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Astron. Astrophys. 345, 36-42 (1999)

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6. Conclusions

Recently, McGaugh & de Blok (1998a,b) have tested thoroughly the hypothesis of dark matter and of modified dynamics. They find that some facts as the Tully-Fisher relation in LSB galaxies are difficult to explain in the dark matter scenario without some fine-tuning between different variables, and are naturally predictable under the modified dynamics hypothesis. Moreover, MOND successfully overcame all the tests done by McGaugh & de Blok. In this sense, this work contributes to assess the viability of MOND. Our main conclusion is that MOND presents severe problems with regard to the question of the local and global stability of small gas-rich galaxies. The local stability of the gaseous component could only be achieved if the adopted distance for these galaxies is smaller than the usual determinations. However, this is not a satisfactory solution because not only the required distance is outside the admissible range, but then MOND fails to explain the property that the observed rotation curve is a scaled version of the rotation curve derived from the HI alone, and the combined gas + star stability of the disc would remain doubful even in this case. A study of the [FORMULA] parameter in modified dynamics may strengthen even more our conclusions.

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© European Southern Observatory (ESO) 1999

Online publication: April 12, 1999