Search

NGC 2024 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, 303 → 202, 322 → 221, 505 → 404, and 523 → 422. Maps of the ridge are used to provide temperatures and densities, with a focus on the dense-core positions. The formaldehyde transition ratios 303 → 202/322 → 221 and 505 → 404/523 → 422 offer measurements of the kinetic temperature, while the ratio 303 → 202/505 → 404 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 ~2 × 106 cm–3 at far-infrared (FIR) core positions and H2CO column densities in the range of 6 × 1014 to 1 × 1015 cm–2 are derived. Using the derived properties in combination with previous submillimeter continuum data, core masses of ~2 M ☉ are found within a 15'' beam size. H2CO fractional abundances are calculated and resemble previous values found in similar star-forming regions—between 2 × 10–9 and 5 × 10–9. The virial theorem applied to FIR cores 3, 4, 5, and 6 suggests that all four cores are unstable against gravitational collapse.

International audience; Stars form in the densest, coldest, most quiescent regions of molecular clouds. Molecules provide the only probes that can reveal the dynamics, physics, chemistry, and evolution of these regions, but our understanding of the molecular inventory of sources and how this is related to their physical state and evolution is rudimentary and incomplete. The Spectral Legacy Survey (SLS) is one of seven surveys recently approved by the James Clerk Maxwell Telescope (JCMT) Board of Directors. Beginning in 2007, the SLS will produce a spectral imaging survey of the content and distribution of all the molecules detected in the 345 GHz atmospheric window (between 332 and 373 GHz) toward a sample of five sources. Our intended targets are a low-mass core (NGC 1333 IRAS 4), three high-mass cores spanning a range of star-forming environments and evolutionary states (W49, AFGL 2591, and IRAS 20126), and a photodissociation region (the Orion Bar). The SLS will use the unique spectral imaging capabilities of HARP-B/ACSIS (Heterodyne Array Receiver Programme B/Auto-Correlation Spectrometer and Imaging System) to study the molecular inventory and the physical structure of these objects, which span different evolutionary stages and physical environments and to probe their evolution during the star formation process. As its name suggests, the SLS will provide a lasting data legacy from the JCMT that is intended to benefit the entire astronomical community. As such, the entire data set (including calibrated spectral data cubes, maps of molecular emission, line identifications, and calculations of the gas temperature and column density) will be publicly available.

Odin has successfully observed the molecular core rho Oph A in the 572.5 GHz rotational ground state line of ammonia, NH3 (J,K = 1,0 - 0,0). The interpretation of this result makes use of complementary molecular line data obtained from the ground (C17O and CH3OH) as part of the Odin preparatory work. Comparison of these observations with theoretical model calculations of line excitation and transfer yields a quite ordinary abundance of methanol, X(CH3OH) = 3e-9. Unless NH3 is not entirely segregated from C17O and CH3OH, ammonia is found to be significantly underabundant with respect to typical dense core values, viz. X(NH3) = 8e-10.

For the first time, a search has been conducted in our Galaxy for the 119 GHz transition connecting to the ground state of O2, using the Odin satellite. Equipped with a sensitive 3 mm receiver (Tsy ...

This paper reports new submillimeter molecular line observations of NGC 7129, a reflection nebula and star-forming region. Maps of 12CO and 13CO 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°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.

We present results from a survey of a 900 arcmin2 region of the Orion B molecular cloud, including NGC 2068, NGC 2071, and HH 24/25/26, at 850 μm 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 1.0 M☉. 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 × 105 AU with a radial power-law exponent γ = 0.75.

