We report the highest-redshift detection of [O I] 63 <inline-formula><tex-math id="TM0001" notation="LaTeX">$\mu$</tex-math></inline-formula>m from a luminous quasar, J2054<inline-formula><tex-math id="TM0002" notation="LaTeX">$-$</tex-math></inline-formula>0005, at <inline-formula><tex-math id="TM0003" notation="LaTeX">$z=6.04$</tex-math></inline-formula> based on the Atacama Large Millimeter/sub-millimeter Array (ALMA) Band 9 observations. The [O I] 63 <inline-formula><tex-math id="TM0004" notation="LaTeX">$\mu$</tex-math></inline-formula>m line luminosity is <inline-formula><tex-math id="TM0005" notation="LaTeX">$(4.5\pm 1.5) \times 10^{9} L_{\odot }$</tex-math></inline-formula>, corresponding to the [O I] 63 <inline-formula><tex-math id="TM0006" notation="LaTeX">$\mu$</tex-math></inline-formula>m-to-far-infrared luminosity ratio of <inline-formula><tex-math id="TM0007" notation="LaTeX">$\approx$</tex-math></inline-formula>6.7 <inline-formula><tex-math id="TM0008" notation="LaTeX">$\times 10^{-4}$</tex-math></inline-formula>, which is consistent with the value obtained in the local Universe. Remarkably, [O I] 63 <inline-formula><tex-math id="TM0009" notation="LaTeX">$\mu$</tex-math></inline-formula>m is as bright as [C II] 158 <inline-formula><tex-math id="TM0010" notation="LaTeX">$\mu$</tex-math></inline-formula>m, resulting in the [O I]-to-[C II] line luminosity ratio of <inline-formula><tex-math id="TM0011" notation="LaTeX">$1.3\pm 0.5$</tex-math></inline-formula>. Based on a careful comparison of the luminosity ratios of [O I] 63 <inline-formula><tex-math id="TM0012" notation="LaTeX">$\mu$</tex-math></inline-formula>m, [C II] 158 <inline-formula><tex-math id="TM0013" notation="LaTeX">$\mu$</tex-math></inline-formula>m, and dust continuum emission to models of photodissociation regions, we find that J2054<inline-formula><tex-math id="TM0014" notation="LaTeX">$-$</tex-math></inline-formula>0005 has a gas density <inline-formula><tex-math id="TM0015" notation="LaTeX">$\log (n_{\rm H}/{\rm cm}^{-3}) = 3.7\pm 0.3$</tex-math></inline-formula> and an incident far-ultraviolet radiation field of <inline-formula><tex-math id="TM0016" notation="LaTeX">$\log (G/G_{\rm 0}) = 3.0\pm 0.1$</tex-math></inline-formula>, showing that [O I] 63 <inline-formula><tex-math id="TM0017" notation="LaTeX">$\mu$</tex-math></inline-formula>m serves as an important coolant of the dense and warm gas in J2054<inline-formula><tex-math id="TM0018" notation="LaTeX">$-$</tex-math></inline-formula>0005. A close examination of the [O I] and [C II] line profiles suggests that the [O I] line may be partially self-absorbed; however, deeper observations are needed to verify this conclusion. Regardless, the gas density and incident radiation field are in broad agreement with the values obtained in nearby star-forming galaxies and objects with [O I] 63 <inline-formula><tex-math id="TM0019" notation="LaTeX">$\mu$</tex-math></inline-formula>m observations at <inline-formula><tex-math id="TM0020" notation="LaTeX">$z=1$</tex-math></inline-formula>-3 with the Herschel Space Observatory. These results demonstrate the power of ALMA high-frequency observations targeting [O I] 63 <inline-formula><tex-math id="TM0021" notation="LaTeX">$\mu$</tex-math></inline-formula>m to examine the properties of photodissociation regions in high-redshift galaxies....

We present Atacama Large Millimetre/submillimetre Array (ALMA) observations of the [O III] 88 $\mu {\rm m}$ emission of a sample of thirteen galaxies at $z = 6$ to 7.6 selected as [C II]-emitting companion sources of quasars. To disentangle the origins of the luminous Oxygen line in the $z\, \gt\, 6$ Universe, we looked at emission-line galaxies that are selected through an excellent star-formation tracer [C II] with star-formation rates between 9 and 162 $\rm {\rm M}_{\odot }\,yr^{-1}$. Direct observations reveal [O III] emission in just a single galaxy ($L_\mathrm{[O\, {\small III}]}/L_\mathrm{[C\, {\small II}]}$$\, = 2.3$), and a stacked image shows no [O III] detection, providing deep upper limits on the $L_\mathrm{[O\, {\small III}]}/L_\mathrm{[C\, {\small II}]}$ ratios in the $z \gt 6$ Universe ($L_\mathrm{[O\, {\small III}]}/L_\mathrm{[C\, {\small II}]}$$\, \lt 1.2$ at $3 \sigma$). While the fidelity of this sample is high, no obvious optical/near-infrared counterpart is seen in the JWST imaging available for four galaxies. Additionally accounting for low-z CO emitters, line stacking shows that our sample-wide result remains robust: The enhanced $L_\mathrm{[O\, {\small III}]}/L_\mathrm{[C\, {\small II}]}$ reported in the first billion years of the Universe is likely due to the selection towards bright, blue Lyman-break galaxies with high surface star-formation rates or young stellar populations. The deep upper limit on the rest-frame 90 μm continuum emission ($\lt 141 \mu$Jy at $3 \sigma$), implies a low average dust temperature ($T_\mathrm{dust} \lesssim 30\,$ K) and high-dust mass ($M_\mathrm{dust} \sim 10^8\, \mathrm{M}_\odot$). As more normal galaxies are explored in the early Universe, synergy between JWST and ALMA is fundamental to further investigate the ISM properties of the a broad range of samples of high-z galaxies....

<BR /> Aims: The evolution of dwarf galaxies is dramatically affected by gaseous and dusty outflows, which can easily deprive their interstellar medium of the material needed for the formation of new stars, simultaneously enriching their surrounding circumgalactic medium (CGM). In this Letter, we present the first evidence of extended [CII] 158 μm line and dust continuum emission in local dwarf galaxies hosting star-formation-driven outflows. <BR /> Methods: By stacking the [CII], far-infrared, and near-UV (NUV) emission obtained from Herschel and GALEX data, we derived the average radial profiles, and compared the spatial extension of gas, dust, and stellar activity in dwarf galaxies. <BR /> Results: We find that [CII] and dust emissions are comparable to each other, and more extended than the NUV continuum. The [CII] size is in agreement with that measured for z &gt; 4 star-forming galaxies, suggesting that similar mechanisms could be at the origin of the observed atomic carbon reservoir around local and high-z sources. The cold dust follows the [CII] emission, going beyond the stellar continuum as opposed to what is typically observed in the early Universe where measurements can be affected by the poor sensitivity and faintness of dust emission in the CGM of high-z galaxies. <BR /> Conclusions: We attribute the extended [CII] and dust continuum emission to the presence of galactic outflows. As local dwarf galaxies are considered analogs of primordial sources, we expect that comparable feedback processes can be at the origin of the observed [CII] halos at z &gt; 4, dominating over other possible formation mechanisms....

