Water Line Profiles Research Articles

The Way of Water: ALMA Resolves H2O Emission Lines in a Strongly Lensed Dusty Star-forming Galaxy at z ∼ 3.1

We report Atacama Large Millimeter/submillimeter Array (ALMA) high-resolution (≲0.3″) observations of water emission lines p-H2O(202 − 111), o-H2O(321 − 312), p-H2O(422 − 413), in the strongly lensed galaxy HATLASJ113526.2-01460 at redshift z ∼3.1. From the lensing-reconstructed maps of water emission and line profiles, we infer the general physical properties of the interstellar medium (ISM) in the molecular clouds where the lines arise. We find that the water vapor lines o-H2O(321 − 312), p-H2O(422 − 413) are mainly excited by far-infrared (FIR) pumping from dust radiation in a warm and dense environment, with dust temperatures ranging from 70 to ∼100 K, as suggested by the line ratios. The p-H2O(202 − 111) line, instead, is excited by a complex interplay between FIR pumping and collisional excitation in the dense core of the star-forming region. This scenario is also supported by the detection of the medium-level excitation of CO resulting in the line emission CO (J = 8–7). Thanks to the unprecedented high resolution offered by the combination of ALMA capabilities and gravitational lensing, we discern the different phases of the ISM and locate the hot molecular clouds into a physical scale of ∼500 pc. We discuss the possibility of J1135 hosting an active galactic nucleus in its accretion phase. Finally, we determine the relation between the water emission lines and the total IR luminosity of J1135, as well as the star formation rate as a function of water emission intensities, comparing the outcomes to local and high-z galactic samples from the literature.

A 6-DoF maneuvering model for the rapid estimation of hydrodynamic actions in deep and shallow waters

We present a modular mathematical model and a reference technique for the rapid estimation of maneuvering trajectories and motion time histories of single- and twin-screw propulsion ships. Heave, roll and pitch radiation damping are estimated from a non-linear unified seakeeping/maneuvering time-domain tool using numerical decay tests and then implemented to a 6–DoF model in the form of critical damping and natural period. Short waves are idealised by numerical integration along the vessel's waterline profile and associated hydrodynamic actions are implemented in a response curve format. For the rapid assessment of hull in-plane hydrodynamic forces, derivatives are implemented via semi-empirical methods, CFD or model test data. Results are validated against experiments available for zig-zag and turning cycle trajectories of vessels with different hull forms and propulsion configurations. It is concluded that the approach presented is feasible for the prediction of maneuvering trajectories of existing or new-build vessels and for estimating the evasive velocity in way of contact before grounding.

Herschel water maps towards the vicinity of the black hole Sgr A*

Aims. We study the spatial distribution and kinematics of water emission in a ~8 × 8 pc2 region of the Galactic center (GC) that covers the main molecular features around the supermassive black hole Sagittarius A* (Sgr A*). We also analyze the water excitation to derive the physical conditions and water abundances in the circumnuclear disk (CND) and the “quiescent clouds”. Methods. We presented the integrated line intensity maps of the ortho 110 − 101, and para 202 − 111 and 111 − 000 water transitions observed using the On the Fly mapping mode with the Heterodyne Instrument for the Far Infrared (HIFI) on board Herschel. To study the water excitation, we used HIFI observations of the ground state ortho and para H218O transitions toward three selected positions in the vicinity of Sgr A*. In our study, we also used dust continuum measurements of the CND, obtained with the Spectral and Photometric Imaging REceiver (SPIRE) instrument. Using a non-local thermodynamical equilibrium (LTE) radiative transfer code, the water line profiles and dust continuum were modeled, deriving H2O abundances (XH2O), turbulent velocities (V t), and dust temperatures (Td). We also used a rotating ring model to reproduce the CND kinematics represented by the position velocity (PV) diagram derived from para 202 − 111 H2O lines. Results. In our H2O maps we identify the emission associated with known features around Sgr A*: CND, the Western Streamer, and the 20 and 50 km s−1 clouds. The ground-state ortho water maps show absorption structures in the velocity range of [−220,10] km s−1 associated with foreground sources. The PV diagram reveals that the 202 − 111 H2O emission traces the CND also observed in other high-dipole molecules such as SiO, HCN, and CN. Using the non-LTE code, we derive high XH2O of ~(0.1–1.3) × 10−5, V t of 14–23 km s−1 , and Td of 15–45 K for the CND, and the lower XH2O of 4 × 10−8 and V t of 9 km s−1 for the 20 km s−1 cloud. Collisional excitation and dust effects are responsible for the water excitation in the southwest lobe of the CND and the 20 km s−1 cloud, whereas only collisions can account for the water excitation in the northeast lobe of the CND. We propose that the water vapor in the CND is produced by grain sputtering by shocks of 10–20 km s−1, with some contribution of high temperature and cosmic-ray chemistries plus a photon-dominated region chemistry, whereas the low XH2O derived for the 20 km s−1 cloud could be partially a consequence of the water freeze-out on grains.