We present the results of a search for CO 1 ? 0 emission from NGC 147 and M32, two of the four dwarf elliptical companions of M31. Return of gas from evolved stars to the interstellar medium of these galaxies should have resulted in detections, but we find instead upper limits of 4100 and 5100 M? of H2 for NGC 147 and M32, respectively. Including and earlier H I limit, we find that the gaseous interstellar medium (ISM) of NGC 147 comprises less than 2% of what is expected. The large published H I mass limit for M32 prevents us from reaching a similarly extreme conclusion for this galaxy. These results stand in stark contrast to what is seen in NGC 185 and NGC 205, where the observed gas is approximately what is expected from stellar mass return, although some of the gas in NGC 205 probably had an external origin. There are no obvious differences in masses or luminosities that would explain the results. The proposal that differences may be related to the recent interaction histories of the galaxies with M31 is rendered moot by the lack of orbital information but does not seem to be viable for NGC 147 and NGC 185. We can offer no convincing explanation for these puzzling results, although they may point to a fundamental gap in our understanding of galaxy evolution.

We present CO 1 → 0 and 2 → 1 observations of NGC 205, which is a dwarf elliptical galaxy and a companion to M31. It has long been suggested that NGC 205 has interacted with M31 in the past. The total mass of gas (molecular, atomic, and X-ray emitting) associated with NGC 205 is ~106 M☉, which is 1 order of magnitude less than the mass that should have been returned to its ISM by evolved stars during its lifetime. A burst of star formation began in NGC 205 ~5 × 108 yr ago, ending a few million yr ago; while some of the mass that was returned to the ISM would be used up by the starburst, star formation is a notoriously inefficient process. Moreover, the gas in NGC 205 is rotating, while the stars are not, so any gas returned to the ISM should have zero net angular momentum. We suggest that the angular momentum was added when the preexisting gas interacted with an external gas cloud, either in the disk of M31 or, perhaps less likely, in the region surrounding it. The recent starburst could have been triggered by the interaction, and the blast waves from ensuing supernovae would then have removed most of the remaining gas. Sufficient time has passed since these events for planetary nebulae to have contributed most of the gas we see in this galaxy.

The central region of the Monoceros R2 molecular cloud has been studied using molecular line maps, maps in continuum emission, and an M-band (4.7 μm) absorption spectrum toward Mon R2 IRS 3. Maps were made in the emission lines CO (3-2) H2CO (51,5-41,4), and HCN (4-3), all with a 14'' beam size. CO (2-1) and 13CO (3-2) spectra were obtained at a dozen positions. Maps of continuum emission were made at 1300 μm (25'' resolution), 1100 μm (20'' resolution), 800 μm (14'' resolution), and 450 μm (14'' resolution). The M-band spectrum of IRS 3 has a velocity resolution of 5.2 km s-1 and shows fundamental vibrational band absorption lines of CO and 13CO over a range of rotational states. The CO map has numerous intensity peaks which, if interpreted as clumps, have masses from 0.1 to 3 M☉. The large velocity dispersion of these structures implies that they cannot be gravitationally bound. The brightest CO-emitting gas shows no bipolar distribution with velocity. Diffuse CO-emitting gas with low velocities does have a generally bipolar distribution, but there are no collimated lobes pointing to a particular source. We conclude that the source (or sources) of the very extended Mon R2 outflow is (are) now inactive. The highest velocity gas is found toward the embedded young stellar object IRS 3, suggesting that IRS 3 is the source of a compact outflow, unresolved at our 14'' resolution. The presence of blueshifted CO in the absorption spectrum supports the interpretation of IRS 3 as an outflow source. The H2CO and HCN maps demonstrate that much of the dense gas is distributed within three structures having different velocities. The fundamental band absorption lines of 13CO show two gas temperatures in the line of sight to IRS 3. The colder (45 K) is identified as gas in the clump surrounding IRS 3, which is seen in emission lines of CO, H2CO, and HCN. The warmer (310 K) we interpret as gas very close to IRS 3. From the submillimeter continuum maps we identify 11 clumps whose masses lie in the range 3-10 M☉. A clump that is prominent in the continuum maps but not in the molecular line maps is attributed to heated dust inside the compact H II region, where molecules have been destroyed.