Molecular outflows are expected to play a key role in galaxy evolution at high redshift. To study the impact of outflows on star formation at the epoch of reionization, we performed sensitive Atacama Large Millimeter/submillimeter Array observations of OH 119 μm toward J2054-0005, a luminous quasar at z = 6.04. The OH line is detected and exhibits a P-Cygni profile that can be fitted with a broad blueshifted absorption component, providing unambiguous evidence of an outflow, and an emission component at near-systemic velocity. The mean and terminal outflow velocities are estimated to be v _out ≈ 670 and 1500 km s^‑1, respectively, making the molecular outflow in this quasar one of the fastest at the epoch of reionization. The OH line is marginally spatially resolved for the first time in a quasar at z &gt; 6, revealing that the outflow extends over the central 2 kpc region. The mass outflow rate is comparable to the star formation rate ( ${\dot{M } }_{\mathrm{out } }/\mathrm{SFR}\sim 2$ ), indicating rapid (∼10⁷ yr) quenching of star formation. The mass outflow rate in a sample of star-forming galaxies and quasars at 4 &lt; z &lt; 6.4 exhibits a positive correlation with the total infrared luminosity, although the scatter is large. Owing to the high outflow velocity, a large fraction (up to ∼50%) of the outflowing molecular gas may be able to escape from the host galaxy into the intergalactic medium....

We characterize the physical properties of star-formation-driven outflows in a sample of 29 local dwarf galaxies drawn from the Dwarf Galaxy Survey. We made use of Herschel/PACS archival data to search for atomic outflow signatures in the wings of individual [CII] 158 μm spectra and in their stacked line profile. We find a clear excess of emission in the high-velocity tails of 11 sources, which can be explained with an additional broad component (tracing the outflowing gas) in the modeling of their spectra. The remaining objects are likely hosts of weaker outflows that can still be detected in the average stacked spectrum. In both cases, we estimate the atomic mass outflow rates which result to be comparable with the star-formation rates of the galaxies, implying mass-loading factors (i.e., outflow efficiencies) of the order of unity. Outflow velocities in all the 11 galaxies with individual detections are larger than (or compatible with) the escape velocities of their dark matter halos, with an average fraction of 40% of gas escaping into the intergalactic medium (IGM). Depletion timescales due to outflows are lower than those due to gas consumption by star formation in most of our sources, ranging from one hundred million to a few billion years. From the energetic point of view, our outflows are mostly consistent with momentum-driven winds generated by the radiation pressure of young stellar populations on dust grains, although the energy-driven scenario is not excluded if considering a coupling efficiency up to 20% between the energy injected by supernovae and the interstellar medium. Overall, our results suggest that, despite their low efficiencies, galactic outflows can regulate the star-formation history of dwarf galaxies. Specifically, they are able to enrich with metals the circumgalactic medium of these sources, bringing on average a non-negligible amount of gas into the IGM, where it will no longer be available for new star formation. Our findings are suitable for tuning chemical evolution models attempting to describe the physical processes shaping the evolution of dwarf galaxies. <P />Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA....

We report Atacama Large Millimeter/submillimeter Array Band 3 observations of CO(6-5), CO(7-6), and [C I](2-1) in B14-65666 ("Big Three Dragons"), one of the brightest Lyman-break galaxies at z &gt; 7 in the rest-frame ultraviolet continuum, far-infrared continuum, and emission lines of [O III] 88 μm and [C II] 158 μm. CO(6-5), CO(7-6), and [C I](2-1), whose 3σ upper limits on the luminosities are approximately 40 times fainter than the [C II] luminosity, are all not detected. The L _{[C II]}/L _CO(6-5) and L _{[C II]}/L _CO(7-6) ratios are higher than the typical ratios obtained in dusty star-forming galaxies or quasar host galaxies at similar redshifts, and they may suggest a lower gas density in the photodissociated region in B14-65666. By using the (1) [C II] luminosity, (2) dust mass-to-gas mass ratio, and (3) a dynamical mass estimate, we find that the molecular gas mass (M _mol) is (0.05-11) × 10¹⁰ M _⊙. This value is consistent with the upper limit inferred from the nondetection of mid-J CO and [C I](2-1). Despite the large uncertainty in M _mol, we estimate a molecular gas-to-stellar mass ratio (μ _gas) of 0.65-140 and a gas depletion time (τ _dep) of 2.5-550 Myr; these values are broadly consistent with those of other high-redshift galaxies. B14-65666 could be an ancestor of a passive galaxy at z ≳ 4 if no gas is fueled from outside the galaxy....

We present new neutral atomic carbon [C I] (³P₁ → ³P₀) mapping observations within the inner ∼7 kpc and ∼4 kpc of the disks of NGC 3627 and NGC 4321 at a spatial resolution of 190 pc and 270 pc, respectively, using the Atacama Large Millimeter/Submillimeter Array (ALMA) Atacama Compact Array (ACA). We combine these with the CO(2−1) data from PHANGS-ALMA, and literature [C I] and CO data for two other starburst and/or active galactic nucleus (AGN) galaxies (NGC 1808, NGC 7469) with the aim of studying: (a) the spatial distributions of C I and CO emission; (b) the observed line ratio R_{C I/CO} = I_{[C I](1−0)}/I_CO(2−1) as a function of various galactic properties; and (c) the abundance ratio of [C I/CO]. We find excellent spatial correspondence between C I and CO emission and nearly uniform R_{C I/CO} ∼ 0.1 across the majority of the star-forming disks of NGC 3627 and NGC 4321. However, R_{C I/CO} strongly varies from ∼0.05 at the center of NGC 4321 to &gt; 0.2 − 0.5 in NGC 1808's starbursting center and NGC 7469's center with an X-ray-luminous AGN. Meanwhile, R_{C I/CO} does not obviously vary with ⟨U⟩, which is in line with predictions from photodissociation-dominated region (PDR) models. We also find a mildly decreasing R_{C I/CO} value with an increasing metallicity over 0.7 − 0.85 Z_⊙, which is consistent with the literature. Assuming various typical interstellar medium (ISM) conditions representing giant molecular clouds, active star-forming regions, and strong starbursting environments, we calculated the (non)local-thermodynamic-equilibrium radiative transfer and estimated the [C I/CO] abundance ratio to be ∼0.1 across the disks of NGC 3627 and NGC 4321, similar to previous large-scale findings in Galactic studies. However, this abundance ratio likely experiences a substantial increase, up to ∼1 and ≳1 − 5 in NGC 1808's starburst and NGC 7469's strong AGN environments, respectively. This result is in line with the expectations for cosmic-ray dominated region (CRDR) and X-ray dominated region (XDR) chemistry. Finally, we do not find robust evidence for a generally CO-dark-and-C I-bright gas in the disk areas we probed....

