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Fundamental Cosmic Distance ScaleNaples, May 3, 2011
Wendy FreedmanCarnegie Observatories
Measuring the Hubble Constant
Allan Sandage (1926-2010)
UnProgress in Measuring Ho
Factor of 2 Era
HST
Era of Percent Precision
Some history
Despite 60 years of effort, the Hubble constant was not measured to better than a factor of two
Solving the Twilight Zone Problem • Use HST to measure Cepheids in galaxies to 20 Mpc,
apply to calibrate a set of secondary distance indicators• Use the secondary indicators to extend scale to 100 Mpc
Twilight Zone
Philosophy of Key Project: Calibrate multiple methods to reduce risk of systematic errors
Tully-Fisher relation
surface brightness fluctuations
Dn-σ relation – fundamental plane
Type Ia supernovae
Cepheids
The Leavitt Law
Leavitt (1908)Leavitt & Pickering (1912)
Cepheid Parameters: Optimizing Searches
• Cepheid amplitudes decrease with increasing λ
• Interstellar reddening decreases as λ−1
For detection: Cepheid searches best undertaken in the blue
To minimize the effects of dust: observations best in the red
HST: V and IMadore & Freedman (1991)
Multi-wavelength Distances Using Cepheids
M33 NGC 6822
, HST
VRIB
AB ~1 mag
A4.5 ~ 0.01 mag
Madore et al (2009)WLF et al (1991)
Larson objects in mirror
Key Project Sampling Strategy
• Power-law sampling
Madore & Freedman (2002, 2005)
• Equally-spaced observations
aliasing
The Hubble Key Project
Example Key Project Cepheids
Turner et al.; Phelps et al.
NGC 4414 NGC 2090
V
I
M100M100
• 12 V points• 4 I points
• cosmic-ray split
• fixed roll angle
• ALLFRAME/DoPHOT
Key Project Observations
Key Project Cepheids
• Composite I-band PL relation
• 24 galaxies• ~800 Cepheids• PL dispersion
~0.1 mag (LMC)
Ferrarese et al. (2000)
Comparison of Cepheid Distances
(Madore, Freedman, Lee, Sakai)PNLF versus Cepheids
TRGB versus Cepheids
Ferrarese et al. (2000):
(Jacoby, Ciardullo)
SBF versus Cepheids
(Tonry et al.)
GCLF versus Cepheids
(Harris, Whitmore)
Key Project Results
Hubble H0 Key Project (2001)Freedman et al. (2001)
1st tick mark
Hubble (1929)
Calibration of Secondary Methods
SNIa
TF
Cepheids• Type Ia supernovae• Tully-Fisher relation• Fundamental plane (ellipticals)• Surface-brightness fluctuations• Type II supernovae
FP versus SBF SNIa versus SBF
Blakeslee et al. (2001) Ahjar et al. (2001)
Calibration of the Tully-Fisher Relation
H0 = 71 ± 3 ± 7 km/sec/Mpc
Sakai et al. (2001)
Fundamental plane calibration
Kelson et al. (2000) H0 = 78 ± 5 ± 9 km/sec/Mpc
Type Ia Supernovae
• BVI Hubble diagrams for SNIa• Decline-rate relation
(Phillips, Hamuy, Riess et al.)• dispersion ~0.16 mag (8% in
distance)• 6 Cepheid calibrators
Gibson et al. (2000)
H0 = 71 2 7 km/sec/Mpc
Systematic Effects (1)
Reddening:
• 0.04 < E(B-V) < 0.36• V, I (H: NICMOS)• agreement to 1%
Macri et al. (2001),WLF et al. (1994)
V
I
H
Systematic Effects (con’t)2. Metallicity: 3. Calibration: (e.g., maser galaxy:NGC 4258,
HST Cepheid parallaxes) 4. Velocity Flows: 1-2% at 30,000 km/s
Herrnstein et al. (1999); Macri et al 2006 Benedict et al. 2007
HST Key Project Sandage et al. 2004
Metallicity
• empirical tests: M31, M101• comparison with TRGB• ~10% difference over afactor of 10 in [O/H]
Final Combined Key Project Results
WLF et al. (2001)
H0 = 72 ± 3 (stat.)± 7 (sys.)
km/sec/Mpc
Recent Measurements Post HST KP
NGC 4258’s maser disk
Distance of NGC 4258• From proper motion and radial velocity
7.3 0.4 Mpc Herrnstein et al Nature
• From Cepheids7.5 0.3 Mpc Macri et al ApJ 652
(alternatively equate the two and derivem-M(LMC) = 18.41 0.14)
SHOES program
• Supernovae and H0 for the Equation of State• Riess et al 2009, 2011• Differential Cepheid distances to NGC 4258
– NGC 4536 NGC 4639 NGC 3982– NGC 3370 NGC 3021 NGC 1309– NGC 5584 NGC 4038
• 240 SNe Ia at z < 0.1• H0 = 73.8 2.4 km/sec/Mpc
Recent Measurements of H0
H0 = 73.8 2.4 km/sec/Mpc (Riess et al 2011)
(Riess et al 2009)
240 SNe Ia z < 0.1
Carnegie Supernova Project (CSP)
Swope 1-meter Magellan 6.5-meterDupont 2.5-meter
Low z: High z:
•u’BVg’r’i’YJHK photometry• 2.5-meter spectroscopy
• YJ photometry• Magellan 6.5-meter
0 < z < 0.1 0.1 < z < 0.7
CSP Hubble Diagram for Low-z Supernovae
Folatelli et al. 2009
Most of scatter isconsistent with peculiar velocities.
