Dark matter ( DM ) halos of Sc –Im galaxies satisfy structural scaling laws analogous to the fundamental plane relations for elliptical galaxies .
Halos in less luminous galaxies have smaller core radii r _ { c } , higher central densities \rho _ { \circ } , and smaller central velocity dispersions \sigma .
If dwarf spheroidal ( dSph ) and dwarf Magellanic irregular ( dIm ) galaxies lie on the extrapolations of these correlations , then we can estimate their baryon loss relative to that of Sc – Im galaxies .
We find that , if there had been no enhanced baryon loss relative to Sc – Im galaxies , typical dSph and dIm galaxies would be brighter by \Delta M _ { B } \simeq - 4.0 mag and \Delta M _ { B } \simeq - 3.5 mag , respectively .
Instead , the galaxies lost or retained as gas ( in dIm galaxies ) baryons that could have formed stars .
Also , dSph and dIm galaxies have DM halos that are more massive than we thought , with \sigma \sim 30 km s ^ { -1 } or circular-orbit rotation velocities V _ { circ } \sim 42 km s ^ { -1 } .
Comparison of DM and visible matter parameter correlations confirms that , at M _ { V } _ { > } \atop { { } ^ { \sim } } -18 , dSph and dIm galaxies form a sequence of decreasing baryon-to-DM mass ratios in smaller dwarfs .
We show explicitly that galaxy baryon content goes to ( almost ) zero at V _ { circ } _ { < } \atop { { } ^ { \sim } } 42 \pm 4 km s ^ { -1 } , in agreement with V _ { circ } as found from our estimate of baryon depletion .
Our results suggest that there may be a large population of DM halos that are dark and undiscovered .
This helps to solve the problem that the initial fluctuation spectrum of cold dark matter predicts more dwarf galaxies than we observe .