Probing the Universe for Gravitational Waves Barry C. Barish Caltech University of Illinois 16-Feb-06 Crab Pulsar

16-Feb-06LIGO - University of Illinois2 G  = 8   General Relativity the essential idea  Overthrew the 19 th -century concepts of absolute space and time  Gravity is not a force, but a property of space & time » Spacetime = 3 spatial dimensions + time » Perception of space or time is relative  Concentrations of mass or energy distort (warp) spacetime  Objects follow the shortest path through this warped spacetime; path is the same for all objects

16-Feb-06LIGO - University of Illinois3 After several hundred years, a small crack in Newton’s theory ….. perihelion shifts forward an extra +43”/century compared to Newton’s theory

16-Feb-06LIGO - University of Illinois4 A new prediction of Einstein’s theory … Light from distant stars are bent as they graze the Sun. The exact amount is predicted by Einstein's theory.

16-Feb-06LIGO - University of Illinois5 Confirming Einstein …. A massive object shifts apparent position of a star bending of light Observation made during the solar eclipse of 1919 by Sir Arthur Eddington, when the Sun was silhouetted against the Hyades star cluster

16-Feb-06LIGO - University of Illinois6 A Conceptual Problem is solved ! Newton’s Theory “instantaneous action at a distance” Einstein’s Theory information carried by gravitational radiation at the speed of light

16-Feb-06LIGO - University of Illinois7 Einstein’s Theory of Gravitation  Gravitational waves are necessary consequence of Special Relativity with its finite speed for information transfer  Gravitational waves come from the acceleration of masses and propagate away from their sources as a space-time warpage at the speed of light gravitational radiation binary inspiral of compact objects

16-Feb-06LIGO - University of Illinois8 Einstein’s Theory of Gravitation gravitational waves Using Minkowski metric, the information about space-time curvature is contained in the metric as an added term, h . In the weak field limit, the equation can be described with linear equations. If the choice of gauge is the transverse traceless gauge the formulation becomes a familiar wave equation The strain h  takes the form of a plane wave propagating at the speed of light (c). Since gravity is spin 2, the waves have two components, but rotated by 45 0 instead of 90 0 from each other.

16-Feb-06LIGO - University of Illinois9 Russel A. Hulse Joseph H.Taylor Jr Source: Discovered and Studied Pulsar System PSR with Radio Telescope The The The Evidence For Gravitational Waves

16-Feb-06LIGO - University of Illinois10 The evidence for gravitational waves Hulse & Taylor   17 / sec Neutron binary system separation = 10 6 miles m 1 = 1.4m  m 2 = 1.36m  e = period ~ 8 hr PSR Timing of pulsars Prediction from general relativity spiral in by 3 mm/orbit rate of change orbital period

16-Feb-06LIGO - University of Illinois11 “Indirect” evidence for gravitational waves

16-Feb-06LIGO - University of Illinois12 Direct Detection Detectors in space LISA Gravitational Wave Astrophysical Source Terrestrial detectors LIGO, TAMA, Virgo, AIGO

16-Feb-06LIGO - University of Illinois13 Gravitational Waves in Space LISA Three spacecraft, each with a Y-shaped payload, form an equilateral triangle with sides 5 million km in length.

16-Feb-06LIGO - University of Illinois14 Network of Interferometers LIGO detection confidence GEO Virgo TAMA AIGO locate the sources decompose the polarization of gravitational waves

16-Feb-06LIGO - University of Illinois15 The frequency range of astronomy  EM waves studied over ~16 orders of magnitude »Ultra Low Frequency radio waves to high energy gamma rays

16-Feb-06LIGO - University of Illinois16 Frequencies of Gravitational Waves The diagram shows the sensitivity bands for LISA and LIGO

16-Feb-06LIGO - University of Illinois17 laser Gravitational Wave Detection Laser Interferometer free masses h = strain amplitude of grav. waves h =  L/L ~ L = 4 km  L ~ m

