Context. Molecular oxygen, O-2, has been expected historically to be an abundant component of the chemical species in molecular clouds and, as such, an important coolant of the dense interstellar medium. However, a number of attempts from both ground and from space have failed to detect O-2 emission.Aims. The work described here uses heterodyne spectroscopy from space to search for molecular oxygen in the interstellar medium.Methods. The Odin satellite carries a 1.1m sub-millimeter dish and a dedicated 119 GHz receiver for the ground state line of O-2. Starting in 2002, the star forming molecular cloud core rho OphA was observed with Odin for 34 days during several observing runs.Results. We detect a spectral line at v(LSR)= + 3.5 km s(-1) with = vFWHM = 1.5 km s(-1), parameters which are also common to other species associated with rho OphA. This feature is identified as the O-2 (N-J = 1(1)- 1(0)) transition at 118 750.343 MHz.Conclusions. The abundance of molecular oxygen, relative to H-2, is 5 x 10(-8) averaged over the Odin beam. This abundance is consistently lower than previously reported upper limits.

NGC2024 is a star-forming region in Orion B that contains a dense molecular ridge. A number of dense cores are seen by their dust emission. This area is investigated using observations of four formaldehyde transitions-namely, 3(03) -> 2(02), 3(22) -> 2(21), 5(05) -> 4(04), and 5(23) -> 4(22). Maps of the ridge are used to provide temperatures and densities, with a focus on the dense-core positions. The formaldehyde transition ratios 3(03) -> 2(02)/3(22) -> 2(21) and 5(05) -> 4(04)/5(23) -> 4(22) offer measurements of the kinetic temperature, while the ratio 3(03) -> 2(02)/5(05) -> 4(04) allows the evaluation of number densities. The resulting temperatures are very warm (45-85 K), with no observed variation between the core centers and their envelopes. H2CO number densities of similar to 2 x 10(6) cm(-3) at far-infrared (FIR) core positions and H2CO column densities in the range of 6 x 10(14) to 1 x 10(15) cm(-2) are derived. Using the derived properties in combination with previous submillimeter continuum data, core masses of similar to 2 M-circle dot are found within a 15 '' beam size. H2CO fractional abundances are calculated and resemble previous values found in similar star-forming regions-between 2 x 10(-9) and 5 x 10(-9). The virial theorem applied to FIR cores 3, 4, 5, and 6 suggests that all four cores are unstable against gravitational collapse.

We present results from a survey of a 1300 arcmin2 region of the Orion B South molecular cloud, including NGC 2024, NGC 2023, and the Horsehead Nebula (B33), obtained using the Submillimetre Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope (JCMT). Submillimeter continuum observations at 450 and 850 μm are discussed. Using an automated algorithm, 57 discrete emission features ("clumps") are identified in the 850 μm map. The physical conditions within these clumps are investigated under the assumption that the objects are in quasi-hydrostatic equilibrium. The best-fit dust temperature for the clumps is found to be Td = 18 ± 4 K, with the exception of those associated with the few known far-infrared sources residing in NGC 2024. The latter internally heated sources are found to be much warmer. In the region surrounding NGC 2023, the clump dust temperatures agree with clump gas temperatures determined from molecular line excitation measurements of the CO molecule. The bounding pressure on the clumps lies in the range log(k-1P cm3 K-1) = 6.1 ± 0.3. The cumulative mass distribution is steep at the high-mass end, as is the stellar initial mass function. The distribution flattens significantly at lower masses, with a turnover around 3-10 M☉.

SCUBA-2 is a wide-field camera due to replace the Submillimetre Common User Bolometer Array (SCUBA) on the James Clerk Maxwell telescope in 2006. Unlike previous sub-millimetre imagers which have used discrete bolometers, SCUBA-2 has two DC-coupled, monolithic, filled arrays with a total of ˜10,000 bolometers. It will offer simultaneous imaging of a 50 arcmin2 field of view at wavelengths of 850 and 450 microns. SCUBA-2 is expected to have a huge impact on the study of galaxy formation and evolution in the early Universe as well as star and planet formation in our own Galaxy. Mapping the sky to the same S/N up to 1000 times faster than SCUBA, it will also act as a pathfinder for the new submillimetre interferometers such as ALMA. We describe SCUBA-2's unique capabilities and their expected impact on sub-millimetre astronomy and give an update on the status of the instrument.

