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Results for “MOLECULAR GAS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
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NASA NTRS1990

Molecular gas and star formation in the centers of Virgo spirals

The CO and H alpha flux distributions for a sample of Virgo spirals were mapped out in an attempt to understand the coupling between gas dynamics and star formation in spiral galaxies. A broad range of morphological types were observed (types Sab through Scd) under the hypothesis that the gas dynamics is most influential in determining the overall appearance of a spiral galaxy. Only non-barred spirals were considered so that the well-studied but complicated properties of bars and their role in inducing star formation would not be a factor. All galaxies were chosen from the Virgo cluster to eliminate uncertainties due to distance errors. Since the dynamical seat of a spiral is at its center, it was expected that the dynamics of the central region would influence global properties of the rest of the disk. This could happen through the existence or absence of an inner Lindblad resonance (according to the degree of central concentration of mass) to modulate swing amplification of spiral waves, or the persistence of an oval distortion to initiate an instability which leads to spiral structure.

Canzian, Blaise↗
NASA NTRS1990

High angular resolution mm- and submm-observations of dense molecular gas in M82

Researchers observed CO(7-6), CO(3-2), HCN(3-2) and HCO+(3-2) line emission toward the starburst nucleus of M82 and have obtained an upper limit to H13CN(3-2). These are the first observations of the CO(7-6), HCN(3-2) and HCO+(3-2) lines in any extragalactic source. Researchers took the CO(7-6) spectrum in January 1988 at the Infrared Telescope Facility (IRTF) with the Max Planck Institute for Extraterrestrial Physics/Univ. of California, Berkeley 800 GHz Heterodyne Receiver. In March 1989 researchers used the Institute for Radio Astronomy in the Millimeter range (IRAM) 30 m telescope to observe the CO(3-2) line with the new MPE 350 GHz Superconductor Insulator Superconductor (SIS) receiver and the HCN(3-2) and HCO+(3-2) lines with the (IRAM) 230 GHz SIS receiver (beam 12" FWHM, Blundell et al. 1988). The observational parameters are summarized.

Wild, W.↗
NASA NTRS1990

Molecular gas in intermediate luminosity IRAS galaxies

Single dish CO (J = 1-0) measurements are reported for 29 galaxies of intermediate IR lumionosity in the IRAS Bright Galaxy sample, at distances in the range 20-40 Mpc. Most of the galaxies were mapped at 3-7 points with a 55 arcsec beam. The total H2 masses, assuming a standard Galactic CO-to-H2 conversion ratio, lie in the range of 500 million to 20 billion solar masses. The mean ratio of L(FIR)/M(H2) for this intermediate luminosity sample is approximately three times that found for Virgo spirals and approximately one-third of that found for a sample of higher-luminosity IRAS Bright Galaxies.

Tinney, C. G.↗
NASA NTRS1991

Molecular gas in luminous infrared galaxies

Radio observations of 60 bright IRAS galaxies with redshifts of 1500-25,000 km/sec are reported. Data obtained in the 1-0 line of CO using the 12-m NRAO radio telescope during 1985-1988 are presented in extensive tables, graphs, and line profiles and analyzed along with similar data on 29 less distant IRAS bright galaxies (Tinney et al., 1990). The galaxies are found to have H2 masses of (1-60) x 10 to the 9th solar mass and a mean ratio of H2 to warm dust of 540 + or - 290, corresponding to a total gas/dust ratio of 900-1100. The discrepancy between this value and that for the Galaxy (about 150) is tentatively attributed to the presence of undetected cold dust or errors in interpreting the IR data. The mechanisms which might be responsible for the high ratios of IR luminosity to H2 mass (2-220 solar luminosity per solar mass) are discussed.

Sanders, D. B.↗
NASA NTRS1993

Molecular gas content of galaxies in the Hydra-Centaurus supercluster

A survey of bright spiral galaxies in the Hydra-Centaurus supercluster for the CO(1-0) transition at 115 GHz was performed with the 15m Swedish-ESO submillimeter telescope (SEST). A total of 30 galaxies have been detected in the CO(1-0) transition out of 47 observed, which is a detection rate over 60%. Global physical parameters of these galaxies derived from optical, CO, HI, and IR measurements compare very well with properties of galaxies in the Virgo cluster.

