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Fast motions of galaxies in the Coma I cloud: a case of Dark Attractor?

I.D. Karachentsev O.G. Nasonova H.M. Courtois 1
1 Cosmologie Observationnelle
IPNL - Institut de Physique Nucléaire de Lyon
Abstract : We notice that nearby galaxies having high negative peculiar velocities are distributed over the sky very inhomogeneously. A part of this anisotropy is caused by the "Local Velocity Anomaly", i.e. by the bulk motion of nearby galaxies away from the Local Void. But a half of the fast-flying objects reside within a small region RA = [11.5h, 13.0h], Dec. = [+20\circ, +40\circ], known as the Coma I cloud. According to Makarov & Karachentsev (2011), this complex contains 8 groups, 5 triplets, 10 pairs and 83 single galaxies with the total mass of 4.7\star10^13M\odot. We use 122 galaxies in the Coma I region with known distances and radial velocities VLG < 3000 km/s to draw the Hubble relation for them. The Hubble diagram shows a Z-shape effect of infall with an amplitude of +200 km/s on the nearby side and -700 km/s on the back side. This phenomena can be understood as the galaxy infall towards a dark attractor with the mass of \sim 2\star10^14M\odot situated at a distance of 15 Mpc from us. The existence of large void between the Coma and Virgo clusters affects probably the Hubble flow around the Coma I also.
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Submitted on : Thursday, October 13, 2011 - 9:44:20 AM
Last modification on : Tuesday, November 19, 2019 - 2:40:06 AM

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I.D. Karachentsev, O.G. Nasonova, H.M. Courtois. Fast motions of galaxies in the Coma I cloud: a case of Dark Attractor?. The Astrophysical Journal, American Astronomical Society, 2011, 743, pp.123. ⟨10.1088/0004-637X/743/2/123⟩. ⟨in2p3-00631732⟩



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