Letters of Intent received in 2016

LoI 2018-1895
GA Symposium: Structure, kinematics and stellar populations of the Magellanic system

Topics

1. The structure of the Magellanic Clouds: bar(s) versus disk(s) and sub-structural components as a function of age and chemistry. Gas distribution. Variable stars (e.g. Cepheids, RR Lyrae stars, eclipsing binaries) as tracers.
2. Satellites and Streams of the Magellanic Clouds: satellites of satellites and assembly of galaxies, minor mergers and dark matter.
3. The star formation history and chemical evolution of the Magellanic system.
4. Internal kinematics (proper motion and radial velocity) of the Magellanic Clouds. Can we recognize and characterise sub-structural components?
5. The orbits of the Magellanic Clouds, their origin and interaction. The Magellanic Stream. Simulations and extent of the Milky Way potential.
6. Foreground and background objects to the Magellanic system. How well can we establish their influence and use them as reference systems for motion and dust?
7. Stellar clusters of the Magellanic system: number, distribution, origin, chemistry, dynamics and structure. Interplay with field populations.
8. Stellar evolution in the Magellanic system: star formation and star’s death. Extremely hot/blue and cool/red objects.
9. Results from current large-scale surveys: e.g. VMC at VISTA, STEP at VST, DES, SMASH and MagLites at CTIO, OGLE-IV, Gaia. The South Ecliptic Pole region.
10. Future projects: radial velocity and chemistry (e.g. 4MOST and MOONs, APOGEE-S), proper motion, variable stars and stellar parameters (e.g. LSST, Euclid, eRosita), gas (e.g. SKA).

Rationale

The Magellanic Clouds are the nearest gas-rich dwarf satellite galaxies of the Milky Way and illustrate a typical example of an early phase of a minor merger event, the collision of galaxies that differ in mass by at least a factor of ten. Our view of the Magellanic Clouds is rapidly changing thanks to the arrival of sophisticated instrumentation across the wavelength spectrum. About a decade ago we were astonished to discover that these two galaxies may have only recently (a few Gyr ago) entered our system, instead of having orbited around the Milky Way for close to a Hubble time. This has generated a wealth of studies aimed at explaining the structure of the Large Magellanic Cloud (LMC), the Small Magellanic Cloud (SMC), the Magellanic Bridge and Stream. Furthermore, with the increased number of deep imaging observations we have discovered potential satellites of the Magellanic Clouds and new streams possibly associated with tidal stripping events. At the same time, we are strengthening our detailed knowledge of the innermost regions of the galaxies where signatures of past evolution are encoded. We have also come to terms with the galaxies being more massive than we used to think, which has non-negligible implications for the dynamical mass and potential of the Milky Way.

Results from optical and infrared large-scale survey projects, undertaken in the past decade, have strengthened stellar populations as important diagnostics of galaxy properties. Cepheid stars have, for example, revealed the large range of distances spanned by the system, supporting its history of interaction. Intermediate-age red clump and old red giant branch stars have shown significantly extended populations, while blue horizontal branch stars have indicated protuberances and possible streams in the outskirts of the galaxies. The complementary view provided by old RR Lyrae stars is yet to be revealed, except for the very central regions of the Magellanic Clouds where, e.g. the LMC bar is protruding and the most metal poor stars were discovered. Detailed star formation history maps across wider areas and of higher spatial resolution have been constructed for the SMC, and equivalent maps for the LMC are expected soon. From a kinematical point of view, we have shown that survey data can trace effectively trace the motion of stellar populations and that the chemical information we can derive, albeit for limited types and numbers of stars, is highly valuable, to understand the internal structure of galaxies as well as the geometry and chemical evolution of the whole system, e.g. the origin of the Stream. For the first time, we begin to link the distribution of age and metallicity with the kinematics and structure of stellar populations in order to quantify the formation and evolution of the Magellanic Clouds.

Within the next two years important observing programs targeting the Magellanic Clouds will reach completion and provide unique datasets through which the study of stellar populations will unfold. Moreover, the upcoming releases of Gaia data (in 2016 – comprising of the South Ecliptic Pole region in the outskirts of the LMC – and 2017) are expected to already shed new light on the precision by which stellar population parameters can be characterised. At this stage, a symposium devoted to the Magellanic Clouds would be tremendously advantageous. It would provide a crucial platform to present an up-to-date view of the Magellanic system, to compare and combine results from different teams and projects, and to stimulate a discussion that will bring us to better understand our neighbouring galaxies in their role as important suppliers of material to the Milky Way halo, demonstrating and quantifying the processes related to galaxy interactions, as well as group accretion in general that may be applicable to more distant systems. The overall perspective of the Magellanic Clouds was addressed at a meeting in Perth (2012), while the most recent meeting on the Magellanic Clouds focused on feedback processes, star formation and the interstellar medium (STSci 2015). This symposium will differ from it because of its emphasis on stellar populations, structure and kinematics. It will also provide an up-to-date and comprehensive view of the system.

Future developments are manifold. On one side, there will be a spectroscopic revolution with the availability of multi-object spectrographs like 4MOST and MOONs, capable of observing thousands of objects simultaneously across relatively large fields of views. We will enter an era of spectroscopic survey projects that will beautifully complement the rich photometry collected thus far. On the other side, the development of more powerful imagers and their deployment for frequent observations of the Magellanic Clouds will push our sensitivity even further. This will allow us to use stellar populations diagnostics all across the Hertzsprung-Russell diagram with unprecedented precision (e.g. LSST). Furthermore, a crucial step forward in spatial resolution in the radio domain will revolutionise our view of the gas within the system (e.g. SKA). While most of these developments will culminate in the 2020s discussions on the goals, strategies, and above all the formulations of the most relevant scientific questions are already advanced. It is therefore timely to organise a symposium that brings together the communities that are, at this stage, actively involved in shaping the future facilities and projects for the study of the Magellanic system.

Confirmed SOC members:
1. Vasily Belokurov, University of Cambridge, United Kingdom
2. Alceste Z. Bonanos, National Observatory of Athens, Greece
3. Maria-Rosa L. Cioni, Leibniz Institute for Astrophysics Potsdam, Germany
4. Andrew A. Cole, University of Tasmania, Australia
5. Richard de Grijs, KIAA at Peking University, China
6. Elena D’Onghia, University of Wisconsin-Madison, United States of America
7. Douglas P. Geisler, Universidad de Concepión, Chile
8. Leo A. Girardi, INAF-Astronomical Observatory of Padova, Italy
9. Eva K. Grebel, Heidelberg University, Germany
10. François Hammer, Observatory of Paris, France
11. Vanessa A. McBride, University of Cape Town and SAAO, South Africa
12. Naomi M. McClure-Griffiths, Australian National University, Australia
13. David Nidever, NOAO, United States of America
14. Vincenzo Ripepi, INAF-Astronomical Observatory of Capodimonte, Italy
15. Igor Soszyński, University of Warsaw, Poland
16. Annapurni Subramaniam, Indian Institute of Astrophysics, India