1. 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 HISTORY OF UNIVERSE  SHAPE DEPENDS ON DARK ENERGY and HOW IT CHANGES

2. SN HUBBLE DIAGRAMS  1997: Perlmutter et al. 1997, ApJ, 483, 565 — 7 SNe at z>0.35 — Consistent with Flat &  =1  1998/9: 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 — Deceleration  Acceleration at z~0.46  2005: Astier et al. 2005, ApJ, 607, 665 — 71 SNe at z<1 — w=-1.023±0.090 — No constraint on change of w  2012?: 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

3. SN HUBBLE DIAGRAMS  1997: Perlmutter et al. 1997, ApJ, 483, 565 — 7 SNe at z>0.35 — Consistent with Flat &  =1  1998/9: 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 — Deceleration  Acceleration at z~0.46  2005: Astier et al. 2005, ApJ, 607, 665 — 71 SNe at z<1 — w=-1.023±0.090 — No constraint on change of w  2012?: 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 What is the expansion history for z>1.7?

4. GRB LUMINOSITY INDICATORS

5. CALIBRATION OF SIX LUMINOSITY INDICATORS SPECTRAL LAG VARIABILITY PEAK PHOTON ENERGY TIME OF JET BREAK MINIMUM RISE TIME NUMBER OF PEAKS

6. PRIOR WORK: Author (Reference) # GRBs# Lum Ind. Schaefer (2001, three public talks) 8 GRBs2 (  lag,V) Schaefer (2003, ApJLett, 583, 67) 9 GRBs2 (  lag,V) Bloom et al. (2003, ApJ, 594, 674) 16 GRBs1 (  break ) Xu, Dai, Liang (2005, ApJ, 633, 603) 17 GRBs1 (  break ) Firmani et al. (2005, MNRAS, 360, 1) 15 GRBs1 (  break ) Liang & Zhang (2005, ApJ, 633, 611) 15 GRBs1 (  break ) Schaefer (This work)60 GRBs5 (  lag,V,E p,  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)

7. ACCURACY FOR INDIVIDUAL SNe & GRBs:  µ (overall) OBJECT MedianBest SNe* 0.23 mag0.15 mag GRB 0.60 mag0.21 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

8. ‘Standard’ cosmology: Flat Universe with  M =0.27±0.04, Cosmological Constant [w=-1 and unchanging for w=P/  c 2 ] 60 GRB HUBBLE DIAGRAM

9. ‘Standard’ cosmology: Flat Universe with  M =0.27±0.04, Cosmological Constant [w=-1 and unchanging for w=P/  c 2 ] 8 NEW GRBs SINCE JANUARY

10. DERIVED DISTANCES DEPEND LITTLE ON ASSUMED COSMOLOGY ‘Standard’ cosmology [  M =0.27, Flat Universe, w 0 = -1, w= 0] versus Best Fit cosmology [  M =0.27, Flat Universe, w 0 = -1.4, w = 1.3]

11. ‘Standard’ cosmology: Flat Universe with  M =0.27±0.04, Cosmological Constant [w=-1 and unchanging for w=P/  c 2 ] 60 GRB HUBBLE DIAGRAM

12. ‘Standard’ cosmology: Flat Universe with  M =0.27±0.04, Cosmological Constant [w=-1 and unchanging for w=P/  c 2 ] APPEARS TO BE FLAT AT z>2.5

13. ‘Standard’ cosmology: Flat Universe with  M =0.27±0.04, Cosmological Constant [w=-1 and unchanging for w=P/  c 2 ] APPEARS TO BE FLAT AT z>2.5

14. SEARCH FOR BEST COSMOLOGY Cosmological Constant at 2.8  level Cosmological Constant at 2.3  level Assume Flat Universe, marginalize over  M Assume Equation of state; w=P/  c 2, let w vary as w 0 +wz or w 0 +w a *z/(1+z) Cosmological Constant has w=-1 and w=w a =0 w = w 0 + w z w = w 0 +w a *z/(1+z)

15. Assume Flat Universe with w 0 = -1.4 and w = 1.3 WHAT IS BEST  M ? One Sigma: 0.25<  M <0.59

16. SEARCH FOR BEST COSMOLOGY Cosmological Constant rejected at 3.5  level Cosmological Constant rejected at 3.7  level Assume Flat Universe with  M =0.27±0.04, w = w 0 + w z w = w 0 +w a *z/(1+z)

17. Best Fit cosmology: Flat Universe with  M =0.27±0.04, w 0 = -1.4, w=dw/dz = 1.3, w=P/  c 2 =w 0 +wz BEST FIT COSMOLOGY

18. FIRST RESULTS FROM NEW METHOD  GRB HUBBLE DIAGRAM FLATTENS FOR z>2.5: Best fit has w 0 = -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

19. 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 indicators are 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.

20. 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…

21. 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...)