We have made high-resolution (4'') observations of the 2.6 mm continuum and CO (1-0) line emission associated with the young stellar object DG Tau B. The aperture-synthesis CO map clearly shows that redshifted emission is symmetrically distributed about the DG Tau B optical jet and extends at least 6000 AU to the northwest of the unresolved continuum source. By contrast, blueshifted CO emission is confined to a compact region, which is less than 500 AU in radius. Within 1000 AU of the star, the redshifted CO emission is elongated, brightest along its central axis, and unresolved in the transverse direction. Beyond 1000 AU, the flow broadens and begins to bifurcate. The morphology of the CO emission provides compelling evidence that the extended molecular outflow is driven by the highly collimated atomic jet. The spatial correspondence between knots in the optical jet and successive broadenings of the outflow supports the hypothesis that the molecular outflow is produced by the action of multiple working surfaces in a time-varying jet.

Using high-resolution infrared CO spectroscopy new results have been obtained on the environment of high-mass young stellar objects (YSOs). In particular, a new class of neutral, warm and dense outflows has been discovered. The infrared outflows appear a general phenomenon of the activity of high-mass YSOs. With well-defined and often multiple velocities they seem to correspond to episodic and violent mass-loss events from the central source. In addition, a shell of warm, quiescent gas, is formed near the massive star. All these dynamical elements influence the chemistry inside the giant molecular clouds. Beside CO in solid and in gas phase, detection in the infrared has been attempted of simple molecules like CH4, C2H2, H2O and ion H3+ toward few of these sources.

Molecular oxygen, O2 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 O2 emission. The work described here uses heterodyne spectroscopy from space to search for molecular oxygen in the interstellar medium. The Odin satellite carries a 1.1 m sub-millimeter dish and a dedicated 119 GHz receiver for the ground state line of O2. Starting in 2002, the star forming molecular cloud core rho Oph A was observed with Odin for 34 days during several observing runs. We detect a spectral line at v(LSR) = 3.5 km/s with dv(FWHM) = 1.5 km/s, parameters which are also common to other species associated with rho Ohp A. This feature is identified as the O2 (N_J = 1_1 - 1_0) transition at 118 750.343 MHz. The abundance of molecular oxygen, relative to H2,, is 5E-8 averaged over the Odin beam. This abundance is consistently lower than previously reported upper limits., Comment: 10 pages, 11 figures, accepted for publication in A&A

We report the carbon isotope ratio in nearby molecular clouds LkHα 101, AFGL 490, and Mon R2 IRS 3. The vibrational transition bands of CO ν = 2 ← 0 and CO ν = 1 ← 0 were observed with high resolution near-infrared spectroscopy (R = 23,000) to measure the relative abundance of CO to CO. The isotopic ratios are CO/CO = 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 (AV = 10–70 mag), well shielded from destructive FUV field. It is questionable that the selective photo-destruction of CO 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 CO/CO ratio. Higher resolution spectroscopy (R ∼ 100,000) is the key to go for the accurate measurement of isotope ratio.

We present results from a survey of a 1300 arcmin^2 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. Submillimeter continuum observations at 450 microns and 850 microns are discussed. Using an automated algorithm, 57 discrete emission features (``clumps'') are identified in the 850 micron 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 T_d = 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^-1 P cm^3 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 turn-over around 3 -- 10 M_sun., Comment: 41 pages, 16 figures, accepted by ApJ

SCUBA-2, which replaces SCUBA (the Submillimeter Common User Bolometer Array) on the James Clerk Maxwell Telescope (JCMT) in 2006, is a large-format bolometer array for submillimeter astronomy. Unlike previous detectors 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 sq-arcmin 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 submillimeter interferometers such as ALMA. SCUBA-2's absorber-coupled pixels use superconducting transition edge sensors operating at 120 mK for performance limited by the sky background photon noise. The monolithic silicon detector arrays are deep-etched by the Bosch process to isolate the pixels on silicon nitride membranes. Electrical connections are made through indium bump bonds to a SQUID time-domain multiplexer (MUX). We give an overview of the SCUBA-2 system and an update on its status, and describe some of the technological innovations that make this unique instrument possible., 16 pages, 14 figures, Invited talk at SPIE Glasgow 21-25 June 2004, Conference 5498

