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• La Barbera et al. (2012): https://academic.oup.com/mnras/article/426/3/2300/988992?login=false
  • This paper studied the optical-optical and optical-NIR color out to 8R_e for a sample of 673 massive early-type galaxies (ETGs) with M*>3×10^10 soloar mass, selected from SDSS-based SPIDER survey. Radial profiles of colors, as well as stellar age and metallicity derived from stellar population synthesis modelling are obtained. Generally, the outer regions are older and more metal-poor than the cores of the galaxies, and the trend is strongest for the most massive galaxies with M*>10^11 solar mass. Furthermore, the age gradient is more significant in ETGs residing in higher density environment. These results are consistent with the picture that the envelope of massive galaxies is made up of accreted small satellites (i.e. minor mergers) whose stars were born during the first stages of galaxy formation.
• Wang et al. (2019): https://ui.adsabs.harvard.edu/abs/2019MNRAS.487.1580W/abstract
  • This paper studies the stellar halo of isolated central galaxies by stacking the HSC images. The sample covers a wide range of stellar mass, 9.2<lg(M*)<11.4, and out to radii of 120kpc. A strong self-similarity of the stellar halo profiles is found, albeit the large galaxy-to-galaxy scatter. Color profiles show a minimum at some radius, beyond which the color of the outer halo turns red again. This effect is most pronounced for the most massive galaxies in their sample.

Galaxy cluster: central galaxy profiles and intra-cluster light