A New Perspective on the Blue Tilt Phenomenon of Extragalactic Globular Cluster Systems

Recent observations reveal that some early-type galaxies show a color-magnitude relation of blue globular clusters (GCs) in the color-magnitude diagrams, which is referred to as 'blue tilt'. This phenomenon is interpreted as a mass-metallicity relation -- metallicities of blue GCs increase with increasing mass, and thus provides a crucial clue to the chemical enrichment processes of GCs as a function of their mass. However, some galaxies show 'non-tilt' or even 'reverse blue tilt' on the blue GC sequence, and thus the origin of blue tilt still remains a puzzle. In this study, we put forward the theoretical explanation for the phenomenon and discuss its implications towards galaxy formation scenarios.