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Michele Cappellari

Dr Michele Cappellari

Dr Michele Cappellari

Research Fellow

Interests and expertise (Subject groups)

Grants awarded

Benchmark for galaxy formation: modelling 10K galaxies in 3D

Scheme: University Research Fellowship

Organisation: University of Oxford

Dates: Oct 2015-Sep 2018

Value: £303,720.59

Summary: For millennia humanity has aspired at understanding our place and origins in the Universe. Less than a century ago, we discovered we live in a galaxy like millions of others populating the Universe. For this reason, today finding our origins means studying how galaxies came into existence. Observations of galaxies in the nearby and distant Universe, together with numerical simulations, which describe how galaxies assemble over time, have provided a scenario in which the Universe is dominated by a mysterious dark matter of unknown nature. In this picture, the primordial gas is attracted by the dominant dark matter and forms the stars, which constitute the galaxies we see in the sky. This model makes detailed prediction for a close connection between the shape and mass of galaxies and of the dark matter of which they are surrounded. Surprisingly there are few quantitative observations confirming the model predictions. And even the existence of dark matter is sometimes questioned. This situation arises by the fact that large amounts of observations are needed to measure dark matter in galaxies: one needs three-dimensional data, describing the motion of the gas and the stars as well as the chemical composition of the stars at every position in the galaxy. In the proposed project I will use the expertise gained during the previous years of my fellowship, in combination with data from the largest three-dimensional galaxy survey, to measure dark matter for 10,000 galaxies. This unique information will provide a quantitative benchmark for galaxy formation models for some years to come.

Tracing the cosmic growth of the total mass in galaxies

Scheme: University Research Fellowship

Organisation: University of Oxford

Dates: Oct 2010-Sep 2015

Value: £526,457.44

Summary: Since the beginning of history, humanity has constantly been intrigued with the question of our origin. This has led to a number of scenarios to describe our Universe and position in it. Less than a century ago it has been realized that the Universe is composed of billions of galaxies like the Milky Way, in which we live. For this reason, today, the quest of our origin involves an understanding of how galaxies form and evolve. There are two complementary approaches to study the formation of galaxies. One can observe nearby objects, which can be analysed in detail due to their vicinity, and contain the fossil record of billions of years of evolution. Or one can observe the distant galaxies whose light reaches us after billions of years of travel through space. For this reason we can see them as they were when the Universe was young and the galaxies were still forming. These two approaches, together with numerical simulations, have provided a scenario, in which the Universe is dominated by a mysterious dark matter (DM) and galaxies grow in mass, in a hierarchical fashion, by the co-addition of smaller pieces, under the influence of gravity. A fundamental limitation affects the comparisons with the predictions of the models, especially for galaxies at large distances, when the Universe was less than half of its current age. The problem is that, while the simulations directly predict the MASSES of the stars and DM in galaxies, the observations only provide the LUMINOSITY of the stars. The luminosity constitutes the tip of the iceberg of the underlying stellar and DM mass distribution associated to the galaxies. In this project I am measuring the evolution of the galaxy mass from a time in which the Universe was 1/4 of its current age, to the present day. These new mass measurements will be compared to the mass predictions of galaxy formation models to provide a stringent test of the current hierarchical galaxy formation paradigm.

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