key term - $M_{BH}- ext{sigma}$ Relation

Definition

The $M_{BH}- ext{sigma}$ relation is an empirical correlation between the mass of the supermassive black hole (M$_{BH}$) at the center of a galaxy and the velocity dispersion ($ ext{sigma}$) of the stars in the galaxy's bulge. This relationship suggests a fundamental connection between the growth and evolution of supermassive black holes and the properties of their host galaxies.

5 Must Know Facts For Your Next Test

1. The $M_{BH}- ext{sigma}$ relation suggests that the growth of supermassive black holes is closely linked to the formation and evolution of their host galaxy's bulge.
2. Galaxies with larger bulge velocity dispersions tend to have more massive central black holes, indicating a co-evolutionary process between the two components.
3. The $M_{BH}- ext{sigma}$ relation is observed to hold across a wide range of galaxy types, from elliptical galaxies to the bulges of spiral galaxies.
4. The tight correlation between $M_{BH}$ and $ ext{sigma}$ implies that the formation and growth of supermassive black holes are regulated by the same physical processes that govern the dynamics of the host galaxy's bulge.
5. The $M_{BH}- ext{sigma}$ relation is a crucial tool for estimating the masses of supermassive black holes in galaxies where direct measurements are not possible.

Review Questions

• Explain how the $M_{BH}- ext{sigma}$ relation suggests a co-evolutionary process between supermassive black holes and their host galaxy's bulge.
  • The $M_{BH}- ext{sigma}$ relation indicates that the mass of the supermassive black hole at the center of a galaxy is closely linked to the velocity dispersion of the stars in the galaxy's bulge. This tight correlation suggests that the growth and evolution of the supermassive black hole and the formation of the host galaxy's bulge are intimately connected. The physical processes that govern the dynamics of the bulge, such as the gravitational potential and mass distribution, also play a role in regulating the growth and accretion of the central black hole. This co-evolutionary process likely involves feedback mechanisms, where the black hole's activity can influence the properties of the surrounding galaxy, and vice versa.
• Describe how the $M_{BH}- ext{sigma}$ relation is used to estimate the masses of supermassive black holes in galaxies where direct measurements are not possible.
  • The $M_{BH}- ext{sigma}$ relation provides a way to estimate the mass of the supermassive black hole at the center of a galaxy based on the velocity dispersion of the stars in the galaxy's bulge. Since direct measurements of black hole masses are challenging and only possible for a limited number of nearby galaxies, the $M_{BH}- ext{sigma}$ relation serves as a valuable tool for inferring the masses of black holes in more distant galaxies. By measuring the velocity dispersion of the stars in the bulge, which can be done using spectroscopic observations, the $M_{BH}- ext{sigma}$ relation can be applied to estimate the mass of the central supermassive black hole. This indirect method of black hole mass estimation has been widely used to study the demographics and co-evolution of black holes and their host galaxies across cosmic time.
• Analyze how the $M_{BH}- ext{sigma}$ relation has contributed to our understanding of the connection between galaxy mergers, active galactic nuclei, and the growth of supermassive black holes.
  • The $M_{BH}- ext{sigma}$ relation has been instrumental in elucidating the link between galaxy mergers, the triggering of active galactic nuclei (AGN), and the growth of supermassive black holes. Galaxy mergers can lead to the rapid inflow of gas and dust towards the centers of the merging galaxies, fueling the accretion and growth of the central black holes. The $M_{BH}- ext{sigma}$ relation suggests that this growth of the black hole is coupled to the properties of the host galaxy's bulge, as the velocity dispersion of the bulge stars is a reflection of the overall gravitational potential and mass distribution. By studying the $M_{BH}- ext{sigma}$ relation in merger remnants and AGN host galaxies, researchers have gained valuable insights into how the co-evolution of black holes and their host galaxies is influenced by the transformative events of galaxy mergers and the associated black hole accretion and feedback processes.

Related terms

Supermassive Black Hole:

An extremely massive black hole, with masses ranging from millions to billions of times the mass of the Sun, typically found at the center of galaxies.

Galaxy Bulge: The spherical, high-density central region of a galaxy, composed primarily of older stars with random orbits.

Velocity Dispersion: The range of velocities of stars within a galaxy or a specific region of a galaxy, which is related to the gravitational potential and the mass distribution.