The ESA Herschel Space Observatory was successfully launched on 14 May2009, and is currently operating in its routine science phase. Due to the rapidly evolvingnature of the mission at this point a short summary with pointers to more up-to-dateadditional information is provided here.

SPIRE, the Spectral and Photometric Imaging Receiver, is Herschel’ssubmillimetre camera and spectrometer. It comprises a three-band imaging photometeroperating at 250, 350 and 500 μm, and an imaging Fourier TransformSpectrometer (FTS) covering 194–671 μm. The instrument design and itsin-flight performance, calibration and data processing are outlined by Griffin etal. (2010) and Swinyard et al.(2010) in the Astronomy &Astrophysics special issue on first results from Herschel. Here weprovide a brief update on the status of SPIRE including some recent and futureenhancements to the data processing and calibration.

An overview is given of the capabilities of the HIFI instrument on board of the HerschelSpace Observatory, its observing modes and its calibration. With the superb spectralresolution and wide frequency coverage of HIFI a plethora of astrophysical studies aredone.

Recent rapid advancements in wide and deep surveys at millimeter and submillimeter (mm and submm) wavelengths have led to successive discoveries of numerous mm/submm-bright galaxies (SMGs), i.e., dusty extreme starburst population in the early universe. They contribute significantly to the cosmic star formation rate density at z > 1, and evolutionally links to bright quasars and the most massive giant elliptical galaxies have also been suggested. After brief overview of the mm/submm deep surveys to date, characteristics of deep surveys at mm/submm waveband is discussed; the ground-based long-wavelengths (~1 mm) deep surveys are complementarly to short-wavelengths submm surveys with Herschel in order to address the redshift distribution of dusty starburst galaxies. Some recent hot issues of SMGs are also described, including discovery of ultra-bright population, the origin of extreme starburst in SMGs, discovery of a protoquasar-like SMG in the core of a protocluster, and a quest for high-redshift (z > 4) SMGs.

Herschel has opened new windows into studying the evolution of rapidly star-forming galaxies out to high redshifts. Today’s massive starbursts are characterized by star formation rates (SFRs) of  ~100 + M⊙ / yr and display a chaotic morphology and nucleated star formation indicative of a major merger. At z ~ 2, galaxies of similar mass and SFR are characterized by ordered rotation and distributed star formation. The emerging cold accretion paradigm provides an intuitive understanding for such differences. In it, halo accretion rates govern the supply of gas into star-forming regions, modulated by strong outflows. The high accretion rates at high-z drive more rapid star formation, while also making disks thicker and clumpier; the clumps are expected to be short-lived in the presence of strong galactic outflows as observed. Hence equivalently rapid star-formers at high redshift are not analogous to local merger-driven starbursts, but rather to local disks with highly enhanced accretion rates.

We show that for ionization-driven chemistry in molecular clouds with very sub-solar (but non-vanishing) metallicities, OH replaces CO as the most abundant molecule containing at least one heavy element. Old Population-II stars, with observed metallicities ≲10-3times solar, may have formed in such OH-dominated star-forming clouds, shortly after the heavy elements were first produced at the epoch of reionization in the early Universe.

Deep far-infrared photometric surveys studying galaxy evolution and the nature of the cosmic infrared background are a key strength of the Herschel mission. The PACS Evolutionary Probe (PEP) guaranteed time key program obtains deep photometric surveys of some of the key extragalactic multiwavelength fields at wavelengths between 70 and 160 μm. This contribution gives an overview of first science results, illustrating the potential of Herschel in providing calorimetric star formation rates for various high redshift galaxy populations, thus testing and superseding previous extrapolations from other wavelengths, and enabling a wide range of galaxy evolution studies.

The Herschel Key Project SHINING performs a study of the ISM in star forming and activeinfrared bright galaxies (starbursts, AGN, (U)LIRGs, interacting and low metallicitygalaxies) at local and intermediate redshifts. Here we present some surprising andpromising first results from parts of this programme, including spatially resolved PDRdiagnostics, line deficit diagnostics, and large scale molecular outflows traced by the OHmolecule.

