Submillimeter dust continuum emission traces high molecular column densities and, thus,dense cloud regions in which new stars are forming. Surveys of the Galactic plane in suchemission have the potential of delivering an unbiased view of high-mass star formationthroughout the Milky Way. The location of the APEX telescope on the Chajnantor plateau inChile is ideally suited for mapping the inner Galaxy. ATLASGAL, The APEX Telescope LargeArea Survey of the Galaxy at 870 μm, is a survey of the Galactic planeusing the Large APEX Bolometer Camera (LABOCA), in the Galactic longitude and latituderanges of  ±60 and  ±1.5°, respectively. This survey is providing an unbiased sample ofcold dusty clumps in the Galaxy at submillimeter wavelength and a variety of molecularline follow-up observations have been started to characterize the physical and chemicalconditions in the newly found clumps. Here, first results from this survey and itsfollow-up programs are described.

Over the past 3 years, we have conducted a survey of 100 square degrees of the southern Galactic plane with the Mopra radiotelescope (HOPS). The survey includes observations of multiple spectral lines in the 12 mm band, with the most important being the water maser transition at 22.2 GHz and the non-metastable inversion transitions of ammonia. We report on initial results from HOPS, including the detection of 540 water masers, about two-thirds of which appear to be new detections. We also find widespread emission in the NH3 (1,1) line, as well as detec tions in the NH3 (2,2), (3,3), (6,6) and (9,9) lines.

Photodissociation regions (PDRs) are gas phases in which far-ultraviolet radiation plays a significant role in the heating and/or chemistry (Tielens & Hollenbach 1985). X-ray dissociation regions (XDRs) are regions in which X-rays dominate the heating and/or chemistry (Moloney et al. 1996). Much progress has been mode in modeling PDRs (e.g., Röllig et al. 2007) and XDRs (e.g., Meijerink et al. 2007) and the models predict several line intensities and line ratios of atomic and molecular species that are good diagnostics for discriminating between the two. I will discuss the theoretical models in light of the most recent observations.

We study the relationship between the H2 and CO abundances in simulated molecular clouds using a fully dynamical model of magnetized turbulence coupled to a detailed chemical network. We find that the CO-to-H2 conversion factor for a given molecular cloud, the so-called X-factor, is determined primarily by the mean extinction of the cloud, rather than by its metallicity. Our results explain the discrepancy observed in low metallicity systems between cloud masses derived from CO observations and other techniques such as infrared emission, and predict that CO-bright clouds in low metallicity systems should be systematically larger and/or denser than Milky Way clouds.

We show that the XCO factor, which converts the CO luminosityinto the column density of molecular hydrogen has similar values for dense, fullymolecular gas and for diffuse, partially molecular gas. We discuss the reasons of thiscoincidence and the consequences for the understanding of the interstellar medium.

We report a study of the relation between dust and gas over a 100 deg2 area inthe Taurus molecular cloud. We compare the H2 column density derived from dustextinction with the CO column density derived from the 12CO and 13COJ = 1 → 0 lines. We derive the visual extinction from reddeningdetermined from 2MASS data. The comparison is done at an angular size of 200′′,corresponding to 0.14 pc at a distance of 140 pc. We find that the relation between visualextinction AV and N(CO) is linear betweenAV ≃ 3 and 10 mag in the region associated with theB213–L1495 filament. In other regions the linear relation flattens forAV ≳ 4 mag. Accounting for the observed relation between thecolumn density of CO and CO2 ices and AV, we find alinear relationship between the column of carbon monoxide and dust for observed visualextinctions up to the maximum value in our data  ≃23  mag.

The Herschel HIFI Key Program, Galactic Observations ofTerahertz C+ (GOT C+) is a survey of[CII] 1.9 THz emission throughout the Galaxy. Comparison of the first results of thissurvey with HI and CO isotopomer emission reveals excess [CII] emission beyond thatexpected from HI and CO layers alone, and is best explained as coming from a hidden layerof H2 gas, the so-called ISM “dark gas”.

