Bibcode
Aguerri, J. A. L.; Agulli, I.; Diaferio, A.; Dalla Vecchia, C.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 468, Issue 1, p.364-377
Advertised on:
6
2017
Citations
18
Refereed citations
17
Description
Galaxies in clusters are strongly affected by their environment. They
evolve according to several physical mechanisms that are active in
clusters. Their efficiency can strongly depend on the orbital
configuration of the galaxies. Our aim is to analyse the orbits of the
galaxies in the cluster Abell 85, based on the study of the galaxy
velocity anisotropy parameter. We have solved the Jeans equation under
the assumption that the galaxies in A 85 are collisionless objects,
within the spherically symmetric gravitational potential of the
virialized cluster. The mass of the cluster was estimated with X-ray and
caustic analyses. We find that the anisotropy profile of the full galaxy
population in A 85 is an increasing monotonic function of the distance
from the cluster centre: on average, galaxies in the central region
(r/r200 < 0.3) are on isotropic orbits, while galaxies in
the outer regions are on radial orbits. We also find that the orbital
properties of the galaxies strongly depend on their stellar colour. In
particular, blue galaxies are on less radial orbits than red galaxies.
The different families of cluster galaxies considered here have the
pseudo phase-space density profiles Q(r) and Qr(r) consistent
with the profiles expected in virialized dark matter haloes in N-body
simulations. This result suggests that the galaxies in A 85 have reached
dynamical equilibrium within the cluster potential. Our results indicate
that the origin of the blue and red colours of the different galaxy
populations is the different orbital shape rather than the accretion
time.
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