DISENTANGLING BARYONS AND DARK MATTER IN THE SPIRAL GRAVITATIONAL LENS B1933+503

Journal Article · Tue May 01 04:00:00 EDT 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/750/1/10· OSTI ID:22034634

Suyu, S H; Treu, T; Auger, M W ^[1]; Hensel, S W; Schneider, P ^[2]; McKean, J P ^[3]; Fassnacht, C D ^[4]; Halkola, A ^[5]; Norbury, M ^[6]; Jackson, N ^[7]; Thompson, D ^[8]; Koopmans, L V. E. ^[9]; Matthews, K ^[10]

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1. Department of Physics, University of California, Santa Barbara, CA 93106-9530 (United States)
2. Argelander-Institut fuer Astronomie, Auf dem Huegel 71, 53121 Bonn (Germany)
3. ASTRON, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo (Netherlands)
4. Department of Physics, University of California Davis, 1 Shields Avenue, Davis, CA 95616 (United States)
5. Excellence Cluster Universe, Technische Universitaet Muenchen, Boltzmannstr. 2, 85748 Garching (Germany)
6. Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Santa Barbara, CA 93117 (United States)
7. Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom)
8. Large Binocular Telescope Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
9. Kapteyn Astronomical Institute, P.O. Box 800, 9700 AV Groningen (Netherlands)
10. Caltech Optical Observatories, California Institute of Technology, Pasadena, CA 91125 (United States)

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{sub 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{sup +0.07}{sub -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 {approx}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{sub DM,2.2} = 0.43{sup +0.10}{sub -0.09}. The contribution of the disk to the total circular velocity at 2.2 disk scale lengths is 0.76{sup +0.05}{sub -0.06}, suggesting that the disk is marginally submaximal. The stellar mass of the disk from our modeling is log{sub 10}(M{sub *}/M{sub Sun }) = 11.06{sup +0.09}{sub -0.11} assuming that the cold gas contributes {approx}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.

• OSTI ID: 22034634
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 750; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTROPHYSICS
AXIAL SYMMETRY
BARYONS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
DIAGRAMS
GALACTIC EVOLUTION
GALAXIES
GRAVITATIONAL LENSES
INTERFEROMETRY
LENGTH
MASS
MASS DISTRIBUTION
NONLUMINOUS MATTER
RED SHIFT
ROTATION
THREE-DIMENSIONAL CALCULATIONS