E+a galaxies

Definition

e+a galaxies, or 'post-starburst' galaxies, are a category of galaxies that exhibit both early-type galaxy characteristics and a recent burst of star formation. These galaxies show features typical of elliptical galaxies, like smooth, featureless light profiles, alongside spectral signatures indicating a burst of star formation that has occurred relatively recently, often within the last 1 billion years. This unique combination makes them key to understanding galaxy evolution and the star formation processes occurring in different environments.

5 Must Know Facts For Your Next Test

1. e+a galaxies have a spectral signature that indicates a recent episode of star formation, while their morphology resembles that of older elliptical galaxies.
2. They are thought to represent a transitional phase in galaxy evolution, bridging the gap between active star-forming galaxies and quiescent elliptical galaxies.
3. The presence of e+a galaxies suggests that significant interactions or mergers may have triggered their recent starbursts, altering their evolutionary paths.
4. e+a galaxies are often identified in surveys of galaxy clusters, where interactions among members can enhance star formation activity.
5. Studying e+a galaxies helps astronomers understand the mechanisms behind star formation quenching and the role of environment in galaxy evolution.

Review Questions

• How do e+a galaxies differ from traditional elliptical and spiral galaxies in terms of their formation history?
  • e+a galaxies differ from traditional elliptical and spiral galaxies because they exhibit characteristics of both types. While they have the smooth, featureless appearance typical of elliptical galaxies, their recent burst of star formation indicates an active past similar to spiral galaxies. This suggests that e+a galaxies have undergone significant transformations in their history, often due to interactions or mergers that triggered this renewed activity.
• Discuss the significance of the spectral features observed in e+a galaxies and what they reveal about their evolutionary status.
  • The spectral features observed in e+a galaxies are crucial for understanding their evolutionary status. These features indicate a mix of old stellar populations typical of elliptical galaxies and younger stars resulting from recent bursts of star formation. By analyzing these spectra, astronomers can deduce when the starburst occurred and how it influences the galaxy's overall structure and future evolution. This duality makes e+a galaxies essential for studying how different environmental factors can affect a galaxy's life cycle.
• Evaluate the role that interactions and mergers play in the formation of e+a galaxies and their implications for our understanding of galaxy evolution.
  • Interactions and mergers play a pivotal role in the formation of e+a galaxies by triggering bursts of star formation that alter their evolutionary trajectory. These events can compress gas within a galaxy, leading to enhanced star production before eventually transitioning into a more quiescent state resembling that of traditional ellipticals. Understanding these processes is essential for evaluating broader theories about galaxy evolution since they highlight the influence of environmental factors on star formation rates and galactic morphology over cosmic time.

Related terms

Starburst Galaxy: A galaxy experiencing an exceptionally high rate of star formation compared to its typical levels, often triggered by interactions or mergers with other galaxies.

Spectral Classification: A method used in astronomy to categorize stars and galaxies based on their spectra, revealing information about their temperature, composition, and velocity.

Galaxy Evolution: The study of how galaxies change over time, including their formation, growth, interactions, and the processes that lead to different types of galaxies.