5'4'2 Numerical models of population evolution

1
5.4.2 Numerical models of population evolution

• Skarma Kim

2
Beatrice Tinsley (1941-1981)

• World-famous astronomer who made major
  contributions to the field of cosmology.
• Evolution of Galaxies and its Significance for
  Cosmology
• Dr. Tinsleys profound and impressive research
  helped to develop our understanding the expansion
  of the universe among other things. Her work
  formed the basis for contemporary studies of
  galactic evolution.

3
Charlot, Worthey Bressan (1996)

• Charlot et al. give a clear insight into the
  strengths and limitations of model populations
  through detailed comparison of results obtained
  with three independent modeling codes.

4

• The population becomes steadily redder, the
  colors change fairly slowly after 5Gyr.

5
(No Transcript)
6
Schweizer Seitzer (1992)

• Fig 5.21 suggests that age differences do
  contribute significantly to the spread in galaxy
  colors by showing a two-color distribution 34
  elliptical galaxies.

7
See Fig 5.21 (p.320)
8
Good spectrum Vs. broad-band color

• Consider first galaxies with measurable emission
  lines.
• The rate at which the stars of a disk galaxy emit
  ionizing photons can be determined from the
  strength I of the Ha emission line at 657nm in
  the galaxys spectrum.

9
Kennicutt, Tamblyn Congdon (1994)
10
Absorption-line spectrum

• In practice integrated galaxy spectra never have
  high spectral resolution because the random
  velocities of stars within the population give
  rise to significant spectral broadening that
  washes out all narrow spectral features.
• The first step in an analysis of an integrated
  spectrum is to determine from it the values of up
  to a dozen such spectral indices.

11
Casuo et al. (1996)

• The dependence of one of the most widely studied
  spectral indices, Mg2, upon Z and the age t of a
  coeval stellar population.