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At Iliad 13.751-3, Hector heeds Polydamas' advice to rally the Trojans by gathering their best fighters together and debating their next move (13.736-47). The speech is followed by a simile that has puzzled some commentators, in which Hector is compared to a snowy mountain as he moves through the Trojan ranks. The passage runs as follows: ‘Πουλυδάμα σὺ μὲν αὐτοῦ ἐρύκακε πάντας ἀρίστους,αὐτὰρ ἐγὼ κεῖσ’ εἶμι καὶ ἀντιόω πολέμοιο·αἶψα δ’ ἐλεύσομαι αὖτις ἐπὴν εὖ τοῖς ἐπιτείλω.’ἦ ῥα, καὶ ὁρμήθη ὄρεϊ νιφόεντι ἐοικὼςκεκλήγων, διὰ δὲ Τρώων πέτετ’ ἠδ’ ἐπικούρων. 755οἳ δ’ ἐς Πανθοΐδην ἀγαπήνορα Πουλυδάμανταπάντες ἐπεσσεύοντ’, ἐπεὶ Ἕκτορος ἔκλυον αὐδήν.‘Polydamas, hold all the best men here, while I go there and face the battle. I shall swiftly come back again, when I have given my orders to the men.’ He spoke and rushed off appearing like a snowy mountain, crying out, and flew through the ranks of the Trojans and their allies, and they all rushed to the kindly-minded Polydamas, Panthoos’ son, when they heard Hector's voice.

We report on balanced SIS receivers covering the astronomical important 180-720 GHz submillimeter atmospheric window. To facilitate remote observations and automated spectral line surveys, fully synthesized local oscillators are employed. High-current-density Nb-AlN-Nb superconducting-insulating-superconducting (SIS) tunnel junctions are used as the mixing element. The measured double-sideband (DSB) 230 GHz receiver noise temperature, uncorrected for optics loss, ranges from 50K at 185 GHz, 33K at 246 GHz, to 51K at 280 GHz. In this frequency range the mixer has a DSB conversion gain of 0 +- 1.5 dB. The measured 460 GHz double-sideband receiver noise temperature, uncorrected for optics loss, is 32K at 400 GHz, 34K at 460 GHz, and 61K at 520 GHz. Similar to the 230 GHz balanced mixer, the DSB mixer conversion gain is 1 +- 1 dB. To help optimize performance, the mixer IF circuits and bias injection are entirely planar by design. Dual-frequency observation, by means of separating the incoming circular polarized electric field into two orthogonal components, is another important mode of operation offered by the new facility instrumentation. Instrumental stability is excellent supporting the LO noise cancellation properties of the balanced mixer configuration. In the spring of 2012 the dual-frequency 230/460 SIS receiver was successfully installed at Caltech Submillimeter Observatory (CSO), Mauna Kea, HI., Comment: Accepted for publication in IEEE/TST

Objective—To determine efficacy of a single intra-articular injection of an autologous platelet concentrate for treatment of osteoarthritis in dogs. Design—Randomized, controlled, 2-center clinical trial. Animals—20 client-owned dogs with osteoarthritis involving a single joint. Procedures—Dogs were randomly assigned to a treatment or control group. In all dogs, severity of lameness and pain was scored by owners with the Hudson visual analog scale and the University of Pennsylvania Canine Brief Pain Inventory, respectively, and peak vertical force (PVF) was determined with a force platform. Dogs in the treatment group were then sedated, and a blood sample (55 mL) was obtained. Platelets were recovered by means of a point-of-use filter and injected intra-articularly within 30 minutes. Control dogs were sedated and given an intra-articular injection of saline (0.9% NaCl) solution. Assessments were repeated 12 weeks after injection of platelets or saline solution. Results—Dogs weighed between 18.3 and 63.9 kg (40.3 and 140.6 lb) and ranged from 1.5 to 8 years old. For control dogs, lameness scores, pain scores, and PVF at week 12 were not significantly different from pretreatment values. In contrast, for dogs that received platelet injections, lameness scores (55% decrease in median score), pain scores (53% decrease in median score), and PVF (12% increase in mean PVF) were significantly improved after 12 weeks, compared with pretreatment values. Conclusions and Clinical Relevance—Results suggested that a single intra-articular injection of autologous platelets resulted in significant improvements at 12 weeks in dogs with osteoarthritis involving a single joint.

A common analysis procedure minimizes the ln-likelihood that a set of experimental observables matches a parameterized model of the observation. The model includes a description of the underlying physical process as well as the instrument response function (IRF). In the case investigated here, the National Ignition Facility (NIF) neutron time-of-flight (nTOF) spectrometers, the IRF is constructed from measurements and models. IRF measurements have a finite precision that can make significant contributions to determine the uncertainty estimate of the physical model’s parameters. We apply a Bayesian analysis to properly account for IRF uncertainties in calculating the ln-likelihood function used to find the optimum physical parameters.

We present results from a comprehensive submillimeter spectral survey toward the source Orion South, based on data obtained with the Heterodyne Instrument for the Far-Infrared instrument on board the Herschel Space Observatory, covering the frequency range of 480 to 1900 GHz. We detect 685 spectral lines with signal-to-noise ratios (S/Ns) > 3 sigma, originating from 52 different molecular and atomic species. We model each of the detected species assuming conditions of Local Thermodynamic Equilibrium. This analysis provides an estimate of the physical conditions of Orion South (column density, temperature, source size, and VLSR). We find evidence for three different cloud components: a cool (T-ex similar to 20-40 K), spatially extended (> 60 ''), and quiescent (Delta V-FWHM similar to 4 km s(-1)) component; a warmer (T-ex similar to 80-100 K), less spatially extended (similar to 30 ''), and dynamic (Delta V-FWHM similar to 8 km s(-1)) component, which is likely affected by embedded outflows; and a kinematically distinct region (T-ex > 100 K; V-LSR similar to 8 km s(-1)), dominated by emission from species that trace ultraviolet irradiation, likely at the surface of the cloud. We find little evidence for the existence of a chemically distinct "hot-core" component, likely due to the small filling factor of the hot core or hot cores within the Herschel beam. We find that the chemical composition of the gas in the cooler, quiescent component of Orion South more closely resembles that of the quiescent ridge in Orion-KL. The gas in the warmer, dynamic component, however, more closely resembles that of the Compact Ridge and Plateau regions of Orion-KL, suggesting that higher temperatures and shocks also have an influence on the overall chemistry of Orion South.

