The Observable Universe: Redshift, Distances and the Hubble-Law Max Camenzind Bremen @ Sept 2010
Key Facts Universe 1. The Universe is expanding and presently even accelerating. Hubble Expansion: Space is stretched This implies some beginning 2. Relic Radiation: CMBR, WMAP, 3. Matter distribution is clumpy 4. Matter is dominated by Dark Matter (DM). Only a Relativistic Cosmos can explain all these facts.
1. The Universe is Expanding Until 1929, the Universe of galaxies was thought to be static. In 1929, Edwin Hubble published the first distance redshift correlation, based on Cepheid distances for the galaxies. The Universe of galaxies is expanding: c*z = H0*d : [H0] = km/s/mpc
Hubble Expansion Expansion of Space
Variable Stars - Cepheids Some stars show intrinsic magnitude variations, not due to ecclipses in binary systems. Important Example: δ Cephei Lightcurve of δ Cephei
Henrietta Leavitt (1868-1921) discovered Cepheids Period-Luminosity (PL) Relation (1912) Lightcurve of Cepheids Large & Small Magellanic Clouds Period versus Magnitude of Cepheids in SMC
Cepheids as Distance Indicator
The Period (Duration) of Pulsation correlates with the Luminosity 1. Measure Period 2. Determine Luminosity 1. Measure apparent magnitude 2. Distance! The Luminosity of the observed Star ~1500L
1923 - Hubble measures the Distance to M 31 via Cepheids Hubble discovers Cepheids in M 31 Debate solved! 100-inch Hooker Telescope, Mt. Wilson Edwin Hubble
The Universe Expands Until 1929, the Universe has been considered to be static (Newton, Einstein). 1929: Edwin Hubble published first Redshifts of Galaxies RedshiftCorrelation, on the basis of Cepheid Distances: z = (λb λg)/λg The Universe of Galaxies expands V=c z = H d : [H ] = km/s/mpc
Galaxy Spectra have characteristic Absorption lines ~ Stars
Spectrum Galaxy depends on age
z = 4,58 Since 1963: Quasars have characteristic Emission Line Spectra z = 4,96
Hubble 1929
Hubble Correlation??
Hubble Extension
tomorrow The Universe expands (Hubble 1929) today yesterday Big Bang
Woody Allen If the Universe expands - why can I not find a parking lot? Answer:??? Source: Web, http://www.monerohernandez.com/galeria/woodyallen.html
Ad History of H0
The 2nd Great Debate
Hubble Key Project (2001) H0 = 72 +/- 8
Solution Hubble KeyProject 2003 All Data
Meaning of the Hubble Constant 1. H0 determines the Scale of the Universe: RH = c/h0 = 4200 Mpc : Hubble-Radius observable Universe is therefore limited. 2. H0 determines the age of the Universe: th = 1/H0 = 14 Billion years: Hubble-Age, effective age depends on density. Important: The Hubble-age is only a measure for the true age of the Universe! This age depends on many other Parameters (see LCDM model)!
The Cosmic Distance Ladder Parallax: ~500 pc (Hipparcos), 100 kpc (GAIA) Spectroscopic Parallax (via Distance module): 10 kpc RR Lyrae Stars: ~100 kpc Cepheids (104 LS): ~ 30 Mpc Typ 1a Supernovae (109 LS): 10,000 Mpc GAIA
Distances for Galaxies Geometrical Distances (mostly impossible). Standard-Candles: d² = L / 4π f (i) RR-Lyrae Stars (~ 0,5 Solar mass), Riesensterne der Spektralklasse A, F, Pulsationsveränderliche (h Bereich) (ii) Delta Cephei Stars ( < 20 Mpc) (iii) brightest stars (not well defined) (iv) Central stars in Planetary nebulae (v) Supernovae of Typ Ia ( z < 2 )
SN Ia as Standard Candles SNe become as bright as the centers Of galaxies. SN 1994D CO White Dwarf at Chandrasekhar limit
Types of Supernovae in Astronomy
Typical SN Ia Maximal Brightnes LightcurvesWidth (Stretching)
Accretion onto WD SN Ia Red giant White Dwarf White dwarf accretes H of the Red Giant H fusion He Form a Helium shell Mass can accumulate Chandrasekhar limit [ What is the Chandrasekhar limit? ]
