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Context. Molecular outflows from high-mass young stellar objects provide an excellent way to study the star formation process, and investigate if they are scaled-up versions of their low-mass counterparts.

The dense cores which conceive and cradle young stars can be explored through continuum emission from associated dust grains. We have performed a wide field survey for dust sources at 1.2 millimetres in the ρ Ophiuchi molecular cloud, covering more than 1 square degree in an unbiased fashion. We detect a number of previously unknown sources, ranging from extended cores over compact, starless cores to envelopes surrounding young stellar objects of Class 0, Class I, and Class II type. We analyse the mass distribution, spatial distribution and the potential equilibrium of the cores. For the inner regions, the survey results are consistent with the findings of previous narrower surveys. The core mass function resembles the stellar initial mass function, with the core mass function shifted by a factor of two to higher masses (for the chosen opacity and temperature). In addition, we find no statistical variation in the core mass function between the crowded inner regions and those in more isolated fields except for the absence of the most massive cores in the extended cloud. The inner region contains compacter cores. This is interpreted as due to a medium of higher mean pressure although strong pressure variations are evident in each region. The cores display a hierarchical spatial distribution with no preferred separation scale length. However, the frequency distribution of nearest neighbours displays two peaks, one of which at 5000 AU can be the result of core fragmentation. The orientations of the major axes of cores are consistent with an isotropic distribution. In contrast, the relative orientations of core pairs are preferentially in the NW-SE direction on all separation scales. These results are consistent with core production and evolution in a turbulent environment. Finally, we report the discovery of a new, low-mass Class 0 object candidate and its CO outflow.

We present an unbiased search for molecular hydrogen emission in the L1688 cloud within the ρ Ophiuchi molecular cloud complex. Our near-infrared survey covers a connected region of extent 35´ $\times$35´. We detect several new H2flows but the total number of detected outflows is low and is consistent with the paucity of Class 0 and Class 1 sources in the molecular cloud. From the spatial distribution, their collimation and the individual shapes of the bow shocks, we suggest possible candidates for the outflow sources. Most of the candidate driving sources are deeply embedded in dense cores of the molecular cloud. A very young outflow arises from the newly discovered Class 0 source MMS 126. Two major outflows in the NE–SW direction arise from the YLW 15 and YLW 16 Class I sources. Three additional outflows, which both extend over several arcminutes, arise from the Class I sources YLW 31 and YLW 52. Flow directions are generally NE–SW, perpendicular to the elongation directions of the cloud filaments. The apparent extents of molecular flows are related to either the widths of cloud filaments or to the separation between filaments. The estimated jet power needed to continuously drive and excite the detected portions of the shocked H2outflows lies in the range 0.02-0.2 $L_\odot$. Given the critical dependence on the environment, however, the total sizes and powers of the outflows may be considerably larger.

We present narrow-band near-infrared images of the high-mass star formation region S233IR. We detect several groups of molecular hydrogen knots aligned with known outflows. Images in vibrationally-excited H2and [Fe II] reveal the excitation distributions across the main two conspicuous bow shocks. Emission from the [Fe II] line is strong and located at the apex of both bow shocks as well as other locations within the northern bow where we distinguish a compact Mach disk through its [Fe II] emission. The H2emission is not restricted to the bow wings but distinct components are detected near the bow apices. The data are broadly comparable to steady bow shocks of speed 60–80 km s-1possessing dissociative caps and C-type flanks. Nevertheless, non-steady bow shock behavior is essential to interpret all aspects of the bow structures. In this respect, the S233 bow caps may be in the neutral transformation stage from J-type to C-type.

Plateau de Bure Interferometer high-spatial resolution CO observations combined with near-infrared H2data disentangle at least seven (possibly even nine) molecular outflows in the massive star-forming region IRAS?19410+2336. Position–velocity diagrams of the outflows reveal Hubble-like relationships similar to outflows driven by low-mass objects. Estimated accretion rates are of the order of $10^{-4}\,M_{\odot}$?yr-1, sufficiently high to overcome the radiation pressure and form massive stars via disk-mediated accretion processes. The single-dish large-scale mm continuum cores fragment into several compact condensations at the higher spatial resolution of the PdBI which is expected due to the clustering in massive star formation. While single-dish data give a simplified picture of the source, sufficiently high spatial resolution resolves the structures into outflows resembling those of low-mass star-forming cores. We interpret this as further support for the hypothesis that massive stars do form via disk-accretion processes similar to low-mass stars.

