THE GAMMA-RAY BURST HUBBLE DIAGRAM TO z=6.6 Brad Schaefer Louisiana State University HUBBLE DIAGRAMS PLOT DISTANCE vs. REDSHIFT SHAPE OF PLOT EXPANSION.

THE GAMMA-RAY BURST HUBBLE DIAGRAM TO z=6.6

Brad SchaeferLouisiana State University

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Redshift (z)

Distance Modulus

HUBBLE DIAGRAMS

PLOT DISTANCE vs. REDSHIFT

SHAPE OF PLOT EXPANSION HISTORY OF UNIVERSE

SHAPE DEPENDS ON DARK ENERGY and HOW IT CHANGES

SN HUBBLE DIAGRAMS1997: Perlmutter et al. 1997, ApJ, 483, 565

— 7 SNe at z>0.35— Consistent with Flat & =11998/9: Perlmutter et al. 1999, ApJ, 517, 565

Riess et al. 1998, AJ, 116, 1009

— 42 & 16 SN 0.16<z<0.83— Universe will expand forever— Expansion is accelerating— “Dark Energy” is ‘pushing’2004: Riess et al. 2004, ApJ, 607, 665

— 10 SNe at 1<z<1.76 with HST— DecelerationAcceleration at z~0.462005: Astier et al. 2005, ApJ, 607, 665

— 71 SNe at z<1 — w=-1.023±0.090— No constraint on change of w2012?: http://snap.lbl.gov/

— ~2000 SNe at z<1.7

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Distance Modulus

WHAT IT TOOK TO CONVINCE THE COMMUNITY:

Duplication by other groups Deep search for problems and

complexities Confirmation by other methods

SN HUBBLE DIAGRAMS1997: Perlmutter et al. 1997, ApJ, 483, 565

— 7 SNe at z>0.35— Consistent with Flat & =11998/9: Perlmutter et al. 1999, ApJ, 517, 565

Riess et al. 1998, AJ, 116, 1009

— 42 & 16 SN 0.16<z<0.83— Universe will expand forever— Expansion is accelerating— “Dark Energy” is ‘pushing’2004: Riess et al. 2004, ApJ, 607, 665

— 10 SNe at 1<z<1.76 with HST— DecelerationAcceleration at z~0.462005: Astier et al. 2005, ApJ, 607, 665

— 71 SNe at z<1 — w=-1.023±0.090— No constraint on change of w2012?: http://snap.lbl.gov/

— ~2000 SNe at z<1.7

WHAT IT TOOK TO CONVINCE THE COMMUNITY:

Duplication by other groups Deep search for problems and

complexities Confirmation by other methods

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Redshift (z)

Distance Modulus

What is the expansion

history for z>1.7?

LAG: VARIABILITY: (delay between peaks in hard and soft photons) (RMS scatter between light curve and smooth LC)

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Time (Sec)

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TIME

BRIGHTNESS

LAG

RMS

GRB LUMINOSITY INDICATORS

MINIMUM RISE TIME: NUMBER OF PEAKS:(fastest time over which GRB brightens) (how many isolated significant local maxima)

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RISETIME

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Time (Sec)

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PEAK PHOTON ENERGY: TIME OF JET BREAK: (photon energy with the highest flux {like the 'color'}) (when afterglow fading speeds up)

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Epeak

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T-Tburst(days)

Brightness

Tjet break

PEAK PHOTON ENERGY: TIME OF JET BREAK: (photon energy with the highest flux {like the 'color'}) (when afterglow fading speeds up)

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Epeak

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T-Tburst(days)

Brightness

Tjet break

CALIBRATION OF SIX

LUMINOSITY INDICATORS

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-3 -1 1

Log(Lag)

Log(L)

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-4 -3 -2 -1 0

Log(V)

Log(L)

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1 2 3 4

Log(Epeak)

Log(L)

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1 2 3 4

Log(Epeak)

Log(E

gamma

)

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-3 -2 -1 0 1 2

Log(RTmin)

Log(L)

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Npeak

Log(L)

SPECTRAL LAG VARIABILITY PEAK PHOTON ENERGY

TIME OF JET BREAK MINIMUM RISE TIME NUMBER OF PEAKS

PRIOR WORK:Author (Reference) # GRBs # Lum Ind.Schaefer (2001, three public talks) 8 GRBs 2 (lag,V)

Schaefer (2003, ApJLett, 583, 67) 9 GRBs 2 (lag,V)

Bloom et al. (2003, ApJ, 594, 674) 16 GRBs 1 (break)

Xu, Dai, Liang (2005, ApJ, 633, 603) 17 GRBs 1 (break)

Firmani et al. (2005, MNRAS, 360, 1) 15 GRBs 1 (break)

Liang & Zhang (2005, ApJ, 633, 611) 15 GRBs 1 (break)

Schaefer (This work) 60 GRBs 5 (lag,V,Ep, break, rise)

THIS WORK: 60 GRBs 27 with z>2, 14 with z>3, 6 with z>4, and 2 with z>6 26 with SWIFT, 16 with HETE, 8 with BATSE, 6 with KONUS, 3 with SAX, 1 with INTEGRAL

Combine information from all 5 luminosity indicators to get best luminosity

Must simultaneously fit cosmology and luminosity relations

GRB HUBBLE DIAGRAM

(Schaefer 2003)

ACCURACY FOR INDIVIDUAL SNe & GRBs: µ (overall)

