A New Spiral Arm of the Galaxy: The Far 3 kpc Arm

@article{Dame2008ANS,
  title={A New Spiral Arm of the Galaxy: The Far 3 kpc Arm},
  author={Thomas M. Dame and Patrick Thaddeus},
  journal={The Astrophysical Journal Letters},
  year={2008},
  volume={683},
  pages={L143 - L146}
}
We report the detection in CO of the far-side counterpart of the well-known expanding 3 kpc arm in the central region of the Galaxy. In a CO longitude-velocity map at b = 0° the far 3 kpc arm can be followed over at least 20° of Galactic longitude as a faint lane at positive velocities running parallel to the near arm. The far arm crosses l = 0° at +56 km s−1, quite symmetric with the –53 km s−1 expansion velocity of the near arm. In addition to their symmetry in longitude and velocity, we find… 

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