The formation of stars from gas drives the evolution of galaxies. Yet, it remains one of the hardest processes to understand when trying to connect observations of modern and high-redshift stellar and galaxy populations to models of large scale structure formation. It has become clear that the star formation rate at redshifts z > 2 drops off rather more quickly than was thought even five years ago. Theoretical models have tended to overpredict the star formation rate at these high redshifts substantially, primarily due to overcooling. Overcooling in galaxies typically occurs because of unphysical radiative cooling. As a result, insufficient turbulence is driven by stellar feedback in galaxies. I show that such turbulence has the net effect of strongly inhibiting star formation, despite its ability to locally promote star formation by compression. Radiation pressure appears less likely to be a dominant driver of the turbulence than has been argued, but supernova and magnetorotational instabilities remain viable mechanisms. Gravity alone cannot be the main driver, as otherwise well-resolved models without feedback would accurately predict star formation rates. Star formation rate surface density correlates well with observed molecular gas surface density, as well as with other tracers of high density material. Correlation does not, however, necessarily imply causation. In this case, it appears that both molecule formation and star formation occur as a consequence of gravitational collapse, with molecules typically playing an important but not an essential role in cooling. The basic concept that gravitational instability drives star formation remains a true guide through the thickets of complexity surrounding this topic. I finally briefly note that understanding ionization heating and radiation pressure from the most massive stars will likely require much higher resolution models (sub-parsec scale) than resolving supernova feedback.

All stars are born in molecular clouds, and most in giant molecular clouds (GMCs), which thus set the star formation activity of galaxies. We first review their observed properties, including measures of mass surface density, Σ, and thus mass, M. We discuss cloud dynamics, concluding most GMCs are gravitationally bound. Star formation is highly clustered within GMCs, but overall is very inefficient. We compare properties of star-forming clumps with those of young stellar clusters (YSCs). The high central densities of YSCs may result via dynamical evolution of already-formed stars during and after star cluster formation. We discuss theoretical models of GMC evolution, especially addressing how turbulence is maintained, and emphasizing the importance of GMC collisions. We describe how feedback limits total star formation efficiency, ε, in clumps. A turbulent and clumpy medium allows higher ε, permitting formation of bound clusters even when escape speeds are less than the ionized gas sound speed.

Wide-field far-infrared/submillimeter continuum maps of molecular clouds by the Herschel Space Observatory GBS and HOBYS surveys are revealing the star-forming substructures that lead to star formation in dense gas. In particular, these maps have revealed the central role in clouds of filaments, likely formed through turbulent motions. These filaments appear to be non-isothermal and fragment into cores only when their column densities exceed a stability threshold. Organizations of filament networks suggest the relative role of turbulence and gravity can be traced in different parts of a cloud, and filament intersections may lead to larger amounts of mass flow that form the precursors of high-mass stars or clusters.

CO clouds can be non-self-gravitating in high pressure environments, while most should be strongly self-gravitating at low metallicities and ambient pressures. In the LMC, which is HI-rich, GMC formation and destruction should generally include molecule formation and destruction. In M51, which is CO-rich, GMCs grow by coalescence. The Milky Way is between these two situations. In all cases, large clouds form by accretion of gas and smaller clouds independently of the presence of molecules. GMCs in the Milky Way are analogous to dust lanes and spurs in other galaxies. The virial parameter α usually decreases monotonically with increasing cloud mass in surveys, which implies that small scale structure is formed by turbulence. Hierarchies of sequences with decreasing α should be present in cloud complexes from sub-solar masses up to the ambient Jeans mass (107M⊙).

Determining an evolutionary clock for high-mass star formation is an important step towards realizing a unified theory of star formation, as it will enable qualitative studies of the associated high-mass stars to be executed. Our recent studies have shown that masers have great potential to accurately trace the evolution of these regions. We have investigated the relative evolutionary phases associated with the presence of combinations of water, methanol and hydroxyl masers. Comparison between the characteristics of coincident sources has revealed strong evidence for an evolutionary sequence for the different maser species, a result that we now aim to corroborate through comparisons with chemical clocks.

