1. Cosmology with 300,000 standard sirens Big Bang Observer (BBO) and DECIGO: C.Cutler & D.Holz, PRD 80, 104009 (2009) 4 very sensitive mini-LISAs

2. NS/NS BBO Noise Curve

3. for a 3-yr observation w/

4. BBO’s angular resolution --consistent with earlier results by Cornish&Crowder(2005)

5. BBO’s distance error (from noise)

6. Actually, BBO’s distance error is dominated by Weak Lensing Holz&Linder (2005)

7. Number of Galaxies in Error Cylinder Hubble Ultra Deep Field:

8. Cosmological Parameter Extraction What goes in: Assume have measured 250,000 NS-NS binaries out to z=3, with perfectly determined redshifts, z. Fit for 5 parameters: & wher e Following standard convention, also assume forecasted Planck prior: constrains to ~1%, plus a constraint on of Hubble scale at decoupling.

9. 2.5e5 NSs up to z=3 to 0.1% For to 0.025%

10. 2.5e5 NSs up to z=3 to ~0.01 to ~0.1

11. With more accurate analysis of lensing effects, and including priors from next-generation ground-base DE projects (Stage III): 20,000 --- Hirata, Holz & Cutler (2010)

12. Of course, BBO is far in the future, and by the time it flies, DE FoM of 20,000 may be no big deal. On the other hand, this method of measuring D(z) is highly independent of others, and potentially has far better systematics.

13. Caveat re a Selection Effect Hirata pointed out : the probability of correctly identifying the host galaxy has a small but non-negligible dependence on its magnification: higher means higher SNR, so a smaller error box and a brighter galaxy. If not accounted for, would lead to systematic bias in. Possible ways of “correcting” for this effect: 1) Use the gamma-ray burst sources to calibrate it out. I.e., using those same ~1000 galaxies to create a new synthetic data set, giving the “calibration” binaries random orientations and coalescence times. Analyze the data 2 different ways: with and without the benefit of the exact sky location. The difference is an estimate of the systematic bias. 2) Include this effect in a proper Bayesian analysis. Would need to include more parameters, especially a parametrized model of the NS-NS merger rate as a function of z, galaxy type, etc.

14. 1. Early Warning System for ALL short/hard gamma-ray bursts (assuming they are due to mergers) Other Astrophysics from BBO/Decigo (1)  BBO will predict time and location of ALL NS-NS and BH- NS mergers, months in advance. Because of beaming, probably only a small fraction, will lead to observable gamma- ray bursts.  We will learn which kinds of mergers (components, masses, orientations) lead to observable bursts, and which do not. In particular, BBO will tell us binary’s orientation, so we can study beaming.  Can still look for afterglows, even when there are no observed gamma rays (so-called “orphan afterglows”).

15. Other Astrophysics from BBO/Decigo (2) 2. Detect mergers of Intermediate Mass BHs to z>20 Estimated rate ~30/yr, with ~20/yr at z > 10, based on merger-tree simulations by Volonteri, assuming MBHs do grow from stellar BH remnants. (By comparison, for same model, Einstein Telescope would detect ~2/yr, almost all at z<8.)

16. When we eventually build a deci-Hz space-based GW mission approaching the target sensitivities of BBO or Decigo, then Offer cosmological measurements with very high accuracy, and potentially far better systematics. Catalogue of Inspiraling Compact Binaries will be a Goldmine Summary: Plus: A complete catalogue of all NS and BH binary mergers in the universe. an All-sky gamma-ray burst monitor, high-z IMBHs, weak lensing, strong lensing, …..

17. extras

18. BBO/Decigo as WL mission 1Gpc-

19. E.g., BBO’s measurement of lensing convergence power spectrum would be more accurate than the most ambitious other proposed WL missions.

20. Other Astrophysics from BBO/Decigo  Early Warning System for ALL short/hard gamma-ray bursts.  Detect mergers of Intermediate Mass BHs to z>20 (estimated rate: ~30/yr, with ~20/yr at z > 10).  Strong Lensing: expect hundreds of “multiply- imaged” (in GWs) binaries, with time-delays of order a year, and measured to <0.1 sec. Can probe structure of lensing galaxies/clusters.

