We present a 12CO 2-1 map of M51 (Schuster et al. 2006) at 11″ resolution observed with HERA at the IRAM-30m telescope. The map covers the companion galaxy NGC5195 as well as the south-western arm out to 12 kpc. Using the IRAM-30m data and the clump finding procedure GAUSSCLUMPS (Stutzki et al. 1990), we obtain the masses, positions, peak temperatures and more intrinsic properties as i.e. deconvolved sizes of Giant Molecular Associations (GMAs) in M51 (Hitschfeld et al. 2007, in prep.).

Some results of Galaxy star clusters and associations observation are presented.

We are studying the molecular clouds in the region around G333.6-0.2 in a number of 3-mm transitions from different molecular species, to probe, among other things, the turbulent properties. The observations are being made by on-the-fly mapping with the 22-m diameter single-dish Mopra radio telescope. See Bains et al. (2006) and Cunningham et al. (2006 in these proceedings) for more details. During 2004 and 2005 we obtained 13 CO (1 – 0), C18O, CS (2 – 1) and C34S data. Using the different molecular tracers gives complementary information about the gas density structure, due to the different critical densities, and different isotopomers allows correction for optical depth effects.

We examine the intensity of scattered near-infrared (NIR) light in the case of interstellar clouds illuminated by the normal interstellar radiation field. We have developed a way to convert the observed surface brightness into estimates of the column density and have estimated the accuracy of the new method. The NIR intensities can be converted into reliable estimates of the column density in regions with AV up to almost 20 magnitudes. The errors can be further reduced with detailed radiative transfer modelling and by using the lower resolution information that is provided by the colour excess data of background stars. Therefore, NIR scattered light is a promising new way to map quiescent interstellar clouds at a high, even sub-arcsecond resolution.

An overall uvby β photometric survey of the structure of the star-forming fields located toward the Monoceros-Canis Major-Puppis-Vela region of the Milky Way is presented.

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.

Blue compact dwarf (BCD) galaxies are low-metallicity objects undergoing violent star formation (Searle & Sargent 1972). We present our ongoing work on integral field spectroscopy (IFS) of the two prototypical BCD galaxies IIZw70 and IZw18 (Papaderos et al. 2002). Two-dimensional spectroscopy allows us to collect simultaneously the spectra of many different regions of an extended object, combining photometry and spectroscopy in the same data set. The great advantage of using IFS for the investigation of galaxies is that it allows us to obtain data on the galaxies' positions, velocity fields and star-forming properties all in one data cube. The observations were taken with the instruments INTEGRAL/WYFFOS at the WHT (ORM, La Palma) and PMAS installed on the 3.5m telescope at the CAHA, covering a spectral range from λ 3600 to 6800 Å. The data are mainly used to study the ionized gas and stellar clusters. Our main goal is to investigate the presence of spatial variations in ionization structure indicators, physical conditions and gaseous metal abundances, in these galaxies (Vílchez & Iglesias-Páramo 1998). We also study the kinematical properties of the ionized gas, as well as systematic variations of ionization structure and physical-chemical parameters as a function of the surface-brightness in Hα emission. Maps of the relevant emission lines are presented.

We discuss the results of HI survey of the LMC and a catalog of HI clouds.

It has been recently shown by several authors that fragmentation of pre-stellar gas (i.e. at densities from 104 to 1010 particles cm−3 and temperatures of order 10-30 K) depends on the gas thermodynamics much more than it was anticipated in earlier studies, in which only an isothermal behaviour has been assumed for the gas. Here we review the results of a number of numerical hydrodynamic simulations (e.g. Li et al. 2003, Jappsen et al. 2005, Bonnell et al. 2006) in which departure from isothermality has been attempted by employing a polytropic equation of state (eos) with exponent different from unity. In particular, in these studies it has been shown that the dominant fragmentation scale of pre-stellar gas, and hence the peak of the initial mass function (IMF), depends on a polytropic exponent that changes value, from below to above unity, at a critical density (Larson 2005). Furthermore, this piecewise polytropic eos depends on the gas metallicity and fundamental constants. Therefore, the peak of the IMF depends, in turn, also on the gas metallicity and fundamental constants rather than on initial conditions, as it has been previously suggested (e.g. Larson 1995). Hence, we are for the first time in a position to infer theoretically the notion of a universal IMF (at least for its low-mass end).

