Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.stsci.edu/institute/itsd/information/streaming/archive/Astrophysics2020/ValeriMakarov111507Hi_supporting/ValeriMakarov.pdf Дата изменения: Tue Sep 25 16:26:37 2012 Дата индексирования: Wed Feb 6 05:03:29 2013 Кодировка: Поисковые слова: universe

Detection of Relic Gravitational Waves and Rotation of the Universe via 1-microarcsecond Triangulation of the Sky Valeri Makarov


Short gravitational waves
Orbiting binary stars, supernova explosions, coalescence of binary neutron stars and encounters of stars in dense clusters generate tensor metric perturbations (gravitational waves) propagating away from the source They result in radial and transverse deflection of light rays from background sources GRT predicts negligibly small astrometric effects from predictable sources of GW in the Galaxy Future facilities LISA and BBO hold best prospects for detection of short GW

Astrophysics 2020: Large space missions beyond the next decade

2


Relic GW
Models of early Universe predict long-wavelength gravitational radiation background, e.g. inflation or anisotropic phases Different modes of polarization and power spectrum can be present today, with energy density up to GW h2 10-9, none detected yet A plane monochromatic, linearpolarized GW propagating along the axis of a cylinder of test particles changes its shape, and bends light rays from distant sources in the transverse directions

g = h cos t ( xx - yy )
3

Astrophysics 2020: Large space missions beyond the next decade


Proper motions induced by long waves
Distant sources (quasars) in the transverse directions to the wave vector are displaced from their "true" positions Instantaneous angular displacement is not observable but it changes periodically with time as the wave propagates which can be measured as "proper motion"
1 2

r r = h sin sin (l cos 2 - m sin 2 ) r

Astrophysics 2020: Large space missions beyond the next decade

4


Vector spherical harmonic signatures of GW
Because of the quadrupole nature of GW, ~80% of power spectrum is carried by 2nd order vector harmonics of the proper motion field

= E +
m = -1 m 1 secular aberration

r

1

1

m = -1

rm T1 +

m = -2

E +
m 2

2

2

m = -2

rm T2 + ...

residual rotation

gravitational waves
5

Astrophysics 2020: Large space missions beyond the next decade


Triangulation of sky
The ancient technique of angular triangulation can be brought to ~1 as by modern interferometry 6 equidistant quasars make the simplest triangulation network ~300 quasars are needed to realize the broadband capabilities and reach sensitivities ~ hGW = 5·10-13 at 10-8 Hz Detection of GW from anisotropic phases in early Universe is probable in coherent spectral lines
Astrophysics 2020: Large space missions beyond the next decade

6


Tentative design
· Two Michelson interferometers with articulating siderostats and mutually orthogonal baseline vectors, plus two guide interferometers to monitor attitude changes by locking on guide stars, tied into a rigid external metrology system Technology proven at JPL at ~100 pm for 1 hr, needed ~20 pm

·

Astrophysics 2020: Large space missions beyond the next decade

7


GW energy density limits and sensitivity
Planned missions LISA and BBO operate at high frequency modes that reentered the horizon well before the matterradiation equality and before the Big Bang nucleosynthesis (log 11 Hz, T 1 Mev) A Space Triangulation mission (GIST) will probe the epoch of nucleosynthesis in both monochromatic and broad-band regimes
BB nucleosynthesis

Astrophysics 2020: Large space missions beyond the next decade

8


Rotation of universe
Global rotation (and rotational perturbations, curls) are plausible in many cosmological models, with interesting consequences Estimated present-day rotation range 10-13 rad/yr (very slow) to 10-10 rad/yr (very fast) GIST capability is in the middle of the range ~ 5·10-13 rad/yr, but... a local gyroscope frame is needed Rotation of Earth around the Sun and rotation of the Sun around the Galactic barycenter are natural Machian frames, but... remains to be seen if the first-order magnetic harmonic can be tied to a local gyroscope in a self-consistent way
Astrophysics 2020: Large space missions beyond the next decade

9


Other astrophysical capabilities
Detection of habitable rocky planets around M dwarfs and white dwarfs Weak microlensing jitter from free-floating planetoids and comets in open clusters Dark matter potential profile of the Galactic halo Masses of black holes in stellar binaries ...

Astrophysics 2020: Large space missions beyond the next decade

10