The barred spiral galaxy NGC 613 has a star-forming ring in the center, and near-infrared observations have previously shown that the star formation activity on the eastern and western sides of the ring is asymmetric. We examined the dynamics and physical state of the molecular gas in the ring using high-resolution (~15 pc) ¹²CO(1-0), ¹²CO(3-2), and ¹³CO(1-0) observations with ALMA. Using a dendrogram, we identified 111 molecular clouds in the bar and ring, and found that the virial parameter (α_vir) gradually decreases (α_vir &lt; 2) toward the confluence of the northern bar and eastern ring, while the virial parameter is large (α_vir &gt; 2) around the corresponding confluence in the western side of the ring. A non-LTE analysis using RADEX showed that the temperature and density of the molecular gas increase downstream of the eastern point of confluence, whereas they change irregularly on the western side. The star formation efficiency is (1.7 ± 0.2) × 10^-8 yr^-1 in the eastern side of the ring, which is substantially higher than the (0.9 ± 0.3) × 10^-8 yr^-1 for the western side of the ring. Position-velocity diagrams show that the relative velocity of the gas between the bar and the ring is ~70 km s^-1 in the east, while it reaches ~170 km s^-1 in the west. We suggest that the star formation activity in the central region of NGC 613 depends strongly on the relative velocity of the gas between the bar and the ring....

We present a 154 pointing IRAM NOEMA mosaic of the CO(1-0) line emission in and around the nearby starburst galaxy M82. The observations, complemented by zero-spacing observations, reach a spatial resolution of ~30 pc (~1"9) at 5.0 km s^-1 spectral resolution, sufficient to resolve the molecular gas in the central starburst disk, the outflow, and the tidal streamers. The resulting moment and peak brightness maps show a striking amount of structure. Using a clump decomposition algorithm, we analyze the physical properties (e.g., radii R, line widths σ, and masses M) of ~2000 molecular clouds. To first order, the clouds' properties are very similar, irrespective of their environment. This also holds for the size-line width relations of the clouds. The distribution of clouds in the σ²/R versus column density Σ space suggests that external pressure does not play a significant role in setting their physical parameters in the outflow and streamers. We find that the clouds in the streamers stay approximately constant in size (R ~ 50 pc) and mass (M ~ 10⁵ M_⊙) and do not vary with their projected distance from M82's center. The clouds in the outflow, on the other hand, appear to decrease in size and mass with distance toward the southern outflow. The reduction in the molecular gas luminosity could be indicative of cloud evaporation of embedded clouds in the hot outflow....

Atomic carbon (C I) has been proposed to be a global tracer of the molecular gas as a substitute for CO, however, its utility remains unproven. To evaluate the suitability of C I as the tracer, we performed [C I](³P₁-³P₀) [hereinafter [C I](1-0)] mapping observations of the northern part of the nearby spiral galaxy M 83 with the Atacama Submillimeter Telescope Experiment (ASTE) telescope and compared the distributions of [C I](1-0) with CO lines [CO(1-0), CO(3-2), and ¹³CO(1-0)], H I, and infrared (IR) emission (70, 160, and 250 μm). The [C I](1-0) distribution in the central region is similar to that of the CO lines, whereas [C I](1-0) in the arm region is distributed outside the CO. We examined the dust temperature, T_dust, and dust mass surface density, Σ_dust, by fitting the IR continuum-spectrum distribution with a single-temperature modified blackbody. The distribution of Σ_dust shows a much better consistency with the integrated intensity of CO(1-0) than with that of [C I](1-0), indicating that CO(1-0) is a good tracer of the cold molecular gas. The spatial distribution of the [C I] excitation temperature, T_ex, was examined using the intensity ratio of the two [C I] transitions. An appropriate T_ex at the central, bar, arm, and inter-arm regions yields a constant [C]$/$[H₂] abundance ratio of ~7 × 10^-5 within a range of 0.1 dex in all regions. We successfully detected weak [C I](1-0) emission, even in the inter-arm region, in addition to the central, arm, and bar regions, using spectral stacking analysis. The stacked intensity of [C I](1-0) is found to be strongly correlated with T_dust. Our results indicate that the atomic carbon is a photodissociation product of CO, and consequently, compared to CO(1-0), [C I](1-0) is less reliable in tracing the bulk of "cold" molecular gas in the galactic disk....

We investigate the molecular gas properties of galaxies across the main sequence of star-forming (SF) galaxies in the local Universe using ¹²CO(J = 1&amp;-0), hereafter ¹²CO, and ¹³CO(J = 1&amp;-0), hereafter ¹³CO, mapping data of 147 nearby galaxies obtained in the COMING project, a legacy project of the Nobeyama Radio Observatory. In order to improve the signal-to-noise ratios of both lines, we stack all the pixels where ¹²CO emission is detected after aligning the line center expected from the first-moment map of ¹²CO. As a result, ¹³CO emission is successfully detected in 80 galaxies with a signal-to-noise ratio larger than three. The error-weighted mean of the integrated-intensity ratio of ¹²CO to ¹³CO lines (R₁₂₁₃) of the 80 galaxies is 10.9, with a standard deviation of 7.0. We find that (1) R₁₂₁₃ positively correlates to specific star-formation rate (sSFR) with a correlation coefficient of 0.46, and (2) both the flux ratio of IRAS 60 μm to 100 μm (f₆₀/f₁₀₀) and the inclination-corrected linewidth of ¹²CO stacked spectra ( $\sigma _{ { \rm ^{12}CO},i}$ ) also correlate with sSFR for galaxies with the R₁₂₁₃ measurement. Our results support the scenario where R₁₂₁₃ variation is mainly caused by changes in molecular gas properties such as temperature and turbulence. The consequent variation of the CO-to-H₂ conversion factor across the SF main sequence is not large enough to completely extinguish the known correlations between sSFR and M_mol/M_star (μ_mol) or star-formation efficiency (SFE) reported in previous studies, while this variation would strengthen (weaken) the sSFR&amp;-SFE (sSFR&amp;-μ_mol) correlation....

Galactic winds are essential to the regulation of star formation in galaxies. To study the distribution and dynamics of molecular gas in wind, we imaged the nearby starburst galaxy NGC 1482 in CO (J = 1 → 0) at a resolution of 1″ (≍100 pc) using the Atacama Large Millimeter/submillimeter Array. Molecular gas is detected in a nearly edge-on disk with a radius of 3 kpc and a biconical outflow emerging from the central 1 kpc starburst and extending to at least 1.5 kpc perpendicular to the disk. In the outflow, CO gas is distributed approximately as a cylindrically symmetrical envelope surrounding the warm and hot ionized gas traced by Hα and soft X-rays. The velocity, mass outflow rate, and kinetic energy of the molecular outflow are ${v}_{ { \rm{w } } }\sim 100\,\mathrm{km}\,{ { \rm{s } } }^{-1}$ , ${\dot{M } }_{ { \rm{w } } }\sim 7\,{M}_{\odot }\,{\mathrm{yr } }^{-1}$ , and ${E}_{ { \rm{w } } }\sim 7\times {10}^{54}\,\mathrm{erg}$ , respectively. ${\dot{M } }_{ { \rm{w } } }$ is comparable to the star formation rate ( ${\dot{M } }_{ { \rm{w } } }/\mathrm{SFR}\sim 2$ ) and E_w is ∼1% of the total energy released by stellar feedback in the past $1\times {10}^{7}\,\mathrm{yr}$ , which is the dynamical timescale of the outflow. The results indicate that the wind is starburst driven....

