4.4-4.5 Rotation of Elliptical Galaxies and AGN Flashcards
What supports elliptical galaxies, and how was this proven?
Turbulence
- Very little rotation (bulk rotation) was observed
- A big velocity dispersion was observed
What can be concluded about stellar orbits in ellipticals?
They have relaxed and energy is redistributed among all stars in the galaxy
Describe the similarities with star motion and gas theory
Stars = particles in an ideal gas moving in random directions
- Bell distribution on an intensity wavelength curve as few stars are moving towards or away from us and we can measure a gaussian profile of velocity along the los
When using the Doppler formula with the Maxwell-Boltzmann distribution, what does the FWHM depend on?
We get a Gaussian distribution for the intensity, and FWHM depends on the temperature and mass
What can be deduced that the FWHM for the Dopper Maxwell distribution depends on T and m?
Temperature represents the energy carried by the moving mass
Mass dependece suggests that different species should show different broadening, and this is observed
What does the Faber Jackson relationship show?
Luminosity is proportional to velocity dispersion^4
What is the similarity and difference between the Tully Fischer relation?
They have the luminosity proportional to the fourth power of the velocity, and the velocity dispersion
TF: Spirals
FJ: Ellipticals
What is the Virial Theorem?
2K + U = 0 for a closed system in equilibrium
What does the fundamental plane do for observations for the FJ relationship?
It maximises the correlation between the three observable quantites
- Surface brightness, Radius and velocity dispersion
What are Seyfert galaxies?
Ones which have a very bright nucleus
What causes the emission lines observed in optical spectra of nuclei?
The recombination of gas
What causes broadening in the optical spectra of nuclei?
The hgih velocity of the gas molecules from the galaxy rotation
What are active galactic nuclei?
A compact region at the centre of a galaxy that has a much higher than normal luminosity
What are radio loud galaxies?
Galaxies with strong emission at radio frequencies
- Can get dual lobe emission from the nucleus in the form of collimated jets
What are quasars?
Quasi stellar radio sources
- Point sources at high redshift, with a nucleus that outshines the host galaxy