21. Pie in the Sky?BBO:

22. One idea: 6-satellite BBO/Decigo +ET

23. Example of possible plan: Step 1. One mini-LISA +ET : rates, gamma ray bursts, high-z IMBHs Step 2. Two mini-LISAs + ET: high – precision cosmology Step 3. Full BBO: Inflationary GW background.

24. Caveat re Calibration BBO interferometry in BBO Mission Concept Study (Phinney et al., 2003) is very “LISA-like”: no applied forces along sensitive direction. Later it was realized that this design would greatly oversaturate current UV photodiodes. Harry et al.(2006) proposed a more “LIGO-like” design,with forces on the test mass to keep photodiode operating near dark fringe. But this spoils calibration accuracy unless the force is measured very accurately. DECIGO is in same situation. We have spoken with several instrumentalists, and are optimistic that this is a solvable problem; e.g., 1)Widen beam onto array of ~1000 photodiodes 2)Use interferometry to measure applied force

25. BBO/Decigo as WL mission Comparable to most ambitious/optimistic other WL experiments, such as JDEM or LSST, which measure WL shear thru correlations in galaxy shape distortions. We estimate that BH-BH binaries likely contribute about as much to as NS-NS binaries. Though we assume the BH-BH merger rate is ~1/20 the NS-NS rate, each is ~25 times larger.

26. Recent work: more careful analysis of WL error. for single source for N sources Cutler&Holz(2009) estimated that for N sources at same z: That’s correct if you take an average, but because the distribution of magnifications is quite skew, the average is not the best estimator. The maximum likelihood estimator gives: for N>4 sources see Hirata,Holz&Cutler(2010); Shang&Haiman(2010)

27. Decigo Roadmap 200708091011121314151617181920212223242526 Mission Objectives Test of key technologies Observation run of GW Detection of GW w/ minimum spec. Test FP cavity between S/C Full GW astronomy Scope 1 S/C 1 arm 3 S/C 1 interferometer 3 S/C, 3 interferometer 3 or 4 units DECIGO Pathfinder (DPF) Pre-DECIGO DECIGO R&D Fabrication R&D Fabrication R&D Fabrication from Kawamura

28. Decigo: Pre-conceptual design Differential FP interferometer Arm length: 1000 km Mirror diameter: 1 m Laser wavelength ： 0.532  m Finesse: 10 Laser power: 10 W Mirror mass: 100 kg S/C: drag free 3 interferometers Laser Photo- detector Arm cavity Drag-free S/C Arm cavity Mirror from Kawamura

29. Optical Follow-ups Recall that BBO gives and a small error box on sky. Optical astronomers must still provide 300,000 redshifts. Is this realistic? By the time BBO flies, the LSST could have determined photometric redshifts (accurate to 2-3%) for a large fraction of galaxies over 1/3 of the sky. There are several proposed wide-field spectroscopic surveys. E.g., BigBOSS would meaure ~5 million spectroscopic redshifts per year (~4,000 at a time) for galaxies in the range 0.2 < z < 3.5, over an area of 14,000 sq. degrees. (WFMOS instrument on Subaru telescope would have been Comparable to BigBoss, but their funding was just cut.)

30. ,, Nominal BBO parameters (used in paper) Laser power = 300 x LISA, mirror D ~ 10 x LISA, arm length = 0.01 x LISA, = 0.01 x LISA

31. Binaries as standard GW sirens D (using quadrupole approximation for simplicity) + higher order terms x F(angles)

32. If we can build a deci-Hz space-based GW mission approaching the target sensitivities of BBO or Decigo, and with excellent calibration accuracy (at level), then Offer cosmological measurements, with far better accuracy than with any other proposed methods, and potentially far better systematics (modulo those 2 caveats). inspiraling Compact Binaries will be a Cosmology Goldmine Summary: Copyright 2010. All rights reserved. Plus: great WL mission, gamma-ray burst monitor, high-z IMBHs, strong lensing, …..

33. If we can build a deci-Hz space-based GW mission approaching the target sensitivities of BBO or Decigo, and with excellent calibration accuracy (at level), then Offer cosmological measurements with very hight accuracy, and potentially far better systematics. inspiraling Compact Binaries will be a Cosmology Goldmine Summary: Copyright 2010. All rights reserved. Plus: All-sky gamma-ray burst monitor, high-z IMBHs, weak lensing, strong lensing, …..