We present the results of ^{12}CO(J = 1-0) and ^{13}CO(J = 1-0) simultaneous mappings toward the nearby barred spiral galaxy NGC 4303 as part of the CO Multi-line Imaging of Nearby Galaxies (COMING) project. Barred spiral galaxies often show lower star-formation efficiency (SFE) in their bar region compared to the spiral arms. In this paper, we examine the relation between the SFEs and the volume densities of molecular gas n(H₂) in the eight different regions within the galactic disk with CO data combined with archival far-ultraviolet and 24 μm data. We confirmed that SFE in the bar region is lower by 39% than that in the spiral arms. Moreover, velocity-alignment stacking analysis was performed for the spectra in the individual regions. Integrated intensity ratios of ^{12}CO to ^{13}CO (R_12/13) ranging from 10 to 17 were the results of this stacking. Fixing a kinetic temperature of molecular gas, n({H_2}) was derived from R_12/13 via non-local thermodynamic equilibrium (non-LTE) analysis. The density n(H₂) in the bar is lower by 31%-37% than that in the arms and there is a rather tight positive correlation between SFEs and n(H₂), with a correlation coefficient of ̃0.8. Furthermore, we found a dependence of n({H}_2) on the velocity dispersion of inter-molecular clouds (∆V/sin i). Specifically, n(H₂) increases as ∆V/sin i increases when ∆V/sin i &lt; 100 km s^-1. On the other hand, n(H₂) decreases as ∆V/sin i increases when ∆V/sin i &gt; 100 km s^-1. These relations indicate that the variations of SFE could be caused by the volume densities of molecular gas, and the volume densities could be governed by the dynamical influence such as cloud-cloud collisions, shear, and enhanced inner-cloud turbulence....

We examined radial variations in molecular-gas based star formation efficiency (SFE), which is defined as star formation rate per unit molecular gas mass, for 80 galaxies selected from the CO Multi-line Imaging of Nearby Galaxies project (Sorai et al. 2019, PASJ, 71, S14). The radial variations in SFE for individual galaxies are typically a factor of 2-3, which suggests that SFE is nearly constant along the galactocentric radius. We found an averaged SFE in 80 galaxies of (1.69 ± 1.1) × 10^-9 yr^-1, which is consistent with Leroy et al. (2008, AJ, 136, 2782) if we consider the contribution of helium to the molecular gas mass evaluation and the difference in the assumed initial mass function between the two studies. We compared SFE among different morphological (i.e., SA, SAB, and SB) types, and found that SFE within the inner radii (r/r₂₅ &lt; 0.3, where r₂₅ is the B-band isophotal radius at 25 mag arcsec^-2) of SB galaxies is slightly higher than that of SA and SAB galaxies. This trend can be partly explained by the dependence of SFE on global stellar mass, which probably relates to the CO-to-H₂ conversion factor through the metallicity. For two representative SB galaxies in our sample, NGC 3367 and NGC 7479, the ellipse of r/r₂₅ = 0.3 seems to cover not only the central region but also the inner part of the disk, mainly the bar. These two galaxies show higher SFE in the bar than in the spiral arms. However, we found an opposite trend in NGC 4303; SFE is lower in the bar than in the spiral arms, which is consistent with earlier studies (e.g., Momose et al. 2010, ApJ, 721, 383). These results suggest a diversity of star formation activities in the bar....

Observations of the molecular gas in galaxies are vital to understand the evolution and star-forming histories of galaxies. However, galaxies with molecular gas maps of their whole discs at 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 (FIR) flux in ¹²CO, ¹³CO, and C¹⁸O J = 1-0 lines. The total molecular gas mass was derived using the standard CO-to-H₂ 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, or 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....

The ¹²CO (J = 1→0) velocity fields of a sample of 20 nearby spiral galaxies, selected from the CO Multi-line Imaging of Nearby Galaxies (COMING) legacy project of Nobeyama Radio Observatory, have been analyzed by Fourier decomposition to determine their basic kinematic properties, such as circular and noncircular velocities. On average, the investigated barred (SAB and SB) galaxies exhibit a ratio of noncircular to circular velocities of molecular gas larger by a factor of 1.5-2 than non-barred (SA) spiral galaxies at radii within the bar semimajor axis a_b at 1 kpc resolution, with a maximum at a radius of R/a_b ≈ 0.3. Residual velocity field images, created by subtracting model velocity fields from the data, reveal that this trend is caused by kpc-scale streaming motions of molecular gas in the bar region. Applying a new method based on radial velocity reversal, we estimated the corotation radius R_CR and bar pattern speed Ω_b in seven SAB and SB systems. The ratio of the corotation to bar radius is found to be in a range of R≡ R_CR/a_b ≈ 0.8-1.6, suggesting that intermediate (SBb-SBc), luminous barred spiral galaxies host fast and slow rotator bars. Tentative negative correlations are found for Ω_b vs. a_b and Ω_b vs. total stellar mass M_*, indicating that bars in massive disks are larger and rotate slower, possibly a consequence of angular momentum transfer. The kinematic properties of SAB and SB galaxies, derived from Fourier decomposition, are compared with recent numerical simulations that incorporate various rotation curve models and galaxy interactions....

We examined radial variations in molecular-gas based star formation efficiency (SFE), which is defined as star formation rate per unit molecular gas mass, for 80 galaxies selected from the CO Multi-line Imaging of Nearby Galaxies project (Sorai et al. 2019, PASJ, 71, S14). The radial variations in SFE for individual galaxies are typically a factor of 2-3, which suggests that SFE is nearly constant along the galactocentric radius. We found an averaged SFE in 80 galaxies of (1.69 ± 1.1) × 10^-9 yr^-1, which is consistent with Leroy et al. (2008, AJ, 136, 2782) if we consider the contribution of helium to the molecular gas mass evaluation and the difference in the assumed initial mass function between the two studies. We compared SFE among different morphological (i.e., SA, SAB, and SB) types, and found that SFE within the inner radii (r/r₂₅ &lt; 0.3, where r₂₅ is the B-band isophotal radius at 25 mag arcsec^-2) of SB galaxies is slightly higher than that of SA and SAB galaxies. This trend can be partly explained by the dependence of SFE on global stellar mass, which probably relates to the CO-to-H₂ conversion factor through the metallicity. For two representative SB galaxies in our sample, NGC 3367 and NGC 7479, the ellipse of r/r₂₅ = 0.3 seems to cover not only the central region but also the inner part of the disk, mainly the bar. These two galaxies show higher SFE in the bar than in the spiral arms. However, we found an opposite trend in NGC 4303; SFE is lower in the bar than in the spiral arms, which is consistent with earlier studies (e.g., Momose et al. 2010, ApJ, 721, 383). These results suggest a diversity of star formation activities in the bar....

