Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993a%26a...271..381b&link_type=abstract
Astronomy and Astrophysics, Vol.271, NO. 2/APR, P. 381, 1993
Astronomy and Astrophysics
Astrophysics
14
Scientific paper
The main goal of this paper is to determine for a given galaxy to what extent its X-ray emission properties can restrict the class of mass models that is selected by its stellar dynamics. Here we focus on NGC 4472, for which the currently available stellar dynamical data extend out to ~R_e_, while the X-ray data sample the region out to ~7R_e_. We show that both the best fit stellar dynamical model that can be proposed without invoking the presence of dark matter with M/L_B_ ~ 7.2 (which is actually judged to be not acceptable in a X^2^-analysis) and the model that, within a 3σ confidence level, contains the largest amount of dark matter in diffuse form (M/L_B_ ~ 47, M_D_ ~ 7M_L_, r_D_ ~ 7r_L_) lead to remarkably similar X-ray emission and temperature profiles, when such emission is described by means of one standard set of steady-state cooling flow equations. We have also performed a semi-empirical test where the density distribution of the gas is assumed (to match in detail the whole X-ray emission profile) and the temperature profiles corresponding to the various optically selected potential wells are inferred from the condition of hydrostatic equilibrium. The basic conclusion remains proved, i.e. that the predicted temperature profiles for models with or without dark matter are very similar to each other. If the interstellar gas is assumed to have a solar chemical composition and the intracluster pressure is not too high, then the predicted temperature for the models consistent with the stellar dynamical data is close to 1 keV. The emission-weighted temperature is found to be in better agreement with the value of ~1.9 keV favored by Ginga if a sizable value of the intracluster pressure is assumed.
Bertin Giuseppe
Pignatelli Ezio
Saglia Roberto P.
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