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Epoch of Galaxy Quenching

When Sep 07, 2020 09:00 AM to
Sep 11, 2020 09:00 PM
Where Kavli Institute for Cosmology, Cambridge
Contact Name
Contact Phone 01223 337516
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Understanding the Decline in Star Formation from Cosmic Noon to the Present

7th – 11th September 2020, Kavli Institute for Cosmology, Cambridge, UK


The goal of this conference is to bring together an international community of researchers in observational and theoretical astrophysics, to work towards a solution to one of the most important problems in modern extra-galactic astronomy: why do galaxies stop forming stars?  

The past ten billion years of cosmic history has seen a dramatic decline in star formation from a peak at z ~ 2 to the present. As a result, the vast majority of stars that will ever exist in the Universe have already been formed. Massive galaxies have transitioned from being invariably star forming to predominantly non-star forming (or quenched). Over the same epoch, the dominant morphological type of galaxies has transformed from discs and irregulars to spheroids, and the internal kinetic energy of galaxies has evolved from an ordered to disordered state, with an accompanying significant reduction in net angular momentum.  

Understanding the physical origins of the fundamental changes within galaxies throughout the epoch of quenching has proved extremely challenging. However, over the past decade three revolutionary new techniques have emerged which may help us to finally resolve this problem:
• Wide-field IFU surveys capable of making spatially resolved measurements of star formation and quenching in galaxies (e.g. Atlas3D, SAMI, CALIFA, MaNGA & MUSE surveys)
• The advent of radio, sub-mm, and far infrared facilities able to probe the gas (atomic and molecular) and dust content of galaxies across cosmic time (e.g. ALMA, VLA, Herschel)

 • Cosmological hydrodynamical simulations, which model the evolution of dark matter and baryons simultaneously in a self-consistent manner (e.g. Eagle, Illustris, Illustris-TNG)
By combining these profound advances in the field with extensive photometric and spectroscopic galaxy surveys across this epoch (e.g. SDSS, GAMA, COSMOS, CANDELS) and the exploratory power of semi-analytics (e.g. LGalaxies, GalForm), we may now be in a position to resolve the physics of quenching and explain the major transitions at the heart of galaxy evolution.  

Key Scientific Questions:

1) Star Formation & Gas Content: What is the origin of the star forming main sequence (SFR -M* relation)? How does the main sequence evolve from cosmic noon to the present? What physical processes set the Kennicutt-Schmidt relation between gas surface density and the surface density of star formation rate? How does the gas content of galaxies impact star formation? How does star formation efficiency (and its inverse: depletion time) vary within and between galaxies? What can we learn about quenching from observations and simulations of gas in the IGM, CGM and ISM?

2) The Role of Feedback: Is AGN feedback needed to quench massive galaxies? If so, by which specific mechanism(s) does it operate (e.g. heating vs. outflows)? What observational evidence exists for each scenario? Is supernova feedback responsible for regulating star formation in low mass galaxies? Are other feedback mechanisms important for galaxy quenching (e.g. cosmic rays, magnetic fields)? How do different feedback processes work together in simulations of galaxy evolution? What physical processes set the peak of the halo mass – stellar mass relation?

3) The Role of Environment: How does environment impact the star formation and quenching of central and satellite galaxies? What is the role of the dark matter halo in quenching? By what physical mechanisms do dense cluster environments quench satellite galaxies? Is galactic conformity real? If so, what is the mechanism by which quenching is ‘contagious’?

4) Structure & Kinematics: What is the origin of the close connection between galactic star formation and structure/ kinematics/ morphology? How does galactic structure evolve from z ~ 2 to the present? Which processes engender the transition from discs to spheroids (e.g. major and minor mergers vs. violent disk instabilities)? How does this structural evolution impact star formation?

5) Chemical Composition: How do the chemical compositions of star forming and quenched galaxies compare? What can we learn about the quenching process from measurements of metallicity in gas and stellar populations (e.g. outflows vs. strangulation)? Do contemporary models accurately reproduce the changes in metallicity of galaxies over the epoch of quenching?

6) The Future: How will the next generation of astronomical facilities (e.g. JWST, VLT-MOONS, LSST, EUCLID, WFIRST and the ELTs) help to resolve outstanding questions in galactic star formation and quenching? What is next for theory and simulations? What do we still not know?


  • Asa Bluck (Co-chair), University of Cambridge, UK
  • Emma Curtis-Lake (Co-chair), University of Cambridge, UK
  • Michele Cappellari, University of Oxford, UK
  • Stephen Eales, University of Cardiff, UK
  • Sara Ellison, University of Victoria, Canada
  • Julie Hlavacek-Larrondo, University of Montreal, Canada
  • Roberto Maiolino, University of Cambridge, UK
  • Yingjie Peng, Peking University, China.
  • Joop Schaye, University of Leiden, Netherlands
  • Deborah Sijacki, University of Cambridge, UK



Registration is not yet open; details will be posted here in due course.


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