Measuring the Hubble Constant - INAF-OAC · Measuring the Hubble Constant . Allan Sandage...

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!