ar X iv : a st ro - p h / 98 12 11 8 v 1 7 D ec 1 99 8 Two – component galaxy models : phase – space constraints By LUCA CIOTTI
نویسنده
چکیده
The properties of the analitycal phase–space distribution function (DF) of two–component spherical self–consistent galaxy models, where one density distribution follows the Hernquist profile, and the other a γ = 0 model, with different total masses and core radii (H0 models), presented in Ciotti (1998, C98), are here summarized. A variable amount of radial Osipkov– Merritt (OM) orbital anisotropy is allowed in both components. The necessary and sufficient conditions that the model parameters must satisfy in order to correspond to a model where each one of the two distinct components has a positive DF (the so–called model consistency) are analytically derived, together with some results on the more general problem of the consistency of two–component γ1 + γ2 models. The possibility to add in a consistent way a black hole (BH) at the center of radially anisotropic γ models is also discussed. In the particular case of H0 models, it is proved that a globally isotropic Hernquist component is consistent for any mass and core radius of the superimposed γ = 0 halo; on the contrary, only a maximum value of the core radius is allowed to the γ = 0 component when a Hernquist halo is added. The combined effect of halo concentration and orbital anisotropy is successively investigated.
منابع مشابه
ar X iv : a st ro - p h / 98 12 12 1 v 1 7 D ec 1 99 8 Nuclear kpc - sized disks of spiral galaxies
A complex structure of nuclear disks of normal spiral galaxies is illustrated on the example of five galaxies, observed at 6m telescope. A problem of gravitational stability of nuclear disks is shortly discussed.
متن کاملar X iv : a st ro - p h / 98 12 32 8 v 1 1 7 D ec 1 99 8 MOND in the Early Universe
I explore some consequences of Milgrom’s modified dynamics for cosmology. There appear to be two promising tests for distinguishing MOND from CDM: (1) the rate of growth of structure and (2) the baryon fraction. These should be testable with observations of clusters at high redshift and the microwave background, respectively.
متن کاملar X iv : a st ro - p h / 98 12 35 8 v 1 1 8 D ec 1 99 8 RXTE OBSERVATIONS OF LMC X - 1
The luminous X-ray binary and black-hole candidate LMC X-1 has been observed with the Rossi X-ray Timing Explorer (RXT E) to search for quasi-periodic oscillations (QPO), previously reported in its high state. The source was observed monthly in a series of nine observations. Analysis of the temporal variations shows no evidence for QPO or other periodic changes, but correlations between the hig...
متن کاملar X iv : a st ro - p h / 98 12 27 2 v 1 1 5 D ec 1 99 8 Constraints on the Unseen Galaxy Population from the Ly α Forest Kenneth
Here we describe results of our attempt to determine what types of galaxies are responsible for the Lyα forest absorption systems, based on our ongoing imaging and spectroscopic survey of faint galaxies in fields of HST spectroscopic target QSOs. Our primary conclusions are that the bulk of the Lyα forest arises in more or less normal galaxies (that span the normal range of luminosity and morph...
متن کامل