The evolution of giant molecular clouds (GMCs), which are the main sites of star formation, is essential for unraveling how stars form and how galaxies evolve. We analyzed the M33 CO(J = 2–1) data with spatial resolution of 39 pc obtained by ALMA-ACA 7 m array combined with IRAM 30 m. We identified 736 GMCs and classified them into three types; Type I: associated with no Hii regions, Type II: associated with Hii regions with the Hα luminosity L(Hα) < 1037.5 erg s-1, Type III: associated with Hii regions with L(Hα) > 1037.5erg s-1. We found that mass, size, and velocity dispersion of GMCs slightly increase in the order of Type I, II, and III GMCs. Type III GMCs mainly exist in the spiral arm, while many of Type I and Type II GMCs are distributed in the inter-arm. Assuming that the star formation proceeds steadily, we roughly estimated the total GMC lifetime of 30 Myr.

The Magellanic Clouds offer the opportunity to obtain a spatially resolved view of external galaxies at reduced metallicity with no distance ambiguity. Our ALMA observations of the active star-forming region N83C in the Small Magellanic Cloud (SMC) revealed subparsec-scale molecular structures in 12CO and 13CO (2-1) emission Muraoka et al. (2017). We found strong CO peaks associated with Young Stellar Objects(YSOs) and derived a typical gas density of ∽104 cm−3 and gas temperature of 40-60 K from the excitation analysis. The high gas density and temperature are presumably due to the effect of the HII region under the low-metallicity environment. We have found that the column density ratios N(CI)/N(CO) are generally high throughout the cloud compared with the Galaxy, ranging from 0.2 to 2.0. A peak of the ratio is observed toward a CO peak associated with a massive protostar.

Formaldehyde (H2CO) and its deuterated forms can be produced both in the gas phase and on grain surfaces. However, the relative importance of these two chemical pathways is unclear. Our recent single dish observation of formaldehyde and its deuterated species suggests that they form mostly on grain surfaces although some gas-phase contribution is expected at the warm HMPO stage. Since the single dish beam is larger, and since these high-mass star-forming regions are clustered and complex, it is however unclear whether the emission arises from the protostellar sources or from starless/pre-stellar cores associated with them. Therefore, interferometric observations are needed to separate the emission originating from the small and dense cores, to disentangle their formation routes and then being able to use them as powerful diagnostic tools of the physical and chemical properties of high-mass star forming regions.

Planck cold clump G163.82-8.44 is part of the Auriga-California Molecular Cloud. It was observed with Herschel PACS and SPIRE instruments as part of the Herschel open time key programme Galactic Cold Cores. Follow-up ground-based molecular line observation of NH3 was performed to the densest part of the filament with the Effelsberg-100m telescope. We detected two different velocity components with a separation of 0.5 km/s. We performed radiative transfer modeling with two 3-dimensional spheres to characterise the temperature and density of the dense cores. We have found that the temperatures of the two cores are almost the same, 10.8 K and 11.1 K and their mass and size ratios are 1:10 and 1:5, respectively.

Star formation and interstellar medium (ISM) structure were investigated in the Taurus, Auriga, Perseus and California (TAP) nearby star forming regions. Properties of the cold ISM was derived using AKARI FIR all sky maps, the Osaka-1.85m CO survey focusing to the all-sky Planck catalogue of Galactic Cold Clumps (PGCC). As many as 1041 infrared point sources were classified as young stellar object (YSO) based on multiband photometric data, and 384 of those are associated to a PGCC object. About 30% of the TAP PGCC clumps have associated YSOs.