SCUBA-2, which replaces the Submillimetre Common User Bolometer Array (SCUBA) (Mon. Not. R. Astron. Soc. 303 (1999) 659) on the James Clerk Maxwell telescope in 2006, will be the first CCD-like array for submillimeter astronomy. Unlike previous detectors 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 an 8A—8 arcmin field of view at wavelengths of 850 and 450 I¼m. 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. SCUBA-2's absorber-coupled pixels use superconducting transition edge sensors (Ph.D. Thesis, Stanford, 1995) operating at 120 mK for photon noise limited performance. The monolithic silicon detector arrays are deep-etched by the Bosch process to isolate the pixels on silicon nitride membranes (Nucl. Instr. and Meth. A, these proceedings). Electrical connections are made through indium bump bonds to a backplane that incorporates a SQUID time-domain multiplexer. We describe the key technologies that make SCUBA-2 possible and give an update on the considerable progress in the detector development and instrument design that has taken place over the last 2 years

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., 5 pages, 3 figures, accepted by A&A, special Odin Letters issue

Odin has successfully observed three regions in the Orion A cloud, i.e. Ori KL, 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/H2 = 5E-9., 4 pages with 2 figures, accepted for publication in A&A

We have mapped the submillimeter emission from the 1(10)-1(01) transition of ortho-water in the W3 star-forming region. A 5'x5' map of the W3 IRS4 and W3 IRS5 region reveals strong water lines at half the positions in the map. The relative strength of the Odin lines compared to previous observations by SWAS suggests that we are seeing water emission from an extended region. Across much of the map the lines are double-peaked, with an absorption feature at -39 km/s; however, some positions in the map show a single strong line at -43 km/s. We interpret the double-peaked lines as arising from optically thick, self-absorbed water emission near the W3 IRS5, while the narrower blue-shifted lines originate in emission near W3 IRS4. In this model, the unusual appearance of the spectral lines across the map results from a coincidental agreement in velocity between the emission near W3 IRS4 and the blue peak of the more complex lines near W3 IRS5. The strength of the water lines near W3 IRS4 suggests we may be seeing water emission enhanced in a photon-dominated region., Accepted to A&A Letters as part of the special Odin issue; 4 pages

New molecular (13CO J=3-2) and dust continuum (450 and 850 micron) SCUBA maps of the NGC7129 star forming region are presented, complemented by C18O J=3-2 spectra at several positions within the mapped region. The maps include the Herbig Ae/Be star LkHalpha 234, the far-infrared source NGC 7129 FIRS2 and several other pre-stellar sources embedded within the molecular ridge. The SCUBA maps help us understand the nature of the pre-main sequence stars in this actively star forming region. A deeply embedded submillimeter source, SMM2, not clearly seen in any earlier data set, is shown to be a pre-stellar core or possibly a protostar. The highest continuum peak emission is identified with the deeply embedded source IRS6, a few arcseconds away from LkHalpha 234, and also responsible for both the optical jet and the molecular outflow. The gas and dust masses are found to be consistent, suggesting little or no CO depletion onto grains. The dust emissivity index is lower towards the dense compact sources, beta ~1 - 1.6, and higher, beta ~ 2.0, in the surrounding cloud, implying small size grains in the PDR ridge, whose mantles have been evaporated by the intense UV radiation., Comment: Accepted by ApJ

New wide-field images of the Rho Ophiuchus molecular cloud at 850 and 450 microns obtained with SCUBA 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 north-east region of the image. The properties of this source (diameter ~5000 AU, mass ~0.3-1 Msun) suggest that it is a pre-protostellar core. Two arcs of emission are seen in the direction of the north-west extension of the VLA 1623 outflow. The outer arc appears relatively smooth at 850 microns and is estimated to have a mass of ~0.3 Msun, while the inner arc breaks up into a number of individual clumps, some of which are previously identified protostars., Comment: 9 pages, 2 color figures; accepted for publication in ApJ Letters

