We present the high-resolution 12CO(J = 1 − 0), 13CO(J = 1 − 0) and 12CO(J = 3 − 2) maps toward a GMA located on the southern arm region of M31 using Nobeyama 45 m and ASTE 10 m telescopes. The GMA consists of two velocity-components, i.e., red and blue. The blue component shows a strong and narrow peak, whereas the red one shows a weak and broad profile. The red component has a lower 12CO(J = 1 − 0)/13CO(J = 1 − 0) ratio (~ 5) than that of the blue one (~ 16), indicating that the red component is denser than the blue one. The red component could be the decelerated gas if we consider the galactic rotational velocity in this region. We suggest that the red component is “post shock” dense gas decelerated due to a spiral density wave. This could be observational evidence of dense molecular gas formation due to galactic shock by spiral density waves.

We also present results from on-going observations toward NGC 604, which is the supergiant HII region of M33, using Nobeyama 45 m and ASTE 10 m telescopes. The ratio of 12CO(J = 3 − 2) to 12CO(J = 1 − 0) ranges from 0.3 to 1.2 in NGC 604. The 12CO(J = 1 − 0) map shows the clumpy structure while 12CO(J = 3 − 2) shows a strong peak near to the central star cluster of NGC 604. The high ratio gas is distributed on the arc-like or shell-like structure along with Hα emission and HII region detected by radio continuum. These suggest that the dense gas formation and second generation star formation occur in the surrounding gas compressed by the stellar wind and/or supernova in central star cluster.

We discuss how tidal interaction between the Large Magellanic Cloud (LMC), the Small Magellanic Cloud (SMC), and the Galaxy triggers galaxy-wide star formation in the Clouds for the last ~0.2 Gyr based on our chemodynamical simulations on the Clouds. Our simulations demonstrate that the tidal interaction induces the formation of asymmetric spiral arms with high gas densities and consequently triggers star formation within the arms in the LMC. Star formation rate in the present LMC is significantly enhanced just above the eastern edge of the LMC's stellar bar owing to the tidal interaction. The location of the enhanced star formation is very similar to the observed location of 30 Doradus, which suggests that the formation of 30 Doradus is closely associated with the last Magellanic collision about 0.2 Gyr ago. The tidal interaction can dramatically compress gas initially within the outer part of the SMC so that new stars can be formed from the gas to become intergalactic young stars in the inter-Cloud region (e.g., the Magellanic Bridge). The metallicity distribution function of the newly formed stars in the Magellanic Bridge has a peak of [Fe/H] ~−0.8, which is significantly lower than the stellar metallicity of the SMC.

One of the outstanding puzzles about star formation is why it proceeds so slowly. Giant molecular clouds convert only a few percent of their gas into stars per free-fall time, and recent observations show that this low star formation rate is essentially constant over a range of scales from individual cluster-forming molecular clumps in the Milky Way to entire starburst galaxies. This striking result is perhaps the most basic fact that any theory of star formation must explain. I argue that a model in which star formation occurs in virialized structures at a rate regulated by supersonic turbulence can explain this observation. The turbulence in turn is driven by star formation feedback, which injects energy to offset radiation from isothermal shocks and keeps star-forming structures from wandering too far from virial balance. This model is able to reproduce observational results covering a wide range of scales, from the formation times of young clusters to the extragalactic IR-HCN correlation, and makes additional quantitative predictions that will be testable in the next few years.

While the overall star formation rate in a galaxy appears to depend primarily on the gas mass and density, with the timescale for conversion of gas into stars given by the dynamical time, turbulence and explosions are still important for the process of star formation because they control the birth correlations in space and time. Most star formation appears triggered by some specific process, whether it is a galactic spiral shock, the expansion of a superbubble, the compression of a bright-rimmed globule, or some seemingly random compressive event in a supersonically turbulent flow. These processes give space and time sequences for star birth that are well observed. Many examples were given at this conference. Shocks are the link between large-scale but weak galactic processes and small-scale but strong final collapses. The rate limiting step is on the largest scale, where the dynamical time is slowest. Both gravitational instabilities and pressurized triggering seem to work on the same local dynamical time, making it difficult to tell that star formation is highly triggered when observing only galactic scales.

It is a general belief that the starburst activity of a nearby galaxy M82 was triggered in a close encounter with its massive companion M81, a few tens of million years ago. Despite the lack of supernovae observed, multiwavelength radio observations of M82 discovered a considerable number of compact supernova remnant candidates. We use these remnants to estimate the supernova rate (SNR) and the enhanced star-formation (SFR) rate in M82, and compare them with rates in normal galaxies.

