The effect of baryons on the large-scale structure of the Universe

Supervisor: Oliver Hahn

Contact information: oliver.hahn@univie.ac.at 

Co-supervisor: Prof. Dr. Raul Angulo (DIPC Spain)

Expected duration: 9 months

Project description & Goals:

A key question in studies of the large-scale structure of our Universe as a cosmological probe is the role of baryons. While dark matter is dominant in the cosmic energy budget, the effect of baryons cannot be neglected [1]. Precision studies of cosmic structure therefore require a detailed understanding of the differences in the cosmic distribution of baryons and dark matter, even on large scales. In recent work [2], we found that the distribution of baryons, as quantified by the power spectrum, in simulations without subgrid models for star and black hole formation and feedback is already in rough agreement with recent state-of-the-art simulations. The physical implication of this observation is that astrophysical processes roughly balance radiative cooling at first order. This opens the possibility for new effective fluid models for baryons by determining the effective thermal evolution of the cosmic gas distribution. Such an effective EOS model is theoretically much more tractable than full galaxy formation physics and thus has the potential for significant impact. 

Working plan & Milestones (including final thesis):

  1. Literature study as an introduction to the topic
  2. Analysis of existing “two-fluid” dark matter+baryon simulations, and running of similar simulations covering different scales.
  3. Analysis of state-of-the-art large-scale galaxy formation simulations using the same methodology as for #2.
  4. Detailed study of “galaxy formation thermodynamics” and development of effective models using simple fits and more advanced machine learning.
  5. Evaluate the performance of “two-fluid” simulations based on the effective EOS model with galaxy formation simulations and effective models (e.g. [3] and [4])
  6. Write thesis (and, depending on the progress, a short paper on the result)

Requirements / special skills: 1) Should have followed lectures on cosmology and/or cosmic large-scale structure, 2) Advanced (Python) programming skills are a bonus 

References:

 

 

[1] https://arxiv.org/abs/1301.7426

[2] https://arxiv.org/abs/2008.09124

[3] https://arxiv.org/abs/1510.06034

[4] https://arxiv.org/abs/2011.15018

https://arxiv.org/abs/2011.15018