The Caltech Submillimeter Observatory (CSO) is located on top of Mauna Kea, Hawaii, at an altitude of 4.2 km. The existing suite of facility heterodyne receivers covering the submillimeter band is rapidly aging and in need of replacement. To facilitate deep integrations and automated spectral line surveys, a family of remote programmable, synthesized, dual-frequency balanced receivers covering the astronomical important 180 - 720 GHz atmospheric windows is in an advanced stage of development. Installation of the first set of receivers is expected in the spring of 2012. Dual-frequency observation will be an important mode of operation offered by the new facility instrumentation. Two band observations are accomplished by separating the H and V polarizations of the incoming signal and routing them via folded optics to the appropriate polarization sensitive balanced mixer. Scientifically this observation mode facilitates pointing for the higher receiver band under mediocre weather conditions and a doubling of scientific throughput (2 x 4 GHz) under good weather conditions.

We review the introduction and development of a novel method for the characterization of magnetic fields in star-forming regions. The technique is based on the comparison of spectral line profiles from coexistent neutral and ion molecular species commonly detected in molecular clouds, sites of star formation. Unlike other methods used to study magnetic fields in the cold interstellar medium, this ion/neutral technique is not based on spin interactions with the field. Instead, it relies on and takes advantage of the strong cyclotron coupling between the ions and magnetic fields, thus exposing what is probably the clearest observational manifestation of magnetic fields in the cold, weakly ionized gas that characterizes the interior of molecular clouds. We will show how recent development and modeling of the ensuing ion line narrowing effect leads to a determination of the ambipolar diffusion scale involving the turbulent component of magnetic fields in star-forming regions, as well as the strength of the ordered component of the magnetic field.

We report new observations of the fundamental $J=1-0$ transition of HCl (at 625.918GHz) toward a sample of 25 galactic star-forming regions, molecular clouds, and evolved stars, carried out using the Caltech Submillimeter Observatory. Fourteen sources in the sample are also observed in the corresponding H\tscl\ $J=1-0$ transition (at 624.978GHz). We have obtained clear detections in all but four of the targets, often in emission. Absorptions against bright background continuum sources are also seen in nine cases, usually involving a delicate balance between emission and absorption features. From RADEX modeling, we derive gas densities and HCl column densities for sources with HCl emission. HCl is found in a wide range of environments, with gas densities ranging from $10^5$ to $10^7$~cm$^{-3}$. The HCl abundance relative to H$_2$ is in the range of $(3-30)\times10^{-10}$. Comparing with the chlorine abundance in the solar neighborhood, this corresponds to a chlorine depletion factor of up to $\sim$400, assuming that HCl accounts for one third of the total chlorine in the gas phase. The [\tfcl]/[\tscl] isotopic ratio is rather varied, from unity to $\sim$5, mostly lower than the terrestrial value of 3.1. Such variation is highly localized, and could be generated by the nucleosynthesis in supernovae, which predicts a \tscl\ deficiency in most models. The lower ratios seen in W3IRS4 and W3IRS5 likely confine the progenitors of the supernovae to stars with relatively large mass ($\ga$25M$_\sun$) and high metallicity (Z$\sim$0.02)., 11 pages, 5 figures, accepted by ApJ

Accepted: 2009-10-02, 資料番号: SA1000767000

A global climate model experiment is performed to evaluate the effect of irrigation on temperatures in several major irrigated regions of the world. The Community Atmosphere Model, version 3.3, was modified to represent irrigation for the fraction of each grid cell equipped for irrigation according to datasets from the Food and Agriculture Organization. Results indicate substantial regional differences in the magnitude of irrigation-induced cooling, which are attributed to three primary factors: differences in extent of the irrigated area, differences in the simulated soil moisture for the control simulation (without irrigation), and the nature of cloud response to irrigation. The last factor appeared especially important for the dry season in India, although further analysis with other models and observations are needed to verify this feedback. Comparison with observed temperatures revealed substantially lower biases in several regions for the simulation with irrigation than for the control, suggesting that the lack of irrigation may be an important component of temperature bias in this model or that irrigation compensates for other biases. The results of this study should help to translate the results from past regional efforts, which have largely focused on the United States, to regions in the developing world that in many cases continue to experience significant expansion of irrigated land.

We report on a 275-425-GHz tunerless waveguide receiver with a 3.5-8-GHz IF. As the mixing element, we employ a high-current-density Nb-AlN-Nb superconducting-insulating-superconducting (SIS) tunnel junction. Thanks to the combined use of AlN-barrier SIS technology and a broad bandwidth waveguide to thin-film microstrip transition, we are able to achieve an unprecedented 43% instantaneous bandwidth, limited by the receiver's corrugated feedhorn. The measured double-sideband (DSB) receiver noise temperature, uncorrected for optics loss, ranges from 55 K at 275 GHz, 48 K at 345 GHz, to 72 K at 425 GHz. In this frequency range, the mixer has a DSB conversion loss of 2.3 plusmn1 dB. The intrinsic mixer noise is found to vary between 17-19 K, of which 9 K is attributed to shot noise associated with leakage current below the gap. To improve reliability, the IF circuit and bias injection are entirely planar by design. The instrument was successfully installed at the Caltech Submillimeter Observatory (CSO), Mauna Kea, HI, in October 2006.