We present the results of ^{12}CO(J = 1-0) and ^{13}CO(J = 1-0) simultaneous mappings toward the nearby barred spiral galaxy NGC 4303 as part of the CO Multi-line Imaging of Nearby Galaxies (COMING) project. Barred spiral galaxies often show lower star-formation efficiency (SFE) in their bar region compared to the spiral arms. In this paper, we examine the relation between the SFEs and the volume densities of molecular gas n(H₂) in the eight different regions within the galactic disk with CO data combined with archival far-ultraviolet and 24 μm data. We confirmed that SFE in the bar region is lower by 39% than that in the spiral arms. Moreover, velocity-alignment stacking analysis was performed for the spectra in the individual regions. Integrated intensity ratios of ^{12}CO to ^{13}CO (R_12/13) ranging from 10 to 17 were the results of this stacking. Fixing a kinetic temperature of molecular gas, n({H_2}) was derived from R_12/13 via non-local thermodynamic equilibrium (non-LTE) analysis. The density n(H₂) in the bar is lower by 31%-37% than that in the arms and there is a rather tight positive correlation between SFEs and n(H₂), with a correlation coefficient of ∼0.8. Furthermore, we found a dependence of n({H}_2) on the velocity dispersion of inter-molecular clouds (∆V/sin i). Specifically, n(H₂) increases as ∆V/sin i increases when ∆V/sin i &lt; 100 km s^-1. On the other hand, n(H₂) decreases as ∆V/sin i increases when ∆V/sin i &gt; 100 km s^-1. These relations indicate that the variations of SFE could be caused by the volume densities of molecular gas, and the volume densities could be governed by the dynamical influence such as cloud-cloud collisions, shear, and enhanced inner-cloud turbulence....

We present [C I] ≤ft({}³{ { P } }₁\to {}³{ { P } }₀\right), ¹²CO, ¹³CO, and C¹⁸O (J=2\to 1) observations of the central region (radius 1 kpc) of the starburst galaxy NGC 1808 at 30─50 pc resolution conducted with the Atacama Large Millimeter/submillimeter Array. Radiative transfer analysis of multiline data indicates warm ({T}_{{ { k} } }∼ 40{--}80 K) and dense ({n}_{{ { {H} } }₂}∼ {10}^3{--4} cm⁻³) molecular gas with high column density of atomic carbon ({N}_{{ { C}}{ { I } } }∼ 3× {10}¹⁸ cm⁻²) in the circumnuclear disk (central 100 pc). The C I/H₂ abundance in the central 1 kpc is ∼ 3{--}7× {10}^-5, consistent with the values in luminous infrared galaxies. The intensity ratios of [C I]/CO (1─0) and [C I]/CO (3─2), respectively, decrease and increase with radius in the central 1 kpc, whereas [C I]/CO (2─1) is uniform within statistical errors. The result can be explained by excitation and optical depth effects, since the effective critical density of CO (2─1) is comparable to that of [C I]. The distribution of [C I] is similar to that of ¹³CO (2─1), and the ratios of [C I] to ¹³CO (2─1) and C¹⁸O (2─1) are uniform within ∼ 30 % in the central &lt; 400 pc starburst disk. The results suggest that [C I] ≤ft({}³{ { P } }₁\to {}³{ { P } }₀\right) luminosity can be used as a CO-equivalent tracer of molecular gas mass, although caution is needed when applied in resolved starburst nuclei (e.g., circumnuclear disk), where the [C I]/CO (1─0) luminosity ratio is enhanced owing to high excitation and atomic carbon abundance. The [C I]/CO (1─0) intensity ratio toward the base of the starburst-driven outflow is ≲ 0.15, and the upper limits of the mass and kinetic energy of the atomic carbon outflow are ∼ 1× {10}⁴ {M}_ȯ and ∼ 3× {10}⁵¹ {erg}, respectively....

Not Available <P />...

Observations of the molecular gas in galaxies are vital to understanding the evolution and star-forming 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 $3.4 \mu$m 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. <P />...

We present maps of atomic carbon [C I]({}³{ { {P } } }₁\to { { }³{ { P } } }₀) and [C I]({}³{ { {P } } }₂\to { { }³{ { P } } }₁) emission (hereafter [C I] (1-0) and [C I] (2-1), respectively) at a linear resolution ̃1 kpc scale for a sample of one H II, six LINER, three Seyfert, and five starburst galaxies observed with the Herschel Space Observatory. We compare spatial distributions of two [C I] lines with that of CO J=1\to 0 (hereafter CO (1-0)) emission, and find that both [C I] lines distribute similarly to CO (1-0) emission in most galaxies. We present luminosity ratio maps of {L}_{[{ { C}} { { I } }](1-0)}^{\prime }/{L}_CO(1-0)}^{\prime }, {L}_{[{ { C}} { { I } }](2-1)}^{\prime }/{L}_CO(1-0)}^{\prime }, {L}_{[{ { C}} { { I } }](2-1)}^{\prime }/{L}_{[{ { C}} { { I } }](1-0)}^{\prime } (hereafter {R}_{[{ { C}}{ { I } }]}) and 70-to-160 μm far-infrared color of f ₇₀/f ₁₆₀. {L}_{[{ { C}} { { I } }](2-1)}^{\prime }/{L}_CO(1-0)}^{\prime }, {R}_{[{ { C}}{ { I } }]} and {f}₇₀/{f}₁₆₀ are centrally peaked in starbursts; whereas they remain relatively constant in LINERs, indicating that star-forming activity can enhance carbon emission, especially for [C I] (2-1). We explore the correlations between the luminosities of CO (1-0) and [C I] lines, and find that {L}_CO(1-0)}^{\prime } correlates tightly and almost linearly with both {L}_{[{ { C}} { { I } }](1-0)}^{\prime } and {L}_{[{ { C}} { { I } }](2-1)}^{\prime }, suggesting that [C I] lines, similar to CO (1-0), can trace total molecular gas in H II, LINER, Seyfert, and starburst galaxies on kpc scales. We investigate the dependence of {L}_{[{ { C}} { { I } }](1-0)}^{\prime }/{L}_CO(1-0)}^{\prime }, {L}_{[{ { C}} { { I } }](2-1)}^{\prime }/{L}_CO(1-0)}^{\prime } and [C I] excitation temperature, T _ex, on dust temperature, T _dust, and find noncorrelation and a weak and modest correlation, respectively. The ratio of {L}_{[{ { C}} { { I } }](1-0)}^{\prime }/{L}_CO(1-0)}^{\prime } stays a smooth distribution in most galaxies, indicating that the conversion factor of [C I] (1-0) luminosity to H₂ mass ({X}_[{CI](1-0)}) changes with CO (1-0) conversion factor ({α }_CO}) proportionally. Under optically thin and local thermodynamical equilibrium assumptions, we derive a galaxy-wide average carbon excitation temperature of {T}_ex}̃ 19.7+/- 0.5 { { K } }, and an average neutral carbon abundance of X[{CI}]/X[{ { {H } } }₂]̃ 2.5+/- 1.0× {10}^-5 in our resolved sample, which is comparable to the usually adopted value of 3 × 10^-5, but ̃3 times lower than the carbon abundance in local (ultra)luminous infrared galaxies. We conclude that the carbon abundance varies in different galaxy types....

