Angular momentum of galaxy disks

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Discussion Overview

The discussion revolves around the angular momentum of galaxy disks, particularly in the context of their formation and the challenges posed by mergers. Participants explore various hypotheses and models related to the loss of angular momentum during the formation of galaxy disks, touching on theoretical frameworks and observational challenges.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants reference recent simulations that suggest the traditional model of dissipational collapse leads to excessive angular momentum loss in galaxy disks during mergers.
  • One participant argues that Modified Newtonian Dynamics (MOND) provides a compelling explanation for the observed angular momentum results.
  • Another participant mentions historical work by Peratt on plasma cosmology and Birkeland currents, questioning the follow-up on those simulations and their relevance to current discussions.
  • A participant notes that various approaches to disk formation exist, but none are fully satisfactory, emphasizing the complexity of galactic evolution and the limitations of observational data.
  • One participant discusses the "overcooling" problem identified in the original Navarro and White paper, suggesting that stellar winds and supernovae may play a crucial role in preventing excessive collapse and angular momentum loss, while questioning the implications for intergalactic medium metallicity.

Areas of Agreement / Disagreement

Participants express differing views on the mechanisms behind angular momentum loss and the effectiveness of various models. There is no consensus on a singular explanation or model, indicating ongoing debate and exploration of the topic.

Contextual Notes

Participants highlight limitations in current models, including the lack of consideration for stellar evolution in early simulations and the need for higher quality observational data to advance understanding of galaxy disk formation.

hellfire
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As you can read in http://pinot.phys.uvic.ca/~jfn/mywebpage/gxform.html, recent simulations show that the accepted model of dissipational collapse for the formation of galaxy disks, leads to an excessive loss of angular momentum in the disk when mergers are considered. What are the current hypothesis to solve this problem?
 
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This is one of the stronger arguments for MOND which naturally predicts the observed result.
 
I have no idea whether it's totally dead, or merely dormant, but Peratt (he of 'plasma cosmology' fame) made a big song and dance back in the (19)80s about Birkeland currents etc, and somehow managed to get humungeous amounts of (then) supercomputer time to do similations (of spiral galaxies?), leading to some (to me) handwaving about pattern similarity ... whether anyone followed up with more focussed (from my POV, of course) similations, I have no idea!
 
That result does not appear to have yet been published. Perhaps it is a work in progress. There are a number of different approaches to disk formation. None are entirely satisfactory. Galactic evolution is a very complicated field of study and observational data has not beem of the quality and quantity needed to crack the case. We are, however, making good strides. Anyways, here is a very recent paper addressing the issue of disk formation and angular momentum:

A Merger-Driven Scenario for Cosmological Disk Galaxy Formation
http://www.arxiv.org/abs/astro-ph/0503369
 
I took a look to the original paper of Navarro and White written in 1993 and the simulations were done without taking into account the stellar evolution, i.e. energy injection due to stellar winds and supernovae. They seam to call this problem „overcooling”: most of the baryonic matter should collapse into very dense cores. Stellar winds and supernovae could heat the gas avoiding this early and efficient collapse. The problem seams to be related to the fact that the efficiency of galaxy formation was actually low and that there are lots of baryons in the intergalactic medium. If stellar winds and supernovae were indeed the reasons to avoid overcooling and loss of angular momentum, then the IGM should have a considerable metalicity. Is this understanding correct?
 

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