16-Feb-06LIGO - University of Illinois18 Interferometer optical layout laser various optics 10 W 6-7 W 4-5 W W9-12 kW vacuum photodetector suspended, seismically isolated test masses GW channel 200 mW mode cleaner 4 km

16-Feb-06LIGO - University of Illinois19 LIGO Laser Interferometer Gravitational-wave Observatory Hanford Observatory Livingston Observatory Caltech MIT

16-Feb-06LIGO - University of Illinois20 LIGO Livingston, Louisiana 4 km

16-Feb-06LIGO - University of Illinois21 LIGO Hanford Washington 4 km 2 km

16-Feb-06LIGO - University of Illinois22 LIGO Beam Tube 1.2 m diameter - 3mm stainless 50 km of weld 65 ft spiral welded sections Girth welded in portable clean room in the field Minimal enclosure Reinforced concrete No services

16-Feb-06LIGO - University of Illinois23 Vacuum Chambers vibration isolation systems »Reduce in-band seismic motion by orders of magnitude »Compensate for microseism at 0.15 Hz by a factor of ten »Compensate (partially) for Earth tides

16-Feb-06LIGO - University of Illinois24 LIGO vacuum equipment

16-Feb-06LIGO - University of Illinois25 Seismic Isolation suspension system Support structure is welded tubular stainless steel Suspension wire is 0.31 mm diameter steel music wire Fundamental violin mode frequency of 340 Hz Suspension assembly for a core optic

16-Feb-06LIGO - University of Illinois26 LIGO Optics fused silica Caltech dataCSIRO data  Surface uniformity < 1 nm rms  Scatter < 50 ppm  Absorption < 2 ppm  ROC matched < 3%  Internal mode Q’s > 2 x 10 6

16-Feb-06LIGO - University of Illinois27 Core Optics installation and alignment

16-Feb-06LIGO - University of Illinois28 Lock Acquisition

16-Feb-06LIGO - University of Illinois29 Tidal Compensation Data Tidal evaluation 21-hour locked section of S1 data Residual signal on voice coils Predicted tides Residual signal on laser Feedforward Feedback

16-Feb-06LIGO - University of Illinois30 Controlling angular degrees of freedom

16-Feb-06LIGO - University of Illinois31 Interferometer Noise Limits Thermal (Brownian) Noise LASER test mass (mirror) Beam splitter Residual gas scattering Wavelength & amplitude fluctuations photodiode Seismic Noise Quantum Noise "Shot" noise Radiation pressure

16-Feb-06LIGO - University of Illinois32 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

16-Feb-06LIGO - University of Illinois33 Evolution of LIGO Sensitivity  S1: 23 Aug – 9 Sep ‘02  S2: 14 Feb – 14 Apr ‘03  S3: 31 Oct ‘03 – 9 Jan ‘04  S4: 22 Feb – 23 Mar ‘05  S5: 4 Nov ‘05 -

16-Feb-06LIGO - University of Illinois34 Commissioning /Running Time Line Now Inauguration E2 Engineering E3 E5 E9E10 E7 E8 E11 First LockFull Lock all IFO First Science Data S1 S4 Science S2 Runs S3S5S K strain noiseat 150 Hz [Hz -1/2 ] 4x10 -23

16-Feb-06LIGO - University of Illinois35 Rms strain in 100 Hz BW: 0.4x Entering S5 …

16-Feb-06LIGO - University of Illinois36 S5 Run Plan and Outlook  Goal is to “collect at least a year’s data of coincident operation at the science goal sensitivity”  Expect S5 to last about 1.5 yrs  S5 will not be completely ‘hands- off’ RunS2S3S4 S5 Target SRD goal L137%22%75%85%90% H174%69%81%85%90% H258%63%81%85%90% 3- way 22%16%57%70%75% Interferometer duty cycles

16-Feb-06LIGO - University of Illinois37 Science Runs S2 ~ 0.9Mpc S1 ~ 100 kpc E8 ~ 5 kpc NN Binary Inspiral Range S3 ~ 3 Mpc Goal ~ 14 Mpc A Measure of Progress Milky Way AndromedaVirgo Cluster

