Comments

1. #1 Lab Lemming

   April 29, 2009

   I have a very basic cluster question:
   If clusters have white dwarfs in them, then where is all the gas and dust that ought to have been blown off during the giant phase?

2. #2 Steinn Sigurdsson

   April 30, 2009

   Ah, if I knew that I’d be rich and famous…

   We don’t know. There is some in 47Tuc, and I think in M28 or was it M22.

   Other than that, the gas expelled during the AGB phase seems to clear out of the clusters, fast. We don’t know how.
   The obvious possibilities just don’t seem to do it.

3. #3 Craig Heinke

   May 3, 2009

   The argument of Freire et al. (2001) is that the pulsar winds clear out the gas from the AGB phase. Which gives an interesting prediction; that clusters with no MSPs should not clear out the gas and dust. So if a lot of gas and dust were found in, say, omega Centauri (Spitzer?), that would tend to indicate a) there actually aren’t any MSPs there (none have yet been found); and b) that pulsar winds are indeed the clearing agent.

4. #4 Steinn Sigurdsson

   May 3, 2009

   Paper by Spergel postulated this long before then,
   the problem then, and still now, is that the psr wind energetics just don’t seem to be enough – even if you can couple the psr wind efficiently to the ambient ISM

   more to the point, 47 Tuc is one of the few clusters with
   clear evidence for ISM, though I suppose an argument could be made that we’re seeing it leaving

   the Messier object with know ISM (M28 or M22 I forget which)
   has a clear associated PNe

   couple of clusters have clear internal ionized medium from variable psr dm