# hw3 - 1 Also ±nd the uncertainty in this M/L Compare your...

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Ph 444 Problem Set 3 Due: Friday, October 1, 2010 1. Calculate the critical mass density and its uncertainty using the current best estimate of the Hubble constant, H 0 = 70 . 6 ± 1 . 8 km s 1 Mpc 1 . 2. The Millennium Galaxy Catalog yields a local luminosity density in galaxies of j = ((1 . 986 ± 0 . 031) × 10 8 L Mpc 3 ) p H 0 100 km s 1 Mpc 1 P . The dependence on H 0 comes from the use of the Hubble law to calculate distances to galaxies. Calculate the average mass-to-light ratio ( M/L ) in solar units for galaxies that would be required if galaxies produced the critical mass calculated in problem
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Unformatted text preview: 1. Also ±nd the uncertainty in this M/L . Compare your value with the value of M/L ≃ 2 M ⊙ /L ⊙ expected for a “normal” stellar population. 3. Ryden problem 4.4 4. Ryden problem 4.5 Hint: to calculate the pressure you can either start with Ryden equation (4.32) or use the expression for the pressure of a gas of non-interacting particles with number density n , momentum p , and speed v : P = npv/ 3....
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