What is the composition of a galactic halo?
A galactic halo is composed of dark matter, old stars, globular clusters, and hot gas. Dark matter constitutes the majority of the mass, while the stellar component includes old, metal-poor stars. The gas is hot and diffuse, often extending further than the visible components.
How is a galactic halo detected?
A galactic halo is detected through the observation of its constituent stars, globular clusters, and dark matter via their gravitational effects on galactic rotation curves, the motion of stars, and through techniques like gravitational lensing and studying the distribution of surrounding gas and dust.
What role does dark matter play in a galactic halo?
Dark matter constitutes the majority of mass in a galactic halo, providing the gravitational framework necessary for galaxy formation and stability. It affects the rotation curves of galaxies, ensuring that stars and gas in outer regions rotate at high speeds, which cannot be explained by visible matter alone.
What is the function of a galactic halo in galaxy formation?
A galactic halo provides gravitational stability and influences the dynamics of galaxies. It hosts dark matter and older stars, impacting galaxy rotation and protecting against stripping by intergalactic interactions. Halos also play a role in accruing gas, which can fuel star formation in the galaxy.
How do galactic halos affect the rotation curves of galaxies?
Galactic halos, primarily composed of dark matter, influence the rotation curves of galaxies by maintaining high rotational velocities at large radii. This discrepancy from Keplerian decline is due to the gravitational influence of the extended halo mass, which counters orbital decay and suggests the presence of unseen mass beyond the visible galactic disk.