Using our new, large samples of methanol masers at 6.7 GHz (MMB survey; Green et al. (2009)) and 12.2 GHz (Breen et al. 2012), 22 GHz water masers (Breen & Ellingsen 2012), OH masers together with complementary data, we find strong evidence that it is not only the presence or absence of the different maser species that indicates the evolutionary stage of the associated high-mass star formation region (see e.g. Breen et al. (2010)), but that the properties of those masers can give even finer evolutionary details. Most notably, the intensity and velocity range of detected maser emission increases as the star forming region evolves (Breen et al. 2011).

Subsequent work we have undertaken (Ellingsen et al. 2011) has shown that the presence of rare 37.7 GHz methanol masers may signal the end of the methanol maser phase. They show that 37.7 GHz methanol masers are associated only with the most luminous 6.7 and 12.2 GHz methanol masers, which combined with the rarity of these objects is consistent with them being a short lived phase towards the end of the 6.7 GHz methanol maser lifetime.

An independent confirmation of our maser evolutionary timeline can be gained through comparisons with chemical clocks. MALT90 is a legacy survey of 1000s of dense star forming cores at 90GHz, simultaneously observing 16 molecular lines with the Mopra radio telescope (see e.g. Foster et al. 2011). It provides the perfect dataset to test the maser evolutionary timeline due to the targeted lines and the fact that at least one-quarter of the MALT90 sources correspond to maser sites, providing a large enough sample for meaningful analysis. From our preliminary analysis, we find that star formation regions showing similar maser properties also show similar thermal line properties; as would be expected if our evolutionary scenario were accurate.

We have conducted a survey of deuterium fractionation of N2H+, RD(N2H+) ≡ N(N2D+)/N(N2H+), with the Arizona Radio Observatory (ARO) Submillimeter Telescope (SMT) to assess the use of RD(N2H+) as an evolutionary tracer among massive protostellar/cluster cores in early stages. Our sample includes 32 dense cores in various evolutionary stages, from high-mass starless cores (HMSCs), high-mass protostellar objects (HMPOs), to ultra-compact (UC) HII regions, in infrared dark clouds (IRDCs) and high infrared extinction clouds. The results show a decreasing trend in deuterium fractionation with evolutionary stage traced by gas temperature and line width (Fig. 1). A moderate increasing trend of deuterium fractionation with the CO depletion factor is also found among cores in IRDCs and HMSCs. These suggest a general chemical behavior of deuterated species in low- and high-mass protostellar candidates. Upper limits to the ionization degree are also estimated to be in the range of 4 × 10−8 − 5 × 10−6.

We mapped the NH3 (1,1), (2,2), and (3,3) lines of the molecular cloud associated with the Monkey Head Nebula (MHN) with 1′.6 angular resolution using Kashima 34 m telescope. Its kinetic temperature distribution was contrary to what is expected for a molecular cloud at the edge of an expanding H II region and suggested that the massive star associated with S252A compact HII region formed spontaneously rather than through a sequential process.

We performed polarization sensitive VLBI observations of 6.7 GHz methanol masers toward high-mass young stellar objects with clear outflow seen from Spitzer IRAC images in the 4.5 μm band (i.e. EGOs, see Cyganowski et al. 2008) with the EVN to investigate the birthplace of the masers. By comparing direction of the major axis of methanol maser distributions with directions of higher resolution outflow and magnetic field vector, we suggest that the methanol masers toward source G28.83-0.25 may arise from surrounding disk.

We have conducted a mapping survey toward a sample of 17 infrared dust bubbles in three 3 mm waveband CO isotopic lines simultaneously. Such bubbles are candidates to search for triggered massive star formation. We present the data and report preliminary results.

In this report we have presented results of spectral observations of classical T Tauri type stars T Tau and RY Tau. Observational dates were obtained from following sources: spectrograms of the UV range from the IUE archive data, and spectrograms of the visual range obtained in the 2 m telescope of ShAO of the NAS of Azerbaijan (Ismailov et al. 2010). For both of stars on the Scargle method we have searched a periodicity of variations in equivalent widths of emission lines in the optical and UV ranges. In the RY Tau firstly was detected the periodic variability in MgII λ2800 Å emission doublet intensities with a period of 23 days. The observed period had also revealed with the equivalent widths and displacements of components of Hα and H+Hϵ and K CaII emission.

