Anisotropic Locations of Satellite Galaxies: Clues to the Orientations of Galaxies within their Dark Matter Halos - AstrophysicsReport as inadecuate




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Abstract: We investigate the locations of the satellites of relatively isolated hostgalaxies in the Sloan Digital Sky Survey and the Millennium Run simulation.Provided we use two distinct prescriptions to embed luminous galaxies withinthe simulated dark matter halos ellipticals share the shapes of their halos,while disks have angular momenta that are aligned with the net angular momentaof their halos, we find a fair agreement between observation and theory.Averaged over scales r p \le 500 kpc, the satellites of red, high-mass hostswith low star formation rates are found preferentially near the major axes oftheir hosts. In contrast, the satellites of blue, low-mass hosts with low starformation rates show little to no anisotropy when averaged over the same scale.The difference between the locations of the satellites of red and blue hostscannot be explained by the effects of interlopers in the data. Instead, it iscaused primarily by marked differences in the dependence of the mean satellitelocation, <\phi>, on the projected distance at which the satellites are found.We also find that the locations of red, high-mass satellites with low starformation rates show considerably more anisotropy than do the locations ofblue, low-mass satellites with high star formation rates. There are twocontributors to this result. First, the blue satellites have only recentlyarrived within their hosts halos, while the red satellites arrived in the fardistant past. Second, the sample of blue satellites is heavily contaminated byinterlopers, which suppresses the measured anisotropy compared to the intrinsicanisotropy.



Author: Ingolfur Agustsson, Tereasa G. Brainerd

Source: https://arxiv.org/







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