Possibility to locate the position of the H2O snowline in protoplanetary disks through spectroscopic observations

AbstractObservationally locating the position of the H2O snowline in protoplanetary disks is crucial for understanding planetesimal and planet formation processes, and the origin of water on the Earth. In our studies, we conducted calculations of chemical reactions and water line profiles in protoplanetary disks, and identified that ortho/para-H216O, H218O lines with small Einstein A coefficients and relatively high upper state energies are dominated by emission from the hot midplane region inside the H2O snowline. Therefore, through analyzing their line profiles the position of the H2O snowline can be located. Moreover, because the number density of the H218O is much smaller than that of H216O, the H218O lines can trace deeper into the disk and thus they are potentially better probes of the exact position of the H2O snowline in disk midplane.

Herschel-HIFI observations of H2O, NH3, and N2H+toward high-mass starless and protostellar clumps identified by the Hi-GAL survey

Our present understanding of high-mass star formation still remains very schematic. In particular, it is not yet clear how much of the difference between low-mass and high-mass star formation occurs during the earliest star formation phases. The chemical characteristics of massive cold clumps, and the comparison with those of their low-mass counterparts, could provide crucial clues about the exact role that chemistry plays in differentiating the early phases of low-mass and high-mass star formation. Water, in particular, is a unique probe of physical and chemical conditions in star-forming regions. Using the HIFI instrument of Herschel we have observed the ortho-NH3 (1_0-0_0) (572GHz), ortho-H2O (1_10-1_01) (557GHz) and N2H+ (6-5) (559GHz) lines toward a sample of high-mass starless and proto-stellar clumps selected from the "Herschel} Infrared Galactic Plane Survey" (Hi-GAL). We compare our results to previous studies of low-mass and high-mass proto-stellar objects. At least one of the three molecular lines was detected in 4 (out of 35) and 7 (out of 17) objects in the l=59deg and l=30deg galactic regions, respectively. All detected sources are proto-stellar. The water spectra are complex and consist of several kinematic components, identified through a Gaussian decomposition, and in a few sources inverse and regular P-Cygni profiles have been detected. All water line profiles of the l=59deg region are dominated by a broad Gaussian emission feature, indicating that the bulk of the water emission arises in outflows. No such broad emission is detected toward the l=30deg objects. The ammonia line in some cases also shows line wings and an inverse P-Cygni profile, thus confirming that NH3 rotational transitions can be used to probe the dynamics of high-mass star forming regions. Both bolometric and water line luminosity increase with the continuum temperature.

Water in the gas phase

Water in the gas phase

Shocked water in the Cepheus E protostellar outflow

Previous far-infrared observations at low-angular resolution have reported the presence of water associated with low-velocity outflow shocks and protostellar envelopes. The outflow driven by the intermediate-mass class 0 protostar Cep E is among the most luminous outflows detected so far. Using the IRAM 30m telescope, we searched for and detected the para-water line emission at 183 GHz in the Cep E star-forming core. The emission arises from high-velocity gas close to the protostar, which is unresolved in the main beam of the telescope. Complementary observations at 2" resolution with the Plateau de Bure interferometer helped establish the origin of the emission detected and the physical conditions in the emitting gas. The water line profile and its spatial distribution are very similar to those of SiO. We find that the water emission arises from warm ($\sim 200\K$), dense ($(1-2)\times 10^6\cmmt$) gas, and its abundance is enhanced by one to two orders of magnitude with respect to the protostellar envelope. We detect water emission in strong shocks from the high-velocity jet at 1000 AU from the protostar. Despite the large beam size of the telescope, such emission should be detectable with Herschel.

