Non-gravitational heating mechanisms in cosmological simulations of galaxy cluster formation

Lead Research Organisation: University of Cambridge
Department Name: Institute of Astronomy

Abstract

The study of the formation and growth of cosmic structures is one of the most fascinating and challenging fields of astrophysics. Galaxy clusters, the largest objects in the Universe, represent ideal laboratories to study which physical processes are important in shaping the Universe as we see it today. From the study of galaxy clusters one can infer the properties of a number of astrophysical objects and gain knowledge about their mutual interplay. However, it is necessary to consider a vast range of scales, starting from the sphere of influence of very tiny, but very powerful objects - the active black holes, up to the size of galaxy clusters, which harbor these massive black holes, and that are a million times bigger. Numerical simulations are able to track accurately the physical processes acting on this wide range of scales, and thus provide a very powerful tool to understand why galaxy cluster properties are as observed with the new generation of X-ray and optical telescopes. With the increasing power of cosmological simulations, it is possible now for the first time to include faithfully the crucial physical processes, such as the feedback from the active black holes, to obtain a more realistic picture of the cosmic structure formation. However, so far many important aspects of black hole growth and activity have not been explored directly in numerical simulations of structure formation. Therefore, it would be extremely exciting to try to incorporate the complex physics of black hole activity in the numerical schemes. This would allow to explore the Universe at very early times, when the first massive black holes were shining as powerful quasars. Moreover, with these sophisticated numerical models the properties of the present day population of galaxies, whose evolution has been modified by the central black hole activity, could be understood in more depth. Furthermore, a detailed comparison of the numerical simulations with the plethora of new observational data, could give insights which physical processes at certain cosmological epochs are responsible for the evolution of cosmic structures.

Publications

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Di Matteo Tiziana (2008) Direct cosmological simulations of the growth of black holes and galaxies in ASTROPHYSICAL JOURNAL

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Mead J (2010) The impact of AGN feedback and baryonic cooling on galaxy clusters as gravitational lenses in Monthly Notices of the Royal Astronomical Society

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Puchwein E (2010) Intracluster stars in simulations with active galactic nucleus feedback in Monthly Notices of the Royal Astronomical Society

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Sijacki D (2008) Simulations of cosmic-ray feedback by active galactic nuclei in galaxy clusters in Monthly Notices of the Royal Astronomical Society

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Sijacki D (2009) Growing the first bright quasars in cosmological simulations of structure formation in Monthly Notices of the Royal Astronomical Society

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Sijacki D (2011) Gravitational recoils of supermassive black holes in hydrodynamical simulations of gas-rich galaxies in Monthly Notices of the Royal Astronomical Society

 
Description Galaxy clusters, the largest objects in the Universe, represent ideal laboratories to study which physical processes are important in shaping the Universe as we see it today. From the study of galaxy clusters one can infer the properties of a number of astrophysical objects and gain knowledge about their mutual interplay. However, it is
necessary to consider a vast range of scales, starting from the sphere of influence of very tiny, but very powerful objects - the active black holes, up to the size of galaxy clusters, which harbour these massive black holes, and that are a million times bigger. Numerical simulations are able to track accurately the physical processes acting on this wide range of scales, and thus provide a very powerful tool to understand why galaxy cluster properties are as observed with the new generation of X-ray and optical telescopes. Through the research funded by this grant I have shown for the first time how in realistic cosmological environment the first massive black hole are formed. This has been one of the long standing puzzles of astronomy since we observe very distant quasars which are powered by supermassive black holes with more than a billion Solar masses. Previously it has been believed that possibly there is no sufficient time to grow such supermassive black holes so quickly but my research showed that these objects can form in very special cosmic environments. Also I have explored the impact of supermassive black holes in galaxy groups and clusters, showing that they can significantly alter the properties of their hosts, and I made predictions for optical, X-ray, SZ and gravitational lensing observations. This study demonstrated that there are significant uncertainties in using galaxy clusters as high precision cosmological probes that need to be first understood and calibrated before we can extract high fidelity cosmological parameters from these objects.
Exploitation Route My findings can be used in public outreach and educational purposes. Having a direct interaction between the general public and a researcher greatly helps understanding not only what we are studying in our field but helps public and students form more accurate, comprehensive and informed views of science. Moreover I have found many times over (through public talks etc.) that my research is inspirational and stimulates public (including children and students) to be more involved in science which has very good benefits for the education.
Sectors Education

 
Description My findings have impact on education, general scientific awareness and creative output.
First Year Of Impact 2007
Sector Education
Impact Types Cultural

 
Description Cambridge Science Festival, Open Afternoon Day at the IoA 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact During this event I had the chance to explain to the visitors with a wide range of scientific background what is the research topic I am pursuing, and to highlight its importance. I have also discussed astrophysical questions on different topics, explained physical processes at the base of specific astrophysical phenomena, and helped children to construct and paint planet models to take home.

The activity contributed to the success of the Cambridge Science Festival and to the promotion of the science performed at the IoA, Cambridge.
Year(s) Of Engagement Activity 2009
 
Description Public Open Evening Talk Series at the IoA 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact The total number of audience has been estimated at 190, and it was an extremely positive experience with a long session of questions at the end of the presentation.

My presentation contributed to the success of the Public Open Evening Talk Series at the IoA
Year(s) Of Engagement Activity 2009