18 - Structure of the Universe. Extragalactic Distance Scale. Cepheids M V =-3.35logΠ-2.13+2.13(B-V) Π=period (days) Novae M V (max)=-9.96-2.31log(Δm/day) first 2 mags Planetary Nebulae Luminosity Function M 5007 (brightest)=-4.48
35 SN Ia’s
Correcting for stretch and time dilation
Corrected for Time Dilation (redshift z)
Corrected for Stretch
Slipher (1914-1925) - Radial Velocities of GalaxiesMost (“nearby”) galaxies exhibit spectral shift to longer wavelengths - “redshifts”
Note: data originally published in 1929 PNAS, not 1936!
actually first introduced by Lamaitre in 1927
These are valid only for small z.
For larger z, need to use true relativitstic formulation:
This gives the Hubble Law (for space with flat geometry - which it seems to be) as:
WMAP gives H0=71
“regular” - spherical & centrally condensed (Coma)
“irregular” - not (Virgo)
VLA & Merlin (radio)
1933 - Fritz Zwicky uses the virial theorem to deduce the existence of “dunkle Materie” (dark matter) in the Coma cluster.
Helvetica Physica Acta, 6, 110 (1933)
Considers the possibility there may be “internebular matter” that is giving mass estimates of clusters of galaxies too high a value. Considers independent methods to get masses of individual galaxies...
“Method iv involves the observation of gravitational lens effects. Measurements of deflecting angles combined with data on the absolute distance of the “lens nebula” from the observer suffice to determine the mass of the lens nebula. The chances for the successful application of this method grow rapidly with the size of the available telescopes.” - Zwicky, ApJ, 86, 217 (1937).
X-ray emission from Perseus Cluster. Probably >50% of all baryonic matter.
Accounts for a fraction of the “dark matter”. The rest is “non-baryonic”.
Abell 1795 “cooling flow”
CfA - single slice
CfA “hockey puck”