Year: 2012
Type: article
Abstract: Measuring the relative mass contributions of luminous and dark matter in spiral galaxies is important for understanding their formation and evolution. The combination of a galaxy rotation curve and strong lensing is a powerful way to break the disk–halo degeneracy that is inherent in each of the methods individually. We present an analysis of the 10 image radio spiral lens B1933+503 at z l = 0.755, incorporating (1) new global very long baseline interferometry observations, (2) new adaptive-optics-assisted K -band imaging, and (3) new spectroscopic observations for the lens galaxy rotation curve and the source redshift. We construct a three-dimensionally axisymmetric mass distribution with three components: an exponential profile for the disk, a point mass for the bulge, and a Navarro–Frenk–White (NFW) profile for the halo. The mass model is simultaneously fitted to the kinematics and the lensing data. The NFW halo needs to be oblate with a flattening of a / c = 0.33 +0.07 −0.05 to be consistent with the radio data. This suggests that baryons are effective at making the halos oblate near the center. The lensing and kinematics analysis probe the inner ∼10 kpc of the galaxy, and we obtain a lower limit on the halo scale radius of 16 kpc (95% credible intervals). The dark matter mass fraction inside a sphere with a radius of 2.2 disk scale lengths is f DM, 2.2 = 0.43 +0.10 −0.09 . The contribution of the disk to the total circular velocity at 2.2 disk scale lengths is 0.76 +0.05 −0.06 , suggesting that the disk is marginally submaximal. The stellar mass of the disk from our modeling is log 10 ( M * / M ☉ ) = 11.06 +0.09 −0.11 assuming that the cold gas contributes ∼20% to the total disk mass. In comparison to the stellar masses estimated from stellar population synthesis models, the stellar initial mass function of Chabrier is preferred to that of Salpeter by a probability factor of 7.2.
Source: The Astrophysical Journal
Authors: S. H. Suyu, S. W. Hensel, J. P. McKean, C. D. Fassnacht, T. Treu, A. Halkola, M. Norbury, N. Jackson, P. Schneider, D. Thompson, M. W. Auger, L. V. E. Koopmans, K. Matthews
Institutions: University of Bonn, University of California, Santa Barbara, Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Max Planck Institute for Mathematics, Netherlands Institute for Radio Astronomy, University of California, Davis, Excellence Cluster Universe, Technical University of Munich, Las Cumbres Observatory Global Telescope Network, University of Manchester, University of Arizona, University of Groningen, California Institute of Technology
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, David and Lucile Packard Foundation, National Aeronautics and Space Administration, W. M. Keck Foundation, California Institute of Technology, National Radio Astronomy Observatory, Associated Universities, Deutsche Forschungsgemeinschaft, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Science and Technology Facilities Council
OpenAlex ID: W2132532884