Unlocking the Universe: Gravitational Waves and LIGO Exploration

1. Probing the Universe for Gravitational Waves: A First Glimpse with LIGOBarry C. BarishCaltechPenn State10-April-03 "Colliding Black Holes"Credit:National Center for Supercomputing Applications (NCSA) LIGO-G030020-00-M

2. A Conceptual Problem is solved ! Newton’s Theory “instantaneous action at a distance” Gmn= 8pTmn Einstein’s Theory information carried by gravitational radiation at the speed of light Penn State -- Colloquium

3. Einstein’s Theory of Gravitation • a 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 Penn State -- Colloquium

4. 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, hmn. In the weak field limit, the equation can be described with linear equations. If the choice of gauge is thetransverse traceless gaugethe formulation becomes a familiar wave equation • The strain hmn 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 450 instead of 900 from each other. Penn State -- Colloquium

5. Detecting Gravitational Waves Laboratory Experiment a la Hertz Experimental Generation and Detection of Gravitational Waves gedanken experiment Penn State -- Colloquium

6. The evidence for gravitational waves • Neutron binary system • separation = 106 miles • m1 = 1.4m • m2 = 1.36m • e = 0.617 Hulse & Taylor 17 / sec · · • Prediction • from • general relativity • spiral in by 3 mm/orbit • rate of change orbital • period period ~ 8 hr PSR 1913 + 16 Timing of pulsars Penn State -- Colloquium

7. “Indirect”detection of gravitational waves PSR 1913+16 Penn State -- Colloquium

8. Direct Detection Gravitational Wave Astrophysical Source Terrestrial detectors LIGO, TAMA, Virgo,AIGO Detectors in space LISA Penn State -- Colloquium

9. Detection in space The Laser Interferometer Space Antenna LISA • Center of the triangle formation is in the ecliptic plane • 1 AU from the Sun and 20 degrees behind the Earth. Penn State -- Colloquium

10. Detection on Earth simultaneously detect signal LIGO Virgo GEO TAMA AIGO decompose the polarization of gravitational waves detection confidence locate the sources Penn State -- Colloquium

11. Frequency range of astrophysics sources Audio band • Gravitational Waves over ~8 orders of magnitude • Terrestrial detectors and space detectors Space Terrestrial Penn State -- Colloquium

12. Frequency range of astronomy • EM waves studied over ~16 orders of magnitude • Ultra Low Frequency radio waves to high energy gamma rays Penn State -- Colloquium

13. A New Window on the Universe Gravitational Waves will provide a new way to view the dynamics of the Universe Penn State -- Colloquium

14. Astrophysical Sourcessignatures • 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 Signals “stochastic background” Penn State -- Colloquium

15. The effect … Leonardo da Vinci’s Vitruvian man Stretch and squash in perpendicular directions at the frequency of the gravitational waves Penn State -- Colloquium

16. Detecting a passing wave …. Free masses Penn State -- Colloquium

17. Detecting a passing wave …. Interferometer Penn State -- Colloquium

18. The challenge …. I have greatly exaggerated the effect!! If the Vitruvian man was 4.5 light years high, he would grow by only a ‘hairs width’ LIGO Interferometer Concept Penn State -- Colloquium

19. As a wave passes, the arm lengths change in different ways…. Interferometer Concept • Arms in LIGO are 4km • Measure difference in length to one part in 1021 or 10-18 meters • Laser used to measure relative lengths of two orthogonal arms …causing the interference pattern to change at the photodiode Penn State -- Colloquium

20. One meter ~ 40 inches Human hair ~ 100 microns Wavelength of light ~ 1 micron Atomic diameter 10-10 m Nuclear diameter 10-15 m LIGO sensitivity 10-18 m How Small is 10-18 Meter? Penn State -- Colloquium

21. DESIGN CONSTRUCTION OPERATION SCIENCE Detector R&D LIGO Laboratory MIT + Caltech ~140 people Director: Barry Barish LIGO Science Collaboration 44 member institutions > 400 scientists Spokesperson: Rai Weiss UK Germany Japan Russia India Spain Australia $ National Science Foundation LIGO Organization Penn State -- Colloquium

