Transcript Gravitational physics program

LISA
Laser Interferometer
Space Antenna
Status of Gravitational Physics Program
Jo van den Brand
NIKHEF – Annual Scientific Meeting 2005
http://www.esa.int/science/lisa
LISA
October 3, 2005
Introduction
Einstein gravity :
G  8 T
Gravity as a geometry
Space and time are physical objects
Gravitational waves
LISA
•
Dynamical part of gravitation, all space is filled
•
Very large energy, almost no interaction
•
Ideal information carrier, almost no scattering or
attenuation
•
The entire Universe has been transparant for GWs,
all the way back to the Big Bang
Gravitational waves `squeeze space: small effects
Proper distance between xm and xm +dxm
Define
Wave equation
Plane GW propagating in z-direction
Amplitude, frequency and duration
LISA
Bar detectors: IGEC collaboration
Built to detect gravitational waves from compact objects
LISA
Mini-GRAIL: a spherical `bar’ in Leiden
SFERA
LISA
Interferometric detectors: an international dream
GEO600 (British-German)
Hanover, Germany
LIGO (USA)
Hanford, WA and Livingston, LA
TAMA300 (Japan)
Mitaka
LISA
AIGO (Australia),
VIRGO (French-Italian)
Wallingup Plain, 85km north of Perth Cascina, Italy
Network of Interferometers
LIGO
GEO
decompose
polarization
of
detection
locatethe
the
confidence
sources
gravitational waves
LISA
Virgo
AIGO
TAMA
Virgo
LISA
Interferometer Concept
…causing the
interference pattern to
change at the
photodiode
LISA
As a wave
passes,
Suspended
the
arm
Masses
lengths
change in
different
ways….
VIRGO Optical Scheme
Input Mode Cleaner (144 m)
3 km long Fabry-Perot
Cavities
Laser 20 W
Power
Recycling
Output Mode
Cleaner (4 cm)
LISA
Virgo – inside the central building
LISA
Mirror suspension
High quality fused silica mirrors
LISA
•
35 cm diameter, 10 cm thickness, 21 kg mass
•
Substrate losses ~1 ppm
•
Coating losses <5 ppm
•
Surface deformation ~l/100
Superattenuators
Possible contributions:

Virgo+ will use
monolythic suspension

Input-mode cleaner
suspension
Input mode cleaner
 Mode cleaner cavity: filters
laser noise, select TEM00
mode
Input beam
inbeam
LISA
Transm. beam
outbeam
Refl. beam
refbeam
Interferometer alignment and control
 Quadrant photodiodes provide the
error signals to control the angular
positions of the mirrors
 High precision ADCs, demod,
filtering, etc. Discussion on Jan.
25th.
LISA
Sensitivity evolution
LIGO started
commissioning first
arm in 1999
LISA
Virgo compared to LIGO
LISA
Virgo-LIGO joint analysis

Working group for burst and inspiral events

Up to now work on simulated data :
–
Project “1a”: Compare analysis pipelines on the same data sets.
–
Project “2b”: Study the advantages of 3 sites for astrophysical
sources
– Sky location, Detection efficiency

3 talks and papers (GWDAW9 and Amaldi 6)
Burst from galactic
center
LISA
Virgo- Bars joint analysis
 AURIGA, ROG
 Burst events and Stochastic signals
 Project starting with software injection
LISA
–
4 hours of data
–
Plan for analysis C6 &C7
Detection of Periodic Sources
•
Pulsars in our galaxy: “periodic”
•
search for observed neutron stars
•
all sky search (computing challenge)
h ~ GIf2ee/cr < 10-24
28 Radio Sources
LISA
Periodic Sources – all sky search
•
LISA
Doppler shifts
•
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.
•
The original frequency is
100 Hz and the maximum
variation fraction is of the
order of 0.0001
•
Note the daily variations.
•
Because of the frequency
variation, the energy of the
wave doesn’t go in a single
bin, so the SNR is highly
reduced.
Optimal detection by re-sampling procedure
•
Use a non-uniform sampling of the received data: if the sampling
frequency is proportional to the (varying) received frequency, the
samples, seen as uniform, represent a constant frequency sinusoid and
the energy goes only in one bin of their FFT.
•
Every point of the sky (and every spin-down or spin-up behavior) needs
a particular re-sampling and FFT.
Original data:
1 year
ALL
SKY SEARCH
3.1E+10
enormous
computing challenge
FFT length (number of points)
Sky points
Spin-down points (1st )
Spin-down points (2nd )
Freq. points (500 Hz)
Total points
3.1E+13
3.1E+06
3.2E+02
1.6E+10
4.8E+32
Comp. power (Tflops)
3.6E+19
LISA
The frequency is
varying, we sample
non-uniformly
(about 13 samples
per period).
The non-uniform
samples, seen as
uniform, give a
perfect sinusoid
and the
periodogram of the
samples has a
single “excited” bin.
VIRGO - Next steps

