Dynamical limits on galactic winds, halo MACHOs and intergalactic globular clusters

We argue that any violent galactic winds following the early epoch of starbursts will significantly weaken the potentials of galaxies, and leave lasting signatures such as a lowered dark halo density and preferentially radial/escaping orbits for halo tracers such as globular clusters. A galaxy is disintegrated if more than half of its dynamical mass is blown off. The presence of dense haloes in galaxies and the absence of intergalactic/escaping globulars should imply an upper limit on the amount of baryons lost in galactic winds of around 4 per cent of the total mass of the galaxy. This translates to limits on the baryons participating in the early starbursts and baryons locked in stellar remnants, such as white dwarfs. The numbers of halo white dwarfs claimed in recent proper motion searches and microlensing observations in the Galactic halo are too high to be consistent with our dynamical upper limits. Similar arguments also imply upper limits for the number of neutron stars and stellar black holes in galaxy haloes. Nevertheless, a milder outflow is desirable, especially in dwarf galaxies, both to lower their cold dark matter central density and to inject metals into the intergalactic medium.