We present the results of ^{12}CO(J = 1-0) and ^{13}CO(J = 1-0) simultaneous mappings toward the nearby barred spiral galaxy NGC 4303 as part of the CO Multi-line Imaging of Nearby Galaxies (COMING) project. Barred spiral galaxies often show lower star-formation efficiency (SFE) in their bar region compared to the spiral arms. In this paper, we examine the relation between the SFEs and the volume densities of molecular gas n(H&lt;SUB&gt;2&lt;/SUB&gt;) in the eight different regions within the galactic disk with CO data combined with archival far-ultraviolet and 24 μm data. We confirmed that SFE in the bar region is lower by 39% than that in the spiral arms. Moreover, velocity-alignment stacking analysis was performed for the spectra in the individual regions. Integrated intensity ratios of ^{12}CO to ^{13}CO (R&lt;SUB&gt;12/13&lt;/SUB&gt;) ranging from 10 to 17 were the results of this stacking. Fixing a kinetic temperature of molecular gas, n({H_2}) was derived from R&lt;SUB&gt;12/13&lt;/SUB&gt; via non-local thermodynamic equilibrium (non-LTE) analysis. The density n(H&lt;SUB&gt;2&lt;/SUB&gt;) in the bar is lower by 31%-37% than that in the arms and there is a rather tight positive correlation between SFEs and n(H&lt;SUB&gt;2&lt;/SUB&gt;), with a correlation coefficient of ̃0.8. Furthermore, we found a dependence of n({H}_2) on the velocity dispersion of inter-molecular clouds (∆V/sin i). Specifically, n(H&lt;SUB&gt;2&lt;/SUB&gt;) increases as ∆V/sin i increases when ∆V/sin i &amp;lt; 100 km s&lt;SUP&gt;-1&lt;/SUP&gt;. On the other hand, n(H&lt;SUB&gt;2&lt;/SUB&gt;) decreases as ∆V/sin i increases when ∆V/sin i &amp;gt; 100 km s&lt;SUP&gt;-1&lt;/SUP&gt;. These relations indicate that the variations of SFE could be caused by the volume densities of molecular gas, and the volume densities could be governed by the dynamical influence such as cloud-cloud collisions, shear, and enhanced inner-cloud turbulence....

We examined radial variations in molecular-gas based star formation efficiency (SFE), which is defined as star formation rate per unit molecular gas mass, for 80 galaxies selected from the CO Multi-line Imaging of Nearby Galaxies project (Sorai et al. 2019, PASJ, submitted).The radial variations in SFE for individual galaxies are typically a factor of 2-3, which suggests that SFE is nearly constant along the galactocentric radius. We found an averaged SFE in 80 galaxies of (1.69 ± 1.1) × 10&lt;SUP&gt;-9&lt;/SUP&gt; yr&lt;SUP&gt;-1&lt;/SUP&gt;, which is consistent with Leroy et al. (2008, AJ, 136, 2782) if we consider the contribution of helium to the molecular gas mass evaluation and the difference in the assumed initial mass function between the two studies. We compared SFE among different morphological (i.e., SA, SAB, and SB) types, and found that SFE within the inner radii (r/r&lt;SUB&gt;25&lt;/SUB&gt; &amp;lt; 0.3, where r&lt;SUB&gt;25&lt;/SUB&gt; is the B-band isophotal radius at 25 mag arcsec&lt;SUP&gt;-2&lt;/SUP&gt;) of SB galaxies is slightly higher than that of SA and SAB galaxies. This trend can be partly explained by the dependence of SFE on global stellar mass, which probably relates to the CO-to-H&lt;SUB&gt;2&lt;/SUB&gt; conversion factor through the metallicity. For two representative SB galaxies in our sample, NGC 3367 and NGC 7479, the ellipse of r/r&lt;SUB&gt;25&lt;/SUB&gt; = 0.3 seems to cover not only the central region but also the inner part of the disk, mainly the bar. These two galaxies show higher SFE in the bar than in the spiral arms. However, we found an opposite trend in NGC 4303; SFE is lower in the bar than in the spiral arms, which is consistent with earlier studies (e.g., Momose et al. 2010, ApJ, 721, 383). These results suggest a diversity of star formation activities in the bar....

The &lt;SUP&gt;12&lt;/SUP&gt;CO (J = 1→0) velocity fields of a sample of 20 nearby spiral galaxies, selected from the CO Multi-line Imaging of Nearby Galaxies (COMING) legacy project of Nobeyama Radio Observatory, have been analyzed by Fourier decomposition to determine their basic kinematic properties, such as circular and noncircular velocities. On average, the investigated barred (SAB and SB) galaxies exhibit a ratio of noncircular to circular velocities of molecular gas larger by a factor of 1.5-2 than non-barred (SA) spiral galaxies at radii within the bar semimajor axis a&lt;SUB&gt;b&lt;/SUB&gt; at 1 kpc resolution, with a maximum at a radius of R/a&lt;SUB&gt;b&lt;/SUB&gt; ≈ 0.3. Residual velocity field images, created by subtracting model velocity fields from the data, reveal that this trend is caused by kpc-scale streaming motions of molecular gas in the bar region. Applying a new method based on radial velocity reversal, we estimated the corotation radius R&lt;SUB&gt;CR&lt;/SUB&gt; and bar pattern speed Ω&lt;SUB&gt;b&lt;/SUB&gt; in seven SAB and SB systems. The ratio of the corotation to bar radius is found to be in a range of R≡ R_CR/a_b ≈ 0.8-1.6, suggesting that intermediate (SBb-SBc), luminous barred spiral galaxies host fast and slow rotator bars. Tentative negative correlations are found for Ω&lt;SUB&gt;b&lt;/SUB&gt; vs. a&lt;SUB&gt;b&lt;/SUB&gt; and Ω&lt;SUB&gt;b&lt;/SUB&gt; vs. total stellar mass M&lt;SUB&gt;*&lt;/SUB&gt;, indicating that bars in massive disks are larger and rotate slower, possibly a consequence of angular momentum transfer. The kinematic properties of SAB and SB galaxies, derived from Fourier decomposition, are compared with recent numerical simulations that incorporate various rotation curve models and galaxy interactions....

