We performed a systematic search for broad-velocity-width molecular features (BVFs) in the disk part of our Galaxy by using the CO J = 1–0 survey data obtained with the Nobeyama Radio Observatory 45 m telescope. From this search, 58 BVFs were identified. In comparisons with the infrared and radio continuum images, 36 BVFs appeared to have both infrared and radio continuum counterparts, and 15 of them are described as molecular outflows from young stellar objects in the literature. In addition, 21 BVFs have infrared counterparts only, and eight of them are described as molecular outflows in the literature. One BVF (CO 16.134–0.553) does not have any luminous counterpart in the other wavelengths, which suggests that it may be an analog of high-velocity compact clouds in the Galactic center.

The l = +13 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, 13CO J = 1−0, H13CN J = 1−0, H13CO+ 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 11 expanding shells with total kinetic energy and typical expansion time E kin ∼ 1051.9 erg and t exp ∼ 104.9 yr, respectively. In addition, the l = +13 region exhibited high SiO J = 2−1/H13CN J = 1−0 and SiO J = 2−1/H13CO+ 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 = +13 region. The nature of the embedded star cluster, which may have supplied 20–70 supernova explosions within 105 yr, is discussed. This work also shows the importance of compact broad-velocity-width features in searching for localized energy sources hidden behind severe interstellar extinction and stellar contamination.

In this paper, we report the discovery of an isolated, peculiar compact cloud with a steep velocity gradient at 2.′6 northwest of Sgr A*. This “Tadpole” molecular cloud is unique owing to its characteristic head-tail structure in the position–velocity space. By tracing the CO J = 3–2 intensity peak in each velocity channel, we noticed that the kinematics of the Tadpole can be well reproduced by a Keplerian motion around a point-like object with a mass of 1 × 105 M ⊙. Changes in line intensity ratios along the orbit are consistent with the Keplerian orbit model. The spatial compactness of the Tadpole and absence of bright counterparts in other wavelengths indicate that the object could be an intermediate-mass black hole.