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A model for the formation of the Local Group

1989; IOP Publishing; Volume: 345; Linguagem: Inglês

10.1086/167885

1538-4357

P. J. E. Peebles, Adrian L. Melott, M. R. Holmes, Lu‐hua Jiang,

Galaxies: Formation, Evolution, Phenomena

view Abstract Citations (57) References (44) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Model for the Formation of the Local Group Peebles, P. J. E. ; Melott, A. L. ; Holmes, M. R. ; Jiang, L. R. Abstract We analyze and present observational tests of a model for the formation of the Local group in which the mass concentration grew by gravitational accretion of low-pressure matter onto two seed masses, around which the Andromeda Nebula and the Galaxy collect, in an otherwise homogeneous initial mass distribution. The evolution of the mass distribution is studied in an analytic approximation and a numerical computation. We check our numerical method for unwanted two-body relaxation and compare the numerical solutions to analytic ones for an isolated hole and spherical infall. We find satisfactory consistency here and in the comparison of numerical and analytic solutions. The two freely adjustable parameters in the model are the initial seed mass and separation, which are adjusted to produce the observed present separation and relative velocity of the two dominant galaxies. We have also some latitude in adjusting the time scale for the cosmological model. We find that if Hubble's constant is adjusted to H_0_ ~ 80 km s^-1^ Mpc^-1^ with density parameter {DELTA} = 1, then the model gives a good fit to the motions of the outer members of the Local Group, the only substantial failure being the motion of NGC 6822. The same model gives particle orbits at r ~ 100 kpc that reasonably approximate the observed distribution of redshifts of the satellites of our Galaxy and gives a circular velocity at r = 8 kpc that is somewhat high compared to the observations in our Galaxy and M31, but is still remarkably close considering the simplicity of the model. Publication: The Astrophysical Journal Pub Date: October 1989 DOI: 10.1086/167885 Bibcode: 1989ApJ...345..108P Keywords: Astronomical Models; Computational Astrophysics; Cosmology; Galactic Evolution; Local Group (Astronomy); Andromeda Galaxy; Gravitational Effects; Hubble Constant; Mass Distribution; Milky Way Galaxy; Red Shift; Astrophysics; GALAXIES: FORMATION; GALAXIES: LOCAL GROUP; GALAXIES: REDSHIFTS full text sources ADS | data products NED (14) SIMBAD (13)