We present results of a 1.1 mm deep survey of the AKARI Deep Field South (ADF-S) with AzTEC mounted on the Atacama Submillimetre Telescope Experiment (ASTE). We obtained a map of 0.25 deg2 area with an rms noise level of 0.32–0.71 mJy. This is one of the deepest and widest maps thus far at millimetre and submillimetre wavelengths. We uncovered 198 sources with a significance of 3.5–15.6σ, providing the largest catalog of 1.1 mm sources in a contiguous region. Most of the sources are not detected in the far-infrared bands of the AKARI satellite, suggesting that they are mostly at z ≥ 1.5 given the detection limits. We construct differential and cumulative number counts of the ADF-S, the Subaru/XMM Newton Deep Field (SXDF), and the SSA 22 field surveyed by AzTEC/ASTE, which provide currently the tightest constraints on the faint end. The integration of the differential number counts of the ADF-S find that the contribution of 1.1 mm sources with  ≥1 mJy to the cosmic infrared background (CIB) at 1.1 mm is 12–16%, suggesting that the large fraction of the CIB originates from faint sources of which number counts are not yet constrained. We estimate the cosmic star-formation rate density contributed by 1.1 mm sources with  ≥1 mJy using the differential number counts and find that it is lower by about a factor of 5–10 compared to those derived from UV/optically-selected galaxies at z ~ 2–3. Clustering analyses of AzTEC sources in the ADF-S and the SXDF find that bright (>3 mJy) AzTEC sources are more strongly clustered than faint (< 3 mJy) AzTEC sources and the average mass of dark halos hosting bright AzTEC sources was calculated to be 1013–1014M⊙. Comparison of correlation length of AzTEC sources with other populations and with a bias evolution model suggests that dark halos hosting bright AzTEC sources evolve into systems of clusters at present universe and the AzTEC sources residing the dark halos evolve into massive elliptical galaxies located in the center of clusters.

We discuss observations of the CO J =  1–0 line from massive galaxies in the early Universe. In the submillimeter galaxies (SMGs) we have observed, the CO line intensity ratios rule out low-J emission dominated by subthermally excited gas. This implies that an interpretation of subthermally excited gas from the 2–1/1–0 line ratio, the basis for the mass density conversion factor derived for ULIRGs in the local universe, is unlikely to apply to SMGs. Our observations can be more physically explained by interstellar media with different filling factors for different gas components.

With a goal toward deriving the physical conditions in external galaxies, we present a survey of formaldehyde (H2CO) and ammonia (NH3) emission and absorption in a sample of starburst galaxies using the Green Bank Telescope. By extending well-established techniques used to derive the spatial density in star formation regions in our own Galaxy, we show how the relative intensity of the 110−111 and 211−212 K-doublet transitions of H2CO can provide an accurate densitometer for the active star formation environments found in starburst galaxies (cf. Mangum et al. 2008). Similarly, we employ the well-established technique of using the relative intensities of the (1,1), (2,2), and (4,4) transitions of NH3 to derive the kinetic temperature in starburst galaxies. Our measurements of the kinetic temperature constrained spatial density in our starburst galaxy sample represent the first mean density measurements made toward starburst galaxies. We note a disparity between kinetic temperature measurements derived assuming direct coupling to dust and those derived from our NH3 measurements which points to the absolute need for direct gas kinetic temperature measurements using an appropriate molecular probe. Finally, our spatial density measurements point to a rough constancy to the spatial density (104.5 to 105.5 cm-3) in our starburst galaxy sample. This implies that the Schmidt-Kennicutt relation between LIR and Mdense: (1) Is a measure of the dense gas mass reservoir available to form stars, and (2) Is not directly dependent upon a higher average density driving the star formation process in the most luminous starburst galaxies.

Multi-wavelength observations of galaxies are revolutionising our understanding of the large-scale star formation patterns in galaxies, and have led to renewed theoretical efforts to understand the physical processes which trigger and regulate star formation on galactic scales. This talk reviews recent progress on this problem and highlights open questions for investigation with Herschel and other new facilities.

The dynamics of stars and gas appear markedly different in flocculent, tidally induced and quasi-stationary spiral galaxies. Numerical simulations show that the gas and stars exhibit fairly chaotic dynamics during a tidal interaction, unlike the predictions of density wave theory. For a flocculent galaxy, the stars and gas tend to be situated in potential minima associated with the stellar distribution. I will demonstrate a possible observational test to distinguish between drivers of spiral structure by comparing the ages of stellar clusters, using the results of the simulations as an example.

With high resolution simulations, we are also starting to resolve giant molecular clouds, and can thus relate the properties of these clouds to the presence of spiral structure. Calculations so far suggest that spiral structure simply defines where the clouds form, rather than directly triggering star formation. In the last section of this review, I highlight recent efforts to produce synthetic HI and CO observations from numerical simulations.

