Searching for non-axisymmetries in NGC 6503: a weak end-on bar

Authors

  • Rachel Kuzio de Naray,

    Corresponding author
    • Department of Physics, Royal Military College of Canada, Kingston, ON, Canada
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    • Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.

  • Cameron A. Arsenault,

    Corresponding author
    • Department of Physics, Royal Military College of Canada, Kingston, ON, Canada
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  • Kristine Spekkens,

    Corresponding author
    • Department of Physics, Royal Military College of Canada, Kingston, ON, Canada
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  • J. A. Sellwood,

    Corresponding author
    1. Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, NJ, USA
    • Department of Physics, Royal Military College of Canada, Kingston, ON, Canada
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  • Michael McDonald,

    Corresponding author
    1. Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA, USA
    • Department of Physics, Royal Military College of Canada, Kingston, ON, Canada
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  • Joshua D. Simon,

    Corresponding author
    1. Observatories of the Carnegie Institution of Washington, Pasadena, CA, USA
    • Department of Physics, Royal Military College of Canada, Kingston, ON, Canada
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    • Visiting Astronomer, Kitt Peak National Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.

  • Peter Teuben

    Corresponding author
    1. Department of Astronomy, University of Maryland, College Park, MD, USA
    • Department of Physics, Royal Military College of Canada, Kingston, ON, Canada
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E-mail: kuzio@rmc.ca (RKdN); cameron.arsenault@forces.gc.ca (CAA); kristine.spekkens@rmc.ca (KS); sellwood@physics.rutgers.edu (JAS); mcdonald@space.mit.edu (MM); jsimon@obs.carnegiescience.edu (JDS); teuben@astro.umd.edu (PT)

ABSTRACT

The isolation, simple apparent structure and low luminosity of the nearby spiral galaxy NGC 6503 make it an ideal candidate for an in-depth kinematic and photometric study. We introduce a new publicly available code, DiskFit, that implements procedures for fitting non-axisymmetries in either kinematic or photometric data. We use DiskFit to analyse new Hα and CO velocity field data as well as H i kinematics from Greisen et al. to search for non-circular motions in the disc of NGC 6503. We find NGC 6503 to have remarkably regular gas kinematics that are well described by rotation only. We also use DiskFit and a new Ks-band image of NGC 6503 to constrain photometric models of the disc, bar and bulge. We find the galaxy to be photometrically dominated by the disc. We find NGC 6503 to contain a faint bar and an exponential bulge which together contribute only ∼5 per cent of the total galaxy light. The combination of our kinematic and photometric DiskFit models suggests that NGC 6503 contains a weak, end-on bar that may have produced its Type II surface brightness profile but is unlikely to be responsible for its strong σ-drop.

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