Letters of Intent received in 2016

LoI 2018-1894
Star Clusters: from the Milky Way to the Early Universe

Topics

- Formation and evolution of globular clusters at high and low-redshift
- Multiple stellar populations in globular clusters
- Dynamics and evolution of globular cluster stellar content and exotic populations (IMBH, stellar mass black holes, gravitational waves sources, compact remnants and X-ray sources)
- Links between globular clusters, nuclear star clusters, ultrafaint dwarfs, ultracompact dwarfs, and dwarf galaxies
- The Gaia revolution for star clusters
- Globular clusters and satellite systems in the Local Group and beyond
- Extragalactic globular clusters: constraints on the formation and evolution from integrated light
- Star clusters and dwarfs as building blocks of galactic halos
- Galactic archeology with ongoing and future large surveys
- The future instrumentation from the ground and space

Rationale

Globular star clusters play a pivotal role for many areas of research in
astrophysics including star formation, stellar evolution and nucleosynthesis,
stellar dynamics, galaxy formation and evolution. They are unique laboratories to
study the interplay among many of the fundamental physical processes lying at the
core of each of these research areas.

Despite the long history of observational and theoretical studies of these systems,
new studies continue to raise new challenges and questions.

It has long been recognized that the high-density environment of globular clusters
can play a key role in driving the formation and evolution of exotic stellar
populations (such as millisecond pulsars, X-ray binaries, blue stragglers,
intermediate-mass black holes etc.). The recent detection of gravitational waves
and the possible role played by dynamical processes in the formation of the black
hole binaries detected by LIGO has provided another example of the connection
between internal cluster environment and its stellar populations.

Observations of multiple stellar populations, characterized by different chemical
and dynamical properties, revealed that globular cluster chemical evolution,
dynamics and formation history are even more complex than previously thought. The
discovery of multiple stellar populations has further strengthened the ties among
the different aspects of the astrophysics of these systems and posed many
challenges for theoretical studies (e.g., for models of the cluster chemical and
star formation history and the related stellar feedback).

In the last decade, a major innovation of hardware and software facilities
revolutionized Monte Carlo and N-body codes: simulating a million bodies for a
Hubble time is now possible, and realistic models of globular clusters are within
arm's reach.

The results of many current and forthcoming observational projects and large-scale
surveys in the Milky Way and nearby systems will shed further light on the stellar
content and chemo-dynamical properties of individual globular clusters, of stars
lost by disrupting and dissolved clusters (tidal tails, streams), and in general on
the formation of our Galaxy. Foremost is the Gaia mission, which will provide
exquisite parallaxes and proper motions for many stars in a large fraction of Milky
Way globular clusters. The APOGEE, Gaia-ESO, GALAH, WEAVE, MOONS, 4MOST
high-resolution spectroscopic surveys in the Milky Way are of also fundamental
importance. In addition to HST, WFIRST and JWST, along with large scale photometric
surveys from the ground such as LSST, will play a major role. On the long run, the
ELTs will extend our view beyond the local volume.

In the larger scale context of galactic and extra-galactic astronomy, globular
cluster systems are one of the fundamental tools used to understand galaxy
formation and evolution; significant efforts and investments in large observational
surveys from ground and space continue to be made in this research area and to
provide important insights both on the internal evolution of globular clusters and
their host galaxies.

This wealth of observations, coupled with theoretical modeling, will also play a
key role in advancing our understanding of the global properties of globular
cluster systems and their similarities and differences with other stellar systems
such as young massive clusters, nuclear star clusters, ultrafaint and dwarf
galaxies.

It is becoming increasingly clear that globular clusters are a cornerstone for
astrophysics, because of the wealth of insights they can provide about many
research areas including cosmology, stellar dynamics, stellar evolution and galaxy
archeology. Progress towards a full understanding of these enigmatic stellar
systems unavoidably requires to take into account the whole variety of physical
processes driving their formation and evolution. The proposed symposium will bring
together researchers working on the broad range of topics relevant to understand
these stellar systems.

The proposed SOC members are:
Gary Da Costa, Australia
Melvyn Davies, Sweden
Mirek Giersz, Poland
Young-Wook Lee, South Korea
Michela Mapelli, Italy
Nadine Neumayer, Germany
Genevieve Parmentier, Germany
Eric Peng, China
Giampaolo Piotto, Italy
Thomas Puzia, Chile
Maurizio Salaris, UK
Alison Sills, Canada
Eline Tolstoy, Netherlands
Kim Venn Canada