The structure of the Fornax dwarf elliptical galaxy. I - The radial profile

Abstract

view Abstract Citations (37) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Structure of the Fornax Dwarf Elliptical Galaxy. I. The Radial Profile Eskridge, Paul B. Abstract The radial profile of the Fornax dwarf elliptical galaxy has been determined from automated starcounts on UK Schmidt Telescope Unit (UKSTU) plates. The ellipticity (e=0.30 +/- 0.02) and position angle (P.A.(1950.0)=40.2^deg^ +/- 2.0^deg^) are in agreement with the results from the deepest data of Hodge and Smith (1974). The profiles obtained for the four plates have been compared with King (1966) models with a wide range of core and tidal radii. The best overall fit, with some variation from plate to plate, is a model with r_t_ =108' +/- 3' and r_c_ = 16.7' +/- 1.8', with a standard deviation of σ= 1.20 and a reduced χ^2^ of 1.02. This value of the core radius is in essential agreement with previous studies. The tidal radius determined is somewhat larger than found by de Vaucouleurs and Ables (1968) or by Hodge and Smith (1974). Using the above values, along with data from the literature, and including the results from a similar calculation based on data for the Sculptor profile (Eskridge 1988b), the formal result for the mass of the Galaxy is found to be M_G_ ~3.7 +/- 1.9 X 10^10^ M_sun_. This is an unacceptably low value given the current accepted values for R_0_ (8.5 kpc) and v_0_ (220 km/s), and is far lower than recent determinations (Olszewski et al. 1986; Little and Tremaine 1986). This argues that the halo dwarfs have not yet reached tidal equilibrium. Exponential law fits have also been made, following the suggestion (Faber and Lin 1983) that the halo dwarfs are as well fit by exponential laws as are many disk systems. The mean best fit has a slope of γ= -0.040 +/- 0.002 arcmin^-1^, with a standard deviation of σ = 2.32 and a reduced χ^2^ of 0.96. Given the distance modulus of Buonanno et al. (1985), this implies a physical scale length of r_e_ ~0.95 kpc. The larger value of σ for the exponential fit argues that a King model is the better description of the Fornax system. However, while the data show deviations from an exponential law in both the innermost and outermost regions, these are not more severe than deviations seen in a number of disk systems. The current data, therefore, do not argue strongly against the hypothesis that the halo dwarfs are the results of ram-pressure stripping of dI systems by the Galactic halo. Publication: The Astronomical Journal Pub Date: October 1988 DOI: 10.1086/114884 Bibcode: 1988AJ.....96.1352E Keywords: Dwarf Galaxies; Elliptical Galaxies; Galactic Structure; Schmidt Telescopes; Star Formation; Stellar Luminosity; Galactic Rotation; Stellar Models; Astrophysics; GALAXIES: INDIVIDUAL; GALAXIES: LOCAL GROUP; GALAXIES: THE GALAXY; GALAXIES: STRUCTURE full text sources ADS | data products SIMBAD (2) NED (1) Related Materials (1) Part 2: 1988AJ.....96.1614E