Poster Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

Galactic Structure from the MALT 90 Survey:  High-Mass Star-Formation in Distant Spiral Arms (#231)

James Jackson 1 , Scott Whitaker 1 , Jill Rathborne 2 , Jonathan Foster 3
  1. Boston University, Boston, MA, United States
  2. CASS, CSIRO, Marsfield, NSW, Australia
  3. Astronomy Department, Yale University, New Haven, Connecticut, USA

Using mm-wave molecular data from the Millimetre Astronomy Legacy Team 90 GHz Survey (MALT 90), we have determined the radial velocities and kinematic distances to 1,912 high-mass star-forming regions.  This is the largest sample of star-forming regions for which reliable distances have been determined.  We resolve the near-far kinematic distance ambiguity by searching for absorption or self-absorption features in the 21 cm H I spectra toward each of the molecular clumps.  The distribution of the high-mass star-forming clumps clearly traces Galactic spiral arm features including the Scutum-Centaurus Arm, the Norma Arm, and the Sagittarius Arm.  Of particular interest is the first detection of the most distant portion of the Scutum-Centaurus Arm at the far kinematic distance (~10 kpc from the Sun).  Since high-mass star-formation occurs almost exclusively in spiral arms, these dense star-forming clumps may provide the best tracers of spiral structure in the Milky Way.