![]() A striking phenomenon in this respect is the existence of very extended stellar haloes around bright central galaxies in galaxy clusters (e.g. The structure of galaxies can be strongly altered by environmental processes, like major and minor mergers, accretion of satellite galaxies, ram pressure stripping and other interactions between galaxies and with the intra-cluster medium. Key words: galaxies: clusters: individual: Hydra I / galaxies: elliptical and lenticular, cD / galaxies: haloes / galaxies: individual: NGC 3311 / galaxies: kinematics and dynamics / galaxies: formation This may in general apply to central cluster galaxies with rising velocity dispersion profiles, where infall processes are important. Previous claims about the cored dark halo of NGC 3311 are therefore probably not valid. Jeans models using one tracer population with a unique density profile are not able to explain the large range of the observed kinematics. The rising velocity dispersion of NGC 3311 apparently is a result of averaging over a range of velocity dispersions related to different tracer populations in the sense of different density profiles and anisotropies. Simple Jeans models illustrate that a range of mass profiles can account for all observed velocity dispersions, including radial MOND models.Ĭonclusions. We interpret this behaviour as the superposition of tracer populations with increasingly shallower radial distributions between the extremes of the inner stellar populations and the cluster galaxies. The upper envelope rises smoothly, joining the velocity dispersion of the outer globular clusters and the cluster galaxies. The lower envelope is about constant at 200 km s −1. If the radial dependence alone is considered, the velocity dispersion does not simply rise but fills an increasingly large range of dispersion values with two well defined envelopes. ![]() Outside 10 kpc the cumulative angular momentum is rising, however, without showing an ordered rotation signal. The inner spheroid of NGC 3311 can be described as a slow rotator. Beyond this radius, both the velocities and the velocity dispersion start to depend on azimuth angle and show a significant intrinsic scatter. We find a homogeneous velocity field and velocity dispersion field within a radius of about 10 kpc. We use PPXF to extract the kinematic information of velocities, velocity dispersions and the high-order moments h 3 and h 4. The slits of the outermost masks reach out to about 35 kpc of galactocentric distance. We performed multi-object spectroscopic observations of the diffuse stellar halo of NGC 3311 using VLT/FORS2 in MXU mode to mimic a coarse “IFU”. We aim to find kinematic signatures of sub-structures in the extended halo of NGC 3311. However, position dependent long-slit measurements show that the kinematics are still not understood.Īims. In the context of Jeans models, a massive dark halo with a large core is needed to explain this finding. Previous work has shown that the line-of-sight velocity dispersion of the stars and globular clusters in the extended halo of NGC 3311 rises up to the value of the cluster velocity dispersion. NGC 3311, the central galaxy of the Hydra I cluster, shows signatures of recent infall of satellite galaxies from the cluster environment. Mendes de Oliveira 3ġ European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, GermanyĮ-mail: Universidad de Concepción, Concepción, Chileģ Universidade de São Paulo, Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Rua do Matão 1226, São Paulo, SP, BrazilĬontext. Astronomical objects: linking to databases. ![]() Including author names using non-Roman alphabets.Suggested resources for more tips on language editing in the sciences Punctuation and style concerns regarding equations, figures, tables, and footnotes
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