Deuterium enhancement of monodeuterated species has been recognized for more than 30 years as a result of chemical fractionation that results from the difference in zero-point energies of deuterated and hydrogenated molecules. The key reaction is the deuteron exchange in the reaction between HD, the reservoir of deuterium in dark interstellar clouds, and the molecular ion, leading to the production of H 2 D + molecule, and the low temperature in dark interstellar clouds favours this production. Furthermore, the presence of multiply deuterated species have incited our group to proceed further and consider the subsequent reaction of H 2 D + with HD, leading to D 2 H + , which can further react with HD to produce . In pre-stellar cores, where CO was found to be depleted, this production should be increased as CO would normally destroy . The first model including D 2 H + and predicted that these molecules should be as abundant as H 2 D + . The first detection of the D 2 H + was made possible by the recent laboratory measurement for the frequency of the fundamental line of para -D 2 H + . Here, we present observations of H 2 D + and D 2 H + towards a sample of dark clouds and pre-stellar cores and show how the distribution of ortho -H 2 D + (1 1,0 –1 1,1 ) can trace the deuterium factory in pre-stellar cores. We also present how future instrumentation will improve our knowledge concerning the deuterium enhancement of .

Prestellar cores are unique laboratories for studies of the chemical and physical conditions preceding star formation. We observed the prestellar core L1544 in the fundamental transition of ortho-H2D+ (1_1,0-1_1,1) at different positions over 100", and found a strong correlation between its abundance and the CO depletion factor. We also present a tentative detection of the fundamental transition of para-D2H+ (1_1,0-1_0,1) at the dust emission peak. Maps in N2H+, N2D+, HCO+ and DCO+ are used, and interpreted with the aid of a spherically symmetric chemical model that predicts the column densities and abundances of these species as a function of radius. The correlation between the observed deuterium fractionation of H3+, N2H+ and HCO+ and the observed integrated CO depletion factor across the core can be reproduced by this chemical model. In addition a simpler model is used to study the H2D+ ortho-to-para ratio. We conclude that, in order to reproduce the observed ortho-H2D+ observations, the grain radius should be larger than 0.3 microns., 24 pages, 9 figures, accepted in ApJ (to be published in July 2006)

We present ~15 arcsecond resolution single-dish imaging of the Horsehead nebula in the CI (1-0) and CO (4-3) lines, carried out using the CHAMP array at the Caltech Submillimeter Observatory (CSO). The data are used together with supporting observations of the (2-1) transitions of the CO isotopologues to determine the physical conditions in the atomic and molecular gas via Photon Dominated Region (PDR) modeling. The CO (4-3)/(2-1) line ratio, which is an excellent tracer of the direction of the incoming UV photons, increases at the western and northern edges of the nebula, confirming that the illumination is provided mostly by the stars σ and گ Orionis. The observed line intensities are consistent with PDR models with an H nuclei volume density of ~3- 7 x 10^4 cm^(-3). The models predict a kinetic temperature of ~12 K and a C^(18)O fractional abundance with respect to H atoms of 2.4 x 10^(-7) in the shielded region, which in turn imply a total molecular mass of ~24 M_☉ in the C^(18)O filament. The outer halo, devoid of C^(18)O, but traced by the CI emission has a comparable density and contributes additional ~13 M_☉ of material, resulting in an upper limit of ~37 M_☉ for the total molecular mass of the nebula.

We present Caltech Submillimeter Observatory 10'' resolution maps of the 3P2 → 3P1 line of neutral atomic carbon (809.3435 GHz) and the J = 7-6 line of CO (806.6518 GHz) covering a region of 2' × 45 around Orion IRc2 in the BN/KL Nebula. The two lines were observed with the same receiver simultaneously, and therefore the two maps have zero relative pointing error. The atomic carbon (C I) emission does not peak toward the IRc2 position and displays a very different spatial distribution with respect to most molecular species. Moderately strong red wings are detected in C I around the region defined by the high-velocity CO gas with a spatial distribution that delineates a shell of ~20'' radius. We propose that CO dissociation in the J-type shocks produced by the interaction of the IRc2 outflows with the surrounding quiescent gas could play a significant role in this enhancement of atomic carbon in that shell.

With the Caltech Submillimeter Observatory, we have carried out an unbiased spectral line survey of Orion KL throughout the 350 μm band (from 795 to 903 GHz). This is the first systematic study of molecular radiation in this frequency range. A total of 541 features, resulting from 929 transitions from a total of 26 species, have been detected. High-excitation transitions from CH3OH, CH3CN, H2CO, HNCO, and C2H5CN indicate the presence of a very hot (~250 K) component at the systemic velocity characteristic of the Hot Core. Physical parameters (column density and rotational temperature) relative to a number of species have been estimated by fitting, in the LTE approximation, the whole 100 GHz spectrum at once, thus taking line blending and optical depth effects properly into account. We also report the tentative detection, for the first time outside the Galactic center region, of the radical NH2, one of the building blocks of the chemistry of ammonia.

We have identified vibrationally excited CH3CH2CN (ethyl cyanide) for the first time in the interstellar medium. Using the Caltech Submillimeter Observatory, the Berkeley-Illinois-Maryland Association Array, and the Caltech Millimeter Array, we have detected several transitions from both the vb = 1 in-plane bending state and the vt = 1 torsional state in the Sgr B2(N-LMH) source. Because these excited states lie near 300 K above ground, vibrationally excited CH3CH2CN is potentially a useful probe of the hottest regions of dense, dusty molecular cloud cores where massive star formation is occurring. In addition, this identification will help account for many unidentified and misidentified spectral lines observed in hot molecular cores.

