AST 346 Lecture 4: Lecture 3 (II)

• School: Stony Brook University
• Department: Astronomy
• Course: AST 346
• Professor: Kenneth Lanzetta

Document Summary

Hubble constant and hubble time: hubble constant: h0 = 100 h km/s/mpc, hubble time: th = 1, for h = 0. 71: th = 14. 1 gyr. Einstein-de sitter universe: consider the friedmann equations in a universe containing only pressureless matter, then: H 2 with k = 0 (cid:18) (cid:19)2. 1: this de nes the critical density : c = 3h 2. Density parameter: the dimensionless density parameter expresses cosmological density in units of the critical density: . C: in terms of the density parameter, the rst friedmann equation is, the density parameter is related to the spatial curvature of the universe. Luminosity distance: consider a source of radial coordinate r and redshift z observed at time t0, relationship between bolometric energy ux f and bolometric luminosity l. L (1+z)24 r2r2(t0: compare with relationship between bolometric energy ux f and bolometric luminos- ity l in euclidean geometry for a source of distance d.