We report the carbon isotope ratio in nearby molecular clouds LkHα 101, AFGL 490, and Mon R2 IRS 3. The vibrational transition bands of 12CO ν = 2 ← 0 and 13CO ν = 1 ← 0 were observed with high resolution near-infrared spectroscopy (R = 23,000) to measure the relative abundance of 13CO to 12CO. The isotopic ratios are 12CO/13CO = 137±9 (LkHα 101), 86±49 (AFGL 490), and 158 (Mon R2 IRS 3), which is twice higher than in the solar neighborhood. The molecular clouds are with high visible extinction (A V = 10–70 mag), well shielded from destructive FUV field. It is questionable that the selective photo-destruction of 13CO plays a major role in biasing isotope ratio. Uncertainty in the Doppler parameters of the unresolved absorption lines, and possible emission filling of fundamental transitions are suspected to account for the high 12CO/13CO ratio. Higher resolution spectroscopy (R ~ 100,000) is the key to go for the accurate measurement of isotope ratio.

Key Odin operational and instrumental features and highlights from our sub-millimetre and millimetre wave observations of H2O, (H2O)-O-18, NH3, (NH3)-N-15 and O-2 are presented, with some insights into accompanying Odin Letters in this A& A issue. We focus on new results where Odin's high angular resolution, high frequency resolution, large spectrometer bandwidths, high sensitivity or/and frequency tuning capability are crucial: H2O mapping of the Orion KL, W3, DR21, S 140 regions, and four comets; H2O observations of Galactic Centre sources, of shock enhanced H2O towards the SNR IC443, and of the candidate infall source IRAS 16293-2422; (H2O)-O-18 detections in Orion KL and in comet Ikeya-Zhang; sub-mm detections of NH3 in Orion KL (outflow, ambient cloud and bar) and rho Oph, and very recently, of (NH3)-N-15 in Orion KL. Simultaneous sensitive searches for the 119 GHz line of O-2 have resulted in very low abundance limits, which are difficult to accomodate in chemical models. We also demonstrate, by means of a quantitative comparison of Orion KL H2O results, that the Odin and SWAS observational data sets are very consistently calibrated.

Observations of the environment of the star-forming region NGC 7129 obtained with an angular resolution of 1' in the 21 cm line of Hi are described. Two features of the image are extensively discussed: (1) a ring of H I emission about 300 in extent and (2) a relatively dense concentration of H I with unusually wide line profiles positionally coincident with the B star BD + 65degrees1638. The H I ring is consistent with photodissociation of H-2 by the interstellar UV radiation field at the surface of an extended molecular cloud in which both BD + 65degrees1638 and NGC 7129 are situated. We further show that BD + 65degrees1638 appears to be an unusual example of a "dissociating star" surrounded by an extensive region of photodissociated H-2 and accompanied by a small H II region. The derived spectral type (B2.5) and the absolute magnitude for BD + 65degrees1638 further suggest that the latter is very close to the birthline. The very young stellar age implied by the parameters of the H I region, considerably less than 10(4) yr, is discussed, and the properties of the H I region are compared with those of the prototype for this rare class of objects. We discuss both aspects within the context of star formation in NGC 7129.

New results from water mapping observations of the Orion KL region using the submm/mm wave satellite Odin (2.1' beam size at 557 GHz), are presented. The ortho-H2O J(K+K-) = 1(1,0) --> 1(0,1) ground state transition was observed in a 7' x 7' rectangular grid with a spacing of 1', while the same line of (H2O)-O-18 was measured in two positions, Orion KL itself and 2' south of Orion KL. In the main water species, the KL molecular outflow is largely resolved from the ambient cloud and it is found to have an extension of 60"- 110". The H2O outflow profile exhibits a rather striking absorption-like asymmetry at the line centre. Self-absorption in the near ( or "blue") part of the outflow ( and possibly in foreground quiescent halo gas) is tentatively suggested to play a role here. We argue that the dominant part of the KL (H2O)-O-18 outflow emission emanates from the compact (size similar to 15") low-velocity flow and here estimate an H2O abundance of circa 10(-5) compared to all H-2 in the flow - an order of magnitude below earlier estimates of the H2O abundance in the shocked gas of the high-velocity flow. The narrow ambient cloud lines show weak velocity trends, both in the N-S and E-W directions. (H2O)-O-18 is detected for the first time in the southern position at a level of similar to 0.15 K and we here estimate an H2O abundance of (1 - 8) X 10(-8).

