Dark Matter Deprivation in Field Elliptical Galaxy NGC 7507

摘要: Previous studies have shown that the kinematics of field elliptical galaxy NGC 7507 do not necessarily require dark matter. This is troubling because, in context LCDM cosmologies, all galaxies should a large matter component. We use penalised pixel fitting software to extract velocities and velocity dispersions from GMOS slit mask spectra. Using Jeans MONDian modelling we produce best fit models dispersion. find has two component stellar halo, with outer halo inner haloes counter rotating. The dispersion profile exhibits an increase at ~70" (~7.9 kpc), reminiscent several other galaxies. Our are those under mild anisotropy which include ~100 times less than predicted by LCDM, although mildly anisotropic completely free almost equally well. models, both isotropic anisotropic, systematically fail reproduce measured radii. rotating implies merger remnant, as does ~70". From simulations it seems plausible caused was spiral-spiral merger. consistent no scenario, however, some can be accommodated, much lower concentrations simulations. indicates may galaxy. Whether or very poor, this odds predictions current cosmological It possible observed could reproduced if significantly flattened along line sight (e.g. due rotation), invoking flattening problematic.