Prospects for Gravitational-Wave
Observations with Advanced LIGO
Raymond Frey
University of Oregon
for the
LIGO Scientific Collaboration
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Outline
•  Introduction to GW detection with LIGO
•  Advanced LIGO
•  Prospects for detection of compact binary mergers
•  Science with advanced detectors – a few examples
relating to PPC
  Direct detection of GW from inflation?
  Precision Hubble relation
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GWs in GR
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Evidence (indirect) for Gravitational Waves
Taylor and Hulse: Pulsar observed for 25 years:
←300 million years from now
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Evidence (indirect) for Gravitational Waves
??
BICEP2
Nope… Not yet.
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Required GW Sensitivity for Detection
•  GW emission requires time varying quadrupole moment of
mass distribution: binary NS/BH as standard source.
•  Gravitational-wave strain, h = δL/ L, is the analog of the
radiation field E in E&M
•  Strain estimate:
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GW Interferometer principle
•
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•
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Michelson interferometer with Fabry-Perot cavity arms.
End mirrors are pendula ⇒ Freely falling test masses
Long baseline: 4 km ( h = δL/ L ) - For h ≈10-21, L ≈ 1 km, then δL ≈ 10-18 m
Fabry-Perot Cavity storage time ∼1 ms (∼100 bounces)
Power recycling (x30)
Noise estimate:
5W
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Antenna Pattern
GWs are transverse, with x and + polarizations: hx(t) , h+(t)
“×” polarization
Detector
response
“+” polarization
RMS sensitivity
h(t) = Fx hx(t) + F+ h+(t)
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Current GW interferometer facilities
LIGO!
4 km!
GEO 600m!
Virgo 3 km!
LSC: LIGO
+GEO
LIGO!
4 km!
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LIGO observatories
•  1.2 m diameter vacuum tube
•  Aligned to a mm
•  Total of 16km fabricated with no leaks
•  1 nTorr
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iLIGO → aLIGO
After several years of data taking at iLIGO
design sensitivity:
•  Lots of experience and many upper limits
•  No GW detections
⇒ Make the detectors (yet) more sensitive!
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Advanced LIGO
LIGO S5
2006
S6
2007
Virgo VS R1
2008
2009
R2
2010
Adv LIGO
GEO HF
R3
2011
2012
2013
2014
2015
Adv Virgo
Install Advanced LIGO
Advanced LIGO
•  Major upgrades
  Lasers, optics,
suspensions
  Limited by Quantum noise
10-22
•  10x better sensitivity
•  1000x bigger search
volume
10-23
•  1st Advanced LIGO
observational run
Sep-Dec 2015
10-24
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New hardware installed
(suspensions here)
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Advanced LIGO as a quantum system
• LIGO is a Heisenberg microscope
• Mirror position (x) – given by the E field
phase and the momentum kick of the
mirror (p) due to radiation pressure are
fundamentally connected by quantum
mechanics:
In the quantum optics
description:
• x → phase (shot) noise
• p → amplitude
(radiation pressure)
noise
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The canonical LIGO GW target:
Compact binary coalescence
•  NS-NS known to exist – predicted rate
•  ~1% of Mc2 into GWs
•  aLIGO range 200-400 Mpc for NS-NS
arXiv: 1003.2480 ,
CQG, (LSC, Virgo)
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Short GRB and binary merger rates
•  Short GRB rate of 8-30 per Gpc3 per year (from Guetta and Piran,
Astron.Astrophys, 2006)
•  Expected NS-NS and NS-BH rates from Aasi et al, CQG, 2010
Broadly consistent for
gamma-ray burst
opening angles in
expected 10-20 deg
range
Clark, et al
arXiv:1409.8149
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Possible Advanced LIGO Run Plan,
ca 2014
aLIGO design
NS-NS
merger
detections
(predicted)
3rd science run, 2017-18?
2nd aLIGO science run, 2016-17?
S5/S6
1st aLIGO science run, Aug 2015
Sep 2015
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aLIGO: ramping up
BNS range (Mpc, average)
LIGO Hanford
LIGO Livingston
ER7, June 2015 (100 kW of 750 kW)
Note: max BNS range
for iLIGO was 20 Mpc
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Connections to PPC
•  Particle Physics
  Neutron star EOS from binary NS mergers – nuclear matter at
extreme density; quark matter?
  Nearby (~galactic) core-collapse supernova – neutrino physics?
•  Cosmology
  Density of binary NS and light black holes (< few hundred M)
  Direct detection of GWs from inflation?
  Tracing cosmological expansion at low redshift
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Connections to PPC
•  Particle Physics
  Neutron star EOS from binary NS mergers – nuclear matter at
extreme density; quark matter?
  Nearby (~galactic) core-collapse supernova – neutrino physics?
•  Cosmology
  Density of binary NS and light black holes (< few hundred M)
  Direct detection of GWs from inflation?
  Tracing cosmological expansion at low redshift
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Search for cosmological GW background
LIGO upper limit, Nature (2009)
aLIGO expected Upper Limit
Boyle & Buonanno
r = 0.2
Barnaby, et al;
Cook & Sorbo
Mandic, et al
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Looks
hard!
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“standard sirens” and cosmology
Binary inspiral system: (lowest
PN order)
“chirp” mass
•  Redshifted
chirp mass is accurately measured from phase evolution
•  Therefore, the amplitude directly determines luminosity distance
•  Note that the redshift is not directly measured
•  Schutz (1986) pointed out that that, with a corresponding
measurement of z, these GW “standard sirens” could be used to make
a measurement of the Hubble parameter which is independent of the
EM distance ladder
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Role of precision H0
•  Advanced GW detectors can measure sirens “only” to z ~ 0.2
  Measurement of H0 (i.e. H(z) for small z)
•  Is this relevant for cosmology?
