated about 30-60 Myrs ago.

Key words: stars: early-type -- ISM: bubbles -- ISM: general -- ISM: kinematics and dynamics -- ISM: structure -- Galaxy: solar neighborhood

Offprint request: T. W. Berghöfer, thomas.berghoefer@desy.de

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