Bar and Spiral Torques in the Triangulum Galaxy M33

  • Robert Groess
  • David L. Block
  • Ivanio Puerari
Conference paper
Part of the Astrophysics and Space Science Library book series (ASSL, volume 319)


The Triangulum Spiral (M33=NGC 598) presents a daunting task to near-infrared observers, due to its huge spatial extent. From the deepest near-infrared (JHKS) images of M33 yet secured, we identify a bar and calculate the gravitational torque, the bar torque as well as the spiral arm torque. Our methodology reveals the presence of a “class 2” bar, meaning that the tangential force field reaches a maximum of ~ 20% relative to the axisymmetric radial force field. Furthermore, we are able for the first time to quantify the Reynolds (1927) spiral arm index for M33 (described as ‘broad’: low arm-interarm contrast), and estimate that the spiral arm torque reaches a maximum of only 15%.


Gravitational torque bar torque spiral arms Triangulum Spiral M33 


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Copyright information

© Springer Science+Business Media New York 2004

Authors and Affiliations

  • Robert Groess
    • 1
  • David L. Block
    • 1
  • Ivanio Puerari
    • 2
  1. 1.School of Computational and Applied MathematicsUniversity of the WitwatersrandJohannesburgSouth Africa
  2. 2.Instituto Nacional de AstrofisicaOptica y ElectronicaPueblaMexico

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