- This event has passed.
CRA seminar (Prof. Massimo Ricotti)
November 7, 2016 @ 3:00 pm - 4:00 pm
Title: The formation of the first star clusters: impact on reionization, JWST observations and near-field cosmology
Abstract: In this talk I will focus on understanding what determines the
morphology of the stellar component in the first low mass galaxies,
using parsec- scale cosmological simulations performed with an
adaptive mesh hydrodynamics code. Although the dense gas in which
stars are formed has a disk structure, stars are found in spheroids
with little rotation. Nearly independent of stellar mass, we observe
a large range of half-light radii for the stars, from a few parsecs to
a few hundred parsecs and surface brightnesses and mass-to-light
ratios ranging from those typical of globular clusters to ultra-faint
dwarf spheroidals (UFDs). This can be understood because although all
stars form in dense stellar clusters, a fraction of these clusters
remain bound after the gas is removed by feedback, but the rest is
destroyed and their stars, which typically have velocity dispersions
of 20 to 40 km/s, expand until they become bound by the dark matter
halo, creating a low-surface brightness dwarf spheroidal galaxy. This model
can explain the origin of the UFD satellites of the Milky Way and
Andromeda, and their old Globular Clusters population. I will discuss
why this result is in agreement with studies of GC formation in a
cosmological context and the implications of clusters formation on
reionization and future observations of the first galaxies by JWST.