16-Feb-06LIGO - University of Illinois38 Astrophysical Sources  Compact binary inspiral: “chirps” »NS-NS waveforms are well described »BH-BH 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) »r-modes  Cosmological Signal “stochastic background”

16-Feb-06LIGO - University of Illinois39 Compact Binary Collisions »Neutron Star – Neutron Star –waveforms are well described »Black Hole – Black Hole –need better waveforms »Search: matched templates “chirps”

16-Feb-06LIGO - University of Illinois40 Template Bank  Covers desired region of mass param space  Calculated based on L1 noise curve  Templates placed for max mismatch of  = templates Second-order post-Newtonian

16-Feb-06LIGO - University of Illinois41 Optimal Filtering  Transform data to frequency domain :  Generate template in frequency domain :  Correlate, weighting by power spectral density of noise: Find maxima of over arrival time and phase Characterize these by signal-to-noise ratio (SNR) and effective distance Then inverse Fourier transform gives you the filter output at all times: frequency domain

16-Feb-06LIGO - University of Illinois42 Matched Filtering

16-Feb-06LIGO - University of Illinois43 Inspiral Searches BNS S3/S4 PBH MACHO S3/S4 Spin is important Detection templates S3 “High mass ratio” Coming soon Mass BBH Search S3/S4 Physical waveform follow-up S3/S4 Inspiral-Burst S4

16-Feb-06LIGO - University of Illinois44 Binary Neutron Star Search Results (S2) cumulative number of events signal-to-noise ratio squared Rate < 47 per year per Milky-Way-like galaxy Physical Review D, In Press

16-Feb-06LIGO - University of Illinois45 Binary Black Hole Search

16-Feb-06LIGO - University of Illinois46 Binary Inspiral Search: LIGO Ranges Image: R. Powell binary neutron star range binary black hole range

16-Feb-06LIGO - University of Illinois47 Astrophysical Sources  Compact binary inspiral: “chirps” »NS-NS waveforms are well described »BH-BH 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) »r-modes  Cosmological Signal “stochastic background”

16-Feb-06LIGO - University of Illinois48 Detection of Burst Sources  Known sources -- Supernovae & GRBs » Coincidence with observed electromagnetic observations. » No close supernovae occurred during the first science run » Second science run – We analyzed the very bright and close GRB  Unknown phenomena » Emission of short transients of gravitational radiation of unknown waveform (e.g. black hole mergers).

16-Feb-06LIGO - University of Illinois49 ‘Unmodeled’ Bursts search for waveforms from sources for which we cannot currently make an accurate prediction of the waveform shape. GOAL METHODS Time-Frequency Plane Search ‘TFCLUSTERS’ Pure Time-Domain Search ‘SLOPE’ frequency time ‘Raw Data’Time-domain high pass filter 0.125s 8Hz

16-Feb-06LIGO - University of Illinois50 Burst Search Results  Blind procedure gives one event candidate »Event immediately found to be correlated with airplane over-flight

16-Feb-06LIGO - University of Illinois51 Burst Source - Upper Limit

16-Feb-06LIGO - University of Illinois52 Gamma-Ray Bursts short and long Credit: Dana Berry/NASA HST Image Credit: Derek Fox Optical counterpart Possible scenario for short GRBs: neutron star/black hole collision Optical counterpart NASA Image Short burst GRB050709Long burst GRB030329

16-Feb-06LIGO - University of Illinois53 Astrophysical Sources signatures  Compact binary inspiral: “chirps” »NS-NS waveforms are well described »BH-BH 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) »r-modes  Cosmological Signal “stochastic background”

16-Feb-06LIGO - University of Illinois54 Detection of Periodic Sources  Pulsars in our galaxy: “periodic” »search for observed neutron stars »all sky search (computing challenge) »r-modes  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.

