The Norma cluster (ACO 3627) – I. A dynamical analysis of the most massive cluster in the Great Attractor     

P. A. Woudt  R. C. Kraan-Korteweg  J. Lucey  A. P. Fairall  S. A. W. Moore 《Monthly notices of the Royal Astronomical Society》2008,383(2):445-457

A detailed dynamical analysis of the nearby rich Norma cluster (ACO 3627) is presented. From radial velocities of 296 cluster members, we find a mean velocity of 4871 ± 54 km s⁻¹ and a velocity dispersion of 925 km s⁻¹. The mean velocity of the E/S0 population (4979 ± 85 km s⁻¹) is offset with respect to that of the S/Irr population (4812 ± 70 km s⁻¹) by  Δ v = 164 km s⁻¹  in the cluster rest frame. This offset increases towards the core of the cluster. The E/S0 population is free of any detectable substructure and appears relaxed. Its shape is clearly elongated with a position angle that is aligned along the dominant large-scale structures in this region, the so-called Norma wall. The central cD galaxy has a very large peculiar velocity of 561 km s⁻¹ which is most probably related to an ongoing merger at the core of the cluster. The spiral/irregular galaxies reveal a large amount of substructure; two dynamically distinct subgroups within the overall spiral population have been identified, located along the Norma wall elongation. The dynamical mass of the Norma cluster within its Abell radius is  1–1.1 × 10¹⁵  h ⁻¹₇₃ M_⊙  . One of the cluster members, the spiral galaxy WKK 6176 which recently was observed to have a 70 kpc X-ray tail, reveals numerous striking low-brightness filaments pointing away from the cluster centre suggesting strong interaction with the intracluster medium.  相似文献   

Tracing intermediate-mass black holes in the Galactic Centre     

U. Löckmann  H. Baumgardt 《Monthly notices of the Royal Astronomical Society》2008,384(1):323-330

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Recovery of the internal orbital structure of galaxies     

G. van de Ven †  P. T. de Zeeuw  R. C. E. van den Bosch 《Monthly notices of the Royal Astronomical Society》2008,385(2):614-646

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The early-type galaxies NGC 1407 and NGC 1400 – I. Spatially resolved radial kinematics and surface photometry     

Max Spolaor  Duncan A. Forbes  George K. T. Hau  Robert N. Proctor  Sarah Brough 《Monthly notices of the Royal Astronomical Society》2008,385(2):667-674

This is the first paper of a series focused on investigating the star formation and evolutionary history of the two early-type galaxies NGC 1407 and NGC 1400. They are the two brightest galaxies of the NGC 1407 (or Eridanus-A) group, one of the 60 groups studied as part of the Group Evolution Multi-wavelength Study.
Here, we present new high signal-to-noise ratio long-slit spectroscopic data obtained at the ESO 3.6-m telescope and high-resolution multiband imaging data from the Hubble Space Telescope /Advanced Camera for Surveys and wide-field imaging from Subaru Suprime-Cam. We spatially resolved integrated spectra out to ∼0.6 (NGC 1407) and ∼1.3 (NGC 1400) effective radii. The radial profiles of the kinematic parameters v _rot, σ, h ₃ and h ₄ are measured. The surface brightness profiles are fitted to different galaxy light models and the colour distributions analysed. The multiband images are modelled to derive isophotal shape parameters and residual galaxy images. The parameters from the surface brightness profile fitting are used to estimate the mass of the possible central supermassive black hole in NGC 1407. The galaxies are found to be rotationally supported and to have a flat core in the surface brightness profiles. Elliptical isophotes are observed at all radii and no fine structures are detected in the residual galaxy images. From our results, we can also discard a possible interaction between NGC 1400, NGC 1407 and the group intergalactic medium. We estimate a mass of  ∼1.03 × 10⁹ M_⊙  for the supermassive black hole in NGC 1407 galaxy.  相似文献   

Dark matter content and internal dynamics of NGC 4697: nmagic particle models from slit data and planetary nebula velocities     

Flavio De Lorenzi  Ortwin Gerhard  Roberto P. Saglia  Niranjan Sambhus  Victor P. Debattista †  Maurilio Pannella  Roberto H. Méndez 《Monthly notices of the Royal Astronomical Society》2008,385(4):1729-1748

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H i aperture synthesis and optical observations of the pair of galaxies NGC 6907 and 6908     

S. Scarano Jr    Felipe R. H. Madsen  Nirupam Roy  J. R. D. Lépine 《Monthly notices of the Royal Astronomical Society》2008,386(2):963-972

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Constraining spiral structure parameters through Galactic pencil-beam and large-scale radial velocity surveys     

I. Minchev  A. C. Quillen 《Monthly notices of the Royal Astronomical Society》2008,386(3):1579-1587

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GHASP: an Hα kinematic survey of spiral and irregular galaxies – VI. New Hα data cubes for 108 galaxies     

B. Epinat  P. Amram  M. Marcelin  C. Balkowski  O. Daigle  O. Hernandez  L. Chemin  C. Carignan  J.-L. Gach  P. Balard 《Monthly notices of the Royal Astronomical Society》2008,388(2):500-550

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Molecular line profiles as diagnostics of protostellar collapse: modelling the 'blue asymmetry' in inside-out infall     

Y. G. Tsamis  J. M. C. Rawlings  J. A. Yates  S. Viti 《Monthly notices of the Royal Astronomical Society》2008,388(2):898-912

The evolution of star-forming core analogues undergoing inside-out collapse is studied with a multipoint chemodynamical model which self-consistently computes the abundance distribution of chemical species in the core. For several collapse periods the output chemistry of infalling tracer species such as HCO⁺, CS and N₂H⁺ is then coupled to an accelerated Λ-iteration radiative transfer code, which predicts the emerging molecular line profiles using two different input gas/dust temperature distributions. We investigate the sensitivity of the predicted spectral line profiles and line asymmetry ratios to the core temperature distribution, the time-dependent model chemistry, as well as to ad hoc abundance distributions. The line asymmetry is found to be strongly dependent on the adopted chemical abundance distribution. In general, models with a warm central region show higher values of blue asymmetry in optically thick HCO⁺ and CS lines than models with a starless core temperature profile. We find that in the formal context of Shu-type inside-out infall, and in the absence of rotation or outflows, the relative blue asymmetry of certain HCO⁺ and CS transitions is a function of time and, subject to the foregoing caveats, can act as a collapse chronometer. The sensitivity of simulated HCO⁺ line profiles to linear radial variations, subsonic or supersonic, of the internal turbulence field is investigated in the separate case of static cores.  相似文献   

Dynamical friction in modified Newtonian dynamics     

Carlo Nipoti  Luca Ciotti  James Binney  Pasquale Londrillo 《Monthly notices of the Royal Astronomical Society》2008,386(4):2194-2198

We have tested a previous analytical estimate of the dynamical friction time-scale in modified Newtonian dynamics (MOND) with fully non-linear N -body simulations. The simulations confirm that the dynamical friction time-scale is significantly shorter in MOND than in equivalent Newtonian systems, i.e. systems with the same phase-space distribution of baryons and additional dark matter. An apparent conflict between this result and the long time-scales determined for bars to slow and mergers to be completed in previous N -body simulations of MOND systems is explained. The confirmation of the short dynamical-friction time-scale in MOND underlines the challenge that the Fornax dwarf spheroidal poses to the viability of MOND.  相似文献