Gravitational Wave Sources From Dense Star Clusters Cole Miller University of Maryland.
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Transcript of Gravitational Wave Sources From Dense Star Clusters Cole Miller University of Maryland.
Gravitational Wave SourcesFrom Dense Star Clusters
Cole Miller
University of Maryland
Outline
• Detection of gravitational radiation.
• Sources in stellar clusters. IMBH-IMBH mergers?
• Sources in galactic nuclei. Extreme mass ratio inspirals. Tidal separation of binaries. IMBH-SMBH mergers.
Gravitational Wave Detectors
http://www.srl.caltech.edu/lisa/graphics/05.LIGO.LISA.jpg
GW Sources in Clusters
• NS-NS merger: rate small compared to disk.
• NS-BH, BH-BH: could be important because of unique formation channels.
• IMBH-BH? Visible only to small distances with LISA.
NS-NS merger rateFrom Kim et al. 2004>10-5/yr at 99% conf
LISA Detection Distance: 1 yr from merger
Will (2004)
IMBH-IMBH in Cluster
• Stellar collisions, evol --> IMBH? See Freitag talk.
• Can more than one IMBH form in cluster? Gurkan, Fregeau, Rasio, in prep.
• If so, visible to great distance. Could be LISA and LIGO sources!
Likelihood of IMBH-IMBH?• 50 - 50 Msun to 200 - 200 Msun visible to
2.5-3 Gpc with AdLIGO (Ilya Mandel) Total volume: few x 1010 Mpc3 Similar for LISA (Will 2004)
• SF rate at z~0.5: ~10-2 Msun/Mpc3/yr.
• Fraction in super star clusters: few x 10%.
• If Mcluster~105 Msun, ~103 clusters/yr formed in this volume.
• If >0.1% of clusters have IMBH-IMBH, interesting rate!
“Madau Plot”: Star Formation Rate
GW Sources in Galactic Nuclei
• M(<few pc)~Mglob
Escape velocity much higher than globulars. Retain binaries, facilitate mergers?
• Merger of stellar clusters with nucleus. Fresh supply of binaries. Muno et al. 2005 IMBHs as well?
Extreme Mass Ratio Inspirals
• BH-SMBH or IMBH-SMBH.
• Goal: simple mapping of SMBH spacetime.
• BH-SMBH uncertainties: Number density of 106 Msun SMBH. Rate of (1) merger, (2) detection w/ LISA.
Binary Tidal Separation by SMBH
• Previously, EMRIs considered by capture of single object due to gravitational radiation.
• But if BH in binary, pericenter distance can be much greater, hence cross section higher. Miller, Freitag, Hamilton, Lauburg (2005) Separation by IMBH in clusters? Pfahl (2005)
• Circularized orbits, no perturbation to plunge.
• Key: calculation of binary fraction and properties.
Single-body capture: distant view
K. Gultekin
Single-body capture: close-up
K. Gultekin
Binary Tidal Separation by SMBH
• Previously, EMRIs considered by capture of single object due to gravitational radiation.
• But if BH in binary, pericenter distance can be much greater, hence cross section higher. Miller, Freitag, Hamilton, Lauburg (2005) Separation by IMBH in clusters? Pfahl (2005)
• Circularized orbits, no perturbation to plunge.
• Key: calculation of binary fraction and properties.
Binary separation: close-up
V. Lauburg
Binary separation: distant view
V. Lauburg
Binary Tidal Separation by SMBH
• Previously, EMRIs considered by capture of single object due to gravitational radiation.
• But if BH in binary, pericenter distance can be much greater, hence cross section higher. Miller, Freitag, Hamilton, Lauburg (2005) Separation by IMBH in clusters? Pfahl (2005)
• Circularized orbits, no perturbation to plunge.
• Key: calculation of binary fraction and properties.
IMBH-SMBH Mergers
• If cluster with IMBH sinks to center, IMBH likely to merge with SMBH later.
• Signal strong enough to detect easily, but still is EMRI.
• Rate? Properties of orbits?
IMBH-SMBH Merger Sequence
Conclusions
• High density in clusters produces many potentially detectable GW sources. BH-BH, BH-IMBH, IMBH-IMBH, IMBH-SMBH.
• Continued input from N-body community is essential!