We report the carbon monoxide isotope ratio in local molecular clouds toward LkHalpha 101, AFGL 490, and Mon R2 IRS 3. The vibrational transition bands of (CO)-C-12 nu = 2 <-- 0 and (CO)-C-13 nu = 1 <-- 0 were observed with high-resolution near-infrared spectroscopy (R = 23; 000) to measure the (CO)-C-12/(CO)-C-13 ratio. The isotopic ratios are (CO)-C-12/(CO)-C-13 = 137 +/- 9 (LkHalpha 101), 86 +/- 49 (AFGL 490), and 158 (Mon R2 IRS 3), which are 1.5 - 2.8 times higher than the local interstellar medium value of (CO)-C-12/(CO)-C-13 = 57 +/- 5 from millimeter (CO)-O-18 emission observations. This is not easily explained by saturation of the (CO)-C-13 absorption. It is also questionable whether the selective photodestruction of (CO)-C-13 can account for the difference between the Galactic trend and the present observation, because the molecular clouds are with high visible extinction (A(V) = 10-70 mag), well shielded from destructive FUV radiation. The molecular gas associated with AFGL 490 and Mon R2 IRS 3 consists of multiple temperature components lying in the lines of sight. In the cool component (T-ex < 100 K), the excitation temperature of (CO)-C-12 is twice that of (CO)-C-13. We attribute the temperature discrepancy to the photon-trapping effect, which makes the radiative cooling of the main isotopomer less effective.

Odin has successfully observed the molecular core rho Oph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (JK = 10 -> 00). The interpretation of this result makes use of compleme ...

The Odin satellite has been used to detect emission and absorption in the 557-GHz H2O line in the Galactic Centre towards the Sgr A* Circumnuclear Disk (CND), and the Sgr A +20 km/s and +50 km/s molecular clouds. Strong broad H2O emission lines have been detected in all three objects. Narrow H2O absorption lines are present at all three positions and originate along the lines of sight in the 3-kpc Spiral Arm, the -30 km/s Spiral Arm and the Local Sgr Spiral Arm. Broad H2O absorption lines near -130 km/s are also observed, originating in the Expanding Molecular Ring. A new molecular feature (the “High Positive Velocity Gas” - HPVG) has been identified in the positive velocity range of +120 to +220 km/s, seen definitely in absorption against the stronger dust continuum emission from the +20 km/s and +50 km/s clouds and possibly in emission towards the position of Sgr A* CND. The 548-GHz H2_18O isotope line towards the CND is not detected at the 0.02 K (rms) level.

Odin has successfully observed three regions in the OrionA cloud, i.e. OriKL, Ori S and the Orion Bar, in the 572.5 GHz rotational ground state line of ammonia, ortho-NH3 (J; K) = ( 1; 0) --> (0; 0), and the result for the Orion Bar represents the first detection in an ammonia line. Several velocity components are present in the data. Specifically, the observed line profile from the Orion Bar can be decomposed into two components, which are in agreement with observations in high-J CO lines by Wilson et al. (2001). Using the source model for the Orion Bar by these authors, our Odin observation implies a total ammonia abundance of NH3/H-2 = 5 X 10(-9).

This paper reports new submillimeter molecular line observations of NGC 7129, a reflection nebula and star-forming region. Maps of (CO)-C-12 and (CO)-C-13 2-1 and 3-2 emission show a cavity surrounded by bright ridges of denser molecular gas. Known molecular outflows in the region issue from deeply embedded sources in these ridges. Only the red lobe of the most prominent outflow is seen clearly, but there is some evidence to suggest that a blue counterjet is escaping through the front of the cavity. We suggest a picture of the region's evolution in which the oldest star, BD+65 degrees 1638, created the cavity by sweeping the surrounding interstellar gas into the surrounding ridges. This led to further star formation, as evidenced by the outflow sources found in the ridges. One of these sources, FIRS 2, thought to be an intermediate-mass analog of a Class 0 young stellar object, is coincident with a pointlike source seen in a near-IR (K') image.

New molecular (13CO J = 3-2) and dust continuum (450 and 850 μm) maps of the NGC 7129 star-forming region are presented. The maps include the Herbig Ae/Be star LkHα 234, the far-infrared source NGC 7129 FIRS 2, and several other prestellar sources embedded within the molecular ridge. The data are complemented with C18O J = 3-2 spectra at several positions within the mapped region. Both the submillimeter and the 13CO emission show a similar morphology, displaying a sharp boundary toward the cavity. The submillimeter maps also reveal a second source, SMM 2, which is not clearly seen in any earlier data set. This is either a prestellar core or possibly a protostar. Also, the highest continuum peak emission is identified with the deeply embedded source IRS 6 a few arcseconds away from LkHα 234. These new 450 and 850 μm observations are combined with previous continuum observations of the three compact far-infrared sources in the field, in order to make fits to the spectral energy distributions and to obtain the source sizes, dust temperatures, luminosities, and masses. For nine positions where both 13CO and C18O spectra are available, gas masses have been obtained and compared with masses derived from the continuum fluxes. The masses are found to be consistent, implying little or no CO depletion onto grains. The dust emissivity index is found to be low toward the dense compact sources, β ~ 1-1.6, and high, β ~ 2.0, in the surrounding cloud.