We present results of the first sub-arcsec resolution mid infrared survey of the southern hemisphere giant H iiregion NGC 3603. We have observed selected fields in the vicinity of the OB cluster at wavelengths of 11.9 μm and 18 μm using TIMMI 2 mounted on the ESO 3.6 m telescope. These fields comprise areas with dense molecular cores, embedded near infrared sources as well as several OH, H2O and CH3OH maser sources, which give indications of ongoing star formation processes. We report the detection of 36 mid infrared point sources and additionally provide flux measurements for 42 knots of diffuse emission. In the area surveyed the protostar IRS 9A is found to be the most luminous source at both 11.9 μm and 18 μm. Located in its immediate vicinity two more sources (IRS 9B and IRS 9C) also exhibit significant 11.9 μm and 18 μm emission, thus providing further indications for IRS 9 being an association of protostars in its own right. Several other 11.9 μm point sources are related to near infrared sources with strong K-band excess emission and/or to maser sources, which classifies them as young sources, too. In contrast, the second strongest 11.9 μm source, IRS 4, appears to be in a more evolved stage. Towards the center of the OB cluster we observe mid infrared emission arising from the three Wolf-Rayet stars WR 43abc, providing evidence for dust production and/or the presence of plasma in their circum stellar envelopes. Spread all over the cluster, we detect a number of sources with mid infrared fluxes close to the sensitivity limit (~0.01 Jy) of our 11.9 μm data, which apparently have very red $K-N$colours. We suggest that these sources are circum stellar disks which are externally heated by the nearby massive stars. Towards the south and west of the OB cluster, large amounts of diffuse emission are found closely correlated with ionized material. We identify at least 7 shocks and ionization fronts, reflecting the enormous impact of the fast stellar winds and ionizing photons, originating from the massive cluster stars, on the adjacent gas and dust. This is impressively emphasized by the shocked and ionized material associated with the heads of the two prominent pillars. Both pillars are easily seen in our 11.9 μm and 18 μm data: the western one rather prominent in emission, the eastern one more pronounced in absorption against a strong diffuse mid infrared background. Among those sources, for which our data do not reveal any point-like mid infrared counterpart, are IRS 1 as well as the three “proplyds”. However, at least for “proplyd” 3 we detect extended, rim-like 11.9 μm emission. Therefore, we consider it likely that NGC 3603's “proplyds” simply represent scaled-down versions of the neighbouring pillars, i.e. remnant density enhancements of the pristine molecular cloud which to date were able to resist the ionizing and photoevaporating radiation from the nearby OB stars.

We report the detection of hard X-ray emission (>2 keV) from a number of point sources associated with the very young massive star-forming region IRAS 19410+2336. The X-ray emission is detected from several sources located around the central and most deeply embedded mm continuum source, which remains undetected in the X-ray regime. All X-ray sources have K-band counterparts, and those likely belonging to the evolving massive cluster show near-infrared colors in the 2MASS data indicative of pre-main-sequence stages. The X-ray luminosities around 1031erg s-1are at the upper end of luminosities known for low-mass pre-main-sequence sources, and mass estimates based on the infrared data indicate that at least some of the X-ray detected sources are intermediate-mass objects. Therefore, we conclude that the X-ray emission is due to intermediate-mass pre-main-sequence Herbig Ae/Be stars or their precursors. The emission process is possibly due to magnetic star-disk interaction as proposed for their low-mass counterparts.