The 692 GHz para ground-state line of D2H+ has been detected at the Caltech Submillimeter Observatory towards the pre-stellar core 16293E. The derived D2H+ abundance is comparable to that of H2D+, as determined by observations of the 372 GHz line of ortho-H2D+. This is an observational verification of recent theoretical predictions (Roberts, Herbst & Millar 2003), developed to explain the large deuteration ratios observed in cold, high-density regions of the interstellar medium associated with low mass pre-stellar cores and protostars. This detection confirms expectations that the multiply deuterated forms of H3+ were missing factors of earlier models. The inclusion of D2H+ and D3+ in the models leads to predictions of higher values of the D/H ratio in the gas phase., 13 pages; accepted in ApJ Letters

We report on the performance of the SHARC II detector, a 12×32 array of ion implanted Si pop-up bolometers. This 384 element detector array was built as a prototype for the High Angular Resolution Widefield Camera for the Stratospheric Observatory for Infrared Astronomy. We will discuss the design process, the characterization of the detectors, and the performance of the array in the SHARC II instrument. SHARC II is now a facility instrument on the Caltech Submillimeter Observatory, providing background-limited imaging at 350 and 450 µm.

International audience; We present a multitransition study in the 13CO(1-0), 12CO(2-1),12CO(3-2) and 12CO(4-3) lines of a parsec scale elongated structure connected to a low-mass dense core. Densities larger than n H 2= 104 cm-3 are inferred in the central regions of this structure, supporting the proposition that it is a genuine filament denser than its environment. The sharp observed drop of the 12CO and 13CO emissions requires a power law density fall-off steeper than r -1 although a single density law cannot reproduce the spatial shift of 0.1 pc between the 13CO and 12CO drops. Our results support the previous proposition that this elongated structure is a filament threaded by helical magnetic fields, channeling the gas inflow onto the dense core.

We discuss how the combination of polarimetry and ion-to-neutral molecular line width ratio measurements permits the determination of the magnitude and orientation of the magnetic field in the weakly ionized parts of molecular clouds. Polarimetry measurements give the field orientation in the plane of the sky and the ion-to-neutral molecular line width ratio determines the angle between the magnetic field and the line of sight. We show the first results obtained with this technique on the M17 and Orion A star-forming region using Hertz 350 µm polarimetry maps and HCO+-to-HCN molecular line width ratios to provide the first view of the spatial orientation of the magnetic field these molecular clouds.

This work was carried out with using the Caltech Submillimeter Observatory and presents the observational study of HDS and D2S towards a sample of Class 0 sources, and dense cores. We report the first detection of doubly deuterated hydrogen sulfide (D2S) in two dense cores and analyze the chemistry of these molecules aiming to help understand the deuteration processes in the interstellar medium. The observed values of the D2S/HDS ratio, and upper limits, require an atomic D/H ratio in the accreting gas of 0.1-1. The study presented in this Letter supports the hypothesis that formaldehyde, methanol and hydrogen sulfide are formed on the grain surfaces, during the cold pre-stellar core phase, where the CO depleted gas has large atomic D/H ratios. The high values for the D/H ratios are consistent with the predictions of a recent gas-phase chemical model that includes H3+ and its deuterated isotopomers, H2D+, D2H+ and D3+ (Roberts et al. 2003)., 14 pages, 2 figures. accepted in ApJL

[Aims] Ionized carbon is the main gas-phase reservoir of carbon in the neutral diffuse interstellar medium (ISM) and its 158 μm fine structure transition [C ii] is the most important cooling line of the diffuse ISM. We combine [C ii] absorption and emission spectroscopy to gain an improved understanding of physical conditions in the different phases of the ISM., [Methods] We present high-resolution [C ii] spectra obtained with the Herschel/HIFI instrument towards bright dust continuum regions in the Galactic plane, probing simultaneously the diffuse gas along the line of sight and the background high-mass star forming regions. These data are complemented by single pointings in the 492 and 809 GHz fine structure lines of atomic carbon and by medium spectral resolution spectral maps of the fine structure lines of atomic oxygen at 63 and 145 μm with Herschel/PACS., [Results] We show that the presence of foreground absorption may completely cancel the emission from the background source in medium spectral resolution PACS data and that high spectral resolution spectra are needed to interpret the [C ii] and [O i] emission and the [C ii]/FIR ratio. This phenomenon may explain part of the [C ii]/FIR deficit seen in external luminous infrared galaxies where the bright emission from the nuclear regions may be partially canceled by absorption from diffuse gas in the foreground. The C+ and C excitation in the diffuse gas is consistent with a median pressure of ~5900 K cm-3 for a mean kinetic temperature of ~100 K. A few higher pressure regions are detected along the lines of sight, as emission features in both fine structure lines of atomic carbon. The knowledge of the gas density allows us to determine the filling factor of the absorbing gas along the selected lines of sight. The derived median value of the filling factor is 2.4%, in good agreement with the properties of the Galactic cold neutral medium. The mean excitation temperature is used to derive the average cooling due to C+ in the Galactic plane : 9.5 × 10-26 erg-1H-1. Along the observed lines of sight, the gas phase carbon abundance does not exhibit a strong gradient as a function of Galacto-centric radius and has a weighted average of C/H = 1.5 ± 0.4 × 10-4., M.G., M.R., A.G. and E.F. acknowledge support from the Centre National de Recherche Spatiale (CNES). This work was partly funded by grant ANR-09-BLAN-0231-01 from the French Agence Nationale de la Recherche as part of the SCHISM project. J.R.G. thanks Spanish MINECO for funding support under grants CDS2009-00038, AYA2009-07304 and AYA2012-32032. M.R. is supported by the 3DICE project, funded by an ERC Starting grant (Agreement number 336474). NRAO is operated by Associated Universities, Inc., under contract with the National Science Foundation.

We report the detection of the ground-state rotational transition JK = 10 → 00 (0a → 0s) of triply deuterated ammonia at 309.91 GHz in the Barnard 1 cloud, obtained with the Caltech Submillimeter Observatory. The observed, integrated, line intensity of 0.307 ± 0.019 K km s-1 implies an ND3 column density of (2 ± 0.9) × 1012 cm-2, for excitation temperatures in the range 5-10 K. Using previously published H2 and NH3 column density estimates in this source, we derive an ND3 fractional abundance with respect to H2 of (1.5 ± 1) × 10-11 and an ND3-to-NH3 abundance ratio of ~8 × 10-4. The observed abundance ratios can be explained in the framework of gas-phase chemical models, in which the dissociative recombination of partially deuterated ions results in a somewhat higher probability for the ejection of hydrogen atoms than deuterium.

