Letters of Intent for 2015

LoI 2015-205
Focus Meeting: The Archaeology of Galaxies


5 August 2015 to 5 August 2015


to be held during the next General Assembly of the IAU, in Honolulu, HI USA Aug. 3-14, United States


Rachel Osten (osten@stsci.edu)

Coordinating division:

Division J Galaxies and Cosmology

Chair of SOC:

Jason Kalirai (STScI)

Chair of LOC:




What are the major uncertainties in our current picture of galaxy assembly, and how can future missions work together to address the problems?

What advances in high-resolution N body simulations are needed to test future observations of the gas, stars, and dark matter in galaxies?



Galaxies are the visible building blocks of the universe. Modern telescopes have provided us both unprecedented views of the structure of nearby galaxies, and a glimpse of what these systems looked like 13 billion years ago shortly after the formation of the Universe. Our current understanding of galaxy formation and evolution is guided by these observations, and suggests that galaxies grow over cosmic time through accretion processes. Yet, despite all the work done to date, many questions remain. We do not really know how galaxies are formed, what controls their shapes, what makes them form stars, how the chemical elements are generated and redistributed through the galaxies, whether the central black holes exert great influence over the galaxies, or what are the global effects of violent events as small and large parts join together in collisions.

Over the next decade, our view of galaxies will be transformed by several new tools. The top-ranked astronomy programs in the 2010 US Decadal Survey, for both ground-based and space-based astrophysics, as well as a top priority for ESA, are facilities with large field of view cameras that will survey thousands of square degrees.  LSST, WFIRST2.4, and Euclid will uncover hundreds of millions of galaxies at exquisite resolution and provide photometric characterization over a panchromatic wavelength baseline that stretches from the UV to the IR. These new studies will be complemented by an array of new ground-based capabilities from Subaru HyperSuprimeCam, DECam, CFHT, SkyMapper, PanSTARRs and others, and form a crucial input to detailed spectroscopic analysis of kinematics, abundances, and mass to light ratios by 30-m ground based telescopes (TMT, GMT, and ELT) and high-resolution imaging and spectroscopy from JWST and ALMA.

The proposed focus meeting will bring together scientists from different communities to collectively create a roadmap for establishing how galaxies - and all of their components - grow over cosmic time. The meeting will address topics on dark matter, feedback and energetics, the interplay of gas and stars, and the evolution of morphologies and metallicity. The meeting will also include a strong focus on new generations of simulations that are now predicting both dark matter and baryon properties at small scales in large galaxies, and able to reproduce substructure that has been observed in nearby systems. Ultimately, our ability to understand the archaeology of galaxies will involve sampling these simulations along specific sightlines and comparing the results to our impressive suite of observations.

The focus meeting will be one day in length, and any day within the two week-long General Assembly is sufficient.

IAU General Assembly
Honolulu, 3-14 August 2015

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