Day 79

Sunday, rain & thunder.  Yesterday was beautiful, walked along Rotweinwonderweg (all red-wine vineyards along the way), had Federweißer ("feather-white", refreshing, immature wine), was delicious.


1986ApJ...301...27B
Contraction of dark matter galactic halos dues to  baryonic infall
Blumenthal, Faber, Flores, Primack


Some evidence (in 1986!) suggests that galaxies consist of roughly 10 percent baryonic matter by mass, and that baryons sink dissipatively by about a factor for 10 in radius during galaxy formation.  Such infall strongly perturbs underlying dark matter distribution, pulling it inward and creating cores that are considerably smaller and denser than would have evolved without dissipation.  Any discontinuity between the baryonic and dark matter mass distributions is smoothed out by the coupled motions of the two components.  If dark halos have large core radii in the absence of dissipation, the infall scenario yields rotation curves that are flat over large distances, in agreement with observations of spiral galaxies.  Such large dissipationless cores may result from large kinetic energy in protogalaxies at maximum expansion (?), perhaps as a result of subclustering, tidal effects, or anisotropic collapse.


* Early description of cluster core contraction (baryonic).


2002MNRAS.334..797S
Constraints on galaxy halo profiles from galaxy-galaxy lensing and Tully-Fisher/Fundamental Plane relations
Seljak


Observations of gg lensing from SDSS are combined with the TF and FP relations to derive constraints on galactic halo profiles.  For both early- and late-type galaxies around L* the rotation velocity decreases significantly from its peak value at the optical radius to the virial radius r200 with vopt/v200 ~ 1.8.  Such a decrease is expected in models in which the halo profile is very concentrated, so that it declines at steeper than the isothermal rate at large radii.  This large decrease can be explained as a result of both a concentrated DM profile and a significant stellar contribution to the rotation velocity at the optical radii.  
Model stellar component with a thin rotationally supported disc or Hernquist profile and use adiabatic DM response model to place limits on the halo concentration as a function of the stellar M/L ratio.  For reasonable values of M/L, find concentration c200 consistent with CDM--no evidence for low concentrations for the majority of haloes in the Universe.  
Discuss origin of the Faber-Jackson relation L~sigma^4 in light of the L~v200^5/2 relation found for early-type galaxies above L* from gg lensing.  Decrease in vopt/v200 with luminosity above L*; at 7L* the ratio is 1.4.  This is expected from the Fundamental plane relation: reduction in the baryonic contribution to the total mass at the optical radius, and a decrease n the optical to virial rotation velocity in the DM profile.  Imply that relations such as TF and FJ are not simply those between the mass of the DM halo and the galaxy luminosity, but also significantly influenced by the baryonic effects on the rotation velocity at optical radii.


* Assuming a flat rotation curve (at optical radii and slightly outwards), what is the deviation at DM virial radius?  This actually changes depending on the halo mass, apparently.  The concentration affects the velocity ratio, which is consistent with LCDM (for reasonable values of M/L ratios).