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LISA Science

LISA Science. Bernard Schutz for the LISA International Science Team Albert Einstein Institute – Max Planck Institute for Gravitational Physics, Golm, Germany and Cardiff University, Cardiff, UK http://www.aei.mpg.de schutz@aei.mpg.de. LISA.

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LISA Science

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  1. LISA Science Bernard Schutz for the LISA International Science Team Albert Einstein Institute – Max Planck Institute for Gravitational Physics, Golm, Germany and Cardiff University, Cardiff, UK http://www.aei.mpg.de schutz@aei.mpg.de

  2. LISA • Joint mission: NASA and ESA have exchanged Letters of Agreement. • NASA: both JPL and GSFC participate • Launch planned 2011 • Technology mission SMART-2 will be launched by ESA in 2006 with experiment packages from Europe and USA. • 20-member science team called LIST (LISA International Science Team), chaired by T Prince and K Danzmann. • LIST working groups involve the wider community, give input on design, data analysis, and scientific goals. LISA Science: 4th LISA International Symposium

  3. Science drivers and current issues • Merging supermassive black holes (SMBH) in galactic centers • Formation, evolution, relation to galaxy formation and mergers, indicators from other observations, cosmological information, numerical modelling • Signals from gravitational capture of small BHs by SMBHs • Event rates, evolution of clusters near SMBHs, modelling of very complex waveform (radiation-reaction), signal extraction from background of distant events, accuracy of tests of BH uniqueness theorems of general relativity • Survey of all galactic binaries with sufficiently short periods • Population statistics, confusion by large population at lower frequencies, confusion limit on signal extraction, information extraction from observations • Backgrounds, astrophysically generated and from the Big Bang • Strength and spectrum of astrophysical backgrounds, production of early-universe radiation, relation to fundamental physics (string theory, branes, …) • Bursts, unexpected sources • Formation of BHs of intermediate to large mass, possible sources in dark matter LISA Science: 4th LISA International Symposium

  4. Wgw = 10-10 Black holes, white dwarfs, Big Bang - 1 8 1 0 -15 6 2 x 1 0 M B H s a t z = 1 o 4 2 x 1 0 M B H s o - 1 9 1 0 -10 - 2 0 1 0 RXJ1914.4+2456 -5 h m g w - 2 1 1 0 0 - 2 2 1 0 6 1 0 M + 1 0 M B H o o Detection threshold (S/N = 5) 5 for a 1-year observation 4U1820-30 - 2 3 1 0 Binary confusion limit 10 - 4 - 3 - 2 - 1 0 1 0 1 0 1 0 1 0 1 0 Frequency (Hz) LISA Science: 4th LISA International Symposium

  5. Issue: LISA measurement theory(Estabrook, Tinto, Armstrong; Dhurandhar & Vinet) • LISA is not just one interferometer. All estimates of LISA sensitivity until now have used just one interferometer. • Estabrook et al have shown that there are many combinations of the 12 signals measured on-board LISA that cancel laser frequency noise and that therefore are clean enough to detect gws. These represent ways of using all the information returned by the 3 arms. • Dhurandhar and Vinet (gr-qc/0112059) have shown that the set of all such combinations has the mathematical structure of a module. • Different combinations have different antenna patterns. Data analysis can switch from one combination to another if a particular source moves into a “hole” in the first pattern. LISA Science: 4th LISA International Symposium

  6. Possible sensitivity improvement LISA Science: 4th LISA International Symposium

  7. A 2.6  106 M Black Hole in our Galaxy LISA’s most exciting goal is to study the formation, growth, space density and surroundings of massive black holes, which are observed in most nearby galaxies. Here is our own! (Eckart & Genzel) LISA Science: 4th LISA International Symposium

  8. Other evidence for MBHs • Velocity fields are measured using • Maser lines • Stellar velocity dispersion • X-ray iron lines • More distant MBHs make jets in AGNs and QSOs, but most are quiet • Twin MBHs: 3C75 LISA Science: 4th LISA International Symposium (Sterl Phinney)

  9. Issue: BH Merger Simulations • Improving all the time: • More stable forms of the field equations • Gauge conditions improved • Run times lengthening • Initial data improving: subtle • Still hungry for computer time. The Discovery Channel funded AEI’s longest simulation to date, and its visualization. LISA Science: 4th LISA International Symposium

  10. Comparisons with PN • 3PN-E1B-ISCO and QC3/QC4 parameters are very close, but PN not converging … • Going byond QC4 … • Longer numerical simulations! • Comparisons with FN needed! • (work in progress … AEI) LISA Science: 4th LISA International Symposium (Baker, Campanelli, Lousto, Takahashi 02)

  11. Issue: Cosmology with SMBH Mergers • Position uncertainties of SMBH mergers are significant, error boxes of order several degrees likely. This dominates uncertainty in range too, makes it impossible on position alone to find galaxy in which merger took place. • Cosmology with SMBHs. If the merger can be associated with a galaxy or cluster, then the uncertainty in position is drastically reduced, the distance error is reduced to ~0.1% (dominated by random velocities of galaxies), and the distance can be compared with the redshift. This would allow tracking of the acceleration history of the Universe. LISA Science: 4th LISA International Symposium

  12. Gravitational capture example10M/106M circular equatorial orbit, fast spin [Finn/Thorne] 1 yr before plunge: r=6.8 rHorizon 185,000 cycles left, S/N ~ 100 1 mo before plunge: r=3.1 rHorizon 41,000 cycles left, S/N ~ 20 heff 1 day before plunge: r=1.3 rHorizon 2,300 cycles left, S/N ~ 7 f (Hz) LISA Science: 4th LISA International Symposium

  13. Issue: How well can we study gravitational captures? • Potential for very fundamental results, mapping spacetime near a Kerr black hole • Nightmare for matched filtering: • Very large parameter space for orbits, perhaps 1030 or more distinguishable sets of parameters • Filters not yet understood, because radiation-reaction problem in strong-field Kerr not solved • Approximate, hierarchical scheme needed • Filtering must be good, because: • Signals from galactic WD binaries need to be removed • More distant capture events provide background, a kind of Olbers limit LISA Science: 4th LISA International Symposium

  14. Galactic binaries • All compact-object binaries (WD, NS, BH) in galaxy with large enough frequency will be observed. • Population statistics will make very important contribution to understanding binary evolution and even stellar evolution. • Coupled with GAIA (ESA Cornerstone mission follow-on to Hipparcos), LISA can help define spatial structure and stellar distribution of Galaxy. • For f < 0.001 Hz, only nearest binaries will be resolved; most form an anisotropic noise. Even at higher frequencies, binary signals must be removed accurately to see other weak sources. LISA Science: 4th LISA International Symposium

  15. Issue: cosmological background • One of the most fundamental goals of GW detection is the cosmological background from the Big Bang. Best observational evidence we are likely to get about fundamental physics. LISA limit around Wgw ~ 10-10. • Standard inflation predicts very weak radiation (Wgw < 10-14), but some brane scenarios and some scenarios of symmetry breaking can produce observable radiation. • Backgrounds from astrophysical sources restrict observing range. Possible window around 1 Hz. LISA Science: 4th LISA International Symposium

  16. LISA follow-on mission • Clear from present science studies that there are three areas where we want to go beyond LISA. • Cosmological background • Angular position improvement for SMBH mergers • Intermediate frequency band: 0.1-1.0 Hz • Relevant now, especially if current LISA could be a component of the next one. Team trying to design in long lifetime, 10 years or more. LISA Science: 4th LISA International Symposium

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