22. The Laboratory Sites Laser Interferometer Gravitational-wave Observatory (LIGO) Hanford Observatory Livingston Observatory Penn State -- Colloquium

23. LIGO Livingston Observatory Penn State -- Colloquium

24. LIGO Hanford Observatory Penn State -- Colloquium

25. LIGObeam tube • LIGO beam tube under construction in January 1998 • 65 ft spiral welded sections • girth welded in portable clean room in the field 1.2 m diameter - 3mm stainless 50 km of weld NO LEAKS !! Penn State -- Colloquium

26. LIGOvacuum equipment Penn State -- Colloquium

27. LIGO Optic Substrates: SiO2 25 cm Diameter, 10 cm thick Homogeneity < 5 x 10-7 Internal mode Q’s > 2 x 106 Polishing Surface uniformity < 1 nm rms Radii of curvature matched < 3% Coating Scatter < 50 ppm Absorption < 2 ppm Uniformity <10-3 Penn State -- Colloquium

28. Core Optics installation and alignment Penn State -- Colloquium

29. Deliver pre-stabilized laser light to the 15-m mode cleaner Frequency fluctuations In-band power fluctuations Power fluctuations at 25 MHz Tidal Wideband 4 km 15m 10-Watt Laser Interferometer PSL IO Laserstabilization • Provide actuator inputs for further stabilization • Wideband • Tidal 10-1 Hz/Hz1/2 10-4 Hz/ Hz1/2 10-7 Hz/ Hz1/2 Penn State -- Colloquium

30. Prestabalized Laserperformance • > 20,000 hours continuous operation • Frequency and lock very robust • TEM00 power > 8 watts • Non-TEM00 power < 10% • Simplification of beam path outside vacuum reduces peaks • Broadband spectrum better than specification from 40-200 Hz Penn State -- Colloquium

31. Composite Video LIGO “first lock” Y Arm Laser X Arm signal Penn State -- Colloquium

32. 2 min Watching the Interferometer Lock Y arm X arm Y Arm Reflected light Anti-symmetricport Laser X Arm signal Penn State -- Colloquium

33. Lock Acquisition Penn State -- Colloquium

34. What Limits Sensitivityof Interferometers? • Seismic noise & vibration limit at low frequencies • Atomic vibrations (Thermal Noise) inside components limit at mid frequencies • Quantum nature of light (Shot Noise) limits at high frequencies • Myriad details of the lasers, electronics, etc., can make problems above these levels Penn State -- Colloquium

35. LIGO Sensitivity Livingston 4km Interferometer May 01 Jan 03 Penn State -- Colloquium

36. Detecting Earthquakes From electronic logbook 2-Jan-02 An earthquake occurred, starting at UTC 17:38. Penn State -- Colloquium

37. Detecting the Earth TidesSun and Moon Penn State -- Colloquium

38. LIGO Sensitivity Livingston 4km Interferometer May 01 First Science Run 17 days - Sept 02 Jan 03 Second Science Run 59 days - April 03 Penn State -- Colloquium

39. In-Lock Data Summary from S1 H1: 235 hrs H2: 298 hrs L1: 170 hrs 3X: 95.7 hrs Red lines: integrated up timeGreen bands (w/ black borders): epochs of lock • August 23 – September 9, 2002: 408 hrs (17 days). • H1 (4km): duty cycle 57.6% ; Total Locked time: 235 hrs • H2 (2km): duty cycle 73.1% ; Total Locked time: 298 hrs • L1 (4km): duty cycle 41.7% ; Total Locked time: 170 hrs • Double coincidences: • L1 && H1 : duty cycle 28.4%; Total coincident time: 116 hrs • L1 && H2 : duty cycle 32.1%; Total coincident time: 131 hrs • H1 && H2 : duty cycle 46.1%; Total coincident time: 188 hrs Triple Coincidence: L1, H1, and H2 : duty cycle 23.4% ; total 95.7 hours Penn State -- Colloquium

