A POSSIBLE EXTENSION OF THE SCUTUM-CENTAURUS ARM INTO THE OUTER SECOND QUADRANT

Yan Sun, Ye Xu, Ji Yang, Fa-Cheng Li, Xin-Yu Du, Shao-Bo Zhang, Xin Zhou
2014 Astrophysical Journal Letters  
Combining HI data from the Canadian Galactic Plane Survey~(CGPS) and CO data from the Milky Way Imaging Scroll Painting (MWISP) project, we have identified a new segment of a spiral arm between Galactocentric radii of 15 and 19~kpc that apparently lies beyond the Outer Arm in the second Galactic quadrant. Over most of its length, the arm is 400-600 pc thick in $z$. The new arm appears to be the extension of the distant arm recently discovered by Dame & Thaddeus (2011) as well as the
more » ... as the Scutum-Centaurus Arm into the outer second quadrant. Our current survey identified a total of 72 molecular clouds with masses on the order of 10$^2$-10$^4$M$_{\sun}$ that probably lie in the new arm. When all of the available data from the CO molecular clouds are fit, the best$-$fitting spiral model gives a pitch angle of 9.3$^{\circ}$ $\pm$0.7$^{\circ}$.
doi:10.1088/2041-8205/798/2/l27 fatcat:54czeik53rcrziqf36ahnqshbq