SN Ia as Standard Candle The brighter the Slower
Lightcurves of SN Ia 10 Billion el Absolute Magnitude: ~ -19,5 mag e Radioactive Decay of 56 Ni 9 days Similarity Ni 56 56 Co Fe delays cooling 56 112 days 56 Fe + e+ Standard Candle
SNe Ia Calibration SN Galaxy 1937C IC 4182 1960F NGC 4496A 1972E NGC 5253 1974G NGC 4414 1981B NGC 4536 1989B NGC 3627 1990N NGC 4639 1998bu NGC 3368 1998aq NGC 3982 Straight mean Weighted mean m-m MB MV 28.36 (12) 31.03 (10) 28.00 (07) 31.46 (17) 31.10 (12) 30.22 (12) 32.03 (22) 30.37 (16) 31.72 (14) -19.56 (15) -19.56 (18) -19.64 (16) -19.67 (34) -19.50 (18) -19.47 (18) -19.39 (26) -19.76 (31) -19.56 (21) -19.57 (04) -19.56 (07) -19.54 (17) -19.62 (22) -19.61 (17) -19.69 (27) -19.50 (16) -19.42 (16) -19.41 (24) -19.69 (26) -19.48 (20) -19.55 (04) -19.53 (06) MI -19.27 (20) -19.21 (14) -19.14 (23) -19.43 (21) m15 0.87 (10) 1.06 (12) 0.87 (10) 1.11 (06) 1.10 (07) 1.31 (07) 1.05 (05) 1.08 (05) 1.12 (03) -19.26 (06) -19.25 (09) Saha et al. 1999
Type Ia Supernovae Projects Establish a cosmological distance indicator in the local universe (z < 0.1) Type Ia Supernovae canshapes, be normalised through evolution light curve colours, spectroscopy their light curve shapes (102 objects) dust colours, spectroscopy excellent relative distances (Phillips 1993, Hamuy et al. gravitational lensing difficult, need mapping of 1996, Riess et al. 1996, 1998, 1999, Perlmutter et al. 1997, Phillips light beam et al. 1999, Suntzeff et al. 1999, Jha et al. 1999, 2003) Measure objects at cosmological distances >120 distant SNe Ia (0.3<z<1.0) published (Garnavich et al. 1998, Riess et al. 1998, Perlmutter et al. 1997, 1999, Tonry et al. 2003, Suntzeff et al. 2004, Barris et al. 2004,
Distances in locale Universe Expansion is linear: Hubble-Law v = cz = H0 D Use Distance Modulus µ = m - M = 5 log(d/10 pc) Distances for Standard Candles (M=const.) m = 5 log(z) + b b = M + 25 5 log([c/h0] / Mpc)
Hubble-Diagram of SN Ia m = 5 log10(cz) + b H 0 = 70 ± 10 km s Mpc
The nearby SN Ia Sample Evidence for good distances
z > 0.1 Friedmann Cosmology Assumption: homogeneous and isotropic universe Null geodesic in a Friedmann-Robertson-Walker metric: 1 z DL = Ω (1 + z )c H0 Ω M κ S Ω κ 8π G = ρm 2 3H 0 [Ω κ (1 + z ) 2 + Ω 3 ( 1 + z ) + Ω M Λ ] 0 Ω 2 k kc = 2 2 R H0 Ω Λc = 2 3H 0 2 Λ 2 dz
Supernovae Projects SN Factory Carnegie SN Project SDSSII ESSENCE CFHT Legacy Survey Higher-z SN Search (GOODS) JDEM/LSST / Satellit Plus local Projects: LOTOSS, CfA, ESC
Distanzmodul Cosmic Supernovae z < 2 Details will depend on expansion law for the Universe. Riess et al. 2007
Hubble-Diagram with SDSSII SNe arxiv:0908.4274
Deviations from Hubble-Law cosmic Expansion z=3 z=2 H le b ub z=1 Distance in 1000 Mpc
Nature of the Dark Energy?
The Future Future experiments will distinguish between a cosmological constant or quintessence ESSENCE, CFHT Legacy Survey, VST, VISTA, NGST, LSST, SNAP
Supernovae Acceleration Probe SNAP
Summary on Hubble Measuring Hubble expansion needs to measure distances beyond Virgo cluster measure expansion of Coma cluster against Virgo! SN Ia obviously are very good standard candles (since 1998) are observable for z < 2. Calibration error < 0.1 mag possible?
Summary Most of galaxies and all Quasars have redshifted Spectra (cosmological redshift, not gravitational). Hubble found: cz = H0 d, z < 0,1. The Hubble Constant has to be calibrated: Cepheids and SN-Methods are nowadays the most important Distance Indicators: H0 = 72+/-5 km/s/mpc. Hubble-Law can be used to measure distances in the Universe upto z < 0.2. For z > 0,2 quadratatic deviations (see LCDM). With this method, the Homogeneity and Isotropy of the Universe also follows from the galaxy distribution for Scales s > 200 Mpc.