Hot and cool water in Herbig Ae protoplanetary disks

The spatial origin and detectability of rotational H2O emission lines from Herbig Ae type protoplanetary disks beyond 70 micron is discussed. We use the recently developed disk code ProDiMo to calculate the thermo-chemical structure of a Herbig Ae type disk and apply the non-LTE line radiative transfer code Ratran to predict water line profiles and intensity maps. The model shows three spatially distinct regions in the disk where water concentrations are high, related to different chemical pathways to form the water: (1) a big water reservoir in the deep midplane behind the inner rim, (2) a belt of cold water around the distant icy midplane beyond the snow-line r>20AU, and (3) a layer of irradiated hot water at high altitudes z/r=0.1...0.3, extending from about 1AU to 30AU, where the kinetic gas temperature ranges from 200K to 1500K. Although region 3 contains only little amounts of water vapour (~3x10^-5 M_Earth), we find this warm layer to be almost entirely responsible for the rotational water emission lines, execpt for the 3 lowest excitation lines. Thus, Herschel will probe first and foremost the conditions and radial extension of region 3, where water is predominantly formed via neutral-neutral reactions and the gas is thermally decoupled from the dust T_gas>T_dust. The observations do not allow for a determination of the snow-line, because the snow-line truncates the radial extension of region 1, whereas the lines originate from region 3. Different line transfer approximations (LTE, escape probability, Monte Carlo) are discussed. A non-LTE treatment is required in most cases, and the results obtained with the escape probability method are found to underestimate the Monte Carlo results by 2%...45%.

Water and ammonia abundances in S140 with the Odin satellite

We have used the Odin satellite to obtain strip maps of the ground-state rotational transitions of ortho-water and ortho-ammonia, as well as CO(5-4) and 13CO(5-4) across the PDR, and H218O in the central position. A physi-chemical inhomogeneous PDR model was used to compute the temperature and abundance distributions for water, ammonia and CO. A multi-zone escape probability method then calculated the level populations and intensity distributions. These results are compared to a homogeneous model computed with an enhanced version of the RADEX code. H2O, NH3 and 13CO show emission from an extended PDR with a narrow line width of ~3 kms. Like CO, the water line profile is dominated by outflow emission, however, mainly in the red wing. The PDR model suggests that the water emission mainly arises from the surfaces of optically thick, high density clumps with n(H2)>10^6 cm^-3 and a clump water abundance, with respect to H2, of 5x10^-8. The mean water abundance in the PDR is 5x10^-9, and between ~2x10^-8 -- 2x10^-7 in the outflow derived from a simple two-level approximation. Ammonia is also observed in the extended clumpy PDR, likely from the same high density and warm clumps as water. The average ammonia abundance is about the same as for water: 4x10^-9 and 8x10^-9 given by the PDR model and RADEX, respectively. The similarity of water and ammonia PDR emission is also seen in the almost identical line profiles observed close to the bright rim. Around the central position, ammonia also shows some outflow emission although weaker than water in the red wing. Predictions of the H2O(110-101) and (111-000) antenna temperatures across the PDR are estimated with our PDR model for the forthcoming observations with the Herschel Space Observatory.

Water masers in red supergiants

Results of long-term monitoring of circumstellar water maser sources in red supergiants are reviewed. The observations were carried out in 1980–2006 on the RT-22 radio telescope at Pushchino Radio Astronomy Observatory. We discuss the results for the semiregular variable M-supergiant VX Sgr and non-variable M-supergiant IRC–10414. In addition to our single-dish data, very-long-baseline interferometry results are invoked. VX Sgr and IRC–10414 display a characteristic water line profile, which suggests the presence of a rotating circumstellar disc and a bipolar outflow.

