Longterm strategy on gravitational wave detection from European groups Barry Barish APPEC Meeting London, UK 29Jan04
International Interferometer Network Simultaneously detect signal (within msec) LIGO GEO Virgo TAMA detection confidence locate the sources AIGO decompose the polarization of gravitational waves 29Jan04 APPEC London 2
Hanford Observatory Simultaneous Detection LIGO 3002 km (L/c = 10 ms) MIT Caltech Livingston Observatory 29Jan04 APPEC London 3
LIGO Livingston Observatory 29Jan04 APPEC London 4
LIGO Hanford Observatory 29Jan04 APPEC London 5
LIGO Organization & Support DESIGN CONSTRUCTION OPERATION SCIENCE Detector R&D LIGO Laboratory MIT + Caltech ~170 people LIGO Scientific Collaboration 44 member institutions > 400 scientists UK Germany Japan Russia India Spain Australia $ U.S. National Science Foundation 29Jan04 APPEC London 6
Goals and Priorities Interferometer performance» Integrate commissioning and data taking consistent with obtaining one year of integrated data at h = 10 21 by end of 2006 Physics results from LIGO I» International Collaboration LIGO Sciece Collaboration (LSC)» Initial upper limit results in 2003; First search results in 2005» Reach LIGO I goals by 2007» Establish an International Network with other detectors (Virgo) Advanced LIGO» R&D and Design toward Advanced LIGO (~ x20 improved sensitivity)» International collaboration and broad LSC participation» Advanced LIGO installation beginning ~ 2007 29Jan04 APPEC London 7
LIGO Commissioning and Science Timeline 29Jan04 APPEC London 8
Lock Acquisition 29Jan04 APPEC London 9
Detecting Earthquakes From electronic logbook 2Jan02 An earthquake occurred, starting at UTC 17:38. 29Jan04 APPEC London 10
Detecting the Earth Tides Sun and Moon Eric Morgenson Caltech Sophomore 29Jan04 APPEC London 11
Tidal Compensation Data Tidal evaluation 21 hour locked section of S1 data Predicted tides Feedforward Feedback Residual signal on voice coils Residual signal on laser 29Jan04 APPEC London 12
Controlling angular degrees of freedom 29Jan04 APPEC London 13
Interferometer Noise Limits Seismic Noise test mass (mirror) Quantum Noise Residual gas scattering "Shot" noise Radiation pressure LASER Wavelength & amplitude fluctuations Beam splitter photodiode 29Jan04 APPEC London 14 Thermal (Brownian) Noise
What Limits LIGO Sensitivity? Seismic noise limits low frequencies Thermal Noise limits middle frequencies Quantum nature of light (Shot Noise) limits high frequencies Technical issues alignment, electronics, acoustics, etc limit us before we reach these design goals 29Jan04 APPEC London 15
LIGO Sensitivity Evolution Hanford 4km Interferometer Dec 01 Nov 03 29Jan04 APPEC London 16
Science Runs Virgo Andromeda Milky Cluster Way A Measure of Progress NN Binary Inspiral Range E8 ~ 5 kpc S1 ~ 100 kpc S2 ~ 0.9Mpc S3 ~ 3 Mpc Design~ 18 Mpc 29Jan04 APPEC London 17
Best Performance to Date. Range ~ 6 Mpc 29Jan04 APPEC London 18
Astrophysical Sources signatures Compact binary inspiral: chirps» NSNS waveforms are well described» BHBH need better waveforms» search technique: matched templates Supernovae / GRBs: bursts» burst signals in coincidence with signals in electromagnetic radiation» prompt alarm (~ one hour) with neutrino detectors Pulsars in our galaxy: periodic» search for observed neutron stars (frequency, doppler shift)» all sky search (computing challenge)» rmodes Cosmological Signal stochastic background 29Jan04 APPEC London 19
Detection of Periodic Sources Pulsars in our galaxy:» search for observed neutron stars» all sky search (computing challenge)» rmodes periodic Frequency modulation of signal due to Earth s motion relative to the Solar System Barycenter, intrinsic frequency changes. Amplitude modulation due to the detector s antenna pattern. 29Jan04 APPEC London 20
Directed searches NO DETECTION EXPECTED Crab Pulsar h =11.4 at present sensitivities ( f ) GW OBS 0 Sh /T Limits of detectability for rotating NS with equatorial ellipticity ε = δi/i zz : 10 3, 10 4, 10 5 @ 8.5 kpc. PSR J1939+2134 1283.86 Hz 29Jan04 APPEC London 21
Two Search Methods Frequency domain Time domain Best suited for large parameter space searches Maximum likelihood detection method + Frequentist approach Best suited to target known objects, even if phase evolution is complicated Bayesian approach First science run use both pipelines for the same search for crosschecking and validation 29Jan04 APPEC London 22
The Data time behavior < S h > < S h > days days < h S > S > < h days days 29Jan04 APPEC London 23
The Data frequency behavior S h S h Hz Hz S h S h Hz Hz 29Jan04 APPEC London 24
PSR J1939+2134 Frequency domain Fourier Transforms of time series Detection statistic: F, maximum likelihood ratio wrt unknown parameters use signal injections to measure F s pdf use frequentist s approach to derive upper limit Injected signal in LLO: h = 2.83 x 10 22 Measured F statistic 29Jan04 APPEC London 25
