105 research outputs found
Cosmic flow around local massive galaxies
Aims. We use accurate data on distances and radial velocities of galaxies
around the Local Group, as well as around 14 other massive nearby groups, to
estimate their radius of the zero-velocity surface, , which separates any
group against the global cosmic expansion.
Methods. Our estimate was based on fitting the data to the velocity
field expected from the spherical infall model, including effects of the
cosmological constant. The reported uncertainties were derived by a Monte Carlo
simulation.
Results. Testing various assumptions about a location of the group
barycentre, we found the optimal estimates of the radius to be
~Mpc for the Local Group, and ~Mpc for a synthetic
group stacked from 14 other groups in the Local Volume. Under the standard
Planck model parameters, these quantities correspond to the total mass of the
group . Thus, we are faced with the
paradoxical result that the total mass estimate on the scale of is only % of the virial mass estimate. Anyway, we conclude
that wide outskirts of the nearby groups do not contain a large amount of
hidden mass outside their virial radius.Comment: 15 pages, 6 figures, 8 tables. Accepted to Astronomy & Astrophysic
Ionized gas outflow in the isolated S0 galaxy NGC 4460
We use integral-field and long-slit spectroscopy to study the bright extended
nebulosity discovered in the isolated lenticular galaxy NGC 4460 during a
recent H-alpha survey of nearby galaxies. An analysis of archival SDSS, GALEX,
and HST images indicates that current star formation is entirely concentrated
in the central kiloparsec of the galaxy disc. The observed ionized gas
parameters (morphology, kinematics and ionization state) can be explained by a
gas outflow above the plane of the galaxy caused by a star formation in the
circumnuclear region. Galactic wind parameters in NGC 4460: outflow velocity,
total kinetic energy - are several times smaller comparing with the known
galactic wind in NGC 253, which is explained substantially lower total star
formation rate. We discuss the cause of the star formation processes in NGC
4460 and in two other known isolated S0 and E galaxies of the Local volume: NGC
404 and NGC 855. We provide evidence suggesting that feeding of isolated
galaxies by intergalactic gas on a cosmological time scale is a steady process
without significant variations.Comment: 11 pages, 7 figures; accepted by MNRA
- …