from DES, BAO, and BBN Eduardo Rozo, University of Arizona On behalf - - PowerPoint PPT Presentation

A Precise Measurement of H0 from DES, BAO, and BBN

Eduardo Rozo, University of Arizona

Statistical challenges for large scale structure in the era of LS LSST

On behalf of the Dark Energy Survey Collaboration

What I Won’t Be Talking About

S15 pivot

10 100 Richness λ 1014 1015 Mass [M]

B17 M17 S17 pivot WL This Work RM+CMB (Baxter et al. 2017) WL (Melchior et al. 2017) WL (Simet et al. 2017) SZ (Saro et al. 2015)

Tom McClintock Tamas Varga

4% systematic uncertainty Mass calibration of the DES redMaPPer cluster catalogue. McClintock et al, on arxiv in ~2 weeks.

What I Won’t Be Talking About

Mass calibration of the DES redMaPPer cluster catalogue.

This work log10hM|λ = 40, z = 0.35i Melchior et al. (2017) Baxter et al. (2018) Simet et al. (2017) Murata et al. 2017 Baxter et al. (2016) Farahi et al. (2016) Saro et al. (2015) Mantz et al. (2016)

14.3 14.4 14.5 14.6 14.7 14.8

Bl Blinded cosmology

Matteo Costanzi

A Precise Measurement of H0 from DES, BAO, and BBN

The Hubble Constant Problem

Freedman 2017.

“The single most important complement to the CMB for measuring the dark energy equation of state at z ∼ 0.5 is a determination of the Hubble constant to better than a few percent.”

Why It Matters

Basic idea:

• In flat LCDM, CMB already constrains all

cosmological parameters.

• CMB accurately predicts both the expansion

history and growth of large scale structure.

• Deviations in any of these observables can provide

evidence of dark energy.

• H0 is the cosmological parameter that varies the

most as we vary dark energy while holding the CMB fixed. H0 constraints are especially powerful probes of dark energy!

An Under-appreciated Fact

Though see Aubourg et al. 2015.

DES+BAO+BBN results in a very clean measurement of H!

BAO+BBN + (any probe of !m) = Hubble constant measurement In a flat LCDM model,

A Precise Measurement of H0 from DES+BAO+BBN

The BAO Story I Usually Hear

BAO = Baryon Acoustic Oscillations

• The CMB measures the sound horizon rs of the photon-

baryon fluid in the early Universe.

• This sound horizon is imprinted into the galaxy density

today: BAO is a standard ruler calibrated by the CMB.

• With rs calibrated, we can use BAO to measure H(z) and

DA using BAO observables.

The BAO Story I Usually Hear

BAO = Baryon Acoustic Oscillations

True but incomplete.

• The CMB measures the sound horizon rs of the photon-

baryon fluid in the early Universe.

• This sound horizon is imprinted into the galaxy density

today: BAO is a standard ruler calibrated by the CMB.

• With rs calibrated, we can use BAO to measure H(z) and

DA using BAO observables.

Th The B BAO S Sto tory ry

Over/under-densities launch density waves.

After decoupling, pressure goes to zero, and so the waves stall. Gravitational accretion preserves the density peak from the stalled waves in the dark matter.

What Does BAO Measure?

The sound horizon scale is imprinted into the galaxy density distribution. What is rs? rs = cst P depends TCMB ! depends on TCMB and Ω#ℎ% t depends on TCMB, Ω&ℎ%. :: assumes no early DE. cs = sound speed = '(/'! t = time to recombination

What Does BAO Measure?

The sound horizon scale is imprinted into the galaxy density distribution. What is rs? rs = cst cs = sound speed = !"/!$ t = time to recombination P depends TCMB $ depends on TCMB and Ω&ℎ( t depends on TCMB, Ω)ℎ(. :: assumes no early DE. Parameters: Ω&ℎ(, Ω)ℎ(

BAO Observables

We don’t measure distances. We measure:

• angles: !s = rs/DA
• redshift intervals: Δz = H(z)rs/c.

Parameters: Ω#ℎ%, Ω'ℎ%, ℎ H(z) depends on: H0 (ℎ), Ω'ℎ%. DA is an integral over H(z).

Bottom Line

A single BAO measurements is degenerate in Ω"ℎ$, Ω%, ℎ. Ω"ℎ$: BBN measures this number Ω%: DES measures this number DES+BAO+BBN can measure h!

0.1 1.0 0.2 0.5 2.0 z 10 20 30 distance/rd √z

DM(z)/rd √z DV (z)/rd √z zDH(z)/rd √z 6dFGS MGS SDSS − II WiggleZ LOWZ CMASS Lyα auto Lyα cross

BAO Measurement

Aubourg et al. 2015

Big Bang Nucleosynthesis

Baryon Density from D/H Measurements

Burles et al. (2001) Cooke et al. (2001)

4

Burles et al. 2001

• D burns to produce He.
• More baryons

faster burn.