The Water Vapor Abundance in Orion KL Outflows

We present the detection and modeling of more than 70 far-IR pure rotational lines of water vapor, including the 18O and 17O isotopologues, towards Orion KL. Observations were performed with the Long Wavelength Spectrometer Fabry-Perot (LWS/FP; R~6800-9700) on board the Infrared Space Observatory (ISO) between ~43 and ~197 um. The water line profiles evolve from P-Cygni type profiles (even for the H2O18 lines) to pure emission at wavelengths above ~100 um. We find that most of the water emission/absorption arises from an extended flow of gas expanding at 25+-5 kms^-1. Non-local radiative transfer models show that much of the water excitation and line profile formation is driven by the dust continuum emission. The derived beam averaged water abundance is 2-3x10^-5. The inferred gas temperature Tk=80-100 K suggests that: (i) water could have been formed in the "plateau" by gas phase neutral-neutral reactions with activation barriers if the gas was previously heated (e.g. by shocks) to >500 K and/or (ii) H2O formation in the outflow is dominated by in-situ evaporation of grain water-ice mantles and/or (iii) H2O was formed in the innermost and warmer regions (e.g. the hot core) and was swept up in ~1000 yr, the dynamical timescale of the outflow.

An Analysis of Water Line Profiles in Star Formation Regions Observed by the [ITAL]Submillimeter Wave Astronomy Satellite[/ITAL

We present spectral line profiles for the 557 GHz 110 → 101 ground-state rotational transition of ortho-H216O for 18 Galactic star formation regions observed by the Submillimeter Wave Astronomy Satellite. Water is unambiguously detected in every source. The line profiles exhibit a wide variety of shapes, including single-peaked spectra and self-reversed profiles. We interpret these profiles using a Monte Carlo code to model the radiative transport. The observed variations in the line profiles can be explained by variations in the relative strengths of the bulk flow and small-scale turbulent motions within the clouds. Bulk flow (infall, outflow) must be present in some cloud cores, and in certain cases this bulk flow dominates the turbulent motions.

Industrial modeling of spirals for optimal configuration and design: spiral geometry, fluid flow and forces on particles

Gravity, centrifugal, drag, lift and friction forces act on a particle during its passage down the curvilinear path of the spiral. The resultant force function dictates the separation of particles on the spiral deck by their size and density. Except for gravity force, all other forces depend on the hydrodynamics prevailing on the spiral. The flow of fluid, in turn, is determined by the spiral geometry. In order to develop a tractable and working model for simulation and design of industrial spirals, we describe the spiral geometry in detail, test the suitability of various empirical power laws for different flow regimes that are available in fluvial hydrology and estimate the magnitude of forces acting on particles. It is shown that of the four laws examined, the transitional or mixed flow power law is seemingly most appropriate for simulating the flow indices, such as the water line profile, local flow velocity, flow depth and flow rate along the spiral trough. The power law involves relatively simple computations and mimics the principal features and broad trends of flows as measured experimentally or simulated by highly computationally intensive solution of the Navier–Stokes equations for spiral geometry. The magnitude of individual forces acting on a particle in most instances is less than 10 −4 N, with considerable overlap between the forces. As a consequence, in general no force overwhelms the other forces and apparently it is the rate of change of forces with size, density, velocity and radial location which drives the separation.

Étude numérique et expérimentale des ondes secondaires de Favre consécutives à la rupture d'un barrage

Free-surface transient flows generate wave propagation. Digital models of this phenomenon are based on Saint Venant's equations and assumptions, which do not consider the impact of stream line curves. In some cases, this approach leads to incorrect forecasts of the water line profile and flow speeds generated, and hence underestimation of the size of the flood zone, for example, or the destructive capacity of the dam-break flow. This paper suggests a more complete model, based on Boussinesq's approach, that yields much more accurate consequence forecasts. Laboratory tests confirmed heights, speeds, and pressures, which were also consistent with conclusions drawn from the Favre diagram. Key words: transient flows, dam failure, Favre waves, flooding, damage. [Journal translation]