We present observations of molecular gas made with the 15-m James Clark Maxwell Telescope toward the sites of OH(1720 MHz) masers in three supernova remnants: W28, W44 and 3C391. Maps made in the 12CO J=3-2 line reveal that the OH masers are preferentially located along the edges of thin filaments or clumps of molecular gas. There is a strong correlation between the morphology of the molecular gas and the relativistic gas traced by synchrotron emission at centimeter wavelengths. Broad CO line widths (dV=30-50 km/s) are seen along these gaseous ridges, while narrow lines are seen off the ridges. The ratio of H2CO line strengths is used to determine temperatures in the broad-line gas of 80 K, and the 13CO J=3-2 column density suggests densities of 10^4-10^5 cm{-3}. These observations support the hypothesis that the OH(1720 MHz) masers originate in post-shock gas, heated by the passage of a supernova remnant shock through dense molecular gas. From the observational constraints on the density, velocity and magnetic field we examine the physical properties of the shock and discuss the shock-production of OH. These OH(1720 MHz) masers are useful ``signposts'', which point to the most promising locations to study supernova remnant/molecular cloud interactions., Comment: ApJ (in press)

Using high-resolution infrared CO spectroscopy new results have been obtained on the environment of high-mass young stellar objects (YSOs). In particular, a new class of neutral, warm and den se outflows has been discovered. The infrared outflows appear a general phenomenon of the activity of high-mass YSOs. With well-defined and often multiple velocities they seem to correspond to episodic and violent mass-loss events from the central source. In addition, a shell of warm, quiescent gas, is formed near the massive star. All these dynamical elements influence the chemistry inside the giant molecular clouds. Beside CO in solid and in gas phase, detection in the infrared has been attempted of simple molecules like CH4, C2H2, H2O and ion H3 + toward few of these sources.

Many young stellar objects are centres of high velocity outflows, as revealed by broad wings on CO emission lines. Emission observations at millimeter wavelengths, because of the sizeable beamwidths employed, do not reveal the properties of gas very near the central YSO. A complementary technique, the observation of absorption lines in the fundamental vibrational band of CO at 4.7 tm, has proved a powerful probe of gas flow close to embedded protostars (e.g. Geballe and Wade 1985, Mitchell et al. 1988a). We present here a high resolution infrared absorption spectrum of W3 IRS5, at ≈ 5 x 105 LӨ the most luminous known YSO, and compare with CO millimeter observations.

A novel method of obtaining the 12 C/ 13 C ratio in molecular clouds consists of combining fundamental band measurements of 13 CO with first-overtone band measurements of 12 CO. Advantages of this infrared absorption technique are described, and a result for NGC 2264 is presented. A high-resolution (6.9 km s −1 ) M band (4.7 μm) spectrum of the source NGC 2264 IRS (=AFGL 989), obtained at the CFHT, shows v=0-1 absorption lines due to 13 CO. A curve-of-growth analysis was carried out to obtain the 13 CO column density

The CO J = 2→1 emission from the high-velocity sources GL 490, GL 2591, M8E-IR, and W3 IRS 5 was mapped, at 21″ resolution. New bipolar outflows are detected from GL 2591, M8E-IR, and W3 IRS 5. The new W3 IRS 5 bipolar outflow (with a lobe separation of 30″) has the same orientation as a very small-scale bipolar outflow (lobe separation of 2.5″) previously found by aperture synthesis, suggesting two episodes of outflow acivity from IRS 5. Observations of 13 CO J = 2→1 are combined with the 12 CO data to determine the mass and other physical properties of the outflowing gas

HCO(+) J = 3-2 emission from the molecular cloud centered on S140 IRS 1 has been observed with a spatial resolution of 20 arcsec. The innermost region of the cloud is characterized by strong HCO(+) J = 3-2 emission elongated in a north-south direction, having the same orientation as the bipolar outflow previously discovered from CO line wings. The HCO(+) J = 3-2 lines exhibit broad, asymmetric wings. The full width of the wings at the position of IRS 1 is 30 km/s. In a nine-point average spectrum, the wings have a total width of 60 km/s. The blue and red wing emissions show no spatial displacement, in contrast to CO line wings. 27 refs.

