Ch 11 - Structure of the Universe

18 - Structure of the UniverseExtragalactic Distance ScaleCepheids MV=-3.35log-2.13+2.13(B-V) =period (days)Novae MV(max)=-9.96-2.31log(m/day)first 2 magsPlanetary Nebulae Luminosity Function M5007(brightest)=-4.48Globular Cluster Luminosity Function MB(turnover)=-6.5Tully-Fisher MH=-10.01log(2vr /sin i)+3.61D- logD=1.333log + C (for relative distances)Brightest Red Supergiants MV=-8.0SN Ia MB(max)=-19.6 (but correct for decline time and redshift)Brightest Galaxy in Cluster MV=-22.82Surface Brightness FluctuationsCepheid Distance ScaleLs for PL relation from Cluster Fitting and a few (~6?) measured parallaxes1997 (Feast & Catchpole) - Hipparcos parallaxes for 223 Cepheids, of which 26 carry a lot of weight (accurate s and spread in P)PLC relation due to width of instability strip (Sandage)Dependent on metallicityAffected by extinction (in near-IR brightnesses are less, too).Blending light with nearby starsDifferent methods give different results

Globular Cluster Luminosity Function

Planetary Nebula Luminosity Function

Tully-Fisher Relation (in near-IR)

D- Relation(recently brightness- D- =fundamental plane)

Brightest Galaxy in Cluster

Supernovae Ias

Correcting for stretch and time dilation35 SN Ias1-day averagesOriginal DataCorrected for Time Dilation (redshift z) Corrected for Stretch

Slipher (1914-1925) - Radial Velocities of Galaxies Most (nearby) galaxies exhibit spectral shift to longer wavelengths - redshifts

UniversalExpansion

Note: data originally published in 1929 PNAS, not 1936!1929 - Hubble enters the pictureThe Hubble Law

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:actually first introduced by Lamaitre in 1927NOTE Implications:This sort of law would be derived by any observer in the universe - everyone sees the same law. Everything is (overall) moving away from everything else at the same rate per unit distance.Universe is expanding - space is expanding, carrying the matter with it.The universe need not have a center for this to be true.The age of a universe with no acceleration/deceleration is simply 1/H0.If universal, such a law allows one to determine the distance of an object from its value of z.

Hubble & Humason 1931 extend Hubble Law to larger distancesH0 from SN Ias

WMAP gives H0=71Large-Scale Structure(on many scales)Groups (N50% of all baryonic matter.Accounts for a fraction of the dark matter. The rest is non-baryonic.

Red: radio synchrotron

Blue: X-rays

Local SuperclusterEven LARGER Scale Structure

CfA - single slice

CfA hockey puckGreat Wall

Local Supercluster

Pisces-Perseus supercluster

Density fluctuations & Non-Hubble Flow

Origin of Structure - Cold Dark Matter

Lensing & Dark Matter

Red: X-ray emitting gasBlue: Lensing materialHUDF - Beckwith et al. (Nov. 2006 AJ 132, 1729-1755)

Galaxy EvolutionFilters