Astronomy and Astrophysics – Astrophysics
Scientific paper
1997-10-13
Astronomy and Astrophysics
Astrophysics
19 pages LaTex, 18 figures. MNRAS, in press. Also available at http://www.astro.unibas.ch/~gerhard/papers/dm6703.ps.gz
Scientific paper
(abridged) We have measured line-of-sight velocity profiles (VPs) in the E0 galaxy NGC 6703 out to 2.6 R_e. From these data we constrain the mass distribution and the anisotropy of the stellar orbits in this galaxy. We have developed a non-parametric technique to determine the DF f(E,L^2) directly from the kinematic data. From Monte Carlo tests using the spatial extent, sampling, and error bars of the NGC 6703 data we find that smooth underlying DFs can be recovered to an rms accuracy of 12%, and the anisotropy parameter beta(r) to an accuracy of 0.1, in a given potential. An asymptotically constant halo circular velocity v_0 can be determined with an accuracy of +- \lta 50km/s. For NGC 6703 we determine the true circular velocity at 2.6 R_e to be 250 +- 40km/s at 95% c.l., corresponding to a total mass in NGC 6703 inside 78'' (13.5 h_50^-1 kpc), of 1.6-2.6 x 10^11 h_50^-1 Msun. No model without dark matter will fit the data; however, a maximum stellar mass model in which the luminous component provides nearly all the mass in the centre does. In such a model, the total luminous mass inside 78'' is 9 x 10^10 Msun and the integrated M/L_B=5.3-10, corresponding to a rise from the center by at least a factor of 1.6. The anisotropy of the stellar distribution function in NGC 6703 changes from near-isotropic at the centre to slightly radially anisotropic (beta=0.3-0.4 at 30'', beta=0.2-0.4 at 60'') and is not well-constrained at the outer edge of the data. Our results suggest that also elliptical galaxies begin to be dominated by dark matter at radii of \sim 10kpc.
Bender Ralf
Gerhard Ortwin
Jeske Gunther
Saglia Roberto P.
No associations
LandOfFree
Breaking the degeneracy between anisotropy and mass: The dark halo of the E0 galaxy NGC 6703 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Breaking the degeneracy between anisotropy and mass: The dark halo of the E0 galaxy NGC 6703, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Breaking the degeneracy between anisotropy and mass: The dark halo of the E0 galaxy NGC 6703 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-562094