Transcript Science with DECIGO

Science with DECIGO
Naoki Seto (Kyoto U)
2008.11.12
The 1st International LISA-DECIGO
Outline
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Quick introduction of DECIGO band
①Stochastic Background from early universe
②Binary subtraction problem
Other science
– ③Dark energy
– ④Intermediate mass black hole (IMBH)
• Summary
DECIGO shares many interesting (and challenging) aspects
with LISA and grand-based detectors
Quick Introduction
LISA
LIGO,VIRGO,LCGT
2nd generation
DECIGO
h~10-23~-24
DECIGO
correlation
1Hz
Frequency (f~1Hz)
1/ 2



f ~ G  ~ 1 6
3 
10
g
cm


LISA
Hz
High density; compact binaries
(NS, stellar mass BH, IMBH,…)
WD+WD
confusion
e.g. Farmer & Phinney 03
DECIGO
DECIGO
correlation
Signal duration (binaries)
 f 
TGW ~ 1

 0.2 Hz 
8/ 3
 MC 


1.2
M
Sun 

5/ 3
yr
Large number (~108) of rotations
with frequency evolution
1yr
NS+NS@z=1
NS+NS
Foreground
with R~105/yr
Deep Window for GWs from Early universe?
Individual NS+NS
GW ~ 1016
Inflation?
Their foreground
(to be removed)
Topics in my talk
③Dark Energy with ~105binaries
④IMBH evolution
②Binary Subtraction
problem
①GW from
Early universe
①Stochastic GW background
GW propagation: almost no interaction, not easy to detect,
But a crucial fossil from very Early universe!!
NASA
GW from Inflation
• An important prediction of inflation
– Origin: Quantum fluctuation
– Energy scale of inflation
h ~ Hinf ~ Vinf1/ 2 ~ (energy scale)2
– Nearly flat spectrum above 10-15Hz (equal time)
GW  (energy scale)4 ~ const
– 0.1Hz: Largely different scale from CMB scale
15
GW  10
Smith et al.2006
Correlation analysis
Two sets of detectors
S1  h  n1
S2  h  n2
No overlap with LISA
But Tinto et al. 01, Hogan & Bender 01
DECIGO
Designed to detect
16
DECIGO
(fTobs)1/4
GW ~ 10
Interesting level
with current constraints
DECIGO
correlation
② Foreground cleaning is essential!
An inevitable problem for GW astronomy
Individual NS+NS
NS,BH binaries
NS+NS merger rate: ~(10/yr)x(10Gpc/300Mpc)3~105/yr~10-3/sec
Other potential foregrounds
popIII SNe,…..? (might be a problem)
Can we remove NS+NSs?
In principle, Yes
• (total fitting parameters)/(data amount)
~(R x Tobs x n) / (f x Tobs)
R: merger rate
Tobs: observational time
n: number of fitting parameters for individual binaries~10
f: band width ~ freqeuncy
~10-3 101 /1=10-2<<1
mass, direction,…
In reality…
• large cycle;~108
Cuter&Harms 06 (for BBO)
– need huge number of templates
• ~1040 templates for 1yr integration
– full coherent integration; difficult
• even with Moore’s law extrapolated to ~2020
• need efficient detection method
– LISA(WD+WD, EMRI), LIGO-pulsar search
» mock LISA data challenge, Einstein@home,...
• requirement for detector sensitivity and configuration
– must detect them in short integration time
– no dead angles
– ongoing: careful evaluation for sensitivity and configuration
③Science with NS+NSs
• Basic characters
– Huge number: ~105/yr
– Excellent clocks
– SNR: weak dependence on redshift z
• asymptotically (1+z)1/6
– Short GRB? or EMW counterpart
• GW localization: ~1min2 with three sets
• redshift estimation
• Dark energy
– dL-z relation, only with basic physics
– Probes for high redshift universe?
④BH (stellar, intermediate mass)
• IMBH:highly unknown
– rate, formation and evolution?
– detectable with high SNR even at high-z
• 1000+1000Msun@z=1: SNR>103
• clue to understand SMBH?
• BH+NS
– test for general relativity (Yagi)
Summary
• Interesting science with DECIGO
– GW background form early universe
• 1Hz: (potential) deep window for GWs
• direct detection of inflation background(?), ….
– Foreground cleaning is essential!!
• LISA (WD+WD,EMRI), Ground-base (unknown pulsars)
– NS+NS: ~105 good clocks available
• use them for cosmology and astrophysics
– IMBHs and more