Probing the Universe for Gravitational WavesBCBAct/talks06... · Run S2 S3 S4 22% 75% 81% H2 58% 63% 81% 85% 90% 57% 69% 16% 37% 74% 22% S5 Target SRD goal L1 85% 90% H1 85% 90% 3-way

Probing the Universe for Gravitational Waves

Barry C. BarishCaltech

University of Illinois16-Feb-06

Crab Pulsar

16-Feb-06 LIGO - University of Illinois 2

Gμν= 8πΤμν

General Relativitythe essential idea

Overthrew the 19th-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) spacetimeObjects follow the shortest path through

this warped spacetime; path is the same for all objects


After several hundred years, a small crack in Newton’s theory …..

perihelion shifts forward an extra +43”/century

compared to Newton’s theory


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.


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


A Conceptual Problem is solved !

Newton’s Theory“instantaneous action

at a distance”

Einstein’s Theoryinformation carried

by gravitational radiation at the speed of light


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 radiationbinary inspiral

of compact objects


Einstein’s Theory of Gravitationgravitational waves

0)1( 2

2

22 =

∂∂

−∇ μνhtc

• Using Minkowski metric, the information about space-time curvature is contained in the metric as an added term, hμν. 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

)/()/( czthczthh x −+−= +μν

• The strain hμν 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.


Russel A. Hulse

Joseph H.Taylor JrSource: www.NSF.gov

Discovered and Studied Pulsar SystemPSR 1913 + 16

withRadio Telescope

The

The EvidenceFor

Gravitational Waves


The evidence for gravitational waves

Hulse & Taylor

•

•

17 / sec

Neutron binary system

•

• separation = 106 miles• m1 = 1.4m• m2 = 1.36m• e = 0.617

period ~ 8 hr

PSR 1913 + 16Timing of pulsars

Predictionfrom

general relativity

• spiral in by 3 mm/orbit• rate of change orbital

period


“Indirect”evidence

for gravitational

waves


Direct Detection

Detectors in space

LISA

Gravitational Wave Astrophysical

Source

Terrestrial detectorsLIGO, TAMA, Virgo, AIGO


Gravitational Waves in Space

LISA

Three spacecraft, each with a Y-shaped payload, form an equilateral triangle with sides 5 million km in length.


Network of Interferometers

LIGO

detection confidence

GEO VirgoTAMA

AIGOlocate the sources

decompose the polarization of gravitational waves


The frequency range of astronomy

EM waves studied over ~16 orders of magnitude» Ultra Low Frequency

radio waves to high energy gamma rays


Frequencies of Gravitational Waves

The diagram shows the sensitivity bands for LISA and LIGO


laser

Gravitational Wave Detection

Laser Interferometer

free massesh = strain amplitude of grav. waves

h = ΔL/L ~ 10-21

L = 4 kmΔL ~ 10-18 m


Interferometer optical layout

laser various optics

6-7 W 150-200 W10 W 4-5 W 9-12 kW

vacuum

photodetector

suspended, seismically isolated test masses

GW channel

200 mW

modecleaner

4 km


LIGOLaser Interferometer

Gravitational-wave ObservatoryHanford Observatory

LivingstonObservatory

Caltech

MIT


LIGOLivingston, Louisiana

4 km


LIGO

Hanford Washington

4 km

2 km


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


Vacuum Chambersvibration isolation systems

» Reduce in-band seismic motion by 4 - 6 orders of magnitude

» Compensate for microseism at 0.15 Hz by a factor of ten

» Compensate (partially) for Earth tides


LIGOvacuum equipment


Seismic Isolationsuspension 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


LIGO Opticsfused silica

Caltech data CSIRO data

Surface uniformity < 1 nm rmsScatter < 50 ppmAbsorption < 2 ppmROC matched < 3%Internal mode Q’s > 2 x 106


Core Opticsinstallation and

alignment


Lock Acquisition


Tidal Compensation DataTidal evaluation 21-hour locked section of S1 data

Predicted tides

Residual signal on voice coils

Residual signal on laser

Feedforward

Feedback


Controlling angular degrees of freedom


Interferometer Noise Limits

Thermal (Brownian)

Noise

LASER

test mass (mirror)

Beamsplitter

Residual gas scattering

Wavelength & amplitude fluctuations photodiode

Seismic Noise

Quantum Noise

"Shot" noiseRadiation pressure


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


Evolution of LIGO SensitivityS1: 23 Aug – 9 Sep ‘02S2: 14 Feb – 14 Apr ‘03S3: 31 Oct ‘03 – 9 Jan ‘04S4: 22 Feb – 23 Mar ‘05S5: 4 Nov ‘05 -


Commissioning /Running Time Line

NowInauguration

1999 2000 2001 2002 20033 4 1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

E2Engineering E3 E5 E9 E10E7 E8 E11

First Lock Full Lock all IFO

10-17 10-18 10-20 10-21

2004 20051 2 3 4 1 2 3 4 1 2 3 4

2006

First Science Data

S1 S4Science S2 RunsS3 S5

10-224K strain noise at 150 Hz [Hz-1/2]4x10-23


102 10310-23

10-22

10-21

10-20

10-19

10-18

Frequency (Hz)

Equi

vale

nt s

trai

n no

ise

(Hz-1

/2)

H1, 20 Oct 05L1, 30 Oct 05SRD curve

Rms strain in 100 Hz BW: 0.4x10-21

Entering S5 …


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’