We report ALMA observations of [C I](³P₁ - ³P₀), ¹³CO, and C¹⁸O(J = 1-0) toward the central region of a nearby Seyfert galaxy NGC 613. The very high resolutions of 0{^''_.}26 × 0{^''_.}23 (=22 × 20 pc) for [C I] and 0{^''_.}42 × 0{^''_.}35 (=36 × 30 pc) for ¹³CO, and C¹⁸O resolve the circumnuclear disk (CND) and star-forming ring. The distribution of [C I] in the ring resembles that of the CO emission, although [C I] is prominent in the CND. This can be caused by the low intensities of the CO isotopes due to the low optical depths under the high temperature in the CND. We found that the intensity ratios of [C I] to ¹²CO(3-2) (R_{CI/CO}) and to ¹³CO(1-0) (R_{CI/^{13}CO}) are high at several positions around the edge of the ring. The spectral profiles of CO lines mostly correspond each other in the spots of the ring and high R_{CI/CO}, but those of [C I] at spots of high R_{CI/CO} are different from those of CO. These results indicate that [C I] at the high R_{CI/CO} traces different gas from that traced by the CO lines. The [C I] kinematics along the minor axis of NGC 613 could be interpreted as a bubbly molecular outflow. The outflow rate of molecular gas is higher than star formation rate in the CND. The flow could be mainly boosted by the active galactic nucleus through its radio jets....

Dense molecular gas tracers in the central 1 kpc region of the superwind galaxy NGC 1808 have been imaged by ALMA at a resolution of 1″ (̃50 pc). Integrated intensities and line intensity ratios of HCN (1-0), H¹³CN (1-0), HCO⁺ (1-0), H¹³CO⁺ (1-0), HOC⁺ (1-0), HCO⁺ (4-3), CS (2-1), C₂H (1-0), and previously detected CO (1-0) and CO (3-2) are presented. SiO (2-1) and HNCO (4-3) are detected toward the circumnuclear disk (CND), indicating the presence of shocked dense gas. There is evidence that an enhanced intensity ratio of HCN (1-0)/HCO⁺ (1-0) reflects star formation activity, possibly in terms of shock heating and electron excitation in the CND and a star-forming ring at radius ̃300 pc. A non-local thermodynamic equilibrium analysis indicates that the molecular gas traced by HCN, H¹³CN, HCO⁺, and H¹³CO⁺ in the CND is dense ({n}_{{ { {H} } }₂}̃ {10}⁵ {cm } }^-3) and warm (20 K ≲ T _k ≲ 100 K). The calculations yield a low average gas density of {n}_{{ { {H} } }₂}̃ {10}²{--}{10}³ {cm } }^-3 for a temperature of {T}_{{ { k} } }≳ 30 { { K } } in the nuclear outflow. Dense gas tracers HCN (1-0), HCO⁺ (1-0), CS (2-1), and C₂H (1-0) are detected for the first time in the superwind of NGC 1808, confirming the presence of a velocity gradient in the outflow direction....

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 ¹²CO (1-0) and ¹²CO (3-2), and continuum (93 and 350 GHz) across the central 1 kpc starburst region at a high resolution of ̃ 1^\prime\prime . 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 (10⁶-{10}⁷ {M}_☉ ) clouds with high star formation efficiency ({SFE}̃ {10}^-8 yr^-1), molecular spiral arms, and a 500 pc pseudo-ring. 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....

We report ALMA observations of molecular gas and continuum emission in the 90 and 350 GHz bands toward a nearby Seyfert galaxy, NGC 613. Radio continuum emissions were detected at 95 and 350 GHz from both the circumnuclear disk (CND) (r ≲ 90 pc) and a star-forming ring (250 ≲ r ≲ 340 pc), and the 95 GHz continuum was observed to extend from the center at a position angle of 20° ± 8°. The archival 4.9 GHz data and our 95 GHz data show spectral indices of α ≲ -0.6 and -0.2 along the jets and in the star-forming ring; these can be produced by synchrotron emission and free-free emission, respectively. In addition, we detected the emission of CO(3-2), HCN(1-0), HCN(4-3), HCO⁺(1-0), HCO⁺(4-3), CS(2-1), and CS(7-6) in both the CND and the ring. The rotational temperatures and column densities of molecules derived from J = 1-0 and 4-3 lines of HCN and HCO⁺ and J = 2-1 and 7-6 of CS in the CND and ring were derived. Furthermore, a non-local thermodynamic equilibrium model revealed that the kinetic temperature of T_k = 350-550 K in the CND is higher than T_k = 80-300 K in the ring, utilizing the intensity ratios of HCN, HCO⁺, and CS. The star-formation efficiency in the CND is almost an order of magnitude lower than those at the spots in the star-forming ring, while the dominant activity of the central region is star formation rather than active galactic nuclei. We determined that the large velocity dispersion of CO extending towards the north side of the CND and decomposing into blueshifted and redshifted features is probably explained by the effect of the radio jets. These results strongly suggest that the jets heat the gas in the CND, in which the feedback prevents star formation. <P />...

A new method to discover obscured active galactic nuclei (AGNs) by utilizing X-ray and infrared data has recently been developed. We carried out a survey of H₂O maser emission toward 10 obscured AGNs with the Nobeyama 45 m telescope. We newly detected the maser emission with a signal-noise-ratio (SNR) of above 4 from two AGNs; NGC 1402 and NGC 7738. We also found a tentative detection with SNR &gt; 3 in NGC 5037. The detection rate of 20% is higher than those of previous surveys (usually several percent). <P />...

In this study, we present the results of ¹²CO(J = 1-0), ¹³CO(J = 1-0), and C¹⁸O(J = 1-0) simultaneous observations of the dwarf galaxy NGC 2976 conducted as a part of the CO Multi-line Imaging of Nearby Galaxies (COMING) project using the Nobeyama 45 m telescope. We investigated the properties of the molecular gas and star formation in NGC 2976. We found that the molecular gas fraction depends on the surface densities of the total gas and the star formation rate, according to the main stellar disks of spiral galaxies. The ratio of ¹²CO(J = 3-2) to ¹²CO(J = 1-0) implies that the temperature of the molecular gas increases with decreases in the surface density of molecular gas. We detected ¹³CO(J = 1-0) by using the stacking method. The ratio between the integrated intensities of ¹²CO(J = 1-0) and ¹³CO(J = 1-0) was 27 ± 11. These ratios imply that the diffuse gas phase is dominant in low surface density regimes. We obtained a lower limit of the ratio between the integrated intensities of ¹²CO(J = 1-0) and C¹⁸O(J = 1-0) of 21. The relation between the surface densities of the total gas and the star formation rate followed a power-law index of 2.08 ± 0.11, which was larger than that between the surface densities of the molecular gas and the star formation rate (1.62 ± 0.17). The steep slope in the relation between the surface densities of the total gas and the star formation rate can be attributed to the rapid increase in the fraction of molecular gas at the surface density of ∼ 10 M_☉. The kinematics of the molecular gas suggest that the bar-like feature rotates with a rigid-body rotation curve rather than a certain pattern speed. <P />...

We present survey data of six NH₃ (J, K) = (1, 1), (2, 2), (3, 3), (4, 4), (5, 5), and (6, 6) lines, simultaneously observed with the Tsukuba 32 m telescope, in the main part of the central molecular zone of the Galaxy. The total number of on-source positions was 2655. The three lower transitions were detected with S/N &gt; 3 at 2323 positions (93% of all the on-source positions). Among 2323, the S/N 's of (J, K) = (4, 4), (5, 5), and (6, 6) exceeded 3.0 at 1426(54%), 1150(43%), and 1359(51%) positions, respectively. Simultaneous observations of the lines enabled us to accurately derive intensity ratios with less systematic errors. Boltzmann plots indicate that there are two temperature components: cold (̃20 K) and warm (̃100 K). Typical intensity ratios of T_mb(2, 2)/T_mb(1, 1), T_mb(4, 4)/T_mb(2, 2), T_mb(5, 5)/T_mb(4, 4), and T_mb(6, 6)/T_mb(3, 3) were 0.71, 0.45, 0.65, and 0.17, respectively. These line ratios correspond to the diversity of the rotational temperature, which results from mixing of the two temperature components. <P />...