NGC 1333 contains numerous young stellar objects and outflows and is a well-studied star formation region. High resolution SiO observations of the NGC 1333 IRAS 4A region showed a highly collimated outflow with a substantial deflection angle. It was also suggested by the observations that the deflection was due to the interaction of the outflow and a dense cloud core (Choi 2005a, 2005b). In order to make a detailed model of the deflected outflow, we have carried out three-dimensional hydrodynamic simulations of outflow/cloud interactions with a hydrodynamic code based on the TVD scheme. In our models, an initial outflow with number density 10 cm−3 and temperature 104 K interacts with a spherical cloud with a power-law density distribution. The cloud has a uniform temperature of 10 K and is surrounded by a homogeneous gas of density 100 cm−3 and temperature 10 K. The radius of the cloud is 0.02 pc, and the outflow has a sectional radius 300 AU. Through the numerical experiments, we found that the deflection angle is mainly determined by the impact parameter and the density ratio between the outflow and the impact zone of the cloud. The deflection angle is, however, not sensitive to the velocity of outflow. Using initial conditions and parameters which are particularly suitable for NGC 1333 IRAS 4A, we can reproduce its bent morphology. We therefore confirm that the northeastern deflected outflow of the NGC 1333 IRAS 4A may be colliding with a dense cloud core and deflected as a result.

The HI Nearby Galaxy Survey (THINGS), is a 21–cm HI line survey of a sample of 34 nearby (3–10 Mpc) galaxies (Walter et al. 2005). The observations were carried out with the VLA and have a velocity resolution of 5 km s−1 or better and an angular resolution of 7″ which at this distance range corresponds to a linear resolution of 100–300 pc. One of the primary goals of THINGS is to look at the fine–scale structure of the Interstellar Medium (ISM) and examine how it varies as a function of Hubble type, star formation rate, galaxy mass, metallicity, etc. We present one of the first science results from this project, an inventory of HI shells in the galaxies NGC 628, NGC 3184, and NGC 6946.

We present an analysis of the fine–scale structure of the neutral ISM as traced via the 21-cm line of atomic hydrogen (HI) in the nearby galaxy M 81. The data show a stunning amount of detail in the form of 330 expanding shells and holes in the neutral ISM of M 81. A comparison with similar structures found in two other spirals and two dwarf galaxies (M 31, M 33, IC 2574 and Holmberg II) reveals that the ISM in M 81 shares a lot of similarities with the two spirals, whereas the structure of its ISM is different to that in dwarf galaxies. The sizes of the HI holes in M 81 range from 80 pc (close to the resolution limit) to 600 pc; the expansion velocities can reach 20 km s−1; estimated ages are 2.5 to 35 Myrs and the energies involved range from 1050 to 3.5 x 1052 ergs. The amount of neutral gas involved is of order 104 to 106 solar masses.

It has been established that massive stars form in dense clusters, when large molecular clouds collapse. However, the high obscuration and small spatial scales make it difficult to investigate the earliest stage of high–mass protostellar objects (HMPOs). Therefore methanol masers are of special interests as they are closely associated with HMPOs and offer high spatial resolution; they probe the massive star formation environment at the unique scale of a few AU (1 mas corresponds to 5 AU at 5 kpc).

We present VLBI observations of methanol masers discovered in an unbiased survey along the Galactic plane. We compare their positions with infrared surveys. In general, the masers do not coincide with infrared objects. That implies they are already present at a very early evolution stage of HMPOs when the dense surroundings still absorb other radiation. In addition we present maps of five methanol masers towards HMPOs with milliarcsecond resolution taken with the recently extended European VLBI Network. These sources show a wide variety of morphologies, indicating they arise in different events going on in close surroundings of HMPOs, i.e. outflows, discs or shocks. One source G23.657−00.127 displays a regularly shaped ring which appears as a great laboratory for further research of a single HMPO. Proper motion studies should reveal an expansion or rotation of the maser components in 2–3 years.

The molecular cloud associated with the Sh 254-258 group of 5 small H II regions appears to be forming a (late)-OB association. We have mapped the associated molecular cloud in the J=2-1 line of the CO molecule over 0.75o × 1o, and the CO J=3-2 line toward the 2 main peaks, with the University of Arizona Heinrich Hertz Submm Telescope (HHT). We propose a scenario for sequential formation of the stars exciting the H II regions, triggered by the compression/heating of the molecular gas.

We present first results from THINGS (The HI Nearby Galaxy Survey), which consists of high quality HI maps obtained with the VLA of 34 galaxies across a wide range of galaxy parameters (Hubble type, mass/luminosity). We compare the distribution of HI to the UV emission in our sample galaxies. In particular we present radial profiles of the HI (tracing the neutral interstellar medium) and UV (mainly tracing regions of recent star formation) in our sample galaxies. The azimuthally averaged HI profiles are compared to the predicted critical density above which organized large-scale star formation is believed to start (this threshold is based on the Toomre-Q parameter, which in turn is a measure for local gravitational instability).