We present a set of time dependent chemical evolution models (based on the UMIST† astrochemistry 2012 code, Woodall et al. (2007); McElroy et al. (2013) for a range of initial physical cloud parameters: 10 K < T < 20 K; 103 cm−3 < n(H2) < 5 · 104 cm−3; 1 < AV < 10 and with estimated values of scaled interstellar ultraviolet radiation field. Our computation model included the full UMIST gas-phase reaction network for 467 species Garrod et al. (2008), Graedel et al. (1982). We compare our chemical model results with the relative abundances of: CO, CH, OH, HCO+, HCN, HNC, NH3, N2H+ and H2CO molecules. We find significant time dependent variations of the chemical ratios of: X(NH3/H2); X(HCO+/H2) and X(HCO+/NH3). We derive an ammonia age spread for the parts of TMC-1 (Taurus Molecular Cloud-1) that looks more complex than previous estimated showed. Age estimates based on X(NH3/H2); X(HCO+/H2) and X(HCO+/NH3) were compared in 3 selected positions, and were found to be very similar (with ±9% differences).

High-mass stars usually form in giant molecular clouds (GMCs) as part of a young stellar cluster, but some isolated O/B stars are observed. What are the initial conditions that lead to the formation of these objects? The aim of this study is to measure the distribution and basic physical properties of the neutral gas associated with isolated intermediate- and high-mass young stellar objects (YSOs) in the Large Magellanic Cloud.

As part of the SAGE Spitzer Legacy program for the LMC, we have identified and confirmed YSOs using Spitzer IRAC photometry and IRS spectroscopy. By examining the spatial coincidence between the YSOs and 12CO(1–0) emission detected by the NANTEN mapping survey, we identified more than one hundred intermediate/massive YSOs in the LMC that appear to be isolated, i.e. not associated with CO emission. Deeper follow-up CO observations by our team with the higher resolution by Mopra Telescope (beam=30”) detected CO emission at the YSO positions for ~80% of the isolated LMC YSOs. We obtained ALMA data of some of the targets during Cycle 2. We targeted a small but representative (in terms of their association with neutral gas tracers) sample of the isolated high-mass YSOs that we have been studying in the LMC. All of our 12 targets are separated by more than 200 pc from known CO clouds. Our analysis of the ALMA data shows that a compact molecular cloud whose mass is a few thousand solar masses or smaller is associated with most of the YSOs.

It is crucially important to observe dense cores in order to investigate the initial condition of star formation since protostars are formed via dynamical collapse of dense cores, inhering the physical properties from their natal dense cores. Here we present the results of ALMA Cycle 0 and Cycle 1 observations of dust continuum emission and molecular rotational lines toward a dense core, MC27 (aka L1521F), which is considered to be very close to the first protostellar core phase. We revealed the spatial/velocity structures of the core are very complex and and suggest that the star formation is highly dynamical.

We have developed a new mm-submm telescope with a diameter of 1.85 m (hereafter, Osaka 1.85-m telescope) installed at the Nobeyama Radio Observatory. The scientific goal is to precisely reveal physical properties of molecular clouds in the Galaxy by obtaining a large-scale distribution of molecular gas, which also can be compared with large-scale observations in various wavelengths. The target frequency is ~230 GHz; simultaneous observations in J = 2–1 lines of 12CO, 13CO and C18O are achieved with a beam size (HPBW) of 2.7 arcmin. Here we present the progress of observations and the scientific results obtained by Osaka 1.85-m telescope. We note that these J = 2–1 data of the Galactic molecular clouds will be precious for the comparison with those of extra-galactic ones that will be obtained with the ALMA with the comparable spatial resolutions.

We present the first results of the new CO J = (2 − 1) observations toward the central molecular zone (CMZ) using the NANTEN2 telescope at an angular resolution of 100″. Large area coverage of 4° × 2° in l and b and a high angular resolution of 100″ enable us to investigate detailed structures of the molecular gas in the CMZ including peculiar molecular filaments perpendicularly to the Galactic plane to b > |0.5°|. The major components of the CMZ, e.g., Sgr A, Sgr B and Sgr C cloud complexes, show high CO J = (2 − 1)/J = (1 − 0) ratios around 0.9, indicating highly excited conditions of the molecular gas, while the local foreground components show less than 0.4. The molecular filaments show the typical ratios of 0.6–0.7 indicate that they are indeed located in the Galactic center.

We revealed a statistically significant clustering in the all sky distribution of AKARI-WISE young stellar objects with large groups of elongated and bush types.

Physical parameters were derived for 100 young stellar objects in the TAPO region.

