Astron. Astrophys. 355, 835-847 (2000)

Investigations of the Local Supercluster velocity field

III. Tracing the backside infall with distance moduli from the direct Tully-Fisher relation

T. Ekholm ^1,2, P. Lanoix ¹, P. Teerikorpi ², P. Fouqué ³ and G. Paturel <sup>1

1</sup> CRAL - Observatoire de Lyon, 69561 Saint Genis Laval CEDEX, France
² Tuorla Observatory, 21500 Piikkiö, Finland
³ ESO, Santiago, Chile

Received 20 December 1999 / Accepted 25 January 2000

Abstract

We have extended the discussion of Paper II (Ekholm et al. 1999a) to cover also the backside of the Local Supercluster (LSC) by using 96 galaxies within from the adopted centre of LSC and with distance moduli from the direct B-band Tully-Fisher relation. In order to minimize the influence of the Malmquist bias we required and .

We found out that if this sample fails to follow the expected dynamical pattern from the Tolman-Bondi (TB) model. When we compared our results with the Virgo core galaxies given by Federspiel et al. (1998) we were able to constrain the distance to Virgo: .

When analyzing the TB-behaviour of the sample as seen from the origin of the metric as well as that with distances from the extragalactic Cepheid PL-relation we found additional support to the estimate given in Paper II. Using a two-component mass-model we found a Virgo mass estimate - , where for . This estimate agrees with the conclusion in Paper I (Teerikorpi et al. 1992).

Our results indicate that the density distribution of luminous matter is shallower than that of the total gravitating matter when . The preferred exponent in the density power law, , agrees with recent theoretical work on the universal density profile of dark matter clustering in an Einstein-deSitter universe (Tittley & Couchman 1999).

Key words: cosmology: theory cosmology: dark matter cosmology: distance scale galaxies: distances and redshifts galaxies: general galaxies: kinematics and dynamics

Send offprint requests to: T. Ekholm

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Contents

• 1. Introduction
• 2. The sample based on direct B-band Tully-Fisher relation
• 3. The vs. diagram for the TF-sample
• 4. Have we found the true TB signature of Virgo?
• 5. The velocity field as seen from the centre of LSC
  • 5.1. The two-component mass model
  • 5.2. vs. diagram for
  • 5.3. Evidence from galaxies with PL-distances
• 6. Discussion
  • 6.1. The Virgo cluster mass, , and behaviour of
  • 6.2. Comparison with the universal density profile
• 7. Summary and conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: March 21, 2000
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