We present simultaneous mappings of J = 1-0 emission of ¹²CO, ¹³CO, and C¹⁸O molecules toward the whole disk (8' × 5' or 20.8 kpc × 13.0 kpc) of the nearby barred spiral galaxy NGC 2903 with the Nobeyama Radio Observatory 45 m telescope at an effective angular resolution of 20″ (or 870 pc). We detected ¹²CO(J = 1-0) emission over the disk of NGC 2903. In addition, significant ¹³CO(J = 1-0) emission was found at the center and bar-ends, whereas we could not detect any significant C¹⁸O(J = 1-0) emission. In order to improve the signal-to-noise ratio of CO emission and to obtain accurate line ratios of ¹²CO(J = 2-1)/¹²CO(J = 1-0) (R_2-1/1-0) and ¹³CO(J = 1-0)/¹²CO(J = 1-0) (R_13/12), we performed the stacking analysis for our ¹²CO(J = 1-0), ¹³CO(J = 1-0), and archival ¹²CO(J = 2-1) spectra with velocity axis alignment in nine representative regions of NGC 2903. We successfully obtained the stacked spectra of the three CO lines, and could measure averaged R_2-1/1-0 and R_13/12 with high significance for all the regions. We found that both R_2-1/1-0 and R_13/12 differ according to the regions, which reflects the difference in the physical properties of molecular gas, i.e., density (n_H_2) and kinetic temperature (T_K). We determined n_H_2 and T_K using R_2-1/1-0 and R_13/12 based on the large velocity gradient approximation. The derived n_H_2 ranges from ̃1000 cm^-3 (in the bar, bar-ends, and spiral arms) to 3700 cm^-3 (at the center) and the derived T_K ranges from 10 K (in the bar and spiral arms) to 30 K (at the center). We examined the dependence of star formation efficiencies (SFEs) on n_H_2 and T_K, and found a positive correlation between SFE and n_H_2 with correlation coefficient for the least-squares power-law fit R² of 0.50. This suggests that molecular gas density governs the spatial variations in SFEs. <P />...

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 ¹²CO (J=1-0) mapping observations of the central r ̃ 4 kpc of NGC 1808 using the Atacama Large Millimeter/submillimeter Array. Four distinct components of molecular gas are revealed at high spatial resolution of 2″ (̃100 pc): (1) a compact (r &lt; 200 pc) circumnuclear disk (CND), (2) r ̃ 500 pc ring, (3) gas-rich 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) a nuclear bar and molecular CND, and (3) an unresolved massive (̃10⁷ 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. Noncircular 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 is {\dot{M } }_{out}/{SFR}̃ 0.2 in the case of optically thin CO (1-0) emission in the outflow, suggesting low efficiency of star formation quenching....

We present the results of ammonia observations toward the center of NGC 3079. The NH₃(J, K) = (1, 1) and (2, 2) inversion lines were detected in absorption with the Tsukuba 32 m telescope, and the NH₃(1, 1) through (6, 6) lines with the VLA, although the profile of NH₃(3, 3) was in emission in contrast to the other transitions. The background continuum source, whose flux density was ̃ 50 mJy, could not be resolved with the VLA beam of ≲ 0{^''_.}09 × 0{^''_.}08. All ammonia absorption lines have two distinct velocity components: one is at the systemic velocity and the other is blueshifted, and both components are aligned along the nuclear jets. For the systemic components, the relatively low temperature gas is extended more than the high temperature gas. The blueshifted NH₃(3, 3) emission can be regarded as ammonia masers associated with shocks by strong winds probably from newly formed massive stars or supernova explosions in dense clouds in the nuclear megamaser disk. Using para-NH₃(1, 1), (2, 2), (4, 4), and (5, 5) lines with VLA, we derived the rotational temperature T_rot = 120 ± 12 K and 157 ± 19 K for the systemic and blueshifted components, respectively. The total column densities of NH₃(0, 0)-(6, 6), assuming T_ex ≈ T_rot, were (8.85 ± 0.70) × 10¹⁶ cm^-2 and (4.47 ± 0.78) × 10¹⁶ cm^-2 for the systemic and blueshifted components, respectively. The fractional abundance of NH₃ relative to molecular hydrogen H₂ for the systemic and blueshifted was [NH₃]/[H₂] = 1.3 × 10^-7 and 6.5 × 10^-8, respectively. We also found the F = 4-4 and F = 5-5 doublet lines of OH ²Π_3/2 J = 9/2 in absorption, which could be fitted by two velocity components, systemic and redshifted components. The rotational temperature of OH was estimated to be T_{rot, OH} ≥ 175 K, tracing hot gas associated with the interaction of the fast nuclear outflow with dense molecular material around the nucleus....

We present the first map of ¹²CO (J = 3 → 2) and the first detection of ¹³CO (J = 3 → 2) in the nearby starburst galaxy with a superwind, NGC 1808. The molecular gas is concentrated in the inner 2 kpc region of the galaxy with extended structure along the galactic bar and along the minor galactic axis. The minor-axis structure can be explained as molecular gas entrained in a galactic wind observed as a dust outflow at optical wavelengths. We have carried out a radiative transfer analysis of the excitation conditions of molecular gas in the starburst region (radius 550 pc) by using the ratios of J = 1 → 0, J = 2 → 1, and J = 3 → 2 emission lines of ¹²CO and ¹³CO, and the large velocity gradient approximation. The beam-averaged density and kinetic temperature of molecular gas can be fitted at n _H2 ≃ 10^3.5 cm^-3 and T_k ≃ 35 K, indicating the presence of warm molecular gas, close to the estimated dust temperature of T_d ≃ 34-37 K. The abundance ratio of the CO isotopologues is found to be [¹²CO]/[¹³CO] ≃ 34. The calculations show that, for the derived physical parameters, J = 2 → 1 and J = 3 → 2 transitions of ¹²CO are optically thick, ¹²CO J = 1 → 0 is moderately optically thick, and all transitions of ¹³CO are optically thin. We have estimated an average CO-H₂ conversion factor of X_CO ≃ 0.8 × 10²⁰ cm^-2 (K km s^-1)^-1 in the central 550 pc by using a simple theoretical model assuming homogeneous, gravitationally bound gas clouds with turbulent velocities. In the same region the molecular gas mass is 3.0 × 10⁸ M_☉ available to fuel the nuclear starburst....

We present large-field (15.7 × 16.9 arcmin²) CO(J = 1→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 ̃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) × 10⁹ M_☉ and (1-4) × 10⁵⁶ 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....