observations of UCDs: no halo at all; theory: cuspy haloes

[Boud Roukema]

On Tue, 6 Jan 2004, Bartosz Lew wrote:

>
> ok, maeybe I messed something up ;)

yep ;)

the whole question is whether we are talking about *stellar* matter
or *nbCDM*


> but the bottomline  still is that UCD are very cuspy ;)

they are very cuspy *stellar* matter (gwiazd)

> but what's with their halo - something that the host galaxy was involved
> that's all I know

yep. the observations seem to show that they have nearly zero nbCDM,
neither cuspy, nor non-cuspy.

So the question in that paper is: how did they lose all their nbCDM?

The simulations show that if the UCDs early on had very low concentrations
of nbCDM, then it's fairly easy to show how these low-concentration haloes
around the UCDs were destroyed in tidal interactions.

However, N-body simulations on cosmo length scales give fairly high
concentrations of nbCDM for these UCDs, and so standard CDM theory
seems to imply that UCDs *should* still have concentrated CDM haloes.

But the observations show they seem to have no haloes at all.

b

> here's the article astro-ph/0307362
>
>
> bart.

> ps. if ths came to you twice - sorry for that