The lines were found to be shifted to short wavelengths as the emission line intensities increased in both UV and optical spectral ranges. The lack of a correlation between the brightness variation and the emission line intensity also suggests that, on the whole, the contribution from the radiation in emission lines for the star RY Tau is insignificant.

On the analysis of T Tau we conclude that there is a significant variation of spectral emission lines in the optical and UV on a time scale of about 33 days and that this variations is periodic. Both of stars shows the periodicity also for observed group of such lines as CIV λ1450 Å, HeII λ 1640 Å, SII λ1756 Å (Ismailov et al. 2010, Ismailov et al. 2011).

Additionally we have carried out spectral energy distributions of this stars in the range 0.36-100 μm which have indicated the excess of spectral radiation in the IR range of spectrum. These excesses of radiations can be explained by the thermal radiation of still unformed bodies at the circumstellar environment. The periodic variability in the spectrum together with the excess of the spectral radiation may be occurred by protoplanets and/or protostars in these young systems. It is showed that possible, planet formation processes mainly to be completed at the time of the formation of classical T Tauri type stars.

We have measured the annual parallax of the water maser source associated with star forming region NGC2264 from observations with VLBI Exploration of Radio Astrometry (VERA). We detected masers at VLSR = 7.2 km s−1. We discussed its driving sources of detected maser spots. One of the maser spots was associated with a centimeter continuum source observed with VLA. Neither optical, infrared nor X-ray sources is catalogued near the spot. The other maser spot is located close to an X-ray source, although there is no optical or infrared counterpart. The proper motion of the former spot was (μα, μδ) = (23.91 ± 4.29, −29.81 ± 4.27) and the proper motion of latter spot was (μα, μδ) = (−0.96 ± 0.58, −6.05 ± 3.06). For the latter spot, the peculiar motion is ∼ 150 km s−1 and it has the high velocity and this may be a jet or an outflow from a young star. The observed parallax is 1.365 ± 0.098 mas, corresponding to the distance of 738+57−50 pc. This value is constant with the photometric distance of NGC2264 previously measured. The fitting result of the parallax is shown in figure 1. We also observed in NH3 (1,1), (2,2), (3,3) lines of NGC2264 with the Kashima 34m telescope. We estimated the star formation efficiency (SFE) of NGC2264 from the dense molecular mass of NH3 and the stellar mass calculated by Teixeira et al. (2012). The SFE is 9 – 12% which is consistent with previous results.

Massive stars govern the evolution of galaxies by providing ionizing photons and energy as well as enriching heavy elements into interstellar medium; however, their formation is still poorly understood. Infrared dark clouds (IRDCs) are cold (< 25 K) and very dense (> 105 cm−3) interstellar clouds which are seen silhouette against the bright Galactic background in mid-IR. With very high column densities (∼ 1023–1025cm−2), IRDCs are believed to be the precursors to massive stars and star clusters (Simon et al. 2006).

We report a remarkable IRDC at (l, b) ∼ (53°.2, 0°.0) which shows a number of bright mid-IR stellar sources along the cloud that are likely young stellar objects (YSOs). There are also several H2 (at 2.122 μm) outflow features in the cloud revealed by UWISH2 (Ukirt Widefield Infrared Survey for H2, Froebrich et al. 2011), in particular where earlier evolutionary stage of YSOs are located. The IRDC was previously partly identified as three separate IRDCs in the MSXDC catalog (Simon et al. 2006), whereas we have found that a long, filamentary cloud extending ∼ 30 pc including these three IRDCs is very well coincident with a CO cloud at v ∼ 23.5 km/s (or at d ∼ 2 kpc) which is clearly distinct from the other velocity components. Therefore, in this study, we investigate the overall star formation activity in this IRDC (IRDC G53.2, hereafter).

We perform the PRF photometry of Spitzer MIPSGAL 24 μm data using MOPEX and build a catalog of YSOs by matching the detected 24 μm sources with published catalogs. The limiting magnitude in 24 μm is ∼ 7.8 mag, and YSO candidates which have counterparts in GLIMPSE I catalog are 354. The YSO candidates are classified using spectral index derived between 2 and 24 μm, following Greene et al. (1994). We also remove the field-star contamination using reference fields where there is no CO cloud; the fraction of each class after reference field analysis is 18, 22, 45, 10, and 5% for Class I, Flat, Class II, Class III, and sources which cannot be classified due to the lack of data. The spatial distribution that earlier classes (i.e., Class I and Flat) are concentrated where far-IR or millimeter emission is strong and larger fraction of Flat objects compared to other low-mass star forming regions (e.g., Evans et al. 2009 and Billot et al. 2010) may imply that the IRDC G53.2 is indeed an active star-forming region in rather early evolutionary stage. Further investigation of each YSO such as SED modeling will reveal detailed information on star formation activity in this intriguing IRDC.