If confirmed, scatterin SN distances is3-4%.
The Carnegie Hubble Program
Remaining Dominant Systematics in Key Project
1. Zero point of Cepheid 5% 1-σPL relation (distance to the LMC)
2. Effects of Metallicity 3.5% 1-σon Cepheid luminosities
3. WFPC-2 photometric 3.5% 1-σzero point
Carnegie Hubble Project (CHP) Team
Barry Madore
Wendy Freedman, PIVicky Scowcroft Eric Persson
Jane Rigby
Violet Mager Laura Sturch Mark Seibert
Two Major Recent Developments in the Cepheid Extragalactic Distance Scale
1. Benedict et al. (2007) Fine Guidance Sensors on HST: First high-precision parallaxes for 10 nearby Milky-Way Cepheids
2. Freedman et al. (2008), Ngeow & Kanbur (2008), Madore et al. (2008): First Spitzer mid-infrared Cepheid PL relations for LMC Cepheids
New Cepheid Parallaxes: HST
Freedman et al.No change to H0
Sandage et al.H0 increases
Difference at long periods
where extragalactic Cepheids lie.
Freedman et al. 2001HST Key Project
Sandage et al. 2004
Benedict et al. 2007
Absolute trig parallaxes2-3 ± 0.2-0.3 milliarcsec
Galactic Parallax Calibration
Benedict et al. (2007)
Calibrate Persson et al.JHK data with parallaxesfrom HST
State of the art:H0 = 73 ± 2 ± 4 km/s/Mpc
• near-infrared photometry• zero point geometric parallax
(m – M)K = 18.45 ± 0.04 mag
Milky Way parallax calibration
WLF + Madore ARAA (2010)
Advantage of Spitzer for the extragalactic distance scale:
At 3.6 µm, Aλ is >20 times smaller than at optical (B-band) wavelengths
Archival Spitzer Observations of LMC Cepheids
Spitzer Infrared Telescope
Spitzer Hubble Constant Exploration Program Overview (PI: W. Freedman)
• 705 hours • 3.6 µm observations of: 37 Milky Way Cepheids (and 4.5 µm)
(anticipating GAIA sample) 85 LMC Cepheids (and 4.5 µm) Nearest spiral galaxy Cepheids Tests for metallicity effects 545 spiral Tully-Fisher galaxies 54 Carnegie Supernova Project galaxies
Spitzer Large Program
Three Metallicity Tests
• Remaining dispersion in LMC Leavitt relation
• Radial gradients in M31 and M33• Mid-IR Cepheid – TRGB comparison
Archival Spitzer Observations of LMC Cepheids
WLF , Madore, Rigby, et al. (2008)
Spitzer IRACobservations3.6, 4.5, 5.8 µm
Single phaseσ = ± 0.16 mag
SAGE LMC studyof star formation (Meixner et al 2006)Serendipitous observations of 70Cepheids
Spitzer Leavitt Relations for the LMC
PL relations for the LMC at 3.6 and 4.5µm (average of 2 phases) compared to the optical B and V bands
AB is a factor of 20 times larger than for 3.6 and 4.5µm
Spitzer: NGC 6822
Single-phase PL relationsfor NGC 6822 (4 IRAC bands)Madore et al (2009)
Multiwavelength fit of Galacticextinction curve : BVRIK+ 3.6, 4.5, 5.8, 8 µm
AB ~1 mag
A4.5 ~ 0.01 mag
Nearby Galaxies
Sculptor Group:NGC 300: ~2 Mpc
Spitzer Tully-Fisher Relation
B, I, H, 3.6 µm Tully-Fisher relations for KeyProject Cepheid galaxiesNOTE: The TF relation can be applied to any spiral galaxy.
± 0.43 § 0.43 ± 0.12± 0.36± 0.36
Spitzer 3.6 and 4.5 µm Milky Way light curves
3.6µm
4.5µm
Spitzer 3.6 and 4.5 µm LMC light curves
3.6µm
4.5µm
Spitzer 3.6 and 4.5 µm SMClight curves
3.6µm
4.5µm
Spitzer LMC Leavitt Law
3.6 µm
V
log P (days)
• 85 LMC Cepheids• 24 phase points
• 3.6 µm: σ = 0.10 mag
• V-band: σ = 0.25 mag
Near- and Mid-IR LMC PL Relations
4.5
3.6
K
H
J
log P
J
4.5
3.6
K
H
CHP Preliminary Results on Ho
LMC + Milky Way Spitzer 3.6 µm calibration
Ho = 73.6 1.5 (stat) 3.1 (sys) km/s/Mpc
To come: • Additional nearby galaxies including N4258• GAIA parallaxes for Milky Way Cepheids• Independent Mid-IR Tully-Fisher calibration
The Carnegie Hubble Project (CHP) : Summary
1. Cepheids LCO, HST, Spitzer, GAIA,JWST
2. Supernovae LCO (CSP), Spitzer3. Mid-IRTF Spitzer, Magellan, JWST
Consistent mid-infrared photometric zero point: from Milky Way through Local Group to Hubble flow.Eliminate current systematics.
Comparison of HST Key Project and CHP H0 Error Budgets
Combining H0 with Planck Results
H0 to ± 10%H0 to ± 2%
+ SN + BAO68 and 95% CL
Freedman & Madore, Ann. Rev. 2010
• WMAP, SHOES, CHP are all consistent with HST KP value of 73 km/s/Mpc with an uncertainty of 5%.
• Accuracies of a few percent are now in sight.
• This will require independent measurements to test for robustness as done for Key Project.
Summary: An unprecedented decade of stability!