The GOGREEN Survey of dense galaxy environments at 1<z<1.5

Updated December 23, 2022, by david.jones

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Principal Investigator: Michael Balogh, University of Waterloo

Program Summary:

Clusters of galaxies are among the most massive structures in the Universe, with up to 1000 trillion times the mass of the Sun in stars, gas and dark matter. Such clusters play a central role in studies of cosmology, galaxy and structure formation, as well as plasma physics and supermassive black hole growth, and for the determination of the nature of dark matter. Their enormous gravitational potentials allow them to act as cosmic "calorimeters", maintaining an observable record of all the energy inputs and outputs associated with galaxy formation over the history of the Universe. They host the most massive galaxies, which are among the first luminous objects to form. Clusters are also the ideal places to study rare and extraordinary perturbations to galaxy evolution, such as hydrodynamic stripping of gas, tidal stripping of matter, and high-speed gravitational encounters. Much of what we have learned about galaxy evolution is thanks to years of research on these systems.

The Gemini Observations of Galaxies in Rich Early ENvironments (GOGREEN) Survey will take advantage of upgraded detectors, which will make Gemini's GMOS spectrographs the best in the world for studying distant galaxy clusters. The survey will obtain multi-object spectroscopy of 21 clusters in the redshift range 1<z<1.5, representing the Universe when it was a third of its present age. The targets are selected to span a wide range of masses, representing the range of building blocks from which today's clusters were built. The sample of over 1000 spectroscopically confirmed members will reach unprecedented stellar masses at this redshift, providing the first look at environmental effects on galaxy evolution at a time when galaxies were growing in a fundamentally different way from today. With up to 15 hours of total integration time on the faintest galaxies, the spectra will allow us to measure the dynamics of different galaxy populations, their stellar populations, and to obtain a robust measurement of the abundance of low-mass, quiescent galaxies. By combining GOGREEN with our existing data on the lower-redshift descendants of these clusters, we will measure the evolution of satellite galaxy dynamics and stellar populations over the last 9.3Gyr of cosmic time. This will provide new leverage to theoretical models, importantly testing them at an epoch where there are currently almost no constraints.