Sept-Dec 05: “Injection” shutdown
–
2-3 months of work
– New injection bench;  Power should go up by a factor 10
– New recycled mirror:  Better controls
– Miscellaneous changes
–


2006: Commissioning + data taking
–
Alignment, controls,…
–
A science run by the end of 2006 (coincidence with LIGO-S5) ?
2007
–

50W laser, New electronics, New mirrors ? (not yet decided)
2011(?): Advanced Virgo
–
LISA
Data taking/Commissioning/Upgrades
2008-9: Virgo +
–

Followed by the new injection system commissioning
200W laser? New beam geometry? New mirrors?...
Gravitational wave antenna in space - LISA
LISA
–
3 spacecraft in Earth-trailing solar orbit
separated by 5 x106 km.
–
Measure changes in distance between
fiducial masses in each spacecraft
–
Partnership between NASA and ESA
–
Launch date ~2013+
LISA Interferometry
 “LISA is essentially a Michelson
Interferometer in Space”
 However
LISA
–
No beam splitter
–
No end mirrors
–
Arm lengths are not equal
–
Arm lengths change continuously
–
Light travel time ~17 seconds
–
Constellation is rotating and
translating in space
Complementarity of Space- & Ground-Based Detectors
Difference of 104 in wavelength:
Like difference between X-rays and IR!
Rotating
Neutron Stars
LISA
LISA will see all the compact white-dwarf and
neutron-star binaries in the Galaxy (Schutz)
LISA
VIRGO
LISA – Technical contributions NL
SRON
 Test equipment for position sensor read-out
electronics in on-ground tests of the satellite
system
 Simulation software modules of the position
sensors, used in system simulations
TNO-TPD
 Test equipment of the Laser Optical Bench
 Decaging Mechanism (TBC)
Bradford Engineering
 Cold Gas propulsion (TBC)
NIKHEF
 ASIC development for read-out electronics
LISA
LISA science: massive black hole mergers
MBH = 0.005Mbulge
LISA
But do they merge?
D. Richstone et al., Nature 395, A14, 1998
Massive black hole mergers


Several observed phenomena
may be attributed to MBH
binaries or mergers
–
X-shaped radio galaxies (see
figure)
–
Periodicities in blazar light
curves (e.g. OJ 287)
–
X-ray binary MBH:
NGC 6240
See review by Komossa
[astro-ph/0306439]
[Merritt and Ekers, 2002]
LISA
EMRI - capture orbits

Filtering the data to find these
orbits in a huge parameter
space

Dealing with source confusion

Challenges:
–
LISA

Stellar-type black holes (10 M)
sometimes fall into supermassive
holes.

Orbits complicated, can have 104 or
more cycles, provide detailed
examination of black-hole geometry.

Tests of black-hole no-hair theorems,
strong-field gravity.
Computing the orbits
Typical EMRI event: 10 M BH
captured by 106 M BH

Production: fundamental physics in the early universe
- Inflation, phase transitions, topological defects
- String-inspired cosmology, brane-world scenarios

Spectrum: slope, peaks give masses of key particles & energies o
transitions.

A TeV phase transition would have left radiation in LISA band.
Primordial gravitational waves
LISA
Logistics

SRON
–

Radboud Universiteit
Nijmegen
–

Department of astrophysics
NIKHEF
–

Netherlands Institute for Space
Research
National institute for nuclear
and particle physics
Vrije Universiteit - Amsterdam
–
Subatomic physics group
Interest expressed by astronomy groups of both
Leiden & Utrecht Universities
Henk Jan Bulten & Gijs Nelemans (RUN) – DAST
representatives NL for LISA (ESA)
LISA
Summary


Collaborate on LISA and VIRGO
–
Component of our particle-astrophysics initiative
–
Exciting new physics program at NIKHEF
NIKHEF commitment
–
NIKHEF
– Thomas Bauer, Harry van der Graaf, Jan Willem van Holten, Frank Linde
– Sipho van der Putte – OIO
–
VU
– Jo van den Brand, Henk Jan Bulten, Tjeerd Ketel
– Gideon Koekoek - AIO
–
Technical impact to be determined
– Mechanical engineering, ASIC design, GRID

Negotiate with SRON, LISA and VIRGO
–
LISA
Define responsibilities
LISA Pathfinder

Goal: demonstrate free-fall of a proofmass, i.e. isolation from
non-gravitational disturbances.

Method: laser interferometry between two proof masses (PMs)
Dimensions: 640 mm x 375 mm x 375 mm
Optical bench
TM1
Sensor housings
TM2
LISA
LISA Science Goals & Sources
Science Objectives:
Observational Targets:
• Determine the role of massive
• Merging supermassive black
black holes in galaxy evolution,
including the origin of seed black
holes
• Make precision tests of Einstein’s
Theory of Relativity
• Determine the population of ultra-
compact binaries in the Galaxy
• Probe the physics of the early
universe
LISA
holes
• Merging intermediate-
mass/seed black holes
• Gravitational captures by
supermassive black holes
• Galactic and verification
binaries
• Cosmological backgrounds