Problem set for Unit 6.
A galaxy is described as: smooth, featureless, no cold gas detected, uniformly old red stellar population, roughly spherical. Classify its likely Hubble type and justify your answer using the physical connections from Lecture 11.
The M-sigma relation is approximately M_BH ∝ σ^4. If galaxy A's bulge stellar velocity dispersion σ is twice galaxy B's, compute the ratio of their predicted black hole masses, M_BH,A / M_BH,B.
A quasar varies significantly in brightness over a timescale of 1 day. Using the light-travel-time argument (a source cannot vary coherently on a timescale shorter than the light-crossing time of its emitting region), estimate the maximum size of the emitting region in light-days, and convert this to AU (1 light-day ≈ 173 AU). Compare this size to the solar system's scale.
OpenStax Astronomy 2e (local reference copy: references/openstax-astronomy-2e-extracted.txt), Chapter 27, Review Questions (the unified model of active galactic nuclei): in 150-250 words, explain how viewing angle and accretion rate in the unified AGN model can account for the observational diversity of Seyfert galaxies, quasars, and radio galaxies.
Submit a clear solution with equations, units, labeled quantities, and a short narrative interpretation for each problem. Show every step; a correct final number without visible work receives partial credit at most.
OpenStax Astronomy 2e (local reference copy: references/openstax-astronomy-2e-extracted.txt), Chapter 26.1-26.3 (galaxy types/properties) and Chapter 27.1-27.4 (active galaxies).
materials/ASTR230/data/ where referenced above.