Recent detections of doubly deuterated ammonia and formaldehyde in L134N and L1689N have renewed interest in deuterium fractionation in cold, dense molecular gas. Chemical models show that the level of fractionation depends critically on the physical conditions, namely, the temperature and density of the molecular gas. Therefore, detailed studies of cold, dense molecular cores are required to constrain the existing chemical networks. We have mapped the core of the remarkable star-forming molecular cloud L1689N in a number of molecular tracers, including singly deuterated species, in order to obtain detailed information on the morphology and kinematics of the molecular gas, as well as the physical conditions in the dense core and the shocked regions associated with the molecular outflows emanating from the embedded far-infrared source IRAS 16293-2422. Our data suggest the presence of two regions of interaction between the molecular outflows and the dense ambient cloud, one of them associated with the SiO peak E1, the other one near the peak of deuterated and doubly deuterated molecular species ~90'' east of the IRAS source. The observed intensities of the CO (3-2), (4-3), and (6-5) emission at these two locations are consistent with those predicted by C shock models with velocities of 15-25 and 8-10 km s-1, respectively. The relatively low shock velocity derived for the deuterium peak explains why no SiO emission has been detected at this location. Deuterated molecular species, such as DCO+ and DCN, in the core of L1689N are kinematically and morphologically distinct from other molecular tracers of the dense gas, such as HCO+, H13CO+, and HCN. The peak of deuterated molecules is also displaced from the extended millimeter dust continuum source located in this region. We use formaldehyde observations to derive the excitation conditions in the dense gas and, subsequently, the D/H ratios in HCO+ and HCN at several locations via large velocity gradient modeling. These ratios are typically ~1% toward the locations of the IRAS source and the SiO peak E1, with much higher values, ~10%, derived toward the deuterium peak. These values fall within the range of predictions of gas-phase chemical models for dense and cold gas, provided that significant accretion of H2O, CO, and other molecular species on the dust grains has occurred. However, some discrepancies between the observations and model predictions remain. For example, contrary to gas-phase model predictions, we derive a higher deuterium fractionation in HCN compared to HCO+.

We present a comprehensive analysis of a broad band spectral line survey of the Orion Kleinmann-Low nebula (Orion KL), one of the most chemically rich regions in the Galaxy, using the HIFI instrument on board the Herschel Space Observatory. This survey spans a frequency range from 480 to 1907 GHz at a resolution of 1.1 MHz. These observations thus encompass the largest spectral coverage ever obtained toward this high-mass star-forming region in the sub-mm with high spectral resolution, and include frequencies $>$ 1 THz where the Earth's atmosphere prevents observations from the ground. In all, we detect emission from 39 molecules (79 isotopologues). Combining this dataset with ground based mm spectroscopy obtained with the IRAM 30 m telescope, we model the molecular emission from the mm to the far-IR using the XCLASS program which assumes local thermodynamic equilibrium (LTE). Several molecules are also modeled with the MADEX non-LTE code. Because of the wide frequency coverage, our models are constrained by transitions over an unprecedented range in excitation energy. A reduced $��^{2}$ analysis indicates that models for most species reproduce the observed emission well. In particular, most complex organics are well fit by LTE implying gas densities are high ($>$10$^6$ cm$^{-3}$) and excitation temperatures and column densities are well constrained. Molecular abundances are computed using H$_{2}$ column densities also derived from the HIFI survey. The distribution of rotation temperatures, $T_{\rm rot}$, for molecules detected toward the hot core is significantly wider than the compact ridge, plateau, and extended ridge $T_{\rm rot}$ distributions, indicating the hot core has the most complex thermal structure., Accepted to ApJ. 92 pages, 24 Figures, 9 Tables. Public data products may not be available yet

A sensitive broadband molecular line survey of the Sagittarius B2(N) star-forming region has been obtained with the HIFI instrument on the Herschel Space Observatory, offering the first high-spectral resolution look at this well-studied source in a wavelength region largely inaccessible from the ground (625-157 um). From the roughly 8,000 spectral features in the survey, a total of 72 isotopologues arising from 44 different molecules have been identified, ranging from light hydrides to complex organics, and arising from a variety of environments from cold and diffuse to hot and dense gas. We present an LTE model to the spectral signatures of each molecule, constraining the source sizes for hot core species with complementary SMA interferometric observations, and assuming that molecules with related functional group composition are cospatial. For each molecule, a single model is given to fit all of the emission and absorption features of that species across the entire 480-1910 GHz spectral range, accounting for multiple temperature and velocity components when needed to describe the spectrum. As with other HIFI surveys toward massive star forming regions, methanol is found to contribute more integrated line intensity to the spectrum than any other species. We discuss the molecular abundances derived for the hot core, where the local thermodynamic equilibrium approximation is generally found to describe the spectrum well, in comparison to abundances derived for the same molecules in the Orion KL region from a similar HIFI survey., Accepted to ApJ. 64 pages, 14 figures. Truncated abstract

We present the —rst detection of two submillimeter lines of HDO in the KL region of Orion: J Ka,Kb \ (848.9619 GHz), and (893.6387 GHz). The —rst line has been mapped at 10A 2 1,2 ] 1 1,1 1 1,1 ] 0 0,0 angular resolution. These transitions involve some of the lowest energy levels of HDO and have the shortest wavelengths accessible from the ground. Therefore, they provide a perfect tool to complement previous works that made use of millimeter HDO transitions involving similar energy levels (1 1,0 ] 1 1,1 at 80.6 GHz, at 241.6 GHz, and others). The two submillimeter lines arise from the moderate 2 1,1 ] 2 1,2 expanding material or ii Plateau ˇˇ km s~1, *v ” 20 km s~1). The emission is very compact in (v LSR D 9 both HDO transitions (no more extended than D40A¨45A) with similar intensities, line shapes, and line widths. The Hot Core seems completely hidden in our data in contrast with the majority of other millimeter-wave observations. This fact can only be explained if the Hot Core is embedded or behind the region of the out—ow. The high line opacity of the submillimeter HDO lines would then hide the Hot Core emission. A comparison with our previously published high angular resolution data para-H 2 O

