Structure Formation

Analytical Models of Cosmic Accretion Shocks and the Role of Environment

After its formation through gravitational collapse, a cosmic structure coninues to accumulate matter from its surroundings. Cosmic accretion shocks are formed where the infalling, accelerated gas meets the gaseous content of the collapsed structures. Such shocks process the enormous amount of kinetic energy present in the accreting gas, and convert part of it to heat, and part of it to kinetic energy of relativistic particles, aka "cosmological cosmic rays". The properties of each shock depend on the properties of the accretor as well as the physical conditions in its immediate environment. We examined how environmental factors affect the properties of accretion shocks, and evaluated the physical impact of accretion shocks on their environment, i.e. the intergalactic gas.
Reference: Pavlidou, V., & Fields, B. D. 2006, ApJ, 642, 734
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The Double Distribution of Dark Matter Halos

How does the process of cosmic structure formation depend on the properties of the environment of forming structures? How does the state of the material surrounding and accreted by a collapsed object depend on the mass of the object and how does it evolve with time? To seek insight to such environment-related questions, we have developed a new analytical tool: a Double Distribution of the number density of cosmic structures with respect to both mass and local overdensity (or underdensity).
Reference: Pavlidou, V., & Fields, B. D. 2005, PhysRevD, 71, 043510
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Can strongly interacting dark matter interact with baryons too?

The "strongly interacting" variation of dark matter is allowed to interact with itself through the strong force. Such interactions are expected to change the details of the structure formation process, resulting in collapsed objects which are less "cuspy". But are strongy interacting dark matter particles also allowed to interact with baryons? To address this question, we have investigated the results of strong dark matter - baryon interactions on primordial nucleosynthesis and on gamma-ray emission from the Milky Way.
Reference:
Cyburt, R.H., Fields, B.D., Pavlidou, V. & Wandelt, B. 2002, PhysRevD, 65, 123503
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