Galaxy halo masses, assembly bias, and implications for galaxy evolution from weak lensing measurements

Rachel Mandelbaum (Carnegie Mellon) // November 14, 2016

Abstract: In the past decade, weak gravitational lensing has become one of the best ways of measuring the masses of the extended dark matter halos in which galaxies reside. Measurements of the dark matter halo masses for galaxies with a given luminosity or stellar mass (observable mass proxies) have revealed a great deal about the connection between halo masses and these more easily observable quantities. After an overview of what such measurements have shown us before, I will describe some recent measurements in the Sloan Digital Sky Survey that illustrate a bimodality in dark matter halo mass at fixed galaxy stellar mass,with red galaxies (with older stellar populations) having dark matter halomasses a factor of 2-3 larger than blue galaxies (younger stellar populations). In addition, I will discuss recent attempts to measure galaxy assembly bias, a dependence of observed properties of galaxies on the formation time of the host dark matter halo. I will discuss the implications of these results for models of galaxy formation and evolution, and also propose future measurements with upcoming datasets that will shed further light on the relevant galaxy formationand evolution processes.

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