Stars in elliptical galaxies move like the bulge or halo stars in spiral galaxies.
a. Why can’t the rotation curve method to determine mass be used for elliptical galaxies?
b. Masses of elliptical galaxies are often derived from their velocity dispersions. This part illustrates how a velocity dispersion can be determined: The intrinsic line-width of a K giant star might be 0.5 Å at a central wavelength λ0 = 5000 Å. Suppose an elliptical galaxy is observed which has a line width of ∆λ = 3 Å. Assume that the increase is wholly due to broadening by random velocities of the constituent stars, and calculate v using the Doppler formula.
Stars in elliptical galaxies move like the bulge or halo stars in spiral galaxies. a. Why...
3. Tremaine et al. (2002) have shown that supermassive black holes in the nuclei of galaxies follow a relation between black hole mass, MB, and the velocity dispersion of the host galaxy bulge component, σ, such that log,o MBH8.0+40logo 200km/ The gravitational radius, Ra. (in a sense the "sphere of influence") of a black hole can be defined by the distance from the center at which the orbital speed of a star due to the black hole alone (i.e. neglecting...