The SLUGGS survey: Combining stellar and globular cluster metallicities in the outer regions of early-type galaxies

摘要: The outer halo regions of early-type galaxies carry key information about their past accretion history. However, spectroscopically probing the stellar component at such galactocentric radii is still challenging. Using DEep Imaging Multi-Object Spectrograph on Keck, we have been able to measure metallicities and globular cluster components in 12 out more than 10R e . We find similar metallicity gradients for metal-poor metal-rich subpopulations, suggesting a common formation process two subpopulations. This conflict with most current theoretical predictions, where clusters are thought be purely accreted mostly formed situ. Moreover, that show trend galaxy mass, being steeper lower mass higher galaxies. what outermost stars suggests active history, larger role played by major mergers, massive conclusion qualitatively consistent expectations from two-phase assembly models. Finally, small difference between 1R may correlate mass. origin this not currently clear.