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We use globular cluster kinematics data, primarily from the SLUGGS survey, tomeasure the dark matter fraction ($f_{\rm DM}$) and the average dark matterdensity ($\left< \rho_{\rm DM} \right>$) within the inner 5 effective radii($R_{\rm e}$) for 32 nearby early--type galaxies (ETGs) with stellar mass log$(M_*/\rm M_\odot)$ ranging from $10.1$ to $11.8$. We compare our results witha simple galaxy model based on scaling relations as well as with cosmologicalhydrodynamical simulations where the dark matter profile has been modifiedthrough various physical processes.  We find a high $f_{\rm DM}$ ($\geq0.6$) within 5~$R_{\rm e}$ in most of oursample, which we interpret as a signature of a late mass assembly history thatis largely devoid of gas-rich major mergers. However, around log $(M_*/M_\odot)\sim 11$, there is a wide range of $f_{\rm DM}$ which may be challenging toexplain with any single cosmological model. We find tentative evidence thatlenticulars (S0s), unlike ellipticals, have mass distributions that are similarto spiral galaxies, with decreasing $f_{\rm DM}$ within 5~$R_{\rm e}$ as galaxyluminosity increases. However, we do not find any difference between the$\left< \rho_{\rm DM} \right>$ of S0s and ellipticals in our sample, despitethe differences in their stellar populations. We have also used $\left<\rho_{\rm DM} \right>$ to infer the epoch of halo assembly ($z{\sim}2-4$). Bycomparing the age of their central stars with the inferred epoch of haloformation, we are able to gain more insight into their mass assembly histories.Our results suggest a fundamental difference in the dominant late-phase massassembly channel between lenticulars and elliptical galaxies.

The SLUGGS Survey: Dark matter fractions at large radii and assembly epochs of early-type galaxies from globular cluster kinematics