Astron. Astrophys. 337, 113-124 (1998)

Discovery of a late-type stellar population associated with the Gould Belt

P. Guillout ^{1, 2}, M.F. Sterzik ¹, J.H.M.M Schmitt ^{1, 3}, C. Motch ² and R. Neuhäuser <sup>1

1</sup> Max-Planck-Institut für Extraterrestrische Physik, D-85740 Garching, Germany
² Observatoire Astronomique, CNRS UMR 7550, 11 rue de l'Université, F-67000 Strasbourg, France
³ Universität Hamburg, Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany

Received 12 March 1998 / Accepted 28 April 1998

Abstract

We report the detection of a late-type stellar population in the direction of the Gould Belt among stars found by cross-correlating the ROSAT All-Sky Survey with the Tycho catalog. Regions of the Gould Belt located between l = and l = exhibit a strong density enhancement of X-ray active stars with associated X-ray luminosities L_X = erg s^-1 typical for very young coronae. In contrast, other regions show average galactic plane characteristics. Stars accounting for the excess appear to extend from the solar vicinity up to about 300 pc towards a quadrant centered on l = , but their distance distribution only extends to 180 pc from the Sun towards l = . The structure can be understood as a disk-like arrangement of stars having the same inclination towards the galactic plane as the Gould Belt and extending to its outer boundary. We suggest that these stars are the residuals of original associations and interpret them as the late-type stellar population of the Gould Belt.

Key words: X-rays: stars stars: late type stars: formation galaxy: stellar content galaxy: structure

Send offprint requests to: P. Guillout, (guillout@rosat.mpe-garching.mpg.de)

SIMBAD Objects

Contents

• 1. Introduction
• 2. The RASS-Tycho/Hipparcos sample
• 3. Gould Belt or Gould Disk ?
  • 3.1. Low sensitivity (S_thr = 0.10 cts s^{- 1})
    • 3.1.1. Expectations
    • 3.1.2. Stellar surface density
    • 3.1.3. Distance distribution
    • 3.1.4. X-ray luminosity distribution
  • 3.2. The Gould Disk scenario
  • 3.3. High sensitivity (S_thr = 0.03 cts s^{- 1})
    • 3.3.1. Expectations
    • 3.3.2. Stellar surface density
    • 3.3.3. Distance distribution
    • 3.3.4. X-ray luminosity distribution
• 4. Number of stars in excess
• 5. Implications of Gould Disk scenario
  • 5.1. 3D spatial distribution
  • 5.2. Relation to the distributed young RASS population
    • 5.2.1. Cygnus (l = 90°)
    • 5.2.2. Taurus (l = 180°)
    • 5.2.3. Orion (l = 200°)
    • 5.2.4. Lupus (l = 330°)
  • 5.3. Star formation history in the solar neighbourhood
• 6. Conclusion and perspectives
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: August 6, 1998
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