OBJECT Median Best

SNe* 0.23 mag 0.15 mag

GRB 0.60 mag 0.21 mag

*Gold & Silver sample from Riess et al. (2004 ApJ, 607, 665)

SN ADVANTAGES: GRB ADVANTAGES: 2.6X more accurate singly Uniquely covers 1.7< z < 6.6 Physics of SNe is well known No problem from extinction (or Ly- clouds)

Results are ‘free’ and now

SN & GRB COMPARISON

One SN is on average 2.6x more accurate than one GRB

‘Standard’ cosmology:

Flat Universe with M=0.27±0.04,Cosmological Constant [w=-1 and unchanging for w=P/c2]

60 GRB HUBBLE DIAGRAM

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Redshift (z)

Distance Modulus (mag)



8 NEW GRBs SINCE JANUARY

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0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0

Redshift (z)


DERIVED DISTANCES DEPEND LITTLE ON ASSUMED COSMOLOGY

‘Standard’ cosmology [M=0.27, Flat Universe, w0 = -1, w= 0] versus

Best Fit cosmology [M=0.27, Flat Universe, w0 = -1.4, w = 1.3]



60 GRB HUBBLE DIAGRAM

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2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

Redshift (z)




APPEARS TO BE FLAT AT z>2.5

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Redshift (z)




APPEARS TO BE FLAT AT z>2.5

Marginalized over M

1 2and contours

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w 0

wa

Cosmological Constant

SEARCH FOR BEST COSMOLOGY

Marginalized over M

1 2and contours

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w 0

w'


Cosmological Constant at 2.8 level Cosmological Constant at 2.3 level

Assume Flat Universe, marginalize over M

Assume Equation of state; w=P/c2, let w vary as w0+wz or w0+wa*z/(1+z)

Cosmological Constant has w=-1 and w=wa=0

w = w0 + w z w = w0+wa*z/(1+z)

Assume Flat Universe with w0 = -1.4 and w = 1.3

WHAT IS BEST M?

One Sigma: 0.25< M <0.59

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0.5

1.0

1.5

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2.5

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

M

/Probability d

M

SEARCH FOR BEST COSMOLOGY

Assumed =0.27±0.041 , 2, 3 contours

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w 0

wa


Assumed =0.27±0.041 , 2, 3 contours

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w 0

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& Gold SilverSupernovae1,2 contours

Cosmological Constant rejected at 3.5 level Cosmological Constant rejected at 3.7 level

Assume Flat Universe with M=0.27±0.04,

w = w0 + w z w = w0+wa*z/(1+z)

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Best Fit cosmology:

Flat Universe with M=0.27±0.04,

w0 = -1.4, w=dw/dz = 1.3, w=P/c2=w0+wz

BEST FIT COSMOLOGY

FIRST RESULTS FROM NEW METHOD

GRB HUBBLE DIAGRAM FLATTENS FOR z>2.5:

Best fit has w0 = -1.4 and w = 1.3

Cosmological Constant rejected at 3.5 level

In good agreement with Gold & Silver SNe

If Dark Energy changes with time, then it is not vacuum energy

QUESTIONS & POTENTIAL PROBLEMS MALMQUIST BIAS:

Very difficult problem to calculate, because conditions for detecting burst as a function of redshift are highly inhomogenous and not well known

GRAVITATIONAL LENSING AMPLIFICATION AND DEAMPLIFICATION BY FOREGROUND GALAXIES:

Any resulting bias is likely to be insignificant (Daniel Holz 2005)

WHAT ARE THE IMPLICATIONS FOR STAR FORMATION IMPLIED BY A FLATTENED HUBBLE DIAGRAM?

Is such a flattening consistent with what we know?

WHAT ARE EFFECTS OF EVOLUTION?I claim the effects will be near-zero because the GRB luminosity

indicatorsare based on quantities like conservation of energy in jet and light

travel time, and these do not evolve with time or metalicity; while it does not matter if the typical luminosities change with time so long as the calibration of the relations is based on the physics of the situation.

FUTURE FIRST RESULT MUST BE CHECKED WITH INDEPENDENT

SAMPLE OF GRBs:

HETE & SWIFT will get ~60 more GRBs with redshifts in ~2 years

FIRST RESULTS MUST SURVIVE SCRUTINY, IMPROVEMENTS, AND PROBLEMS:

Many people need to examine this from many directions

FIRST RESULT MUST BE CONFIRMED/DENIED BY INDEPENDENT METHODS:

Perhaps with lensing or quasars…

CONCLUSIONS NEW METHOD TO MEASURE DARK

ENERGY:

Unique information for 1.7< z < 6.6

FIRST RESULTS:

60 GRBs from 0.2< z < 6.6

HUBBLE DIAGRAM FLATTENS

FOR z>2.5:

Dark Energy changes over time,

(Cosmological Constant rejected at 3.5)

or Hi-z GRBs are brighter by ~3X

(Malmquist bias?)

THIS RESULT MUST BE CONFIRMED OR DENIED BY INDEPENDENT STUDY:

Independent GRB data

(60 more HETE & SWIFT bursts)

Independent methods

(perhaps lensing or quasars...)

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THE GAMMA-RAY BURST HUBBLE DIAGRAM TO z=6.6 Brad Schaefer Louisiana State University HUBBLE DIAGRAMS PLOT DISTANCE vs. REDSHIFT SHAPE OF PLOT EXPANSION.

Documents

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equation of state w

flat universe

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grb hubble diagram slide

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sn hubble diagrams