Run S2 S3 S4

22% 75%

81%

H2 58% 63% 81% 85% 90%

57%

69%

16%

37%

74%

22%

S5 Target

SRDgoal

L1 85% 90%

H1 85% 90%

3-way 70% 75%

Interferometer duty cycles


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 WayAndromedaVirgo Cluster


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”


Compact Binary Collisions

» Neutron Star – Neutron Star

– waveforms are well described» Black Hole – Black Hole

– need better waveforms » Search: matched

templates

“chirps”


Template Bank

Covers desiredregion of massparam spaceCalculatedbased on L1noise curveTemplatesplaced formax mismatchof δ = 0.03

2110 templatesSecond-orderpost-Newtonian


Optimal Filtering

Transform data to frequency domain : Generate template in frequency domain : Correlate, weighting by power spectral density of noise:

)(~ fh)(~ fs

|)(|)(~)(~ *

fSfhfs

h

|)(| tzFind maxima of over arrival time and phaseCharacterize these by signal-to-noise ratio (SNR) and effective distance

dfefS

fhfstz tfi

h

π2

0

*

|)(|)(~)(~

4)( ∫∞

=

Then inverse Fourier transform gives you the filter output

at all times:

frequency domain


Matched Filtering

Inspiral Searches

BNSS3/S4

PBHMACHO

S3/S4

Spin is importantDetection templates S3

“High mass ratio”Coming soon

1

3

100.1

Mass

Mass0.1 1 3

10

BBH SearchS3/S4

Physical waveformfollow-up S3/S4

Inspiral-Burst S4


Binary Neutron Star Search Results (S2)

cum

ulat

ive

num

ber o

f eve

nts

signal-to-noise ratio squared

Rate < 47 per year perMilky-Way-like galaxy

Physical Review D, In Press


Binary Black Hole Search


Binary Inspiral Search: LIGO Ranges

Image: R. Powell

binary neutron star range

binary black hole range






detectors





Detection of Burst SourcesKnown 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 GRB030329

Unknown phenomena» Emission of short transients of gravitational radiation of unknown waveform (e.g. black hole mergers).


‘Unmodeled’ Burstssearch 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’

freq

uenc

y

time

‘Raw Data’ Time-domain high pass filter

0.125s

8Hz


Burst Search ResultsBlind procedure gives one event candidate» Event immediately

found to be correlated with airplane over-flight


Burst Source - Upper Limit


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 GRB050709 Long burst GRB030329


Astrophysical Sourcessignatures




detectors





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.


Pulsars: Target Sources

Credit: Dana Berry/NASA

Accreting Neutron Stars

Credit: M. Kramer

Wobbling Neutron Stars

Bumpy Neutron Star


Directed Pulsar Search

28 Radio Sources


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 RESULT28 known pulsars

NO gravitational waves

e < 10-5 – 10-6

(no mountains > 10 cm

ALL SKY SEARCHenormous computing challenge


Einstein@Home

LIGO Pulsar Search using home pc’s

BRUCE ALLENProject Leader

Univ of Wisconsin Milwaukee

LIGO, UWM, AEI, APS

http://einstein.phys.uwm.edu






detectors





Signals from the Early Universe

Cosmic Microwavebackground

WMAP 2003

stochastic background


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

d(lnf)dρ

ρ1(f)Ω GW

criticalGW =


Stochastic Background Search (S3)Physical Review Letters, In Press

Fraction of Universe’senergy in gravitational waves:

(LIGO band)


Results – Stochastic Backgrounds


Gravitational Waves from the Early Universe

E7

S1S2

LIGO

Adv LIGO

results

projected


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 > 10-18, R90% < 2/day (limited by observation time)» Minimum h ~ 2 x 10-19

» S2: 50% detection efficiency h ~ 10-20

Periodic, or “CW”» S2: (LIGO and GEO600) interferometers -- Targeted 28 known

pulsars» h < 1.7 x 10-24 (J1910-5959D)» e < 4.5 x 10-6 (J2124-3358)» Crab limit on h within 30X of spindown rate, if spindown were

due to GW emission» All sky search ---- Einstein@Home

Stochastic background» S2: 387 hours of cross-correlation measurements for H-L≈ ΩGW < 0.018 +0.007/-0.003 in band 50 Hz < f < 300 Hz (preliminary)» S3: 240 hours of cross-correlation measurements for H-L, H-H» Sensitivity estimated to be ΩGW < 5 x 10-4 50 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 > 10-18, R90% < 2/day (limited by observation time)» Minimum h ~ 2 x 10-19

» S2: 50% detection efficiency h ~ 10-20

Periodic, or “CW”» S2: (LIGO and GEO600) interferometers -- Targeted 28 known

pulsars» h < 1.7 x 10-24 (J1910-5959D)» e < 4.5 x 10-6 (J2124-3358)» Crab limit on h within 30X of spindown rate, if spindown were

due to GW emission» All sky search ---- Einstein@Home

Stochastic background» S2: 387 hours of cross-correlation measurements for H-L≈ ΩGW < 0.018 +0.007/-0.003 in band 50 Hz < f < 300 Hz (preliminary)» S3: 240 hours of cross-correlation measurements for H-L, H-H» Sensitivity estimated to be ΩGW < 5 x 10-4 50 Hz < f < 250 Hz

Astrophysical Results


Gravitational Wave Astronomy

LIGOwill provide a new way to view the dynamics of the

Universe

Documents

Probing the Universe for Gravitational WavesBCBAct/talks06... · Run S2 S3 S4 22% 75% 81% H2 58% 63% 81% 85% 90% 57% 69% 16% 37% 74% 22% S5 Target SRD goal L1 85% 90% H1 85% 90% 3-way