Selection of Homework Questions
Topic 14 : Galaxy Nuclei & Black Holes
(1) Deriving M/L(r) in Galaxy Nuclei :
Key observations which help ascertain the presence of a black
hole in galactic nuclei are the radial dependences of mean rotation, < Vrot >, velocity
dispersion, and surface brightness, µ.
- How can one use these measurements to estimate M/L(r). Include both observational and theoretical details.
- What values and form for M/L(r) would suggest the presence of a black hole.
- How might your approach differ for
- a kinematically cold stellar disk;
- a low luminosity elliptical or bulge;
- a high luminosity elliptical;
- a high luminosity elliptical with small gas disk.
- Why does Vrot(r) provide a less ambiguous constraint on M/L than (r)?
(2) Black Hole Influence :
Over time, a nuclear black hole and a galaxy nucleus can influence one-another:
- How can the presence of a central black hole effect the distribution of stars in a galactic nucleus?
- What factors affect the black hole consumption rate both of stars and, separately, gas.
- When a black hole ingests a star, what determines whether this meal is visible or invisible to us?
(3) Black Holes Demographics :
Although only ~1% of local galaxies are classified as Seyferts (ie classically active), observations of near-nuclear star and gas dynamics suggests that most galaxies harbor nuclear black holes.
- Prior to these direct observations, what other lines of evidence already suggested that most galaxy nuclei might harbor nuclear black holes?
- On what other properties of the galaxy does the black hole mass seem to depend, and how might such dependencies have arisen?