Friday, 10 October 2008

all MW halos have the same mass!

All the satelites of our galaxy have aroundabout the same mass enclosed within a fixed radius (see Strigari et al., arXiv:0808.3772).  Here, the authors have taken a N-body sim + SAM to see whether or not this falls out of current models.  And indeed it does!  The black points show their model results; the red points are from Strigari et al.

Another interesting sidenote: of the 2000ish subhalos that the authors tracked, only 51 became fully fledged satelite galaxies.  This is still twice as many as are observed, but they reckon that optical selection effects can account for this.  (Which you can kinda see from the plot.)  This is essentially because they have completely supressed gas cooling in subhaloes with virial temperatures below 10^4 K.

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