Benjamin
Joachimi





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Welcome to my web pages.

I am a Professor of Astrophysics in the Department of Physics and Astronomy at University College London and a core member of the Cosmoparticle Initiative.

My research focuses on testing the fundamentals of our cosmological model and thereby helping to find an answer to some of the major open questions in physics:
How did structure in the Universe form and evolve, and what role does dark matter play in this?
What is the cause of the recent accelerated expansion of the Universe?
Is Einstein's theory of gravity correct on the largest cosmological scales?
B. Joachimi

To achieve this, I contribute to developing, running, and analysing some of the largest and deepest galaxy surveys ever undertaken:

The ESO Kilo-Degree Survey
Conducted at Paranal Observatory in Chile together with its infrared sister survey, VIKING, KiDS has provided high-quality imaging and 9-band photometry ideally suited for measuring the weak gravitational lensing effect by the large-scale structure of the Universe. I am a co-ordinator of the KiDS weak lensing team.



The ESA Euclid Mission
A space telescope to be launched in 2022, Euclid is designed to provide extremely stable imaging and infrared photometry and spectroscopy in exquisite quality that can only be done in space. I am deputy lead of the Organisational Unit that produces the final data products in the Euclid Ground Segment, and hold several other leadership positions in the Euclid Consortium. My team is responsible for calculating Fourier-space statistics from Euclid's imaging survey.

The DESI Survey
The DESI Survey started in 2021 and is underway to build an unprecedented 3D map of the Universe by observing 35 million galaxies spectroscopically. My main interests are in constraining cosmic structure growth at very high redshifts and linking galaxy properties to their dark matter environment through combinations of DESI with overlapping imaging survey data.

The Legacy Survey of Space and Time
Currently under construction in Chile, the Rubin Observatory will accumulate very deep multi-band imaging over the full Southern extragalactic sky during the 2020s with its flagship LSST survey. I am active in the Rubin Observatory's Dark Energy Science Collaboration, with main interests in enabling the analysis of large-scale structure probes and the synergies with Euclid.

The PAU Survey
The PAU Survey at the William Herschel Telescope at La Palma Observatory fills the niche between spectroscopic and imaging galaxy surveys by taking deep images in 40 narrow passbands. This provides low-resolution spectra for all objects in the field of view, which our survey team uses to explore the galaxy-dark matter connection and to help calibrate larger cosmology surveys.



... you were actually only after pretty pictures? Then look here:
Astronomy Picture of the Day
Hubble Space Telescope Album
The World at Night