Numerous instances of intergalactic star forming regions have been recently reported (see Duc et al. in this proceedings book). They are fueled by gaseous material expelled from parent galaxies. One spectacular example is the HI ring-like structure around the interacting system NGC 5291 (Malphrus et al. 1997) which hosts numerous HII regions (Duc & Mirabel 1998). In order to study how star formation proceeds in this specific environment, we have combined ultraviolet (Galex), Hα, 8 μm (Spitzer) and HI (VLA B-array) images of this system.

We present a comparative study of three dark globules CB52, CB107, and DC267.4-07.5. By means of an accurate photometry, near-IR two-colour diagrams were derived for the stellar backgrounds and used to determine the colour excesses of the reddened stars (Campeggio et al. 2004). By assuming a normal interstellar reddening law (Rieke & Lebofsky 1985), the visual extinction can be obtained as Av = 15.87 E(H–K).

To investigate the interaction of the massive stars with the gas and dust in the active star forming region NGC 6357, located in the Sagittarius spiral arm at a distance of 1.7-2.6 kpc (Massey et al. 2001), we analyzed the distribution of the neutral and ionized gas, and that of the dust, based on Hα, [OIII] and [SII] images obtained with the Curtis-Schmidt telescope at CTIO, radio continuum observations at 1.465 MHz obtained with the Very Large Array (NRAO) in the DnC configuration (synthesized beam = 38″), Hi data from the Parkes survey (angular resolution = 15′), CO(1-0) observations obtained with the Nanten radiotelescope at Las Campanas Observatory (angular resolution = 2.7′), and IR images in the four MSX bands (angular resolution = 18.3″).

We have used Spitzer IRAC and MIPS observations of N44 to identify young stellar objects (YSOs). Sixty YSO candidates with masses ≳4M are identified. We have compared the distribution of YSOs with those of the ionized gas, molecular clouds, and HI gas to study the properties of star formation.

With sensitive radio observations of a Virgo Cluster spiral NGC 4254 we are able to decompose thermal and synchrotron radio emission and, based on the thermal component, construct the SFR distribution within the galaxy, unaffected by dust extinction. The mean SFR per unit area is several times higher than in other galaxies of similar Hubble type. Contrary to other Virgo spirals the SFR distribution is not spatially truncated, in concordance with the observed weak HI deficiency. We propose that the SFR enhancement and the observed disturbed morphology of this galaxy can be attributed to tidal triggering by another nearby cluster member.

A new 7-beam methanol multibeam receiver was successfully commissioned at Parkes Observatory in January 2006, and has begun surveying the Milky Way for newly forming massive stars, that are pinpointed by strong methanol maser emission at 6.7 GHz. The receiver was jointly constructed by Jodrell Bank Observatory and the Australia Telescope National Facility for use on the Parkes and Lovell Telescopes. The whole galactic plane is being surveyed within latitudes ±2°, with a velocity resolution of 0.1 km s−1 and a 5-σ sensitivity of ~0.7 Jy. Altogether 200 days of observing will be required.

Any successful model of star formation must be able to explain the low star forming efficiency of molecular clouds in our Galaxy. If the collapse of gas is regulated only by gravity, then the star formation rate should be orders of magnitude larger than the 1 M per year within our galaxy. The standard model invokes magnetic fields to slow down the rate of collapse, but does not explain star formation in cluster mode, or the lack of observed variations in the chemistry of molecular clouds if they are long-lived entities.

Studies of molecular clouds have shown that they evolve from turbulent gas and dust to form coherent, dense and connected structures. We have conducted a multi-wavelength study of one such molecular cloud, the Perseus star-forming region, which includes Barnard 1 (B1), Barnard 3(B3), Barnard 5 (B5), NGC 1333, IC 348, L1455 and L1448. The data obtained using the Infrared Array Camera (IRAC), Multiple Imaging Photometer (MIPS), the Sub-mm Common User Bolometer Array(SCUBA) and the 2 Micron All Sky Survey (2MASS)provides information about the geometric structure of the dust and gas covering large areas around young stellar objects (YSO), dust temperatures, effect of turbulence and processes of molecule formation and their relevance in the chemical and physical evolution of the cloud. This paper presents our first results.

Theory predicts the triggered formation of molecular clouds stars through the fragmentation and collapse of swept-up ambient gas. Yet the majority of Galactic HI shells show no more than a scattering of small molecular clouds. The Carina Flare supershell (Fukui et al. 1999) is a rare example of an HI shell with a striking molecular component. Here we present the large-scale morphology of the molecular and atomic gas and the location of YSO candidates. A detailed look at two molecular clumps in the shell walls reveals active, intermediate mass star forming regions at various stages of early evolution.