Huchtmeier, W. K.↗
NASA NTRS1993

Molecular gas dynamics applied to low-thrust propulsion

The Direct Simulation Monte Carlo method is currently being applied to study flowfields of small thrusters, including both the internal nozzle and the external plume flow. The DSMC method is employed because of its inherent ability to capture nonequilibrium effects and proper boundary physics in low-density flow that are not readily obtained by continuum methods. Accurate prediction of both the internal and external nozzle flow is important in determining plume expansion which, in turn, bears directly on impingement and contamination effects.

Zelesnik, Donna↗
NASA NTRS1994

Shocked molecular gas around the extremely young source IRAS 03282+3035

We present observations of the shock tracers H2 and SiO around the young stellar object IRAS 03282+3035. This unusual low-luminosity (L approximately = 2 solar luminosity) source drives a strong highly collimated CO outflow, and it is one of the youngest stellar objects known so far. The near-infrared H2 emission, tracing 2000 K gas, comes from extremely high velocity CO bullets along the axis of the blueshifted lobe of the outflow. The millimeter SiO emission, tracing roughly 100 K gas, arises from lower velocity material at the end of the outflow lobe. The lack of high-temperature and high-velocity gas at the end of the outflow lobe indicates there is no not bow shock at the outflow termination. In the context of current jet models this appears to rule out a bow shock driven by a steady state jet. Possible explanations for the structure include a time-dependent jet or a jet dominated by turbulent entrainment.

Bachiller, R.↗
NASA NTRS1997

Infrared Line Emission from Molecular Gas Heated by X-Rays and Energetic Electrons

"I propose to carry out a detailed study using infrared observations (and in some cases, optical and ultraviolet observations) of dense interstellar gas exposed to intense fluxes of X-rays and/or energetic electrons. This is undoubtedly the dominant source of line emission for clouds exposed to X-rays from active galactic nuclei, supernova shocks, or embedded X-ray sources (e.g., X-ray binaries), or to high-temperature or relativistic electrons in galaxy clusters, near powerful radio sources, or supernova remnants. Detailed physical and chemical models of such clouds will be used to analyze infrared observations of the Great Annihilator X-ray source in the Galactic Center, cD galaxies in massive cooling flows, and the nuclei of Seyfert galaxies which will be obtained with the Infrared Space Observatory (ISO), UV and optical observations of the Crab Nebula obtained with the Hubble Space Telescope, and ground-based near-infrared observations of Seyfert nuclei. Results from this work will also be of great relevance to observations obtained with the Submillimeter Wave Astronomical Satellite (SWAS). In the first year of funding of this proposal, my chief collaborators (D.J. Hollenbach and A.G.G.M. Tielens, both of NASA Ames Research Center) and I concentrated on completing our models of the physical conditions in, and the resulting line emission from, dense gas irradiated by X-rays. As noted in the original proposal, some important physical processes were not yet thoroughly incorporated into our models at the time of submission. We completed our modeling of the physical conditions and line emission for essentially the entire range of parameter space (five orders of magnitude in X-ray flux to gas density ratio) occupied by typical dense interstellar clouds in which the gas is mostly neutral and X-rays are important for the ionization, chemistry, and thermal balance.

Maloney, Philip R.↗
NASA NTRS2014

Molecular Gas Clumps from the Destruction of Icy Bodies in the beta Pictoris Debris Disk

Many stars are surrounded by disks of dusty debris formed in the collisions of asteroids, comets and dwarf planets. But is gas also released in such events? Observations at sub-mm wavelengths of the archetypal debris disk around β Pictoris show that 0.3% of a Moon mass of carbon monoxide orbits in its debris belt. The gas distribution is highly asymmetric, with 30% found in a single clump 85 AU from the star, in a plane closely aligned with the orbit of the inner planet, beta Pic b. This gas clump delineates a region of enhanced collisions, either from a mean motion resonance with an unseen giant planet, or from the remnants of a collision of Mars-mass planets.

wavelengths↗