Gravitational Instabilities and Galaxy Evolution

• 23 Sep 2023

For Prelims: Gravitational Instabilities and Galaxy Evolution, Indian Institute of Astrophysics (IIA), Gravitational Instabilities, Spitzer Photometry and Accurate Rotation Curves (SPARC).

For Mains: Gravitational Instabilities and Galaxy Evolution.

Source: TH

Why in News?

Recently, a study has been conducted by the Indian Institute of Astrophysics (IIA), aiming to comprehend the relationship between Gravitational Instabilities and Galaxy Evolution.

Note:

• Gravitational Instabilities refer to a fundamental physical phenomenon that occurs in astrophysical systems, particularly in celestial bodies like galaxies, stars, and planetary systems.
• These instabilities are driven by the force of gravity and play a crucial role in shaping the structure, evolution, and dynamics of these cosmic entities.

What is the Methodology of the Study?

• Researchers compared star formation rates, gas fractions, and time scales for gravitational instability growth in nearby galaxies by analysing the stability levels of a sample of 175 galaxies from the Spitzer Photometry and Accurate Rotation Curves (SPARC) database.
• The study investigated how stability levels in galaxies are regulated, including the potential role of dark matter. It sought to determine whether stars and gas can self-regulate stability levels.
• They compared stability levels in nearby galaxies with those observed at high redshifts, which are considered precursors to galaxies in the local universe.

Redshift:

• Scientists measure cosmic distances via redshift, the extent to which light is shifted towards the red (lower energy) part of the electromagnetic spectrum during its long journey across the universe.
  • The greater the distance, the higher the redshift.

What are the Key Highlights of the Study?

• Spiral Galaxies:
  • Spiral galaxies, such as the Milky Way, exhibited specific characteristics.
    • They had a higher median star formation rate, lower stability, reduced gas fraction, and a smaller time scale for the growth of gravitational instabilities.
• Conversion of Gas to Stars:
  • In spiral galaxies with lower stability, gravitational instabilities efficiently convert a significant amount of gas into stars.
    • This process led to the depletion of gas reservoirs in these galaxies.
• Star Formation Mechanism:
  • The galaxies with marginal stability levels undergo intense star formation activity for a short time scale, depleting gas reserves.
  • In contrast, highly stable galaxies exhibit slower and gradual star formation processes over longer time scales, converting available gas into stars.
• Future & Significance:
  • There is a need for future investigations into the impact of gravitational instabilities on the morphological evolution of galaxies across different redshifts.
  • These insights are crucial for understanding fundamental processes in galaxy formation and evolution.