We present observations of two formaldehyde transitions towards 14 clumps in the Orion B North complex; the ratio of these transitions is an indicator of the kinetic temperature of the molecular gas. The spectra show narrow-line coin potion ts with temperatures 20-30 K, and broader components with rather higher temperatures.

Using SCUBA on the James Clerk Maxwell Telescope, we obtained a map of 850 mum continuum emission from the Orion B molecular cloud. The map is 20'x40' in extent and covers much of the northern half of the giant molecular cloud. A total of 67 discrete continuum sources, or clumps, have been identified, many of which are grouped in three regions, near NGC 2071IR, NGC 2068, and HH 24/25/26. Masses of the sources range from 0.2 to 12 M-.. About half of the area of our 850 mum map is covered by the current release of the 2MASS infrared survey. Of 40 clumps covered by the 2MASS, 14 have associated infrared sources detected in J, H, and K. Maps of (CO)-C-13 J = 2-1 and (CO)-O-18 J = 2-1 line emission were obtained for two regions in order to find the gas column density. Formaldehyde spectra were obtained toward eight of the continuum clumps to determine the gas kinetic temperature. Three of the clumps with measured temperature are hot (T-kin greater than or equal to 80 K) while the other five are cold K) (T-kin less than or equal to 20 K). The gas-to-dust ratios differ substantially between the two regions mapped in CO. In the NGC 2068 region we find close to constant ratios of dust-to-gas emission, except in one compact source. However, in the HH 24/25/26 region the dust-to-gas emission ratio varies substantially with some of the brightest dust continuum sources almost absent in CO emission. One explanation is that CO molecules have frozen onto grains in the dense cores. Why this freeze-out should happen in the HH 24/25/26 cores but not in the NGC 2068 cores remains unexplained. A (CO)-C-12 J = 3-2 map of the NGC 2068 region shows patches of high-velocity gas associated with five of the compact continuum sources. The presence of outflows provides strong evidence that the group of sources south of NGC 2068 is actively forming stars.

We present results from a survey of a 900 arcmin(2) region of the Orion B molecular cloud, including NGC 2068, NGC 2071, and HH 24/25/26, at 850 mum using the Submillimeter Common-User Bolometer Array (SCUBA) on the James Clerk Maxwell Telescope. Following the techniques developed by Johnstone et al., we identify 75 independent objects and compute size, flux, and degree of central concentration. Comparison with isothermal, pressure-confined, self-gravitating Bonnor-Ebert spheres implies that the clumps have internal temperatures of 20-40 K and surface pressures 5.5 < log P/k < 6.5. The clump masses span 0.2-12.3 M-circle dot assuming typical dust temperatures and a dust emissivity kappa (850) = 0.01 cm(2) g(-1). The distribution of clump masses is well characterized by a power-law N(M) proportional to M-alpha with alpha = 1.5-2.0 for M > 1.0 M-circle dot. Significant incompleteness makes determination of the slope at lower masses difficult. The two-point correlation function of the clump separations is measured revealing clustering on size scales r < 1.5 x 10(5) AU with a radial power-law exponent = 0.75.

New wide-field images of the ρ Ophiuchi molecular cloud at 850 and 450 μm obtained with the Submillimeter Common-User Bolometer Array on the James Clerk Maxwell Telescope reveal a wide variety of large-scale features that were previously unknown. Two linear features, each 4' (0.2 pc) in length, extend to the north of the bright emission region containing SM1 and VLA 1623. These features may correspond to the walls of a previously unidentified outflow cavity or the boundary of a photon-dominated region powered by a nearby B star. A previously unidentified source is located in the northeast region of the image. The properties of this source (diameter ~5000 AU, mass ~0.3-1 M) suggest that it is a preprotostellar core. Two arcs of emission are seen in the direction of the northwest extension of the VLA 1623 outflow. The outer arc appears relatively smooth at 850 μm and is estimated to have a mass of ~0.3 M, while the inner arc breaks up into a number of individual clumps, some of which are previously identified protostars.