We have obtained high-resolution (approximately 35 km/s) spectra toward the molecular cloud Sgr B2 at 63 micrometers, the wavelength of the ground-state fine-structure line of atomic oxygen (O(I)), using the ISO-LWS instrument. Four separate velocity components are seen in the deconvolved spectrum, in absorption against the dust continuum emission of Sgr B2. Three of these components, corresponding to foreground clouds, are used to study the O(I) content of the cool molecular gas along the line of sight. In principle, the atomic oxygen that produces a particular velocity component could exist in any, or all, of three physically distinct regions: inside a dense molecular cloud, in the UV illuminated surface layer (PDR) of a cloud, and in an atomic (H(I)) gas halo. For each of the three foreground clouds, we estimate, and subtract from the observed O(I) column density, the oxygen content of the H(I) halo gas, by scaling from a published high-resolution 21 cm spectrum. We find that the remaining O(I) column density is correlated with the observed (13)CO column density. From the slope of this correlation, an average [O(I)]/[(13)CO] ratio of 270 +/- 120 (3-sigma) is derived, which corresponds to [O(I)]/[(13)CO] = 9 for a CO to (13)CO abundance ratio of 30. Assuming a (13)CO abundance of 1x10(exp -6) with respect to H nuclei, we derive an atomic oxygen abundance of 2.7x10(exp -4) in the dense gas phase, corresponding to a 15% oxygen depletion compared to the diffuse ISM in our Galactic neighborhood. The presence of multiple, spectrally resolved velocity components in the Sgr B2 absorption spectrum allows, for the first time, a direct determination of the PDR contribution to the O(I) column density. The PDR regions should contain O(I) but not (13)CO, and would thus be expected to produce an offset in the O(I)-(13)CO correlation. Our data do not show such an offset, suggesting that within our beam O(I) is spatially coexistent with the molecular gas, as traced by (13)CO. This may be a result of the inhomogeneous nature of the clouds.

The environment of L1512, a starless dense core, has been mapped at high angular resolution in the ^(12)CO (J = 2-1) line over more than 1 pc, with a few positions observed in the ^(12)CO (J = 3-2) and (J = 4-3) lines. The gas outside the dense core is structured in several filaments, roughly 1 pc long and ~0.1 pc thick, converging at the dense core position. Small longitudinal (~1 km s^(-1) pc^(-1)) but large transverse (up to 8 km s^(-1) pc^(-1)) velocity gradients are observed. Remarkably, the transverse gradients can be seen to change sign periodically, along at least one of the filaments. Thus, there are oscillations in the toroidal velocity within the filaments, which may be a signature of a magnetohydrodynamic instability developing in filaments permeated by a helical magnetic field. In the case of L1512, according to the analysis of Fiege & Pudritz, the growth rate of the instability is low, corresponding to a timescale of the order of 1 Myr. We deduce from the wavelength of the oscillations that the toroidal component of the magnetic field dominates the poloidal component. The toroidal component helps confine the filaments, which are not otherwise confined by self-gravity (m/m_(vir) ~ 0.2), by the pressure of the galactic H I layer, or by external turbulent pressure. We find that the velocity gradients in the vicinity of the dense core provide an estimate for an upper limit to the accretion rate onto the dense core of Ṁ = 4 × 10-6 M_☉ yr^(-1). For the gas characteristics in the filaments, we find that a broad range of density and temperature is allowed for the gas, from n_(H(_2)) = 2 × 10^3 cm^(-3) for the coldest case (T_k = 20 K) down to n_(H(_2)) = 180 cm^(-3) for the warmest (T_k = 250 K).

We present new high spectral resolution observations of the N2D+ J = 2 yields 1 and J = 3 yields 2 as well as N2H+ J = 3 yields 2 lines, towards dense molecular cores. The hyperfine structure of the N2H+ and N2D+ transitions is clearly resolved in these sources, in excellent agreement with quantum mechanical calculations. Optical depths are determined from the observed spectra, leading to D/H values of the order of 10 - 30% for the N2D+/N2H+ system. There are a large number of hyperfine components and in addition to providing satellites they contribute to the broadening and asymmetric shapes of the N2H+ and N2D+ line profiles. It is therefore important to take into account the detailed hyperfine structure of the transitions when deducing astrophysical parameters from observed data.

With the Caltech Submillimeter Telescope, we have performed an unbiased line survey of Orion-KL in the frequency range 607-725 GHz. We were able to identify lines down to a threshold of 1-2 K in main beam brightness temperature units, and we found 1064 spectral features consisting of 2032 lines, partially blended. Apart from the abundant diatomic rotors such as CO, CS, SO, the spectrum is dominated by CH3OH and SO2, both in terms of numbers of lines and integrated flux. The number of unidentified lines is 155 or 14%. We also report the tentative identification of the new molecule SiH in our data. For some complex organic molecules, we find rotation temperatures and column densities which are much higher than those found in earlier studies. It is likely the cause of this is a significant contribution from a very compact, hot component of the Orion molecular cloud core which was not visible in lower frequency surveys.

Together with C+ and CO, C is an important reservoir of carbon in the interstellar medium. We present recent results on the ground state transition of atomic carbon at 492 GHz, and on submillimeter CO lines in nearby galaxies. We show that atomic carbon is a good tracer of molecular gas in spiral galaxy disks. It has also a contribution to the molecular gas cooling: the cooling due to C and CO are of the same order of magnitude, and amounts typically to 4× 10-5 of the FIR continuum. C and CO cooling becomes significant in ULIRG galaxies like Arp220.It is possible to use CI measurements to diagnose the physical conditions in galaxies. Together with CII/CI, the emissivity ratio CI/FIR can be used as a measure of the non-ionizing UV radiation field in galaxies.

