Cold accretion mode

Definition

Cold accretion mode refers to the process by which gas, particularly hydrogen, flows into a galaxy at low temperatures and in a relatively smooth and continuous manner. This mechanism plays a crucial role in the formation and growth of galaxies, as it allows for the accumulation of mass without the disruptive effects seen in hotter, turbulent flows. Understanding this process helps explain how galaxies acquire their gas and subsequently form stars over cosmic time.

5 Must Know Facts For Your Next Test

1. Cold accretion mode typically occurs in low-mass galaxies where gravitational forces allow for the smooth inflow of gas.
2. This mode is associated with the formation of disk galaxies, as the incoming gas can settle into a rotating disk and facilitate star formation.
3. Cold accretion contributes to the efficient build-up of molecular clouds, which are crucial for star formation in galaxies.
4. Observations indicate that cold accretion is prevalent in the early universe, during a time when galaxies were rapidly forming.
5. Models suggest that cold accretion can help explain the observed scaling relations between galaxy properties, such as stellar mass and metallicity.

Review Questions

• How does cold accretion mode differ from hot accretion mode in terms of its impact on galaxy formation?
  • Cold accretion mode involves gas inflow at low temperatures, allowing for a smooth accumulation of mass without turbulence. This contrasts with hot accretion mode, where gas inflow is high-energy and can create shock waves that disrupt star formation. Cold accretion leads to a more efficient build-up of gas in galaxies, promoting stable conditions for star formation and influencing their evolutionary path.
• What role does cold accretion play in the context of galaxy mergers and their subsequent evolution?
  • In galaxy mergers, cold accretion can supply additional gas to the merged system, enhancing star formation activity post-merger. The smooth inflow of gas from cold accretion can help to refuel the newly formed galaxy's star formation capabilities, allowing it to grow and evolve more rapidly. This interaction highlights how different modes of gas accretion work together to shape galaxies during dynamic events like mergers.
• Evaluate how understanding cold accretion mode influences our knowledge of the cosmic web's structure and galaxy evolution over time.
  • Understanding cold accretion mode provides insights into how gas flows within the cosmic web and influences galaxy formation across cosmic time. It reveals that low-temperature gas streams contribute significantly to the growth of galaxies, especially in the early universe when structures were still forming. This knowledge enhances our comprehension of the distribution of matter within the cosmic web and its effects on galaxy properties, helping to refine models of large-scale structure formation and evolution in the universe.

Related terms

Hot accretion mode: Hot accretion mode involves the inflow of hot gas into a galaxy, often associated with energetic processes like shock heating, which can hinder star formation.

Galaxy mergers: Galaxy mergers occur when two or more galaxies collide and combine, significantly affecting their structure, star formation rates, and overall evolution.

Cosmic web: The cosmic web is the large-scale structure of the universe, consisting of filaments of dark matter and gas that connect clusters and superclusters of galaxies.