Supernova Relic Neutrinos ( SRN ) are a diffuse neutrino signal from all past supernovae
Cosmological supernovae as neutrino and gravitational wave sources
description
Transcript of Cosmological supernovae as neutrino and gravitational wave sources
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Cosmological supernovae as neutrino and gravitational wave sources mHz gravitational wave background from inspiral of compact objects embedded in AGN accretion discs.
Astrophysical Gravitational WaveBackgrounds
Günter SiglAPC (Astroparticule et Cosmologie), Université Paris 7and GReCO, Institut d’Astrophysique de Paris, CNRShttp://www2.iap.fr/users/sigl/homepage.html
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Individual and Diffuse Signals
Thecharacteristic GW amplitudehc(f ) for singleevents is related to theenergyemitted per frequency interval, (dEgw=df )(f )
h2c(f ) =
2(1+z)2
¼2
1d2
L
dEgw
df[f (1+z)] ;
where dL is the luminosity distance.
The signal to noise ratio (SNR) of an individual event is de ned by
SNR2 =
Z f max
f min
dlnfh2
c(f )f Sn
;
where Sn(f ) is the detectors noisebudget.
In termsof cosmology jdt=dzj = [(1+z)H (z)]¡ 1 and an event rateper comovingvolume R(z), the time-averaged GW energy density per logarithmic frequencyinterval is
d½gw
dlnf(f ) =
Z 1
0dz
R(z)1+z
¯¯¯¯dtdz
¯¯¯¯f z
dEgw
df(f z) :
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Event rates and Duty Cycles
The duty cycle is given by multiplying the integrand with the coherence timescale (1+z)tcoh[(1+ z)f ]:
Duty cycle'Z 1
0dzR(z)
4¼r2(z)tcoh[(1+z)f ]H (z)
:
The event rateas seen from Earth is
¡ =
Z 1
0dz
R(z)1+z
dVdz =
Z 1
0dzR(z)
4¼r2(z)(1+z)H (z)
:
with r(z) the comoving coordinate, dr = (1+ z)dt.
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Onion structure of a supernova
Convection, turbulence
Janka, Mueller
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Supernovae as Neutrino and Gravitational Wave Sources
Anisotropic mass motion and neutrino emission in collapse of massive starsleads to gravitational wave emission. At low frequencies anisotropic neutrinoemission of luminosity Lν(t) and anisotropy q(t) dominates and leads to thedimensionless strain at distance D
Dt
tqtLtdD
Gth )()(
2)( N
Individual supernovae (SN) in our Galaxy can give prominent signals inneutrinos in Super-Kamiokande, Amanda, ICECUBE, Uno… and ingravitational waves in Virgo/EGO, LIGO…, but are rare events.
However, backgrounds from cosmological SN may soon be detectableby gadolinium upgrade of Super-K in neutrinos and by gravitational wavedetectors such as the Big Bang Observatory (BBO).
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Illustration for a particular rotating core collapse model by Mueller et al.,Astrophys. J. 603 (2004) 221.
time dependent q
average< q>» 0:45%
Fully 2D, axisymmetric rotating 15M ¯ progenitor, » 3£ 10¡ 9M ¯ released inGW during simulation
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
However, note dependence on progenitor model
average< q>» 3£ 10¡ 5
Fully 2D, axisymmetricnon-rotatingnakedproto-neutronstar, » 1:6£10¡ 10M ¯released in GW during simulation
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
SN rate
neutrino spectragravitational wave spectra
+simulations
+ very massive PopIII starsat z≥15future input from SWIFT…
ordinary SN
≥100Msun PopIII
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
=>diffuse neutrino spectra
stochastic gravitational wave backgroundAndo and Sato, astro-ph/0410061 Buonanno, Sigl, Raffelt, Janka, Mueller,
Phys.Rev.D 72 (2005) 084001
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
At low frequency gravitational wave spectrum always dominated by anisotropicneutrino emission. At high frequency f > 100 Hz convective mass motiondominates.
Note that simulations stop after ~250 msec, during which only about 1/6 of thetotal 3x1053 erg in neutrinos radiated during cooling phase has been emitted Possible enhancement factors in the GW amplitude between ~√6 and ~6(bands in previous figure)
Red vs blue band are different type II SN redshift evolutions
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
The rate of ordinary supernovae is R ~ 1/sec. For Pop III events related toa few hundred solar mass stars the rate RIII is related to the fraction ofbaryons converted into Pop III stars fIII by
3
1
10 s 2.0 III
III
fR
If metals are released, fIII has to be <10-5.However, there are speculations that an observed infrared background exesscould be explained by efficient Pop III formation correponding to fIII ~ 0.1.Metallicity constraints in this case must be circumvented by fall into black hole.
For events with rate R and processes that loose phase coherence after onecycle, at frequencies f < R the signal becomes « stochastic », or « gaussian »,i.e. more than one event is « on » at any given time. Individual events are alsounresolvable at such frequencies because SNR < 1.
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Uncertainties in star formation rates at high redshift
reionization
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
By using more optimistic SFR, Sandick et al, Phys.Rev.D 73 (2006) 104024obtain more optimistic estimates
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Compare this with upper limits, sensitivities, and cosmological predictions
Giovannini
BBO
BBO correlated
SN and PopIII
By the way: Accelerated expansion could decrease conventional inflationsignal by factor 100 ! This makes astrophysical sources more important.
