Journal Article

The Hubble flow around the Local Group

I. D. Karachentsev, O. G. Kashibadze, D. I. Makarov and R. B. Tully

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 393, issue 4, pages 1265-1274
Published in print March 2009 | ISSN: 0035-8711
Published online February 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.14300.x
The Hubble flow around the Local Group

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We use updated data on distances and velocities of galaxies in the proximity of the Local Group (LG) in order to establish properties of the local Hubble flow. For 30 neighbouring galaxies with distances 0.7 < DLG < 3.0 Mpc, the local flow is characterized by the Hubble parameter Hloc= (78 ± 2) km s−1 Mpc−1, the mean-square peculiar velocity σv= 25 km s−1, corrected for errors of radial velocity measurements (∼4 km s−1) and distance measurements (∼10 km s−1), as well as the radius of the zero-velocity surface R0= (0.96 ± 0.03) Mpc. The minimum value for σv is achieved when the barycentre of the LG is located at the distance Dc= (0.55 ± 0.05) DM31 towards Andromeda galaxy (M31) corresponding to the Milky Way (MW)-to-M31 mass ratio MMW/MM31≃ 4/5. In the reference frame of the 30 galaxies at 0.7–3.0 Mpc, the LG barycentre has a small peculiar velocity ∼(24 ± 4) km s−1 towards the Sculptor constellation. The derived value of R0 corresponds to the total mass MT(LG) = (1.9 ± 0.2) 1012 M with Ωm= 0.24 and a topologically flat universe, a value in good agreement with the sum of virial mass estimates for the MW and M31.

Keywords: Local Group; dark matter

Journal Article.  5693 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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