Coordinated spectroscopic radio observations of comet C/1999 H1 (Lee) were undertaken between 1999 May 4 and 1999 October 26, using the Swedish-ESO Submillimetre Telescope, the James Clerk Maxwell Telescope, the Caltech Submillimeter Observatory, the 30 m telescope of the Institut de Radio Astronomie Millimetrique, and the Nancay radio telescope. We report on observations of OH, HCN, CH3OH, H2CO, and CS and on the evolution of their production rates with heliocentric distance between 0.8 and 1.7 AU, where the total outgassing rate ranged between 0.2 and 1.6 × 1029 molecules s-1. HNC was detected unexpectedly in this medium-activity comet with a relatively large HNC/HCN mixing ratio of 12%, close to that measured in comet C/1995 O1 (Hale-Bopp), which cannot be explained by current chemical models of the coma. CO was tentatively detected with a low abundance around 4% relative to water and is clearly underabundant in comparison to that in comets Hyakutake and Hale-Bopp. An upper limit of D/H less than 300 × 10-5 in water was found from a brief search for HDO. Molecular abundances relative to water of the other species around 1 AU are similar to those observed in other comets, although CH3OH (4%) and H2CO (1%) exhibit some of the largest abundances compared with previous comets.

We have developed a niobium titanium nitride (NbTiN) based superconductor-insulator-superconductor (SIS) receiver to cover the 350 micron atmospheric window. This frequency band lies entirely above the energy gap of niobium (700 GHz), a commonly used SIS superconductor. The instrument uses an open structure twin-slot SIS mixer that consists of two Nb/AlN/NbTiN tunnel junctions, NbTiN thin-film microstrip tuning elements, and a NbTiN ground plane. The optical configuration is very similar to the 850 GHz waveguide receiver that was installed at the Caltech Submillimeter Observatory (CSO) in 1997. To minimize front-end loss, we employed reflecting optics and a cooled beamsplitter at 4 K. The instrument has an uncorrected receiver noise temperature of 205K DSB at 800 GHz and 410K DSB at 900 GHz. The degradation in receiver sensitivity with frequency is primarily due to an increase in the mixer conversion loss, which is attributed to the mismatch between the SIS junction and the twin-slot antenna impedance. The overall system performance has been confirmed through its use at the telescope to detect a wealth of new spectroscopic lines.

There is a strong interest in the submillimeter astronomy community to increase the IF bandwidth of SIS receivers in order to better facilitate broad spectral linewidth and continuum observations of extragalactic sources. However, with an increase in receiver IF bandwidth there is a decrease in the mixer stability. This in turn effects the integration efficiency and quality of the measurement. In order to better understand the noise mechanisms responsible for reducing the receiver stability, we employed a technique first described by D.W. Allan and later elaborated upon by Schieder et al. In this paper we address a variety of factors that degrade the noise stability of SIS receivers. The goal of this exercise is to make recommendations aimed at maximizing SIS receiver stability.

We present observations of the 515-422 transition of water vapor at 325.15 GHz taken with the Caltech Submillimeter Observatory telescope toward Orion IRc2. The emission is more extended than that of other molecular species such as CH3OH. However, it is much less extended than the emission of water vapor at 183.31 GHz reported in an earlier paper by Cernicharo and coworkers. A comparison of the line intensities at 325.15 and 183.31 GHz puts useful constraints on the density and temperature of the emitting regions and allows an estimate of H2O abundance, x(H2O), of 10-4 in the Plateau and 10-6 to 10-5 in the Ridge.

We have designed and constructed a Fourier Transform Spectrometer (FTS) for the study of submillimeter-wave mixers and optical components. The FTS has a large aperture (up to 25.4 cm) and small focal ratio (as fast as f/2.5) to achieve a large throughput. It operates in the 100-3750 GHz (3.3-125 cm^(−1)) frequency range with a resolution of up to 75 MHz (0.0025 cm^(−1)). Here we discuss the design goals and provide a detailed description of the construction of the FTS. In addition, we highlight the variety of studies which have been conducted with this instrument, which include characterizing SIS mixers through both direct and heterodyne detection and measuring the properties of optical materials.

We present detections of the 3P1-3P0 fine-structure line of neutral carbon and of the J=3-2 rotational line of carbon monoxide in the ultraluminous infrared galaxy Arp 220, obtained at the Caltech Submillimeter Observatory. C I emission in Arp 220 is found to be at the expected level in relation to the strong far-infrared (FIR) dust emission and to the CO emission, whereas the C II emission seen by the Infrared Space Observatory long-wavelength spectrometer is very weak. The C I data confirm the presence of a large mass of molecular gas in the nucleus of Arp 220, corresponding to a high extinction in the visible (A -->v=1000). For this galaxy, the total cooling due to atomic carbon is comparable to the total cooling due to carbon monoxide. We use the observed C I/CO (1-0) and CO (3-2)/CO (1-0) emissivity ratios, together with the photon-dominated region models, to infer an average gas density of n(H -->2) ≈ 10 -->4 cm -->−3. We estimate the UV radiation field in this galaxy from the FIR continuum, and independently from hydrogen recombination lines, to be about a factor of 40,000 larger than in the solar vicinity (G -->0=4×10 -->4). The relative weakness of the C II fine-structure line is explained by the large gas density, the exceptionally strong UV field, and the large dust opacity. C II emission from high-redshift analogs of Arp 220 may not be as easy to detect as had been anticipated. However, both CO and C I lines will still be strong emitters.

