Lensing effects do not really apply to Andromeda, although searches are made for 'local' (our galactic halo) micro-lensing events that might be caused by mini black holes or Jupiters. [See today's 'Some Consequences of the Baryonic Dark Matter Population' Rudolph E. Schild http://arXiv:astro-ph/0409549 for distant such objects]Mike2 said:I've not seen the data. Are the galactic rotation curves and the lensing effects just as strong for Andromeda as for very distant galaxies? Thanks.
However galactic rotation curves certainly do apply not only to Andromeda but also for the Milky Way itself.
Each galaxy seems to have a massive invisible halo and each galaxy cluster seems to have a massive intergalactic medium, also invisible. Visible matter ~ 4%, Dark Matter ~ 23% of total critical density.
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