Astron. Astrophys. 361, 465-479 (2000)

Mapping the star formation history of Mrk 86

II. Stellar populations and global interpretation

A. Gil de Paz ^* , J. Zamorano and J. Gallego

Departamento de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, Avda. Complutense s/n, 28040 Madrid, Spain (gil@astrax.fis.ucm.es) (AGdP)

Received 23 November 1999 / Accepted 12 July 2000

Abstract

In this paper, continuation of Gil de Paz et al. (Paper I), we derive the main properties of the stellar populations in the Blue Compact Dwarf galaxy Mrk 86. Ages, stellar masses, metallicites and burst strengths have been obtained using the combination of Monte Carlo simulations, a maximum likelihood estimator and Cluster and Principal Component Analysis. The three stellar populations detected show well defined properties. We have studied the underlying stellar population, which shows an age between 5-13 Gyr and no significant color gradients. The intermediate aged (30 Myr old) central starburst show a very low dust extinction with high burst strength and high stellar mass content (910⁶ ). Finally, the properties of 46 low-metallicity (1/10 ) star-forming regions were also studied.

The properties derived suggest that the most recent star-forming activity in Mrk 86 was triggered by the evolution of a superbubble originated at the central starburst by the energy deposition of stellar winds and supernova explosions. This superbubble produced the blowout of a fraction of the interstellar medium at distances of about 1 kpc with high gas surface densities, leading to the activation of the star formation.

Finally, different mechanisms for the star formation triggering in this massive central starburst are studied, including the merging with a low mass companion and the interaction with UGC 4278. We have assumed a distance to Mrk 86 of 6.9 Mpc.

Key words: galaxies: individual: Mrk 86 galaxies: irregular galaxies: star clusters galaxies: stellar content

* Visiting Astronomer (AGdP), Kitt Peak National Observatory, National Optical Astronomy Observatories, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.

Send offprint requests to: A. Gil de Paz

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Contents

• 1. Introduction
• 2. Data-models comparison method
  • 2.1. Determination of the underlying population properties
  • 2.2. Determination of the star-forming regions properties
• 3. Results
  • 3.1. Underlying population
  • 3.2. Central starburst
  • 3.3. Star-forming regions
  • 3.4. Gas diagnostic for the star-forming regions
  • 3.5. Comments on several individual regions
• 4. Global interpretation of the Mrk 86 star formation history
  • 4.1. What has been ocurring during the last 30 Myr?
  • 4.2. What did happen 30 Myr ago?
• 5. Summary and conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: October 2, 2000
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