We collected 27 outflows from the literature and found 8 new ones in the FCRAO CO maps of the Taurus molecular cloud. The total kinetic energy of the 35 outflows is found to be about 3% of the gravitational potential energy from the whole cloud. The feedback effect due to the outflows is minor in Taurus.

The environments surrounding nine Wolf-Rayet stars were studied in molecular emission. Expanding shells were detected surrounding these WR stars (see left panels of Figure 1). The average masses and radii of the molecular cores surrounding these WR stars anti-correlate with the WR stellar wind velocities (middle panels of Figure 1), indicating the WR stars has great impact on their environments. The number density of Young Stellar Objects (YSOs) is enhanced in the molecular shells at ∼5 arcmin from the central WR star (lower-right panel of Figure 1). Through detailed studies of the molecular shells and YSOs, we find strong evidences of triggered star formation in the fragmented molecular shells (Liu et al. 2010).

We present our preliminary results on the application of dendrogram statistics to the carbon monoxide PPV map of the giant molecular cloud G333. We obtain the dendrograms at various merging levels and found the clustering of branches is independent from the merging levels. The statistics of intensity distributions show gravity is possibly significant in this cloud and the gas may be sonic. Application of this method to other molecular lines data are required for further analysis of the cloud properties.

High-mass stars are known to be born within giant molecular clouds (GMCs); However, the exact processes involved in forming a high-mass star are still not well understood. It is clear that high-mass stars do not form in isolation, and that the processes surrounding high-mass star formation may affect the environment of the entire molecular cloud. We are studying the GMC associated with RCW 106 (G333), which is one of the most active massive-star formation regions in the Galactic plane. This GMC, located at l = 333° b = − 0.5°, has been mapped in over 20 molecular line transitions with the Mopra radio telescope (83-110 GHz), in Australia, and with the Swedish-ESO Submillimeter Telescope (SEST) in the 1.2 mm cool dust continuum. The region is also within the Spitzer GLIMPSE infrared survey (3.6, 4.5, 5.8, and 8.0 μm) area. We have decomposed the dust continuum using a clump-finding algorithm (CLUMPFIND), and are using the multiple molecular line traditions from the Mopra radio telescope to classify the type and stage of star formation taking place therein. Having accurate physical temperatures of the star forming clumps is essential to constrain other parameters to within useful limits. To achieve this, we have obtained pointed NH3 observations from the Tidbinbilla 70-m radio telescope, in Australia, towards these clumps.

Super H2O outbursts accompany star formation. We have been studying this phenomenon in Orion KL starting in 1971.8.

A new mechanism is proposed for the formation of filament/core structure by ISRF and clumpy molecular cloud interaction. The derived characterizes of the filament/core network is consistent with that produced by the compressive forcing turbulence model.

We present K-band Integral Field Spectroscopy of six high mass young stellar objects (IRAS~18151–1208, AFGL~2136, S106~IRS4, V645 Cyg, IRAS~19065+0526, and G082.5682+ 00.4040) obtained using the adaptive optics assisted NIFS instrument mounted on the Gemini North telescope. The targets are chosen from the Red MSX Source survey led by University of Leeds. The data show the spectral features of Brγ, H2, and gas phase CO emissions and absorptions with a spectral resolution of R ≈ 5500, which allow a three-dimensional spectro-astrometric analysis of the line emissions. We discuss the results of the ionized jets and winds, and rotating CO torus.

We discuss the roles of protostellar outflow feedback in cluster formation using observational data of nearby cluster-forming regions like rho Oph, NGC1333, and Serpens. The observations suggest that observed protostellar outflow feedback appears to be sufficient both to maintain supersonic turbulence and to dynamically support the parent cluster-forming clumps. However, it is not enough to destroy the parent clumps by the current outflow activity. This implies that star formation process may not be too short and probably last at least for several local dynamical times.