We present new 1.2 mm continuum maps and near- and mid-infrared images of the cometary cloud L1616 located to the west of the Orion OB associations and apparently shaped by the winds and radiation coming from the massive, hot stars in the OB association. The new data reveal evidence for ongoing star formation in the cloud in addition to the known cluster of somewhat more evolved stars illuminating the NGC 1788 reflection nebula in the head of the cometary cloud. The 1.2 mm survey reveals a tight group of dust continuum sources, the brightest of which is seen to drive a powerful near-infrared H2jet, apparently a very young protostar of Class 0 type. The location of the newly discovered protostar with respect to the older cluster and the direction towards the OB association suggests an age sequence due to a wave of star formation driven through the cloud and triggered by the impact of the nearby OB association: the older generation of stars is located on the side of the cloud directly facing the OB association, whereas a new generation of star formation takes place deeper within the cloud.

We have made an unbiased imaging survey of a 1.2 square degree area in the Orion A giant molecular cloud searching for molecular hydrogen emission line features seen in the $v=1$–0 S(1) line at a wavelength of 2.12 μm originating in shocks in outflows from young stellar objects. This survey provides for the first time an unbiased census of outflows over a significant portion of a giant molecular cloud, and yields a sample of outflows free from selection effects and with all objects located at roughly the same, well-known distance. In this paper, we present the data gathered in the course of the survey, provide a comprehensive list of all molecular hydrogen emission features found, and give a list of the 76 candidate outflows identified in the data set.

We present near-infrared and millimetre observations of the large Bok globule CB 34. Two long parallel trails of H2knots are discovered on wide-field images in the 1–0 S(1) 2.12 μm emission line. These parsec scale H2jets extend to the edge of the dark globule where they disappear without the trace of bow shocks. This suggests that the outflows physically extend into a lower density ambient medium where their terminating bows are beyond present detection limits. The two outflows are extremely well collimated and parallel to within 3°. The outflow mechanical luminosity, derived from CO measurements, and the shocked luminosity, estimated from the H2emission, are similar, consistent with jet-driven non-evolving outflow structure. The jets appear to originate from the densest cores, as observed in H13CO+line emission. A central concentration of reddened stars and a lower density halo of less reddened stars within the globule are revealed by JHKphotometry. Disordered motions are observed in the CO $J=2-1$line velocity channel maps and can be driven by the power of the outflows emanating from dense cores. We sketch a picture for the star formation history of the globule in which two star phases have been formed. A weak diffuse emission halo is detected in the near infrared with colours consistent with either scattered light or a ro-vibrational H2cascade. We propose that the halo is produced by ongoing H2formation. Cloud evolution and halo H2formation timescales are then both a few $\times$105yr. Thus, we may be witnessing the formation of a molecular cloud out of diffuse atomic gas. This supports a scheme in which this Bok globule has formed independently rather than through dislocation from a nearby molecular cloud.

We report discovery of a new young stellar object driving a point-symmetric, near-infrared jet and molecular outflow. The YSO is associated with IRAS 06047-1117 and is embedded in a dense molecular cloud core located southeast of Orion A. The jet is seen in the H2$v=1{-}0$line at 2.12 μm and extends over a total length of about ~0.4 pc. The driving source is optically invisible and has near-infrared colors and a spectral energy distribution consistent with a Class I source with an estimated luminosity of 6 $L_{\odot}$. Two Herbig-Haro objects are seen in Hαimages located close to the positions of maximum H2emission.

The ROSAT Deep Surveys in the direction of the Lockman Hole are the most sensitive X-ray surveys performed with the ROSAT satellite. About 70-80% of the X-ray background has been resolved into discrete sources at a flux limit of ~10-15erg cm-2s-1in the 0.5-2.0 keV energy band. A nearly complete optical identification of the ROSAT Deep Survey (RDS) has shown that the great majority of sources are AGNs. We describe in this paper the ROSAT Ultra Deep Survey (UDS), an extension of the RDS in the Lockman Hole. The Ultra Deep Survey reaches a flux level of 1.2 10-15erg cm-2s-1in 0.5-2.0 keV energy band, a level ~4.6 times fainter than the RDS. We present nearly complete spectroscopic identifications (90% ) of the sample of 94 X-ray sources based on low-resolution Keck spectra. The majority of the sources (57) are broad emission line AGNs (type I), whereas a further 13 AGNs show only narrow emission lines or broad Balmer emission lines with a large Balmer decrement (type II AGNs) indicating significant optical absorption. The second most abundant class of objects (10) are groups and clusters of galaxies (~11% ). Further we found five galactic stars and one "normal"emission line galaxy. Eight X-ray sources remain spectroscopically unidentified. We see no evidence for any change in population from the RDS survey to the UDS survey. The photometric redshift determination indicates in three out of the eight sources the presence of an obscured AGN. Their photometric redshifts, assuming that the spectral energy distribution (SED) in the optical/near-infrared is due to stellar processes, are in the range of $1.2 \le z \le 2.7$. These objects could belong to the long-sought population of type 2 QSOs, which are predicted by the AGN synthesis models of the X-ray background. Finally, we discuss the optical and soft X-ray properties of the type I AGN, type II AGN, and groups and clusters of galaxies, and the implication to the X-ray background.

