New Look at the Molecular Superbubble Candidate in the Galactic Center

Abstract

The l = +1. • 3 region in the Galactic center is characterized by multiple shell-like structures and their extremely broad velocity widths. We revisit the molecular superbubble hypothesis for this region, based on high resolution maps of CO J=1-0, 13 CO J=1-0, H 13 CN J=1-0, H 13 CO + J=1-0, SiO J=2-1, and CS J=2-1 lines obtained from the Nobeyama radio observatory 45-m telescope, as well as CO J=3-2 maps obtained from the James Clerk Maxwell telescope. We identified eleven expanding shells with total kinetic energy and typical expansion time E kin ∼ 10 51.9 erg and t exp ∼ 10 4.9 yr, respectively. In addition, the l = +1. • 3 region exhibited high SiO J=2-1/H 13 CN J=1-0 and SiO J=2-1/H 13 CO + J=1-0 intensity ratios, indicating that the region has experienced dissociative shocks in the past. These new findings confirm the molecular superbubble hypothesis for the l = +1. • 3 region. The nature of the embedded star cluster, which may have supplied 20-70 supernova explosions within 10 5 yr, is discussed. This work also show the importance of compact broad-velocity-width features in searching for localized energy sources hidden behind severe interstellar extinction and stellar contamination.