16-Feb-06LIGO - University of Illinois55 Pulsars: Target Sources Credit: Dana Berry/NASACredit: M. Kramer Accreting Neutron StarsWobbling Neutron Stars Bumpy Neutron Star

16-Feb-06LIGO - University of Illinois56 Directed Pulsar Search 28 Radio Sources

16-Feb-06LIGO - University of Illinois57 Detection of Periodic Sources  Known Pulsars in our galaxy  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. NEW RESULT 28 known pulsars NO gravitational waves e < – (no mountains > 10 cm ALL SKY SEARCH enormous computing challenge

16-Feb-06LIGO - University of Illinois58 LIGO Pulsar Search using home pc’s BRUCE ALLEN Project Leader Univ of Wisconsin Milwaukee LIGO, UWM, AEI, APS

16-Feb-06LIGO - University of Illinois59 Astrophysical Sources  Compact binary inspiral: “chirps” »NS-NS waveforms are well described »BH-BH 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) »r-modes  Cosmological Signal “stochastic background”

16-Feb-06LIGO - University of Illinois60 Signals from the Early Universe Cosmic Microwave background WMAP 2003 stochastic background

16-Feb-06LIGO - University of Illinois61 Signals from the Early Universe  Strength specified by ratio of energy density in GWs to total energy density needed to close the universe:  Detect by cross-correlating output of two GW detectors: First LIGO Science Data Hanford - Livingston

16-Feb-06LIGO - University of Illinois62 Stochastic Background Search (S3) Physical Review Letters, In Press Fraction of Universe’s energy in gravitational waves: (LIGO band)

16-Feb-06LIGO - University of Illinois63 Results – Stochastic Backgrounds

16-Feb-06LIGO - University of Illinois64 Gravitational Waves from the Early Universe E7 S1 S2 LIGO Adv LIGO results projected

16-Feb-06LIGO - University of Illinois65  Chirps »S2: 355 hours of coincident (2X, 3X) interferometer operation »Sensitive to D ~ 2 Mpc (NG = 1.14 Milky Way Equiv. Galaxies) »R90% < 50 events/year/MWEG (1 Msun < M1,2 < 3 Msun)  Bursts »S1: For h > , R90% < 2/day (limited by observation time) »Minimum h ~ 2 x »S2: 50% detection efficiency h ~  Periodic, or “CW” »S2: (LIGO and GEO600) interferometers -- Targeted 28 known pulsars »h < 1.7 x (J D) » e < 4.5 x (J ) »Crab limit on h within 30X of spindown rate, if spindown were due to GW emission »All sky search ----  Stochastic background »S2: 387 hours of cross-correlation measurements for H-L  GW < / in band 50 Hz < f < 300 Hz (preliminary) »S3: 240 hours of cross-correlation measurements for H-L, H-H »Sensitivity estimated to be  GW < 5 x Hz < f < 250 Hz  Chirps »S2: 355 hours of coincident (2X, 3X) interferometer operation »Sensitive to D ~ 2 Mpc (NG = 1.14 Milky Way Equiv. Galaxies) »R90% < 50 events/year/MWEG (1 Msun < M1,2 < 3 Msun)  Bursts »S1: For h > , R90% < 2/day (limited by observation time) »Minimum h ~ 2 x »S2: 50% detection efficiency h ~  Periodic, or “CW” »S2: (LIGO and GEO600) interferometers -- Targeted 28 known pulsars »h < 1.7 x (J D) » e < 4.5 x (J ) »Crab limit on h within 30X of spindown rate, if spindown were due to GW emission »All sky search ----  Stochastic background »S2: 387 hours of cross-correlation measurements for H-L  GW < / in band 50 Hz < f < 300 Hz (preliminary) »S3: 240 hours of cross-correlation measurements for H-L, H-H »Sensitivity estimated to be  GW < 5 x Hz < f < 250 Hz Astrophysical Results

16-Feb-06LIGO - University of Illinois66 Gravitational Wave Astronomy LIGO will provide a new way to view the dynamics of the Universe