the gamma-ray burst hubble diagram to z=6.6 brad schaefer louisiana state university hubble diagrams...
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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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Redshift (z)
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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Time (Sec)
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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10 100 1000log(E)
Brightness
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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Brightness
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)
‘Standard’ cosmology:
Flat Universe with M=0.27±0.04,Cosmological Constant [w=-1 and unchanging for w=P/c2]
8 NEW GRBs SINCE JANUARY
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Redshift (z)
Distance Modulus (mag)
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0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0
Redshift (z)
Distance Modulus (mag)
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]
‘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)
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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)
Distance Modulus (mag)
‘Standard’ cosmology:
Flat Universe with M=0.27±0.04,Cosmological Constant [w=-1 and unchanging for w=P/c2]
APPEARS TO BE FLAT AT z>2.5
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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)
Distance Modulus (mag)
‘Standard’ cosmology:
Flat Universe with M=0.27±0.04,Cosmological Constant [w=-1 and unchanging for w=P/c2]
APPEARS TO BE FLAT AT z>2.5
Marginalized over M
1 2and contours
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Cosmological Constant
SEARCH FOR BEST COSMOLOGY
Marginalized over M
1 2and contours
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w 0
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Cosmological Constant
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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0.0 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
Cosmological Constant
Assumed =0.27±0.041 , 2, 3 contours
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-3 -2 -1 0
w 0
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Cosmological Constant
& 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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Redshift (z)
Distance Modulus (mag)
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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Redshift (z)
Distance Modulus (mag)