Astron. Astrophys. 358, 819-834 (2000)

Tidal dwarf candidates in a sample of interacting galaxies ^* **

P.M. Weilbacher ¹, P.-A. Duc ^2,3, U. Fritze von Alvensleben ¹, P. Martin ⁴ and K.J. Fricke <sup>1

1</sup> Universitätssternwarte, Geismarlandstrasse 11, 37083 Göttingen, Germany
² CNRS URA 2052 and CEA, DSM, DAPNIA, Service d'Astrophysique, Centre d'Etudes de Saclay, 91191 Gif-sur-Yvette Cedex, France
³ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
⁴ Canada-France-Hawaii Telescope, P.O. Box 1597, Kamuela, HI 96743, USA

Received 30 July 1999 / Accepted 28 March 2000

Abstract

We present deep optical B,,R images of a sample of 10 interacting systems which were selected for their resemblance to disturbed galaxies at high redshift. Photometry is performed on knots in the tidal features of the galaxies. We calculate a grid of evolutionary synthesis models with two metallicities and various burst strengths for systems consisting of some fraction of the stellar population of a progenitor spiral plus starburst. By comparison with two-color diagrams we interpret the photometric data, select from a total of about 100 condensations 36 star-forming objects that are located in the tidal features and predict their further evolution. Being more luminous by 4 mag than normal HII regions we argue that these objects could be tidal dwarf galaxies or their progenitors, although they differ in number and mean luminosity from the already known tidal dwarf galaxies typically located at the end of tidal tails in nearby giant interacting systems. From comparison with our models we note that all objects show young burst ages. The young stellar component formed in these tidal dwarf candidates contributes up to 18% to the total stellar mass at the end of the starburst and dominates the optical luminosity. This may result in fading by up to 2.5 mag in B during the next 200 Myrs after the burst.

Key words: galaxies: formation galaxies: interactions galaxies: photometry galaxies: evolution

* Based on observations collected at the European Southern Observatory, La Silla, Chile (ESO No 058.A-0260).
** Tables 5-14 are only available in electronic form at the CDS via anonymous ftp to ftp://cdsarc.u-strasbg.fr/pub/cats/J/A+A/358/819 (130.79.128.5) or via http://cds.u-strasbg.fr/cgi-bin/qcat?J/A+A/358/819

Send offprint requests to: P. Weilbacher (weilbach@uni-sw.gwdg.de)

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Contents

• 1. Introduction
• 2. Observations and data reduction
  • 2.1. Data and calibration
  • 2.2. Aperture photometry
• 3. Model
  • 3.1. Modelling the old population
  • 3.2. Input physics
  • 3.3. TDG models
  • 3.4. Model application and limitations
• 4. Results
  • 4.1. AM 0529-565
  • 4.2. AM 0537-292
  • 4.3. AM 0547-244
  • 4.4. AM 0607-444
  • 4.5. AM 0642-645
  • 4.6. AM 0748-665
  • 4.7. AM 1054-325
  • 4.8. AM 1208-273
  • 4.9. AM 1325-292
  • 4.10. AM 1353-272
• 5. Discussion
  • 5.1. Background contamination
  • 5.2. Properties of the TDG candidates
    • 5.2.1. Number and luminosity
    • 5.2.2. Colors and star formation
    • 5.2.3. Burst properties
  • 5.3. Nature of the TDG candidates
    • 5.3.1. Formation of bound objects
    • 5.3.2. Future evolution
• 6. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: June 20, 2000
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