Key project 3: High-Redshift Galaxy Formation – University of Copenhagen

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Key project 3: High-Redshift Galaxy Formation

Galaxies at redshifts z > 5 carry information about reionization, the properties of the dark matter and the formation of the first supermassive black holes. By studying how they formed, their properties and the properties of their central black holes as a function of redshift, we can begin to understand the timing and process of reionization, galaxy formation and evolution.

UltraVISTA: Finding galaxies at the reionization epoch
We stand at the final frontier in our quest to understand the epoch of reionization and the formation of the first galaxies. The current situation is tantalizing; we know of several hundred galaxies at 5.5 < z < 6.7, and according to the most recent WMAP data reionization took place at z = 10.91.4. But we currently know of only a few credible galaxy candidates at z > 6.5. Why do we know so little about the crucial epoch 6 < z < 12?  The principal reason is observational: the discovery of high-redshift galaxies (through Lyman-break or Lyman-α emission selection) can only be achieved via imaging with normal CCD detectors out to z ≈ 6.5. To probe higher redshifts requires imaging at near-infrared wavelengths, since the detectors available till now did not provide the necessary combination of area and depth. This will be possible with VISTA. The VISTA telescope offers a uniquely powerful probe of galaxy formation and evolution, because its large sky area coverage allows the study of a representative volume of the high-redshift universe. As part of the Centre's original research we provided a narrow-band filter for VISTA in return for three nights of guaranteed time.

The UltraVISTA survey is one of 6 public surveys that will be carried out over the next 5-6 years. Data taking started in April 2009, and all data is made publicly available through yearly releases. The survey consists of a coordinated Y, J, H, Ks + narrow-band survey of a large area (0.73 deg2) to the depth necessary to detect galaxies at z > 6.5. The Centre entered the project via its guaranteed-time project. The narrow-band part of UltraVISTA, which will locate the bright end of the luminosity function of Lyman-α emitting galaxies at z = 8.8, will go much deeper than can be reached in the three guaranteed nights. The survey will be undertaken in the COSMOS field (Scoville et al. ApJS, 172, 1, 2007) with the very best available deep multi-frequency supporting data and accessible to X-shooter. UltraVISTA constitutes the only currently feasible route to quantify the evolution of the high-mass end of the galaxy mass function through this important epoch in cosmic history.

 

Unveiling the nature of massive, quiescent, campact high-redishift galaxies

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