This paper examines the kinematics and physical properties of the outflowing gas from seven luminous deeply embedded young stellar objects or protostars: M8E-IR, GL 490, GL 2591, W3 IRS 5, NGC 7538 IRS 1, NGC 7538 IRS 9, and S140 IRS 1. The outflows are seen as blueshifted absorption features in lines of the fundamental band of CO. The CO lines seen in absorption are compared with CO lines seen in emission at mm wavelengths. New CO J = 2-1 emission-line data are presented for the first five of the sources. 60 refs.

High-resolution M band spectra are presented for the seven embedded IR sources W3 IRS 5, S140 IRS1, NGC 7538 IRS 1, NGC 7538 IRS 9, GL 2136, LkH-alpha 101, and MWC 349A, and the data are combined with previously published work for W33A and GL 2591. Cold CO is seen toward all nine sources, with temperatures from 11 K to 66 K. Column densities of cold CO are presented. Hot gas is seen toward eight of the nine objects with temperatures from 120 K to 1010 K. New lower limits to the hot gas density are obtained. The hot gas toward GL 2591, GL 2136, W3 IRS 5, and S140 IRS 1 is probably very near the central source and heated via gas-grain collisions. The optical depth in the silicate feature is strongly correlated with the (C-13)O column density, confirming that silicate optical depth is a useful measure of gas column density. The ratio of solid-to-gaseous CO is obtained for seven sources.

The high molecular abundances seen in IC443 may be due to hot chemistry in shocked gas or to an increase in the cosmic ray ionization rate. New calculations reported here show that shock chemistry dominates over the relevant short time scale.

One-dimensional radial models of the chemistry in cometary comae have been constructed for heliocentric distances ranging from 2 to 0.125 AU. The coma's opacity to solar radiation is included and photolytic reaction rates are calculated. A parent volatile mixture similar to that found in interstellar molecular clouds is assumed. Profiles through the coma of number density and column density are presented for H2O, OH, O, CN, C2, C3, CH, and NH2. Whole-coma abundances are presented for NH2, CH, C2, C3, CN, OH, CO+, H2O+, CH+, N2+, and CO2+.

In its passage through the interstellar gas, a shock imposes massive and irreversible changes on the chemical composition of the gas. The synthesis of molecules from atoms and atomic ions can be highly efficient behind non-dissociative (i.e. slow) shocks. Results of kinetic calculations behind non-dissociative shocks are reviewed here, with emphasis given to the dependence of the postshock molecular composition on initial cloud properties. It is shown that a dense cloud shock can convert essentially all neutral atoms into various molecules. Even in diffuse and unshielded regions, a variety of molecules can attain a high abundance behind shocks. The suggestion that the widespread diffuse cloud species CH+ is shock synthesized is critically examined in the light of new calculations.

On presente un calcul dans lequel on suit les abondances de 108 especes pendant 10 5 ans apres le passage d'un choc de 10 kms −1 dans un nuage interstellaire de densite initiale 100 cm −3 . On donne les abondances de molecules d'hydrocarbures contenant un a six atomes de carbone. Les abondances de colonne des molecules d'hydrocarbures sont donnees et on discute de leurs mecanismes de formation

This paper provides guidance for proper selection of transformers by type to meet various operating conditions encountered in the petroleum industry. Transformer characteristics, utilization of force cooling, loading transformers by temperature, and benefits to be gained by proper maintenance are discussed. Observation of these guidelines can result in economic and most efficient use of power transformers for the petroleum industry.

Post-shock abundances of 105 chemical species are followed after the passage of a 10 kms-1 shock through an interstellar cloud of initial density 104 cm-3. We find significant enhancement in the column densities of H, H2O, NH3, and HS. The column densities of most ions decrease in abundance by rather large factors.

