9 research outputs found
Blueshifted galaxies in the Virgo Cluster
We examine a sample of 65 galaxies in the Virgo cluster with negative radial
velocities relative to the Local Group. Some features of this sample are
pointed out. All of these objects are positioned compactly within a virial zone
of radius 6{\deg} in the cluster, but their centroid is displaced relative to
the dynamic center of the cluster, M87, by 1.1{\deg} to the northwest. The
dwarf galaxies in this sample are clumped on a scale of ~10' (50 kpc). The
observed asymmetry in the distribution of the blueshifted galaxies may be
caused by infall of a group of galaxies around M86 onto the main body of the
cluster. We offer another attempt to explain this phenomenon, assuming a mutual
tangential velocity of ~300 km/s between the Local Group and the Virgo cluster
owing to their being repelled from the local cosmological void.Comment: 10 pages, 4 figures, 1 table. Published in Astrophysics, Vol. 53, No.
1, pp. 32-41, 201
The Hubble flow around the Local Group
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 < D_LG < 3.0 Mpc, the
Local flow is characterized by the Hubble parameter H_loc = (78+/-2)
km/(s*Mpc), the mean-square peculiar velocity sigma_v = 25 km/s, corrected for
errors of radial velocity measurements (~4 km/s) and distance measurements (~10
km/s), as well as the radius of the zero-velocity surface R_0 = (0.96+/-0.03)
Mpc. The minimum value for sigma_v is achieved when the barycenter of the LG is
located at the distance D_c = (0.55+/-0.05) D_M31 towards M31 corresponding to
the Milky Way-to-M31 mass ratio M_MW / M_M31 ~ 4/5. In the reference frame of
the 30 galaxies at 0.7 - 3.0 Mpc, the LG barycenter has a small peculiar
velocity ~(24+/-4) km/s towards the Sculptor constellation. The derived value
of R_0 corresponds to the total mass M_T(LG) = (1.9+/-0.2) 10^12 M_sun with
Omega_m = 0.24 and a topologically flat universe, a value in good agreement
with the sum of virial mass estimates for the Milky Way and M31.Comment: 14 pages, 6 figures, 1 table. Accepted for publication in MNRA
The observed infall of galaxies towards the Virgo cluster
We examine the velocity field of galaxies around the Virgo cluster induced by
its overdensity. A sample of 1792 galaxies with distances from the Tip of the
Red Giant Branch, the Cepheid luminosity, the SNIa luminosity, the surface
brightness fluctuation method, and the Tully-Fisher relation has been used to
study the velocity-distance relation in the Virgocentric coordinates. Attention
was paid to some observational biases affected the Hubble flow around Virgo.
We estimate the radius of the zero-velocity surface for the Virgo cluster to
be within (5.0 - 7.5) Mpc corresponding to (17 - 26)^\circ at the mean cluster
distance of 17.0 Mpc. In the case of spherical symmetry with cosmological
parameter \Omega_m=0.24 and the age of the Universe T_0= 13.7 Gyr, it yields
the total mass of the Virgo cluster to be within M_T=(2.7 - 8.9) * 10^{14}
M_\sun in reasonable agreement with the existing virial mass estimates for the
cluster.Comment: 22 pages, 11 figures, 2 tables. Accepted for publication in MNRA
Local dark energy: HST evidence from the expansion flow around Cen A/M83 galaxy group
A structure with a massive group in its center and a cool expansion outflow
outside is studied around the Cen A galaxy with the use of the Hubble Space
Telescope observations. It is demonstrated that the dynamics of the flow is
dominated by the antigravity of the dark energy background. The density of dark
energy in the cell is estimated to be near the global cosmological density.
This agrees with our previous result from the neighborhood of the Local group.
A notion of the ``Hubble cell'' is introduced as a building block of the local
structure of the universe
On the kinematics of the Local cosmic void
We collected the existing data on the distances and radial velocities of
galaxies around the Local Void in the Aquila/Hercules to examine the peculiar
velocity field induced by its underdensity. A sample of 1056 galaxies with
distances measured from the Tip of the Red Giant Branch, the Cepheid
luminosity, the SNIa luminosity, the surface brightness fluctuation method, and
the Tully-Fisher relation has been used for this purpose. The amplitude of
outflow is found to be ~300 km/s. The galaxies located within the void produce
the mean intra-void number density about 1/5 of the mean external number
density of galaxies. The void's population has a lower luminosity and a later
morphological type with the medians: M_B = -15.7^m and T = 8 (Sdm),
respectively.Comment: Version 1. 14 pages, 8 figures, 2 tables. Accepted to Astrophysics,
Volume 54, Issue
Local dark energy: HST evidence from the vicinity of the M 81/M 82 galaxy group
The Hubble Space Telescope observations of the nearby galaxy group M 81/M 82
and its vicinity indicate that the expansion outflow around the group is
dominated by the antigravity of the dark energy background. The local density
of dark energy in the area is estimated to be near the global dark energy
density or perhaps exactly equal to it. This conclusion agrees with our
previous results for the Local group vicinity and the vicinity of the Cen A/M
83 group.Comment: 17 pages, 1 figur