Internal dynamics and dynamical friction effects in the dwarf spheroidal galaxy in Fornax
نویسندگان
چکیده
In the Fornax dwarf spheroidal galaxy the globular clusters are distributed widely, without any significant central concentration. Oh et al. (2000) pointed out that such a distribution is paradoxical: dynamical friction effects estimated using single-component King models would have forced the globular clusters to spiral down to the center of the galaxy well within a Hubble time. This paper is devoted to a discussion of this paradox. We describe a model in which the stars of the dwarf spheroidal galaxy are embedded in a cloud of dark matter, and each of these components is specified by its own phase space distribution function. This model allows us to fit self-consistently the observed luminosity profile and the spatial variation of the velocity dispersion of the stars. This fitting yields two basic parameters, related to the central density and velocity dispersion, that characterize the phase space distribution of dark matter. The dynamical friction effects calculated on the basis of this self-consistent model are small enough that the observed spatial distribution of the globular clusters poses no difficulty, and the apparent paradox is resolved. Thus we have at hand a model for Fornax that reproduces the main observed features of this dwarf spheroidal galaxy. Subject headings: dark matter – galaxies: dwarf – galaxies: kinematics and dynamics
منابع مشابه
A Large Dark Matter Core in the Fornax Dwarf Spheroidal Galaxy?
We use measurements of the stellar velocity dispersion pro£le of the Fornax dwarf spheroidal galaxy to derive constraints on its dark matter distribution. Though the data are unable to distinguish between models with small cores and those with cusps, we show that a large & 1 kpc dark matter core in Fornax is highly implausible. Irrespective of the origin of the core, reasonable dynamical limits...
متن کاملShell Structure in the Fornax Dwarf Spheroidal Galaxy
We present initial results from a wide field photometric survey of the Fornax dwarf spheroidal (dSph) galaxy. The focus here is on a small overdensity of stars located approximately 17 (670 pc in projection) from the centre of Fornax. Based on imaging data in both V and I bands down to V ≈ 21, the dimensions of the feature are ∼1.7×3.2 (68×128 pc) with an average surface brightness of 25.8 mag/...
متن کاملA Wide-Field Survey of the Fornax Dwarf Spheroidal Galaxy
The results of a photometric survey of the Fornax dwarf spheroidal galaxy are presented herein. Accurate photometry in two colours (V and I) was collected over a 10 deg area centred on the Fornax system with the aim of searching for extra-tidal structure. The data were complete to a magnitude of V = 20, or approximately one magnitude brighter than the Fornax red clump stars. Stars were selected...
متن کاملDiscovery of Low-Luminosity Carbon Stars in the Fornax Dwarf Spheroidal Galaxy with MOS at CFHT
We report circumstances and observational techniques used with the CFHT Multi-Object Spectrograph that led us to the discovery of low-luminosity carbon stars in the Fornax dwarf spheroidal galaxy. We review the carbon star surveys carried out with this system and present our main results. A more detailed study based on our CFHT and ESO observations will be published in the proceedings of the IA...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
عنوان ژورنال:
دوره شماره
صفحات -
تاریخ انتشار 2009