We summarize the first results from the Herschel Gould Belt survey, one of the largest key projects with the Herschel Space Observatory. Our early findings confirm the existence of a close relationship between the prestellar core mass function (CMF) the stellar initial mass function (IMF). Furthermore, they suggest a scenario according to which the formation of prestellar cores occurs in two main steps: 1) complex networks of long, thin filaments form first, probably as a result of interstellar MHD turbulence; 2) the densest filaments then fragment and develop prestellar cores via gravitational instability.

The understanding of the star formation is still on progress. Especially, the formation of high-mass stars is much less understood than the low-mass case. Water, one of the most important molecules in the Universe, might elucidate key episodes in the process of stellar birth, and especially could be a major role in the formation of high-mass stars. We present here the first results of the WISH program, dedicated to the water study in star-forming regions with Herschel, concerning the massive star-forming regions.

Water is a key molecule for tracing physical and chemical processes in star-forming regions. The key program “Water in star-forming regions with Herschel” is observing several water transitions towards low-mass protostars with HIFI. Results regarding the 557 GHz transition of water are reported here showing that the line is surprisingly broad, and consists of several different velocity components. The bulk of the emission comes from shocks, where the abundance is increased by several orders of magnitude to  ~10-4. The abundance of water in the outer envelope is determined to  ~10-8, whereas only an upper limit of 10-5 is derived for the inner, warm envelope.

Within the Herschel key project “The Warm And Dense ISM” (WADI) we systematically observea number of prominent photon-dominated regions (PDRs) to measure the impact of varying UVfields on the energy balance, the chemical and dynamical structure of heated molecularclouds.

We give a brief review of recent work on outflows and infall in regions of high mass starformation.

We summarize the first results from the Herschel Open time Key Program GaS in Protoplanetary Systems (GASPS, P.I.W. Dent). GASPS aims to determine the gas and dust content of  ~240 planet-forming discs with ages 1–30 Myrs in a systematic fashion. Photometry in the far-IR and low-resolution spectroscopy of the fine-structure emissions of OI and CII are obtained with the PACS instrument on board the European space telescope Herschel. Initial modelling of the Herschel and complementary observations of the classical T Tauri star TW Hya and of the Herbig Ae star HD 169142 are presented.

This paper reviews the first results of observations of H2O line emission withHerschel-HIFI towards high-mass star-forming regions, obtained within the WISH guaranteedtime program. The data reveal three kinds of gas-phase H2O: “cloud water” incold tenuous foreground clouds, “envelope water” in dense protostellar envelopes, and“outflow water” in protostellar outflows. The low H2O abundance(10-10−10-9) in foreground clouds and protostellar envelopes isdue to rapid photodissociation and freeze-out on dust grains, respectively. The outflowsshow higher H2O abundances (10-7−10-6) due to grainmantle evaporation and (probably) neutral-neutral reactions.

In this brief review we discuss how some of our basic understanding of chemical processes in interstellar medium has received a boost from the Herschel Space Observatory. With Herschel in operations for over 1 year, it is still early to discuss the full impact of new results and instead I demonstrate the new science enabled by near-complete spectroscopic access to sub-millimeter to far-infrared wavelengths.

The paper focuses on collisional excitation rates of molecules by He, H2 andelectrons relevant to the interstellar medium, it discusses currently available data,presents very recent work and outlines new work being carried out in order to provide easyaccess to these molecular data. In particular outlines of the latest developments in theBASECOL database and of the “Virtual Molecular Data Centre” capabilities are provided.