We have used the Submillimeter High Angular Resolution Camera (SHARC) bolometer camera at the Caltech Submillimeter Observatory to map the distribution of the broadband 350 ?m continuum emission toward the Orion A molecular cloud. A comparison of the 350 ?m flux densities in OMC-1 with previous 1100 ?m measurements indicates a strong spatial variation of the grain emissivity exponent, ?. The lowest value of the exponent (? 1.75) is found toward the Orion Bar photon-dominated region (PDR), while the highest value (? 2.5) is found toward the Orion Ridge north of IRc2. This variation is consistent with the destruction of grain mantles by the UV photons from the Trapezium cluster. The observed spatial variation of ? in OMC-1 suggests that the long-wavelength grain emissivity may also vary significantly in GMC cores on small linear scales (0.5 pc), affecting H2 column density and mass estimates. The 350 ?m continuum emission in the Orion Bar region correlates well with the CO (6-5) peak brightness temperature and is shifted by ~10'' from the molecular component traced by the 13CO (6-5) emission. This indicates that the 350 ?m dust emission in this region originates predominantly in the outer high-temperature PDR layers. Several filamentary structures previously detected in molecular tracers are also seen in our map at flux levels comparable to those seen in the Bar. Over 30 compact dust sources are detected in the OMC-2 and OMC-3 clouds, including a dozen sources not previously known. The average 350/1300 ?m flux ratio based on our data and previous observations of this region (63 ? 19) indicates low dust temperatures (17 ? 4 K, assuming ? = 2) for most of the sources. The brightest 350 ?m source in OMC-3 has a low 350/1300 ?m ratio (~23), indicating a very low dust temperature (~10 K), or a significant opacity at 350 ?m (~2.5). This source appears to be a deeply embedded and cold young protostar. A comparison of the mass estimate for the OMC-2/3 filament based on the 350 ?m continuum emission with previous C18O mass estimates indicates a relatively high grain emissivity, Q(350) = 4 ? 10-4, in this region.

We present new data on the photodissociation regions associated with the reflection nebula NGC7023. 13CO(3-2) emission, delineates a molecular cloud containing a cavity largely devoid of molecular gas around this star. Neutral carbon is closely associated with the 13CO emission while ionized carbon is found inside and at the edges of the cavity. The ionized carbon appears to be, at least in part, associated with HI. We have mapped the northern and southern rims in 12CO(6-5) emission and found a good association with the H2 rovibrational emission, though the warm CO gas permeates a larger fraction of the molecular cloud than the vibrationally excited H2. The results are compared with PDR models. We suggest that a second PDR has been created at the surface of the molecular cloud by the scattered radiation from HD 200775. This second PDR produces a layer of atomic carbon at the surface of the sheet, which increases the predicted [C]/[CO] abundance ratio to 10%, close to the observed value., Comment: 34 pages, 8 figures

The close approach to the Earth of comet C/1996 B2 (Hyakutake) in March 1996 allowed searches for minor volatile species outgassing from the nucleus. We report the detection of deuterated water (HDO) through its 1(sub 01)-0(sub 00) rotational transition at 464.925 GHz using the Caltech Submillimeter Observatory. We also present negative results of a sensitive research for the J(5-4) line of deuterated hydrogen cyanide (DCN) at 362.046 GHz. Simultaneous observations of two rotational lines of methanol together with HDO in the same spectrum allow us to determine the average gas temperature within the telescope beam to be 69 +/- 10 K. We are thus able to constrain the excitation conditions in the inner coma and determine reliably the HDO production rate as (1.20 +/- 0.28) x 10(exp 26)/s on March 23-24, 1996. Available IR, UV and radio measurements lead to a water production rate of (2.1 +/- 0.5) x 10(exp 29)/s at the time of our HDO observations. The resulting D/H ratio in cometary water is thus (29 +/- 10) x 10(exp -5) in good agreement with the values of (30.8(sub - 5.3, sup +3.8) (Balsiger et al. 1995) and (31.6 +/- 3.4) x 10(exp -5) (Eberhardt et al. 1995) determined in comet P/Halley from in situ ion mass spectra. The inferred 3 a upper limit for the D/H ratio in HCN is 1%. Deuterium abundance is a key parameter for studying the origin and the early evolution of the Solar System and of its individual bodies. Our HDO measurement confirms that, in cometary water, deuterium is enriched by a factor of at least 10 relative to the protosolar ratio, namely the D/H ratio in H2 in the primitive Solar Nebula which formed from the collapse of the protosolar cloud. This indicates that cometary water has preserved a major part of the high D/H ratio acquired in this protosolar cloud through ion-molecule isotopic exchanges or grain-surface reactions and was not re-equilibrated with H2 in the Solar Nebula. Scenarios of formation of comets consistent with these results are discussed.

We report the first detection of the submillimeter emission from the 13C isotope of atomic carbon in the interstellar medium. The F=5/2-3/2 component of the 3P2-3P1 transition was observed with the Caltech Submillimeter Observatory in a region ~4' S of Orion IRc2, near the western end of the Orion Bar. The 12C-to-13C isotopic abundance ratio is 58±12 corrected for opacity of the 12C I line and the fractional intensity of the 13C I hyperfine component (60%). This is in agreement with the value for the equivalent ratio in C+. In comparison, our measurement of the C18O-to-13C18O ratio from observations of 2-1 and 3-2 lines toward the same position gives a value of 75±9. Photodissociation region models predict that the 12C-to-13C abundance ratio is particularly sensitive to chemical fractionation effects. If13C+ is preferentially incorporated into 13CO at cloud edges, there will be a dramatic reduction in the abundance of 13C. This is contrary to our observations, implying that the importance of chemical fractionation is small or is compensated for by isotopic-selective photodissociation of 13CO in this region with a large UV illumination.

With the advent of large submillimeter telescopes at high, dry sites, the atmospheric background noise in a moderate bandwidth can be low enough to challenge the ability of instrument designers to produce sufficiently low noise bolometers to be background limited. We compare the predictions for the noise power of a bolometer observing through an emissive atmosphere, considering the effect of atmospheric absorption, telescope optical efficiency, and detector optical efficiency, with measurements through the atmosphere over Mauna Kea.