New results from water mapping observations of the Orion KL region using the submm/mm wave satellite Odin (2.1\arcmin beam size at 557 GHz), are presented. The ortho-H2O \jkktrans{1}{1}{0}{1}{0}{1} ground state transition was observed in a 7arcminx 7arcmin rectangular grid with a spacing of 1\arcmin, while the same line of H218O was measured in two positions, Orion KL itself and 2\arcmin 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\arcsec-110\arcsec. 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 H218O outflow emission emanates from the compact (size ~ 15\arcsec) low-velocity flow and here estimate an H2O abundance of circa 10-5 compared to all H2 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. H218O is detected for the first time in the southern position at a level of ~ 0.15 K and we here estimate an H2O abundance of (1-8) x 10-8. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the Centre National d'Etudes Spatiales (CNES, France). The Swedish Space Corporation (SSC) was the industrial prime contractor and is also responsible for the satellite operation.

Key Odin operational and instrumental features and highlights from our sub-millimetre and millimetre wave observations of H2O, H218O, NH3, 15NH3 and O2 are presented, with some insights into accompanying Odin Letters in this AA H2O observations of Galactic Centre sources, of shock enhanced H2O towards the SNR IC443, and of the candidate infall source IRAS 16293-2422; H218O detections in Orion KL and in comet Ikeya-Zhang; sub-mm detections of NH3 in Orion KL (outflow, ambient cloud and bar) and ρ Oph, and very recently, of 15NH3 in~Orion KL. Simultaneous sensitive searches for the 119 GHz line of O2 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. Odin is a Swedish-led satellite project funded jointly by the Swedish National Space Board (SNSB), the Canadian Space Agency (CSA), the National Technology Agency of Finland (Tekes), and the Centre National d'etudes Spatiales (CNES, France). The Swedish Space Corporation (SSC) has been the prime industrial contractor, and is also responsible for the satellite operation from its Odin Mission Control Centre at SSC in Solna and its Odin Control Centre at ESRANGE near Kiruna in northern Sweden. See also the SNSB Odin web page: http://www.snsb.se/eng_odin_intro.shtml

A high-resolution (0.059/cm) M band (4.6 micron) spectrum of the embedded young stellar object M8E-IR is presented and discussed. The spectrum shows strong absorption to large blueshifts in the rotational lines of the fundamental vibrational band, v = 1-0, of CO. The absorption is interpreted as being due to gas near to, and flowing from, the central object. The outflowing gas is warm (95-330 K) and consists of discrete velocity components with the very high velocities of 90, 130, 150, and 160 km/s. On the basis of a simple model, it is estimated that the observed outflows are less than 100 yr old.

Spectroscopic observations of the IR source W33A, obtained in the M band (4.6 microns) at resolution 0.057/cm using the Fourier-transform spectrometer at the Cassegrain focus of the Canada-France-Hawaii Telescope on July 12-13, 1987, are reported. The spectrum is shown, and equivalent widths and CO column densities are presented in tables. The absorption lines detected indicate the presence of gas at both 23 and 120 K, attributed to the molecular-cloud core and gas near the source, respectively, but very little solid-phase CO.

High-resolution M band (4.6 microns) spectroscopy of GL 2591 is presented. Physical structures noted include an absorption feature with an outflow velocity of about 17 km/s, cold gas (identified with the core of the molecular cloud within which the object is embedded), and very broad C-12O lines formed in a neutral wind. The detection of hot low-velocity gas together with warm high-velocity gas suggests the scenario of a warm neutral wind accelerating from an accretion disk.

The abundances of polyatomic molecules that may be formed by CH3(+) radiative association reactions in dense interstellar molecular clouds are reevaluated. The formation of a number of complex interstellar molecules via radiative association reactions involving ionic precursors other than CH3(+) is also investigated; these additional precursors include CH3O(+), CH3CO(+), CH5(+), HCO(+), NO(+), H2CN(+), C2H2(+), and NH3(+). The results indicate that the postulated gas-phase ion-molecule radiative association reactions could potentially explain the synthesis of most of the more complex species observed in dense molecular clouds such as Sgr B2. It is concluded, however, that in order to be conclusive, laboratory data are needed to show whether or not these reactions proceed at the required rates at low temperatures.