The distances of SNR W41 and overlapping H II regions

Abstract

New H I images from the VLA Galactic Plane Survey show prominent absorption features associated with the supernovae remnant G23.3-0.3 (SNR W41). We highlight the H Iabsorption spectra and the 13CO emission spectra of eight small regions on the face of W41, including four H IIregions, three non-thermal emission regions, and one unclassified region. The maximum velocity of absorption for W41 is 78 ± 2 km s-1 and the CO cloud at radial velocity 95 ± 5 km s-1 is behind W41. Because an extended TeV source, a diffuse X-ray enhancement, and a large molecular cloud at radial velocity 77 ± 5 km s-1 overlap the center of W41, the kinematic distance is 3.9-4.5 kpc for W41. For the H IIregions, our analysis shows that both G23.42-0.21 and G23.07+0.25 are at the far kinematic distances (9.9 kpc and 10.6 kpc, respectively) of their recombination-line velocities (103 ± 0.5 km s-1 and 89.6 ± 2.1 km s-1, respectively), G23.07-0.37 is at the near kinematic distance (4.4 ± 0.3 kpc) of its recombination-line velocity (82.7 ± 2.0 km s-1), and G23.27-0.27 is probably at the near kinematic distance (4.1 ± 0.3 kpc) of its recombination-line velocity (76.1 ± 0.6 km s-1). © 2008. The American Astronomical Society. All rights reserved.