Friday, November 11, 2005

Cosmic string or dark matter

I just received a mail from Rich Murray who has taken many pictures of the region near CSL-1, the "cosmic string lensing" candidate.

For example, the newest picture #31 at the top includes "RML-1" which stands for "Rich Murray Lens 1", but I remain somewhat unconvinced that this rather amateurish picture proves anything.

The primary recipient of the e-mail was Malcolm Fairbairn who just posted an interesting paper arguing that if the CSL-1 event is caused by lensing, it is likely to be a cosmic string rather than a dark matter filament because in the latter case, the corresponding tidally disrupted dark matter halo would have to be as heavy as the Milky Way - and such a halo seems to be absent in other data.

This was always our primary worry - that CSL-1 could be caused by lensing by something that just acts as a string but can be of a rather conventional origin.