40. Compact binary collisions“chirps” • Neutron Star – Neutron Star • waveforms are well described • Black Hole – Black Hole • need better waveforms • Search: matched templates Neutron Star Merger Simulation and Visualization by Maximilian Ruffert& Hans-Thomas Janka Penn State -- Colloquium

41. Searching Technique binary inspiral events • Use template based matched filtering algorithm • Template waveforms for non-spinning binaries • 2.0 post-Newtonian approx. • D: effective distance; a: phase • Discrete set of templates labeled by I=(m1, m2) • 1.0 Msun < m1, m2 < 3.0 Msun • 2110 templates • At most 3% loss in SNR s(t) = (1Mpc/D) x [ sin(a) hIs (t-t0) + cos(a) hIc (t-t0)] Penn State -- Colloquium

42. Sensitivityneutron binary inspirals Star Population in our Galaxy • Population includes Milky Way, LMC and SMC • Neutron star masses in range 1-3 Msun • LMC and SMC contribute ~12% of Milky Way Reach for S1 Data • Inspiral sensitivity Livingston: <D> = 176 kpc Hanford: <D> = 36 kpc • Sensitive to inspirals in • Milky Way, LMC & SMC Penn State -- Colloquium

43. Loudest Surviving Candidate • Not NS/NS inspiral event • 1 Sep 2002, 00:38:33 UTC • S/N = 15.9, c2/dof = 2.2 • (m1,m2) = (1.3, 1.1) Msun What caused this? • Appears to be saturation of a photodiode Penn State -- Colloquium

44. Results of Inspiral Search Upper limit binary neutron star coalescence rate LIGO S1 Data R < 160 / yr / MWEG • Previous observational limits • Japanese TAMA  R < 30,000/ yr / MWEG • Caltech 40m  R < 4,000/ yr / MWEG • Theoretical prediction R < 2 x 10-5 / yr / MWEG Penn State -- Colloquium

45. Gravitational Wave Bursts • Known phenomenalike Supernovae & GRBs • Coincidence with observed electromagnetic observations. • No close supernovae occured during the first science run • Second science run – We are analyzing the recent very bright and close GRB030329 NO RESULT YET • Unknown phenomenaemission of short transients of gravitational radiation of unknown waveform (e.g. black hole mergers). • Search methods: • Time domain algorithm (“SLOPE”): identifies rapid increase in amplitude of a filtered time series (threshold on ‘slope’). • Time-Frequency domain algorithm (“TFCLUSTERS”): identifies regions in the time-frequency plane with excess power Penn State -- Colloquium

46. Time-Frequency Plane Search Pure Time-Domain Search ‘TFCLUSTERS’ ‘SLOPE’ frequency time ‘Unmodelled’ Bursts GOAL search for waveforms from sources for which we cannot currently make an accurate prediction of the waveform shape. METHODS Time-domain high pass filter ‘Raw Data’ 8Hz 0.125s Penn State -- Colloquium

47. h amplitude 0 0 10 time (ms) Determination of Efficiency To measure our efficiency, we must pick a waveform. Efficiency measured for ‘tfclusters’ algorithm 1ms Gaussian burst Penn State -- Colloquium

48. Upper Limit1ms gaussian bursts Result is derived using ‘TFCLUSTERS’ algorithm • Upper limit in straincompared to earlier (cryogenic bar) results: • IGEC 2001 combined bar upper limit: < 2 events per day having h=1x10-20 per Hz of burst bandwidth. For a 1kHz bandwidth, limit is < 2 events/day at h=1x10-17 • Astone et al. (2002), report a one sigma excess of one event per day at strain level of h ~ 2x10-18 90% confidence Penn State -- Colloquium

49. Spinning Neutron Stars“periodic” Maximum gravitational wave luminosity of known pulsars An afterlife of stars Penn State -- Colloquium

50. PSR J1939+2134 1283.86 Hz Directed searches NO DETECTION EXPECTED at present sensitivities Penn State -- Colloquium