A discrete chemo-dynamical model of M87’s globular clusters: Kinematics extending to ∼400 kpc

ABSTRACT We study the mass distribution and kinematics of the giant elliptical galaxy M87 (NGC 4486) using discrete chemo-dynamical, axisymmetric Jeans equation modelling. Our catalogue comprises 894 globular clusters (GCs) extending to a projected radius of ∼430 kpc with line-of-sight velocities and colours, and Multi Unit Spectroscopic Explorer integral field unit data within the central 2.4 kpc of the main galaxy. The gravitational potential for our models is a combination of a luminous matter potential with a varying mass-to-light ratio for the main galaxy, a supermassive black hole and a dark matter (DM) potential with a cusped or cored DM halo. The best-fitting models with either a cusped or a cored DM halo show no significant differences and both are acceptable. We obtain a total mass of $(2.16 \pm 0.38) \times 10^{13} \, \mathrm{M}_{\odot }$ within ∼400 kpc. By including the stellar mass-to-light ratio gradient, the DM fraction increases from ∼26 per cent (with no gradient) to ∼73 per cent within $1\, R_e^{\rm maj}$ (major axis of half-light isophote, 14.2 kpc), and from ∼84 per cent to ∼94 per cent within $5\, R_e^{\rm maj}$ (71.2 kpc). Red GCs have moderate rotation with Vmax/σ ∼ 0.4, and blue GCs have weak rotation with Vmax/σ ∼ 0.1. Red GCs have tangential velocity dispersion anisotropy, while blue GCs are consistent with being nearly isotropic. Our results suggest that red GCs are more likely to be born in situ, while blue GCs are more likely to be accreted.

Simulation of NGC 3769 and its companion NGC 3769A

In this paper two interacted galaxies NGC 3769 and NGC 3769A are simulated by using Intergalactic Gravitational Motion Simulator IGMS code. Through the simulation, the effects of the attraction between the two galaxies are explained how the comapanion galaxy NGC 3769A moves around the main galaxy NGC 3769. At the time (t=850 Myrs.) the situation of the companion comparing to the main galaxy would be in a good agreement with the situation of the two galaxies observed by telescope.

The Enhancement of BAO in the SDSS MGS

We show that redshift-space distortions of galaxy correlations have a strong effect on correlation functions with the signature of the Baryon Acoustic Oscillations (BAO). Near the line of sight, the features become sharper as a result of redshift-space distortions. We analyze the SDSS DR7 main-galaxy sample (MGS), splitting the sample into slices 2.5 deg on the sky in various rotations. Measuring 2D correlation functions in each slice, we do see a sharp bump along the line of sight. Using Mexican-hat wavelets, we localize it to (110 ± 10) h − 1 Mpc and estimate its significance at about 4σ.