• D decreases w/ Ω"ℎ$.

But how to measure?

Primordial D/H Measurement

• Use quasar absorption spectra
• simultaneously model D and H absorption
• Look for low-metallicity lines of sight
• Ensures pristine primordial abundances
• Look for damped Ly-! systems.
• Lots and lots of D and H means high S/N
• Can model several absorption lines

simultaneously!

Cook et al. 2016

0.0 0.2 0.4

Velocity Relative to z

0.0 0.2 0.4 0.6 0.8 1.0

Normalized Flux

0.0 0.5 1.0 Ly↵

HIRES data

0.0 0.5 1.0 Ly 0.0 0.5 1.0 Ly 0.0 0.5 1.0 Ly 0.0 0.5 1.0 Ly✏ 0.0 0.5 1.0 Ly6 −150 −100 −50 +50 +100 +150 0.0 0.5 1.0 Ly7

0.0 0.2 0.4 0.0 0.2 0.4 0.6 0.8 1.0

Normalized Flux

0.0 0.5 1.0 Ly8

HIRES data

0.0 0.5 1.0 Ly9 0.0 0.5 1.0 Ly10 0.0 0.5 1.0 Ly11 0.0 0.5 1.0 Ly12 0.0 0.5 1.0 Ly13 −150 −100 −50 +50 +100 +150 0.0 0.5 1.0 Ly14 Ly15

Cook et al. 2016

0.0 0.2 0.4 0.0 0.2

0.0 0.5 1.0 Ly6 −150 −100 −50 +50 +100 +150 0.0 0.5 1.0 Ly7

Cook et al. 2016

BBN Constraints

• Ω"ℎ$ = ( 2.208 ± 0.052 ) x 10-2
• Dominant error:
• uncertainty in the d(p,%)3He rate.
• ongoing experimental efforts to

better constrain this rate.

• BBN uncertainty is easily sub-dominant

for our analysis.

Dark Energy Survey

Credit: Bjoern Soergel

Collaborating institutions: Funded by:

~4 ~400 sc scientist sts; s; US su suppor

• rt fr

from

• m DOE

E & NS NSF

DES Y1 Results

SPT region

0:00h 1:00h 2:00h 3:00h 4:00h 5:00h 23:00h –50 –45 –40 –35 –30 –25 1.00 1.25 1.50 1.75 2.00

ngal [arcmin–2]

Y1 3x2pt analysis: gg-clustering + gg-lensing + cosmic shear

S8 = !8("/0.3)1/2

DES Year 1 results: 1708.01530

Analysis

• Flat !CDM
• Minimal neutrino mass: ∑m" = 0.06 eV
• BBN from Cooke et al.
• BAO from BOSS, SDSS main, 2dF, 6dF
• DES Y1 combined probes

H0 = 67.2 km/s/Mpc

+1.2 −1.0

Dark Energy Survey Year 1 Results: 1711.00403

Comparison to External Data Sets

Four independent data sets that reach percent level precision:

• Planck:

TT+low-l polarization

• SPTpol:

High-l polarization

• SH0ES:

Distance Ladder (cepheids + SN)

• H0LiCOW

Strong lensing

• Da

Data sets are statistically independent of each other:

• no

no covari rianc nce! e!

• No

No s shared o d obs bservational s systematics!

Consistency

Planck: SPTpol: DES+BAO+BBN: SH0ES: H0LiCOW: !2/DOF = 20.7/11 Ω#, Ω$, h, &8, ns Ω#, Ω$, h, &8, ns Ω#, Ω$, h, &8 h h Significance: 2.1& Al All data is con

• nsistent wi

with flat LCD CDM mod

• del.

DES+BAO+BBN: H0 = 67.2 km/s/Mpc

+1.2 −1.0

Everything: H0 = 69.1 km/s/Mpc

+0.4 −0.6

DES+BAO+BBN: H0 = 67.2 km/s/Mpc

+1.2 −1.0

Everything: H0 = 69.1 km/s/Mpc

+0.4 −0.6

What’s going

• n here?

Intersection of Planck w/ DES+BAO+BBN is at high h

The Impact of Neutrino Masses

Summary

• DES+BAO+BBN measures H0 with the same precision as

Planck, yet is co comp mpletely y deco coupled from m the CMB.

• H0 = 67.2 km/s/Mpc
• There are now 5 measurements of H0 that are:
• Statistically independent
• Share no common observational systematics
• The entire set has an acceptable !2
• No evidence for dynamical dark energy/MG

+1.2 −1.0