Friday, March 04, 2005

Cosmic string lenses

So there is a serious claim that a pair of ellipical galaxies are redshift 0.46 (about 6 billion light years away) [CSL-1] seen separated by 2", are in fact a symmetric lensed image, and the lens must be a cosmic string (Sazhin et al MNRAS 2003).

I've now read the paper and the followup, and the claim is surprisingly good. The galaxies are seen only 20 kpc apart in projection, they are at the same redshift, and have same brightness, colour and spectra, within the resolution of the data. That is somewhat surprising for a random pair of giant ellipticals. The authors argue convincingly that the isophote contours are too round and symmetric to be due to foreground point source (or galaxy) lensing.

Deficit angle implies a string density consistent with a GUT scale of little over 10^15 GeV (depending on where you let the coupling constant run to). If the data works out, then this is a major discovery.

Is this real? I don't know, but the evidence is better than the hype in the press suggests. It is also eminently testable, both by further observations of the galaxy, by looking in the field around to try to see more lenses (by the same string) - which that group has done, more on that next week; and by looking for anomalous fluctuations in the microwave background. Taking a Chandra image of this galaxy pair would be a seriously good idea.


There are many nice places to do science, and scientists, very sensibly go there, meet there and generally try to be there.
One of the nicer is UC Santa Cruz, with the main campus in the hill above the town of Santa Cruz, looking over the Monterey Bay.

Go there, do a tour of Bonny Doon vineyard and then go have dinner at Rosa's by the small boat harbour, or Gayle's in Capitola for light lunch.


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