Aims. A census of molecular hydrogen flows across the entire Orion?A giant molecular cloud is sought. With this paper we aim to associate each flow with its progenitor and associated molecular core, so that the characteristics of the outflows and outflow sources can be established.Methods. We present wide-field near-infrared images of Orion?A, obtained with the Wide Field Camera, WFCAM, on the United Kingdom Infrared Telescope. Broad-band K and narrow-band H2?1-0S(1) images of a contiguous ~8?square degree region are compared to mid-IR?photometry from the Spitzer Space Telescope and (sub)millimetre dust-continuum maps obtained with the MAMBO and SCUBA bolometer arrays. Using previously-published H2?images, we also measured proper motions for H2?features in 33?outflows, and use these data to help associate flows with existing sources and/or dust cores.Results. Together these data give a detailed picture of dynamical star formation across this extensive region. We increase the number of known H2?outflows to?116. A total of 111?H2?flows were observed with Spitzer; outflow sources are identified for 72 of them (12?more H2?flows have tentative progenitors). The MAMBO 1200??m?maps cover 97?H2?flows; 57?of them (59%) are associated with Spitzer sources and either dust cores or extended 1200??m?emission. The H2?jets are widely distributed and randomly orientated. The jets do not appear to be orthogonal to large-scale filaments or even to the small-scale cores associated with the outflow sources (at least when traced with the 11???resolution of the 1200??m?MAMBO observations). Moreover, H2?jet lengths?(L) and opening angles?(?) are not obviously correlated with indicators of outflow source age?? source spectral index, ??(measured from mid-IR photometry), or (sub)millimetre core flux. It seems clear that excitation requirements limit the usefulness of H2as a tracer of L and ? (though jet position angles are well defined).Conclusions. We demonstrate that H2jet sources are predominantly protostellar sources with flat or positive mid-IR spectral indices, rather than disc-excess (or T?Tauri) stars. Most protostars associated with molecular cores drive H2?outflows; however, not all molecular cores are associated with protostars or H2?jets. On statistical grounds, the H2?jet phase may be marginally shorter than the protostellar phase, though it must be considerably (by an order of magnitude) shorter than the prestellar phase. In terms of range and mean value of ?, H2?jet sources are indistinguishable from protostars. The spread in ? observed for both protostars and H2?outflow sources is probably a function of inclination angle as much as source age. The few true protostars without H2?jets are almost certainly more evolved than their H2-jet-driving counterparts, although these later stages of protostellar evolution (as the source transitions to being a ?disc-excess? source) must be very brief, since a large fraction of protostars do drive H2?flows. We also find that the protostars that power molecular outflows are no more (nor no less) clustered than protostars that do not. This suggests that the H2?emission regions in jets and outflows from young stars weaken and fade very quickly, before the source evolves from protostar to pre-main-sequence star, and on time-scales much shorter than those associated with the T?Tauri phase, the Herbig-Haro jet phase, and the dispersal of young stellar objects.

Context.Infrared dark clouds are massive, dense clouds seen in extinction against the IR Galactic background. Many of these objects appear to be on the verge of star and star cluster formation.