We also present two test cases in which a non-isothermal eos has been used in the context of smoothed particle hydrodynamic (SPH) numerical simulations. In the first case star formation is triggered by means of low-mass clump collisions. These calculations have shown that clump collisions can be a relatively efficient mechanism for the formation of solar-mass protostars and their lower-mass companions (efficiency greater or of order 20-25%; Kitsionas & Whitworth 2006). We have also found that in such collisions protostars form mainly by fragmentation of dense filaments along which it is likely that pairs of protostars capture each other in close binaries surrounded by circumbinary discs. In the second case, the use of a polytropic eos with a varying exponent appropriate for the metallicity of starburst regions (Spaans & Silk 2000, 2005) is shown to be sufficient to obtain a top heavy IMF similar to that observed e.g. in the Galactic centre (Klessen, Spaans & Jappsen 2006). These are preliminary results in the direction of revisiting earlier isothermal calculations that were resolving all densities up to the opacity limit for fragmentation (e.g. Bate et al. 2002ab, 2003), this time also taking into account the thermal properties of the gas in the density range between 104 and 1010 particles cm−3. The next step would be to include self-consistent radiation transport in the calculations, the first attempts for which are already in the making (e.g. Whitehouse & Bate 2004).

Atacama Submillimeter Telescope Experiment (ASTE) is a joint project between Japan and Chile for installing and operating a 10 m high precision telescope in the Atacama Desert in order to explore the southern sky through the submillimeter wavelength. We have achieved an accuracy of 19 μm (rms) for the main reflector surface and a stable radio pointing accuracy of about 2 arcsec (rms). A 350 GHz cartridge type SIS mixer receiver achieves good performance with a typical system noise temperature of 150 ~ 250 K in DSB and a main beam efficiency of 0.6 ~ 0.7 during winter nights.

A large scale CO(3-2) imaging survey of nearby galaxies using ASTE is now in progress. One of our goals is to compare our wide area CO(3-2) images with existing CO(1-0) data as well as distributions of massive star formation tracers (i.e., Hα and radio continuum emission) in order to understand the physical mechanism which controls the global star formation properties such as star formation efficiency. Initial CO(3-2) maps of some sample galaxies (M 83, NGC 604 in M 33, NGC 1672, & NGC 7130) are reported.

We perform a 3D-MHD simulation of a self-gravitating isothermal gas layer that is initially penetrated by a uniform magnetic field. The strength of the initial magnetic field is such that the cloud is slightly subcritical. In this system, we input random supersonic turbulence initially. Ion-neutral friction is also introduced in the magnetized gas so that the magnetic diffusion allows gas to go across the magnetic field and form self-gravitating cores. We found that self-gravitating cores are formed in the dense region enhanced by the shock waves if ion-neutral friction is introduced. The time scale of core formation is on the order of the 106 years, which is faster than the usual magnetic diffusion time (107 years) estimated from the initial condition. Our result is consistent with the results of 2D-MHD simulations by Li & Nakamura (2004).

Galactic clusters have well organized directions of their velocities at the instant of birth measured with respect to the local circular velocity. Preferential directions survive more than 100 Myrs. This can only be explained by star formation triggered by spiral arms.

A comprehensive study of clustered star formation in the Rosette Molecular Complex was carried out based on archived data from the 2 Micron All Sky Survey. We presented strong evidence that triggered formation of embedded clusters and stellar aggregates took place in the working shells of the Rosette Nebula, a spectacular HII region excavated by the dozens of OB stars of the emerging massive cluster NGC 2244. Surprisingly, we have identified, within the confines of NGC 2244, a distinct congregation of young stellar objects showing prominent NIR excess that forms an arc like structure in appearance. Its location right to the south-east of the center of the main cluster and its strange morphology indicate most likely an origin from a former working shell of the HII region. This relic arc and the large, fragmented working surface layer of Rosette with the ambient cloud roughly show a concentric origin in morphology. This implies also a common origin of the clusters or stellar aggregates in association. The formation of massive star clusters was evidenced further into the heart of the molecular complex, and structured clustering star formation seemed to have taken place toward the south-east edge of the complex.

Infrared dark clouds (IRDCs) are generally assumed to be a promising hunting ground for tracing very early stages of massive star formation. Observations with Spitzer are a viable tool to probe their interiors that are still dominated by strong dust extinction even at 8 μm. With Spitzer/MIPS, we have observed several IRDCs at 24 and 70 micron. We generally find weak 24 micron sources within the IRDCs. However, at 70 micron these sources remain weak and thus indicate lower luminosities at the current state of evolution. Indications for internal substructures exist, separating regions with compact IR sources from even more dark regions.