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Sensitivities of existing and future ground-based gravitational wave detectors(uncorrelated)
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Active Galactic Nuclei as Photon andGravitational Wave Sources
The bolometric luminosity Lbol of an AGN with central black hole of massM is related to the accretion rate Lacc and the Eddington rate LEdd by
of which a fraction fX is in X-rays between 2 and 10 keV, LX = fX Lbol.
Assume that a fraction fco of accretion is in the form of compact objectsof typical mass m ~ 100 Msun. These objects release a fraction α ~ 0.2 oftheir mass m in gravitational waves during inspiral to the last stable orbit:
Thus, from the observed X-ray luminosity function dn/dLX for AGNs, wecan compute the cosmological gravitational wave background.
Lgw » ´gwf coLacc »´gwf co
fX ´emLX :
Lbol » ´emLacc » f EddLEdd » 1:25£ 1038f Edd
µMM¯
¶ergs¡ 1
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
For ΩSMBH = fraction of critical density in SMBHs, Ωacc = fraction of criticaldensity in accreted gas, ΩX = fraction of critical density of X-rays in the2-10 keV band, facc = fraction of SMBH mass due to accreted gas, fobsc =fraction of obscured emission ~ 0.3, one has
facc ΩSMBH ~ (1 – ηem) Ωacc
ΩX ~ <(1+z)-1> fobsc fX ηem Ωacc
Since ΩX/ΩSMBH ~ 1.3x10-3, <(1+z)-1> ~ 0.4 from AGN evolution data, oneobtains the condition
fobsc facc fX ηem ~ 3x10-3
Observations suggest that ηem is not much smaller than 0.1, and thatSMBH build-up is dominated by accretion facc ~ 1 and NOT by mergersfX ~ 0.1: bolometric emission dominated by infrared.This will be our standard case.
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
The universalphoton spectrum
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
AGN+galaxy clusters
unobscured
Compton thin
Compton thick
Diffuse X-ray background
Comastri, Gilli, Hasinger. astro-ph/0604523
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
The X-ray background between ~1 and ~100 keV is explained by AGNs.
X-ray luminosity function
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
SNR of a 100M ¯ object spirallinginto central black holes of various masses.
107 M ¯
106 M ¯
105 M ¯
Individual events
Sigl, Schnittman, Buonanno, astro-ph/0610680
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
fX = 0.03, ηem = 0.2, (infrared emission dominated, solid line)facc = 1, fco = 0.01, black hole spin a/M = 0.95, for which ηgw ~ 0.2
Time-averagedtotal signal
Confusion noise
Noise induced bysubtractingresolvable eventswith SNR > 15
dR =f co
f X
1Egw
dndlnLX
dLX
where Egw=gravitational wave release per event,goverened by GR
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
The duty factor is the event rate times the time tcoh ~ f/(df/dt) ~ f -8/3 spentemitting at frequency f.
Below a few milli-Hertz > 1 event contributes at any given time and the signalis gaussian. At higher frequencies one would see individual events at final stages
of inspiral. These events also have sufficient SNR to be resolved.
Sigl, Schnittman, Buonanno, astro-ph/0610680
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
The observable total (solid) and resolvable (dashed) chirp rateas function of frequency f.
Sigl, Schnittman, Buonanno, astro-ph/0610680
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
The rate of individual events can thus be approximated by
¡ (f ) ' 102
µf co
0:01
¶ µ102 M ¯
m
¶y¡ 1 for f < 5£ 10¡ 3 Hz
in this scenario. The duration of such a typical event would be
tcoh(f ) ' 0:2µ
102 M¯
m
¶ µ10¡ 3 Hz
f
¶8=3
yr :
Individual eventscould thusbefollowed through frequency spacewith thechar-acteristic frequency evolution for coalescence.Thebackground becomes gaussian (duty cycle > 1) for
f . f gauss ' 2£ 10¡ 3
µf co
0:01
¶3=8 µ102 M ¯
m
¶3=4
Hz:
At frequencies a factor 5-10 lower, thebackground becomes confusion noise.
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Conclusions1
1.) There is a deep connection between neutrino and gravitational wave emission by collapsing massive stars. Both signals have good chances to be seen by future experiments.
2.) Such astrophysical backgrounds could partially mask the inflationary background in the BBO (~0.1 Hz) frequency range. In the ground based frequency range ~100 Hz, these backgrounds would only be detectable by the most advanced third generation detectors.
3.) The supernova type II background is gaussian below ~1 Hz, however the neutron star phase transition background would be pop-corn type.
Günter Sigl, Astroparticules et Cosmologie, ParisData analysis workshop, Paris, November 15, 2006
Conclusions2
4.) The accretion powering Active Galactic Nuclei give rise to electromagnetic emission from the infrared to γ-rays and at the same time to gravitational waves from inspiral of compact objects.
5.) If > 1% of the accreted matter fueling AGNs is in form of compact objects, a continuous background detectable by LISA results below 1 mHz. If the typical compact object masses are > 10 solar masses, individual inspirals should be resolvable above a few mHz with a rate of a few hundred per year.