•  First: Testing the EM distance ladder is important
  (Can it provide constraints on alternative gravity?)
•  With enough events (N), can determine H0 precisely
Dalal,Holz,Nissanke
  Claim error on H0 ~ [3-5%](10/N)0.5
•  A ~1% measurement at small z is cosmologically sensitive:
•  H0 + CMB
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Hubble and Dark Energy Sensitivity
To gauge the sensitivity to
the DE EOS, Dalal et al
calculated the error on H0
and w as a function of the
number of BNS events.
Assumptions:
•  1% CMB Ωmh2
•  flat universe
•  w constant
[Planck]
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Future role of precision H0
•  w(a) and DE FOM
Weinberg, et al. 2012
a = 1/(1+z)
•  From Weinberg et al. (2012):
  Assuming a w0 − wa model for dark
energy, a 1% H0 measurement would
raise the DETF Figure of Merit by 40%
  A precise determination of H0, coupled
to a w(z) parameterization that allows
low-redshift variation, could …
definitively answer the basic question,
“Is the universe still accelerating?”
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EM counterparts of
NS-NS/NS-BH mergers
•  Need redshifts to measure H0
•  Requires independent EM observation of the astrophysical
event
•  Two possibilities:
  short GRB
•  provides space-time coordinates for GW search
•  Allows for EM followup  z
  follow-up of GW trigger
•  e.g. off-axis GRB afterglow or isotropic kilonova afterglow
•  LSST will be ideal
•  Follow-up of GW sources requires good localization on the
sky
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EM counterparts
of NS-NS/NS-BH mergers
Short
GRB
Berger & Metzger
Metzger & Berger
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NS-NS mergers,
EM afterglows (kilonovae), R-process elements
•  NS-NS merger remnant acretion disk powers short GRB
Shibata
•  Bombarded by neutron-rich ejecta from the merger
•  synthesizes heavy nuclei (competes with supernovae)
•  decays make isotropic EM afterglow (a target for EM
followup obs) – “kilonovae”
e.g. Metzger, et al
Shibata
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forging the lanthanides
~ 0.1 solar mass of hot, dense, neutron-rich ejecta
•  kT > 1 MeV
•  ρ ~ 108-1012 g cm-3
Fissions and decays to Co, Ni, which
then decay over days  afterglow
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kilonova evidence
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EM Followups
•  We have enlisted (via an MOU process)
observing partners to do follow ups
•  Had some practice with this in the last months of
iLIGO running (Aug-Sept 2010)
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Astron Astrophys 539 (2012) A124
Astron Astrophys 541 (2012) A155
arXiv:1205.1124
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The 2nd generation GW detector network
LIGO (4km)
2015
GEO (0.6km)
now
Virgo (3km)
2016
Kagra (3km)
~2018
LIGO-India (4km)
~2022
Sky maps
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Moving one LIGO detector to India
Determination of source sky position: NS-NS binary inspirals
LIGO-Virgo
LIGO-Virgo + LIGO India
Fairhurst et al., arXiv:0908.2356; 1010.6192; 1205.6611
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Summary
•  A comprehensive gravitational-wave observing campaign with advanced
interferometric detectors is about to begin
•  No GW detections with initial LIGO, but much progress
  Learned how to improve detectors
  Learned how to analyze GW data and say a little about astrophysics
  Forged partnerships and collaborations (ongoing)
•  To take full advantage of likely GW detections and the full science
opportunity presented by these sensitive instruments, an emerging field of
GW astronomy has spun up
•  With Advanced LIGO (aLIGO) there is promise to make significant
advances in GR and gravity tests, astrophysics, and (maybe) cosmology
Exciting Time!
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Targeting a centennial…
•  1915 Einstein paper: Got the field equations into final form.
•  1916 Einstein paper: Definitive GR paper: theory in final form;
described the success for the perihelion advance of Mercury
•  1917 Einstein paper: Cosmological consequences of GR
•  1918 Einstein paper: Prediction of gravitational waves
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Additional slides…
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GRB 070201
•  Short-duration GRBs are thought to
be predominantly due to NS-NS or
NS-BH mergers
•  GRB 070201 – a short-duration
gamma-ray burst with position
consistent with M31 (Andromeda),
0.8 Mpc away.
•  Such a nearby GRB would have
easily been observed by LIGO if due
to a binary merger
•  This hypothesis ruled out ~99% CL
[Astrophys. J. 681 (2008) 1419]
Revised error box
•  Most likely: SGR in M31
Mazets et al., ApJ 680, 545
(Eiso~1045 erg)
•  Similar result for GRB 051103 in M81
(5 Mpc) ApJ 755 (2012) 2
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Beating the Crab Spindown Limit
•  Crab pulsar is spinning down


•  How much of the spindown power
is going into GWs?
•  ≤ 2% : ApJ 683 (2008)
Also achieved for Vela pulsar
Getting close to spindown limit on other known
pulsars (ApJ 713 (2010) 671 )
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GW signals classification
un-"
modeled"
matched
filter"
Short duration"
Long duration"
Burst search"
Stochastic search"
Inspiral search"
CW search"
Credit: NASA/CXC/ASU/J. Hester et al."
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