PSR J1939+2134 Time domain time series is heterodyned noise is estimated Bayesian approach in parameter estimation: express result in terms of posterior pdf for parameters of interest Data 95% Injected signals in GEO: h=1.5, 2.0, 2.5, 3.0 x 10 21 h = 2.1 x 10 21 29Jan04 APPEC London 26
Results: Periodic Sources No evidence of continuous wave emission from PSR J1939+2134. Summary of 95% upper limits on h: IFO Frequentist FDS Bayesian TDS GEO (1.94±0.12)x10 21 (2.1 ±0.1)x10 21 LLO (2.83±0.31)x10 22 (1.4 ±0.1)x10 22 LHO2K (4.71±0.50)x10 22 (2.2 ±0.2)x10 22 LHO4K (6.42±0.72)x10 22 (2.7 ±0.3)x10 22 Best previous results for PSR J1939+2134: h o < 10 20 (Glasgow, Hough et al., 1983) 29Jan04 APPEC London 27
Upper limit on pulsar ellipticity J1939+2134 h 0 = moment of inertia tensor 2 8π G 4 c I zz f R 2 0 ε gravitational ellipticity of pulsar h 0 < 3 10 22 e < 3 10 4 R (M=1.4M sun, r=10km, R=3.6kpc) Assumes emission is due to deviation from axisymmetry:.. 29Jan04 APPEC London 28
Multidetector upper limits S2 Data Run 95% upper limits Performed joint coherent analysis for 28 pulsars using data from all IFOs. Most stringent UL is for pulsar J16296902 (~333 Hz) where 95% confident that h 0 < 2.3x10 24. 95% upper limit for Crab pulsar (~ 60 Hz) is h 0 < 5.1 x 10 23. 95% upper limit for J1939+2134 (~ 1284 Hz) is h 0 < 1.3 x 10 23. 29Jan04 APPEC London 29
Upper limits on ellipticity S2 upper limits Equatorial ellipticity: Spindown based upper limits ε = Ixx Iyy I zz Pulsars J0030+0451 (230 pc), J21243358 (250 pc), and J1024 0719 (350 pc) are the nearest three pulsars in the set and their equatorial ellipticities are all constrained to less than 10 5. 29Jan04 APPEC London 30
Approaching spindown upper limits For Crab pulsar (B0531+21) we are still a factor of ~35 above the spindown upper limit in S2. Ratio of S2 upper limits to spindown based upper limits Hope to reach spindown based upper limit in S3! Note that not all pulsars analysed are constrained due to spindown rates; some actually appear to be spinningup (associated with accelerations in globular cluster). 29Jan04 APPEC London 31
Advanced LIGO improved subsystems Multiple Suspensions Active Seismic Sapphire Optics Higher Power Laser 29Jan04 APPEC London 32
Anatomy of the projected Advanced LIGO detector performance 10 21 Newtonian background, estimate for LIGO sites Seismic cutoff at 10 Hz Suspension thermal noise Test mass thermal noise 10 22 1 / 2 z )/H (f e,h N ois S train 10 22 10 23 10 23 Initial LIGO Advanced LIGO Unified quantum noise dominates at most frequencies for full power, broadband tuning this topology 10 24 10 24 10 Hz 100 Hz 1 khz Advanced LIGO's FabryPerot Michelson Interferometer is flexible can tailor to what we learn before and after we bring it on line, to the limits of 10 1 10 2 10 3 Frequency (Hz) 29Jan04 APPEC London 33
Design features ACTIVE ISOLATION 40 KG SAPPHIRE TEST MASSES QUAD SILICA SUSPENSION 180 W LASER, MODULATION SYSTEM PRM Power Recycling Mirror BS Beam Splitter ITM Input Test Mass ETM End Test Mass SRM Signal Recycling Mirror PD Photodiode 29Jan04 APPEC London 34
Test Masses / Core Optics Fullsize Advanced LIGO sapphire substrate 29Jan04 APPEC London 35
Isolation: multistage solution 29Jan04 APPEC London 36
Suspensions Prototype triple pendulum suspension 29Jan04 APPEC London 37
Advanced LIGO Cubic Law for Window on the Universe Improve amplitude sensitivity by a factor of 10x number of sources goes up 1000x! Virgo cluster Today Initial LIGO Advanced LIGO 29Jan04 APPEC London 38
Factor 10 better amplitude sensitivity» (Reach) 3 = rate Factor 4 lower frequency bound NS Binaries: for three interferometers,» Initial LIGO: ~20 Mpc» Adv LIGO: ~350 Mpc BH Binaries:» Initial LIGO: 10 M o, 100 Mpc» Adv LIGO : 50 M o, z=2 Stochastic background:» Initial LIGO: ~3e6» Adv LIGO ~3e9 Initial and Advanced LIGO 29Jan04 APPEC London 39
Signals from the Early Universe Strength specified by ratio of energy density in GWs to total energy density needed to close the universe: Ω (f) GW = dρgw d(lnf) Detect by crosscorrelating output of two GW detectors: ρ 1 critical First LIGO Science Data Hanford Livingston 29Jan04 APPEC London 40
Gravitational Waves from the Early Universe results projected S1 E7 S2 LIGO Adv LIGO 29Jan04 APPEC London 41
LIGO Collaboration with Europe GEO has joined LIGO Scientific Collaboration; Full partners in Advanced LIGO, including management» GEOLIGO collaboration on data analysis working very well. Full exchange of data, joint analyses, leadership role by GEO scientists» GEO major partner in Advanced LIGO laser, suspensions, narrow band optics Technical R&D collaboration with Virgo SMA Lyon on Sapphire Optics Coatings Data exchange with Virgo is a long term goal; MOU and working group being formed 29Jan04 APPEC London 42