We present 70 and 160 μm Herschelscience demonstration images of a field in the Orion A molecular cloud that contains the prototypical Herbig-Haro objects HH 1 and 2, obtained with the Photodetector Array Camera and Spectrometer (PACS). These observations demonstrate Herschel's unprecedented ability to study the rich population of protostars in the Orion molecular clouds at the wavelengths where they emit most of their luminosity. The four protostars previously identified by Spitzer3.6–40 μm imaging and spectroscopy are detected in the 70 μm band, and three are clearly detected at 160 μm. We measure photometry of the protostars in the PACS bands and assemble their spectral energy distributions (SEDs) from 1 to 870 μm with these data, Spitzerspectra and photometry, 2MASS data, and APEX sub-mm data. The SEDs are fit to models generated with radiative transfer codes. From these fits we can constrain the fundamental properties of the protostars. We find luminosities in the range 12–84 $L_{\odot}$and envelope densities spanning over two orders of magnitude. This implies that the four protostars have a wide range of envelope infall rates and evolutionary states: two have dense, infalling envelopes, while the other two have only residual envelopes. We also show the highly irregular and filamentary structure of the cold dust and gas surrounding the protostars as traced at 160 μm.

The NGC 1999 reflection nebula features a dark patch with a size of ~10 000 AU, which has been interpreted as a small, dense foreground globule and possible site of imminent star formation. We present HerschelPACS far-infrared 70 and 160 μm maps, which reveal a flux deficit at the location of the globule. We estimate the globule mass needed to produce such an absorption feature to be a few tenths to a few ${M}_{\odot}$. Inspired by this Herschelobservation, we obtained APEX LABOCA and SABOCA submillimeter continuum maps, and Magellan PANIC near-infrared images of the region. We do not detect a submillimer source at the location of the Herschelflux decrement; furthermore our observations place an upper limit on the mass of the globule of ~2.4×10-2${M}_{\odot}$. Indeed, the submillimeter maps appear to show a flux depression as well. Furthermore, the near–infrared images detect faint background stars that are less affected by extinction inside the dark patch than in its surroundings. We suggest that the dark patch is in fact a hole or cavity in the material producing the NGC 1999 reflection nebula, excavated by protostellar jets from the V 380 Ori multiple system.

We present 70 and 160 μm Herschelscience demonstration images of a field in the Orion A molecular cloud that contains the prototypical Herbig-Haro objects HH 1 and 2, obtained with the Photodetector Array Camera and Spectrometer (PACS). These observations demonstrate Herschel's unprecedented ability to study the rich population of protostars in the Orion molecular clouds at the wavelengths where they emit most of their luminosity. The four protostars previously identified by Spitzer3.6–40 μm imaging and spectroscopy are detected in the 70 μm band, and three are clearly detected at 160 μm. We measure photometry of the protostars in the PACS bands and assemble their spectral energy distributions (SEDs) from 1 to 870 μm with these data, Spitzerspectra and photometry, 2MASS data, and APEX sub-mm data. The SEDs are fit to models generated with radiative transfer codes. From these fits we can constrain the fundamental properties of the protostars. We find luminosities in the range 12–84 $L_{\odot}$and envelope densities spanning over two orders of magnitude. This implies that the four protostars have a wide range of envelope infall rates and evolutionary states: two have dense, infalling envelopes, while the other two have only residual envelopes. We also show the highly irregular and filamentary structure of the cold dust and gas surrounding the protostars as traced at 160 μm.

The NGC 1999 reflection nebula features a dark patch with a size of ~10 000 AU, which has been interpreted as a small, dense foreground globule and possible site of imminent star formation. We present HerschelPACS far-infrared 70 and 160 μm maps, which reveal a flux deficit at the location of the globule. We estimate the globule mass needed to produce such an absorption feature to be a few tenths to a few ${M}_{\odot}$. Inspired by this Herschelobservation, we obtained APEX LABOCA and SABOCA submillimeter continuum maps, and Magellan PANIC near-infrared images of the region. We do not detect a submillimer source at the location of the Herschelflux decrement; furthermore our observations place an upper limit on the mass of the globule of ~2.4×10-2${M}_{\odot}$. Indeed, the submillimeter maps appear to show a flux depression as well. Furthermore, the near–infrared images detect faint background stars that are less affected by extinction inside the dark patch than in its surroundings. We suggest that the dark patch is in fact a hole or cavity in the material producing the NGC 1999 reflection nebula, excavated by protostellar jets from the V 380 Ori multiple system.