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Local Group Estimation of Dark Energy & Gravitating Matter. Gene University, Finland. Gene Byrd 1 , D. Chernin 2 , P. Teerikorpi 3 , M. Valtonen 4 , V. P. Dolgachev 2 , L. M. Domozhilova 2 1 Univ. of Alabama, 2 Sternberg Astronomical Institute, Moscow University,
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Local Group Estimation of Dark Energy & Gravitating Matter • Gene University, Finland. • Gene Byrd1, • D. Chernin2, • P. Teerikorpi3, • M. Valtonen4, V. P. Dolgachev2, • L. M. Domozhilova21Univ. of Alabama, • 2Sternberg • Astronomical • Institute, • Moscow University, • Russian Federation, • 3,,4Tuorla Observatory, • Turku University, Finland. • Plot by permission of RamiRekola M31 MW 2 Mpc; 6.5 Mly
Dark energy (DE) first detected by studying recession and distances of galaxies billions of light years) away. (21,600km/s)/1,000 million ly =216 km/s increase in recession in 10 million ly. • Represent DE as uniform constant density. • v= 7.2 • 10-30 g/cm3 = • A very tiny value but almost ¾ of the total density 1 billion ly
Distance R from center • Net acceleration=Gravity deceleration (1/R2) + DE “antigravity”(R) At zero gravity radius, Rv, balance. Gravity and DE antigravity balance. Study dark energy via its effects in our Local Group Rv R MW,M31
Dynamical Regions of Local Group with Dark Energy At zero gravity, Rv gravity deceleration-dark energy “antigravity” balance. Rv = (3M/(8 v ))1/3. Central bound binary: MW-M31 binary as bound system (in,out). Mos Most of mass Expansion beyond Rv. Dwarf galaxies moving out in a spherical static . potential. . Rv R MW,M31 Potential plot: Binary gravitational PLUS dark energy potential.
Local group radial velocities and distances Dark energy dominated dwarf outflow Region. Heavy line best fit. Gravitational central binary region Zero gravity radius HST data: Karachentsev et al. 2009 10 million light years
Use outflow region in V vs R plot to estimate Local Group gravitating mass and dark energy • Small outer members flying out under LG gravity deceleration and DE acceleration. • Time from the center must be ~age of universe . • Find the mass and dark energy which result in observed outward velocities (Vs) at different distances (Rs).
V, Rs consistent with Local Group Mass, age univ. & 7.2x10-30 =ρv Outflow for different LG Masses. M≈4x1012 Solar Masses Best fit. 3.1—5.8 range 10 million light years
Vs, Rs consistent with Local Group Mass , age of universe & 7.2x10-30 =ρv Slope approaches 216 km/s increase in 10 million light years. Same as on billions of ly plot 10 million light years
Conclusions • Dark energy as well as gravitating mass affects motions in groups of galaxies. • Dark energy has the same accelerating effects and distance dependence at scales of millions as it does over billions of light years.
Path of discovery • Gravity: Apple to Moon to Universe • Dark energy: Universe to Local Group M31 MW