Hot Accretion Mode

Definition

Hot accretion mode refers to a process during galaxy formation where hot gas, heated to millions of degrees, falls into the gravitational potential well of a forming galaxy. This mode is characterized by the rapid inflow of gas that creates a hot halo around the galaxy, which can significantly affect star formation rates and the overall evolution of the galaxy. It plays a crucial role in how galaxies acquire their mass and energy during the early stages of their development.

5 Must Know Facts For Your Next Test

1. Hot accretion mode typically occurs in more massive galaxies and is linked to the hot gas halo surrounding them, which can have temperatures exceeding $10^6$ K.
2. In this mode, the high temperature of the infalling gas prevents it from cooling quickly enough to form stars efficiently, leading to lower star formation rates compared to cold accretion.
3. Hot accretion can contribute to the growth of supermassive black holes at the centers of galaxies as the hot gas becomes increasingly dense under gravitational influence.
4. Galaxies experiencing hot accretion often display a characteristic 'red-and-dead' color, indicating older stellar populations due to suppressed star formation.
5. The transition between hot and cold accretion modes can influence the morphology of galaxies and their eventual classification as elliptical or spiral.

Review Questions

• How does hot accretion mode influence star formation in early galaxy development?
  • Hot accretion mode influences star formation by introducing high-temperature gas that prevents rapid cooling. This means that while gas is falling into the galaxy's potential well, it remains too hot to condense into stars effectively. As a result, galaxies in this phase tend to have suppressed star formation rates compared to those dominated by cold accretion mode.
• What role does hot accretion mode play in the evolution of supermassive black holes in galaxies?
  • In hot accretion mode, the inflow of dense hot gas can contribute significantly to the growth of supermassive black holes. As gas accumulates and becomes increasingly concentrated under gravitational forces, it can feed into black holes at the centers of galaxies. This process not only helps in black hole growth but also influences the dynamics and feedback processes within the host galaxy.
• Evaluate how the transition between hot and cold accretion modes affects galaxy morphology and evolution.
  • The transition between hot and cold accretion modes plays a critical role in determining galaxy morphology and evolution. Galaxies in hot accretion mode tend to develop into more massive ellipticals with older stellar populations due to lower star formation rates. In contrast, those experiencing cold accretion tend to evolve into spiral galaxies with ongoing star formation. This shift can lead to varying structures, colors, and dynamics within galaxies, ultimately shaping their long-term development.

Related terms

Cold Accretion Mode: A process where cool gas, rather than hot gas, falls into galaxies at lower temperatures, often leading to higher star formation rates and different evolutionary paths compared to hot accretion.

Baryonic Matter: The normal matter composed of protons, neutrons, and electrons that makes up stars, planets, and galaxies, crucial for understanding the dynamics of accretion processes.

Feedback Mechanisms: Processes by which energy from star formation or supernovae affects the surrounding interstellar medium and can regulate star formation in galaxies.