Structure and Subhalo Population of Halos in a Self‐interacting Dark Matter Cosmology

We study the structure of Milky Way (MW)- and cluster-sized halos in a LambdaCold Dark Matter (CDM) cosmology with self-interacting (SI) dark particles. Thecross section per unit of particle mass has the form sigma =sig_0(1/v_100)^alpha, where sig_0 is a constant in units of cm^2/gr and v_100is the relative velocity in units of 100 km/s. Different values for sigma withalpha= 0 or 1 were used. For small values of sigma = const. (sig_0<0.5), thecore density of the halos at z=0 is typically higher at a given mass for lowervalues of sig_0 or, at a given sig_0, for lower masses. For values of sig_0 ashigh as 3.0, the halos may undergo the gravothermal catastrophe before z=0.When alpha = 1, the core density of cluster- and MW-sized halos is similar.Using sigma = 0.5-1.0x(1/v_100), our predictions agree with the centraldensities and the core scaling laws of halos both inferred from theobservations of dwarf and LSB galaxies and clusters of galaxies. The cumulativeVmax-functions of subhalos in MW-sized halos with (sig_0,alpha) = (0.1,0.0),(0.5,0.0) and (0.5,1.0) agree roughly with observations (luminous satellites)for Vmax > 30 km/s, while at Vmax = 20 km/s the functions are a factor 5-8higher, similar to the CDM predictions. The halos with SI have slightly morespecific angular momentum at a given mass shell and are rounder than their CDMcounterparts. We conclude that the introduction of SI particles with sigma\propto 1/v_100 may remedy the cuspy core problem of the CDM cosmogony, whilethe subhalo population number remains similar to that of the CDM halos.Comment: To appear in ApJ, December 20, 2002. We added plots showing the evolution of the heat capacity profile for halos in the core expansion and gravothermal catastrophe phases. Minor changes in the text were introduce