Galactic-scale studies of γ-rays and sub-mm radiation suggest that a significant amount of neutral interstellar medium is not detectable either in CO or HI (Grenier et al. 2005; Ade et al. 2011). This component is called “dark gas”. Here we argue that cool and dense atomic gas without molecules is responsible for the dark gas. This interpretation is supported by a recent finding of cool HI gas corresponding to the TeV γ-ray shell in the SNR RX J1713.7-3946 (Fukui et al. 2011). Such HI gas is not recognized under a usual assumption of optically thin HI emission but is identified by a careful analysis considering optically thick HI. The typical column density of such HI gas is a few times 1021 cm−2 and is also identified as visual extinction.

We report the results of the submillimeter observations with the ASTE 10 m telescope toward the giant molecular clouds (GMCs) in the Magellanic Clouds to reveal the physical properties of dense molecular gas, the principle sites of star and cluster formation. Six GMCs in the Large Magellanic Cloud have been mapped in the 12CO(J = 3 − 2) transition and 32 clumps are identified in these GMCs at a resolution of 5 pc. These data are combined with 12CO(J = 1 − 0) and 13CO(J = 1 − 0) results and compared with LVG calculations to derive the density and temperature of clumps. The derived density and temperature are distributed in wide ranges. We have made small mapping observations in the 13CO(J = 3 − 2) transition toward 9 representative peak positions of clumps to determine the density and temperature of clumps. These physical properties are constrained well and there are differences in density and temperature among clumps. We suggest that these differences of clump properties represent an evolutionary sequence of GMCs in terms of density increase leading to star formation.

We have carried out the mid-infrared slit spectroscopic observations of sources in the LMC and in NGC 6946 with AKARI/IRC. We investigate the properties of the UIR bands in terms of the star forming activities. We find systematically larger ratios of UIR bands in 6–9 μm to 11.2 μm band in active star forming regions than in the quiet regions. This behavior is consistent with the photo-ionization model of PAHs. Our results suggest that the ratios of UIR bands in 6–9 μm to 11.2 μm band can be used as more efficient and vigorous tools to measure the extent of on-going star formation in remote galaxies rather than just the presence or absence of the features themselves.

The interaction between molecular outflow from a protostar and ambient molecular cloud would play an important role in dissipating circumstellar envelope, changing chemical composition, and triggering next generation star formation. In order to investigate the interaction in submillimeter wavelength, we have made line observations toward the low mass protostar IRAS 13036-7644 (Class 0/I) in the Cha II dark cloud. Although millimeter observations found CO outflow and evidence of mass infall toward the protostar (e.g. Lehtinen 1997), no submillimeter observation has been reported so far.

Large-scale CO observations with the millimeter/submillimeter telescope NANTEN toward a whole FIR loop-like structure whose angular extent is ~20° × 20° around (l, b) ~(109°, − 45°) in Pegasus have been carried out in the 12CO (J = 1 − 0) at 4′ – 8′ grid spacing and the 12CO emitting region in the 13CO (J=1–0) at 2′ grid spacing. The diameter corresponds to ~25 pc at a distance of 100 pc, adopted from that of the star HD886(B2IV) near the center of the loop.

Outflow-cloud interaction is an important issue in discussions about star formation in clusters because it could generate turbulence and restrain star formation activities, as well as it causes outflow-triggered star formation.

A CO survey of the LMC has been completed in the J = 1−0 carbon monoxide emission at 2.6 mm wavelength with NANTEN. This survey has revealed the first complete sample of giant molecular clouds (GMCs) in the LMC at a linear resolution of ∼ 40 pc. The GMCs exhibit a good spatial correlation with youngest stellar clusters often associated with the giant H II regions. The ages of clusters associated with GMCs are fairly young, ≲ 10 Myr, demonstrating that cluster formation is ongoing in these GMCs. In addition, compact groups of the young clusters are often found at the peak position of the GMCs, e.g., N159 and N44, while much looser groups are away from the GMCs. This suggests that the clusters are formed in groups and are dispersed as they become old.