We investigate the relation between the existence and size of radio halos, which are believed to be created by star formation (SF) related energy input into the interstellar medium, and other galaxy properties, most importantly star formation activity and galaxy mass. Based on radio continuum and Hα observations of a sample of seven galaxies we find a direct, linear correlation of the radial extent of gaseous halos on the size of the actively star-forming parts of the galaxy disks. Data of a larger sample of 22 galaxies indicate that the threshold energy input rate into the disk ISM per unit surface area for the creation of a gaseous halo depends on the mass surface density of the galaxy, in the sense that a higher (lower) threshold has to be surpassed for galaxies with a higher (lower) surface density. Because of the good prediction of the existence of a radio halo from these two parameters, we conclude that they are important, albeit not the only contributors. The compactness of the SF-related energy input is also found to be a relevant factor. Galaxies with relatively compact SF distributions are more likely to have gaseous halos than others with more widespread SF activity. These results quantify the so-called “break-out” condition for matter to escape from galaxy disks, as used in all current models of the interstellar medium.

More details can be found Dahlem, Lisenfeld & Rossa, 2006, A&A 457, 121.

I briefly describe two new young star cluster candidates found within 200 pc of the Sun, associated with the 4th-magnitude stars μ Oph and 32 Ori. The μ Oph group (d ≃ 170pc) has a space motion and age (~120± 25 Myr) suspiciously similar to the Pleiades, but lies in the opposite side of the sky behind ~0.9 mag of visual extinction in Ophiuchus. The 32 Ori group is a nearby (d ≃ 90 pc) loose aggregate of ~25-Myr-old post-T Tauri stars co-moving with the massive binary 32 Ori (B5V+B7V) in northern Orion. The 32 Ori group accounts for part of the population of “isolated” Li-rich RASS pre-MS stars in northern Orion.

Turbulence has a significant influence on the chemistry of molecular clouds. Do molecular abundances alter if we use superdiffusion instead of simple diffusion? After our first simplified calculations it seems there is a notable difference.

Stellar winds from O and WR stars transfer large amounts of mechanical energy and momentum into the interstellar medium. They sweep up and compress the interstellar material, creating interstellar bubbles. These structures are detected as optical ring nebulae, as thermal radio continuum sources, as infrared shells, as neutral gas voids and expanding shells in the HI line emission distribution, and as molecular shells.

We present preliminary results for six spiral galaxies from a sample of 25, where we have used the method developed by González & Graham (1996) to search for and analyze azimuthal color gradients across spiral arms. The six galaxies analyzed here are NGC 1703 (SBrb), NGC 3001 (SABrsbc), NGC 3059 (SBrsbc), NGC 3513 (SBrsc), NGC 4593 (RSBrsb), and NGC 4603 (SAsc).

NGC 1703: We found one azimuthal color gradient in NGC 1703. Star formation was traced with the reddening free parameter Q, and the dust lane was located with the (g – J) color. This gradient lies at a distance of 1.45 kpc from the center of the galaxy. In order to get some physical parameters of the star formation processes that are taking place in the spiral arms of the galaxies in our sample, we compared the observed Q profiles with the stellar population synthesis models of Bruzual & Charlot (2003). The fitted Q model is shown in figure 1. If one assumes that stars form in the site of the shock, and that they age as they move away from this birthsite, then distance from the dust lane (at constant radius) parameterizes stellar age. In fact, stretching the model Q to the fit the data fixes the ratio between the distance and the age of the stellar population. If, in addition, the rotational velocity is known, it is possible to find the angular velocity of the spiral pattern. The spiral pattern speeds derived from the gradients (under the assumption that star formation is triggered by the density wave) yield theoretical resonance positions that are coincident with the observed spiral end points, in 3 out of 6 spirals. It would be hard to avoid the conclusion that disk dynamics and star formation are fundamentally related in these objects.

The H2O super maser outbursts were observed in Orion KL in active periods 1979-1987 (F ≤ 8 MJy) and 1998-1999 (F ≤ 4 MJy). The line velocity was VLSR = 7.65 km/s and line width ΔV ~ 0.5 km/s. The emission was linear polarized m ≤ 75%. We studied structure of H2O super maser region with VLBI angular resolution 0.1 mas or 0.05 AU. The emission was determined by high organized structure: a chain of bright (Tb ~ 1016K) compact components (~ 0.05 AU), which are distributed along thin S-form structure 27× 0.3 AU, Tb ~ 1011K, Fig. 1. The brightest components have velocities V ~ 7.65 km/s. The components correspond to tangential direction of the rings, velocities of which are V ~ ΩR and rotation period is ~180 yrs. The highly collimated bipolar outflow 9x0.7 AU and comet-like bullets were observed in the quiescent period 1995 (F= 1 kJy) and second activity period 1998-1999. The central compact (0.05 AU) bright (Tb ~ 1016K) source is ejector of bipolar outflow, which surrounded by a torus. Compact bright features are located in the outflow, which velocities are V ~ 10 km/s in the beginning of activity, and V ~ 3 km/s in the end. The helix structure of outflow is determined by precession with period T ~ 10 yrs. The bullets were ejected in the first period activity. Extraordinary changing of the polarization position angle dX/dV ~ 23o/km/s is determined by nozzle emission.