Dust grains are an important component of star forming regions and are therefore a powerful tracer of the location and mass of prestellar cores. However, the properties of dust grains in such dense regions are poorly constrained, causing difficulties in the modeling of the physical properties of dense cores. One of the fundamental properties of dust grains is their size distribution, which is relatively well-known in the diffuse ISM but not very well constrained in dense regions. Indirect evidence is consistent with the presence of large grains; however, to date, interpreting submm emission measurements or absorption in the near-infrared (NIR)/mid-infrared (MIR) domains is difficult due to the ambiguity between density (and temperature if in emission) variations and grain properties. Recently, we have discovered emission at 3.6 and 4.5 μm towards the densest parts of L183. We have named this effect coreshine, by analogy with the cloudshine, seen at the surface of dark clouds in the near-infrared. This 3.6 and 4.5 μm emission can only be explained by the strong scattering of background interstellar radiation due to micron-size grains and show that the average grain size increase needs to be proportional to the cloud core density gradient to reproduce the observations. We show that the scattering effect is very sensitive to the grain size distribution; therefore these observations will provide a new tool with which to study grain properties. In a subsequent search through about a hundred of dense low mass core regions in the Spitzer Heritage Archive, we find that the effect is present in  ~50% of the sources, including prestellar cores, Class 0 and I sources with or without outflow, showing that the coreshine effect should rapidly become a general observational method to investigate dark cloud and grain properties.

Hot core chemistry, characterized by the evaporation of icy mantle molecules from dust grains and subsequent gas-phase chemistry, seems ubiquitous in hot, dense clouds. Hot core molecules have been observed, not only in high-mass star-forming regions, but also in protoplanetary disks, shocks in young stellar outflows, and so on. Here, we study grain-surface chemistry and chemistry in hot gas in disks and outflows. Our results suggest that observations of molecular lines by the forthcoming ALMA and other facilities will give us information on, for example, grain-surface chemistry in the outer disk, turbulent mixing in the inner disk, and the physical and chemical conditions at the launching points of outflows.

We have found low-mass star-forming regions with extremely high abundances of carbon-chain molecules. Those are L1527 in Taurus and IRAS 15398-3359 in Lupus. In these sources, carbon-chain molecules would be regenerated in a lukewarm region near the protostar, triggered by the evaporation of the CH4 ice. This is new carbon-chain chemistry (Warm Carbon-Chain Chemistry: WCCC) in contrast to the conventional one applied to cold starless cores. Our interferometric observation shows a steep abundance increase of the carbon-chain molecules inward of a radius of 500 − 1000 AU from the protostar. This size corresponds to the temperature range of 20–30 K, which is close to the evaporation temperature of CH4 (25 K). This result is therefore consistent with the WCCC. The discovery of the WCCC sources demonstrates chemical diversity of low-mass star-forming regions. In particular, a remarkable contrast can be seen between the WCCC and the hot corino chemistry known in IRAS 16293-2422. A possible origin for the diversity would be the time scale of the starless-core phase; a shorter contraction time would result in the WCCC. Relatively low deuterium fractionation ratios in L1527 also support this scenario. If so, chemical compositions will tell us an important clue to understand the source-to-source variation of star-formation processes.

Molecules containing one or a few hydrogen atoms and a heavier atom (hydrides) have been predicted to trace FUV radiation. In some chemical models, FUV emission by the central object or protostar of a star forming region greatly enhances some of the hydride abundances. Two massive regions, W3 IRS5 and AFGL 2591, have been observed in hydride lines by HIFI onboard the Herschel Space Observatory. We use published results as well as new observations of CH+ towards W3 IRS5. Molecular column densities are derived from ground state absorption lines, radiative transfer modeling or rotational diagrams. Models assuming no internal FUV are compared with two-dimensional models including FUV irradiation of outflow walls. We confirm that the effect of FUV is clearly noticeable and greatly improves the fit. The most sensitive molecules to FUV irradiation are CH+ and OH+, enhanced in abundance by many orders of magnitude. Modeling in addition also full line radiative transfer, Bruderer et al. (2010b) achieve good agreement of a two-dimensional FUV model with observations of CH+ in AFGL 2591. It is concluded that CH+ and OH+ are good FUV tracers in star-forming regions.