The Herschel Dwarf Galaxy Survey investigates the interplay of star formation activity and the the metal-poor gas and dust of local universe dwarf galaxies using FIR and submillimetre imaging spectroscopic and photometric observations in the 50 to 550 μm window of the Herschel Space Observatory. The dust spectral-energy distributions are well constrained with the new Herschel and MIR Spitzer data. A submillimetre excess is often found in low metallicity galaxies, which, if tracing very cold dust, would highlight large dust masses not easily reconciled in some cases, given the low metallicities and expected gas-to-dust mass ratios. The galaxies are also mapped in the FIR fine-structure lines (63 and 145 μm OI, 158 μm CII, 122 and 205 μm NII, 88 μm OIII) probing the low density ionised gas, the HII regions and photodissociation regions. While still early in the mission we can already see, along with earlier studies, that line ratios in the metal-poor ISM differ remarkably from those in the metal-rich starburst environments. In dwarf galaxies, L[CII]/L(CO) (≥104) is at least an order of magnitude greater than in the most metal-rich starburst galaxies. The 88 μm [OIII] line usually dominates the FIR line emission over galaxy-wide scales, not the 158 μm [CII] line which is the dominant FIR cooling line in metal-rich galaxies. All of the FIR lines together can contribute 1% to 2% of the LTIR. The Herschel Dwarf Galaxy survey will provide statistical information on the nature of the dust and gas in low metallicity galaxies and place constraints on chemical evolution models of galaxies.

We present an analysis of the properties of H i holes detected in 20 galaxies that are part of “The H i Nearby Galaxy Survey”. We detected more than 1000 holes in total in the sampled galaxies. The holes are found throughout the disks of the galaxies, out to the edge of the H i disk. We find that shear limits the age of holes in spirals. Shear is less important in dwarf galaxies which explains why H i holes in dwarfs are rounder, on average than in spirals. Shear is particularly strong in the inner part of spiral galaxies, limiting the lifespan of holes there and explaining why we find that holes outside R25 are larger and older. We proceed to derive the surface and volume porosity and find that this correlates with the type of the host galaxy: later Hubble types tend to be more porous. The size distribution of the holes in our sample follows a power law with a slope of aν ~ −2.9. Assuming that the holes are the result of massive star formation, we derive values for the supernova rate (SNR) and star formation rate (SFR) which scales with the SFR derived based on other tracers. If we extrapolate the observed number of holes to include those that fall below our resolution limit, down to holes created by a single supernova, we find that our results are compatible with the hypothesis that H i holes result from star formation.

Within the key project “Herschel M 33 extended survey” (HerM33es), we are studying the physical and chemical processes driving star formation and galactic evolution in the nearby galaxy M 33, combining the study of local conditions affecting individual star formation with properties only becoming apparent on global scales. Here, we present recent results obtained by the HerM33es team. Combining Spitzer and Herschel data ranging from 3.6 μm to 500μm, along with H i, Hα, and GALEX UV data, we have studied the dust at high spatial resolutions of 150 pc, providing estimators of the total infrared (TIR) brightness and of the star formation rate. While the temperature of the warm dust at high brightness is driven by young massive stars, evolved stellar populations appear to drive the temperature of the cold dust. Plane-parallel models of photon dominated regions (PDRs) fail to reproduce fully the [C ii], [O i], and CO maps obtained in a first spectroscopic study of one 2′ × 2′ subregion of M 33, located on the inner, northern spiral arm and encompassing the H ii region BCLMP 302.

The HERschel Inventory of The Agents of Galaxy Evolution (HERITAGE) in the Magellanic Clouds is using the PACS and SPIRE imaging instruments on Herschel to study the life cycle of baryonic matter in galaxies as traced by dust emission. We summarize results based on the early science demonstration data strip in the Large Magellanic Cloud (LMC) from HERITAGE on the interstellar medium and star formation. We find that the dust in the ISM of the LMC is probably different than dust in the Milky Way. We detect the first Stage 0 young stellar object candidates in an external galaxy.

The last quarter century has seen a tremendous increase in quantitative information on the dust in galaxies. Yet, essential knowledge is still lacking. Recent results underline how determinations of dust mass and dust-to-gas ratio in galaxies are still beset by very considerable uncertainties.

We present the results of the Nobeyama Radio Observatory (NRO) M 33 All Disk (30′ × 30′,or 7.3 kpc  ×  7.3 kpc) Survey of Giant Molecular Clouds (NRO MAGiC) based on12CO(J = 1–0) observations using the NRO 45-m telescope and12CO(J = 3–2) observations using the ASTE 10-m telescope.The spatial resolution of the resultant 12CO(J = 1–0) map is193, corresponding to 81 pc, which is sufficient to identify each Giant Molecular Cloud(GMC) in the disk. We found clumpy structures with a typical spatial scale of ~100 pc, corresponding to GMCs, and no diffuse, smoothly distributed componentof molecular gas at this sensitivity.

We obtained a map of the molecular fraction,fmol = ΣH2/(ΣHi + ΣH2),at a 100-pc resolution. This is the first fmol map covering anentire galaxy with a GMC-scale resolution. The correlation betweenfmol and gas surface density shows two distinct sequences.The presence of two correlation sequences can be explained by differences in metallicity,i.e., higher (~2-fold) metallicity in the central region(r <  1.5 kpc) than in the outer parts. Alternatively,differences in scale height can also account for the two sequences, i.e.,increased scale height toward the outer disk.