NGC 1808 is a nearby barred starburst galaxy with an outflow from the nuclear region. To study the inflow and outflow processes related to star formation and dynamical evolution of the galaxy, we have carried out 12 CO (J = 1 − 0) mapping observations of the central r ∼ 4 kpc of NGC 1808 using the Atacama Large Millimeter/submillimeter Array (ALMA). Four distinct components of molecular gas are revealed at high spatial resolution of 2 (∼ 100 pc): (1) a compact (r < 200 pc) circumnuclear disk (CND), (2) r ∼ 500 pc ring, (3) gasrich galactic bar, and (4) spiral arms. Basic geometric and kinematic parameters are derived for the central 1-kpc region using tilted-ring modeling. The derived rotation curve reveals multiple mass components that include (1) a stellar bulge, (2) nuclear bar and molecular CND, and (3) unresolved massive (∼ 10 7 M ) core. Two systemic velocities, 998 km s −1 for the CND and 964 km s −1 for the 500-pc ring, are revealed, indicating a kinematic offset. The pattern speed of the primary bar, derived by using a cloud-orbit model, is 56 ± 11 km s −1 kpc −1 . Non-circular motions are detected associated with a nuclear spiral pattern and outflow in the central 1-kpc region. The ratio of the mass outflow rate to the star formation rate isṀ out /SF R ∼ 0.2 in the case of optically thin CO (1-0) emission in the outflow, suggesting low efficiency of star formation quenching.

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We present large-field (15.7 $ \times$ 16.9 arcmin$ ^2$ ) CO ($ J$$ =$ 1$ \rightarrow$ 0) observations of the starburst galaxy M 82, at an angular resolution of 22$ ''$ with the NRO 45-m telescope. The CO emission was detected in the galactic disk, outflow (driven by the galactic wind) up to $ \sim$ 2 kpc above the galactic plane in the halo, and in tidal streams. The kinematics of the outflow (including CO line splitting) suggests that it has the shape of a cylinder that is diverging outwards. The mass and kinetic energy of the molecular gas outflow are estimated to be (0.26–1.0) $ \times$ 10$ ^{9}\ M_{\odot}$ and (1–4) $ \times$ 10$ ^{56}$ erg. A clump of CO gas was discovered 3.5 kpc above the galactic plane; it coincides with a dark lane previously found in X-ray observations, and a peak in H I emission. A comparison with H I, hot molecular hydrogen and dust suggests that the molecular gas shows signatures of warm and cool components in the outflow and tidal streams, respectively.

ALMA imaging of the cold molecular medium in the nearby starburst galaxy NGC 1808 is presented. The observations reveal the distribution of molecular gas, traced by 12 CO (1-0) and 12 CO (3-2), and continuum (93 and 350 GHz) across the central 1 kpc starburst region at high resolution of ∼ 1 . A molecular gas torus (radius ∼ 30 pc) is discovered in the circumnuclear disk (CND; central 100 pc), with a high CO (3-2)/CO (1-0) ratio of ∼ 1, surrounded by massive (10 6 -10 7 M ) clouds with high star formation efficiency (SFE ∼ 10 −8 yr −1 ), molecular spiral arms, and a 500 pc pseudoring. The CND harbors a continuum core and molecular gas exhibiting peculiar motion. The new data confirm the line splitting along the minor galactic axis, interpreted as a nuclear gas outflow with average velocity ∼ 180 km s −1 , and show evidence of a velocity gradient of ∼ +0.4 km s −1 pc −1 along the axis. In addition, supershells expanding from the 500 pc ring with maximum velocities of ∼ 75 km s −1 are revealed. The distribution and CO luminosities of molecular clouds in the central 1 kpc starburst region indicate an evolutionary sequence, from gas accretion onto the 500 pc ring from the large-scale bar, to enhanced star formation in the ring, and outflow as feedback.

Observations of the molecular gas in galaxies are vital to understanding the evolution and starforming histories of galaxies. However, galaxies with molecular gas maps of their whole discs having sufficient resolution to distinguish galactic structures are severely lacking. Millimeter wavelength studies at a high angular resolution across multiple lines and transitions are particularly needed, severely limiting our ability to infer the universal properties of molecular gas in galaxies. Hence, we conducted a legacy project with the 45 m telescope of the Nobeyama Radio Observatory, called the CO Multi-line Imaging of Nearby Galaxies (COMING), which simultaneously observed 147 galaxies with high far-infrared flux in 12 CO, 13 CO, and C 18 O J = 1 − 0 lines. The total molecular gas mass was derived using the standard CO-to-H 2 conversion factor and found to be positively correlated with the total stellar mass derived from the WISE 3.4 µm band data. The fraction of the total molecular gas mass to the total stellar mass in galaxies does not depend on their Hubble types nor the existence of a galactic bar, although when galaxies in individual morphological types are investigated separately, the fraction seems to decrease with the total stellar mass in early-type galaxies and vice versa in late-type galaxies. No differences in the distribution of the total molecular gas mass, stellar mass, and the total molecular gas to stellar mass ratio was observed between barred and non-barred galaxies, which is likely the result of our sample selection criteria, in that we prioritized observing FIR bright (and thus molecular gas-rich) galaxies.