# ITC Seminar - Alexa Villaume (UCSC)

## Date:

Tuesday, October 29, 2019, 12:00pm to 1:00pm

## Location:

Phillips

Galactic Archeology of the Brightest Cluster Galaxy M87

The galactocentric radial metallicity gradients of GC systems can be used to probe the assembly histories of galaxies but doing so is complicated by: 1.) a GC system is an aggregate population of several (or many) different subpopulations of different origins, and 2.) computing the gradients with respect to projected galactocentric distances can artificially flatten the gradient. I describe a hierarchical statistical framework measure the radial metallically gradients of the GC subpopulations and its application the brightest cluster galaxy M87 using spectroscopically-derived metallicities for a large sample of GCs. Contrary to much previous work I find that the metal-rich and metal-poor subpopulations have different gradients, indicating they were affected by separate events. Moreover, I find the gradients change between the inner and outer halo, indicating that M87 has at least two merger events in its assembly history. I describe the results of doing weak chemical tagging'' on  physically-motivated spectral stacks of the GC subpopulations and compare these results to the stellar parameters derived spatially-resolved spectroscopy for the galaxy light of M87. I will discuss these results in context of the formation and assembly history of M87 and assess how well predictions from cosmological galaxy formation simulations match our results.