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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

New infrared sources associated with H II regions

The H II regions studied have generally been those which contain OH or H2O maser sources and which have been shown to contain compact condensations of ionized gas which may be connected with star formation processes. A brief account of two such sources, W3 and NGC 7538, is given. On the basis of the reported observations it is concluded that in general H II condensations are infrared sources in the range from 3 to 20 microns. The condensations are hidden optically by large quantities of obscuring matter.

Wynn-Williams, C. G.↗
NASA NTRS2003

[Probing Planck-scale Physics with a Ne-21/He-3 Zeeman Maser]

The Ne-21/He-3 Zeeman maser is a recently developed device which employs co-located ensembles of Ne-21 and He-3 atoms to provide sensitive differential measurements of the noble gas nuclear Zeeman splittings as a function of time, thereby greatly attenuating common-mode systematic effects such as uniform magnetic field variations. The Ne-21 maser will serve as a precision magnetometer to stabilize the system's static magnetic field, while the He-3 maser is used as a sensitive probe for violations of CPT and Lorentz symmetry by searching for small variations in the 3He maser frequency as the spatial orientation of the apparatus changes due to the rotation of the Earth (or placement on a rotating table). In the context of a general extension of the Standard Model of particle physics, the Ne-21/He-3 maser will provide the most sensitive search to date for CPT and Lorentz violation of the neutron: better than 10(exp -32) GeV, an improvement of more than an order of magnitude over past experiments. This exceptional precision will offer a rare opportunity to probe physics at the Planck scale. A future space-based Ne-21/He-3 maser or related device could provide even greater sensitivity to violations of CPT and Lorentz symmetry, and hence to Planck-scale physics, because of isolation from dominant systematic effects associated with ground-based operation, and because of access to different positions in space-time.

Source record↗
DOE OSTI2016

WIDE FIELD CO MAPPING IN THE REGION OF IRAS 19312+1950

We report the results of wide field CO mapping in the region of IRAS 19312+1950. This Infrared Astronomical Satellite ( IRAS ) object exhibits SiO/H{sub 2}O/OH maser emission, and is embedded in a chemically rich molecular component, the origin of which is still unknown. In order to reveal the entire structure and gas mass of the surrounding molecular component for the first time, we have mapped a wide region around IRAS 19312+1950 in the {sup 12}CO J = 1–0, {sup 13}CO J = 1–0 and C{sup 18}O J = 1–0 lines using the Nobeyama 45 m telescope. In conjunction with archival CO maps, we investigated a region up to 20′ × 20′ in size around this IRAS object. We calculated the CO gas mass assuming local thermal equilibrium, the stellar velocity through the interstellar medium assuming an analytic model of bow shock, and the absolute luminosity, using the latest archival data and trigonometric parallax distance. The derived gas mass (225 M {sub ⊙}–478 M {sub ⊙}) of the molecular component and the relatively large luminosity (2.63 × 10{sup 4} L {sub ☉}) suggest that the central SiO/H{sub 2}O/OH maser source is a red supergiant rather than an asymptotic giant branch (AGB) star or post-AGB star.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1982

The development of a magnetically enhanced hydrogen gas dissociation

Application of a dc magnetic field on an RF hydrogen gas dissociator led to the development of a more efficient source of atoms for hydrogen masers. The influence of the applied magnetic field on the plasma and some details of the resulting enhancement of the dissociation efficiency are discussed. Ways that this improved efficiency can result in the enhancement of the operation and field life of hydrogen masers, as well as aid the development of spaceborne masers, are considered.

Maleki, L.↗
DOE OSTI2017

Detection of HC{sub 3}N maser emission in NGC 253

We report the detection of maser emission from the J=4--3 transition of HC{sub 3}N at 36.4 GHz toward the nearby starburst galaxy NGC 253. This is the first detection of maser emission from this transition in either a Galactic or extragalactic source. The HC{sub 3}N maser emission has a brightness temperature in excess of 2500 K and is offset from the center of the galaxy by approximately 18″ (300 pc), but close to a previously reported class I methanol maser. Both the HC{sub 3}N and methanol masers appear to arise near the interface between the galactic bar and the central molecular zone, where it is thought that molecular gas is being transported inwards, producing a region of extensive low-velocity shocks.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

Survey of Water and Ammonia in Nearby Galaxies (SWAN): Resolved Ammonia Thermometry, and Water and Methanol Masers in the Nuclear Starburst of NGC 253

We present Karl G. Jansky Very Large Array molecular line observations of the nearby starburst galaxy NGC 253, from SWAN, the Survey of Water and Ammonia in Nearby galaxies. SWAN is a molecular line survey at centimeter wavelengths designed to reveal the physical conditions of star-forming gas over a range of star-forming galaxies. NGC 253 has been observed in four 1 GHz bands from 21 to 36 GHz at 6″ ∼ 100 pc) spatial and 3.5 km s{sup −1} spectral resolution. In total we detect 19 transitions from 7 molecular and atomic species. We have targeted the metastable inversion transitions of ammonia (NH{sub 3}) from (1, 1) to (5, 5) and the (9, 9) line, the 22.2 GHz water (H{sub 2}O) (6{sub 16}--5{sub 23}) maser, and the 36.1 GHz methanol (CH{sub 3}OH) (4{sub −1}--3{sub 0}) maser. Using NH{sub 3} as a thermometer, we present evidence for uniform heating over the central kpc of NGC 253. The molecular gas is best described by a two kinetic temperature model with a warm 130 K and a cooler 57 K component. A comparison of these observations with previous ALMA results suggests that the molecular gas is not heated in photon-dominated regions or shocks. It is possible that the gas is heated by turbulence or cosmic rays. In the galaxy center we find evidence for NH{sub 3}(3, 3) masers. Furthermore, we present velocities and luminosities of three water maser features related to the nuclear starburst. We partially resolve CH{sub 3}OH masers seen at the edges of the bright molecular emission, which coincides with expanding molecular superbubbles. This suggests that the masers are pumped by weak shocks in the bubble surfaces.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

3-cm fine structure masers: A unique signature of supermassive black hole formation via direct collapse in the early universe

The direct collapse black hole (DCBH) scenario describes the isothermal collapse of a pristine gas cloud directly into a massive, M{sub BH} = 10{sup 4}–10{sup 6}M{sub ⊙} black hole. In this paper we show that large H i column densities of primordial gas at T∼10{sup 4} K with low molecular abundance—which represent key aspects of the DCBH scenario—provide optimal conditions for the pumping of the 2p-level of atomic hydrogen by trapped Lyα photons. This Lyα pumping mechanism gives rise to an inverted level population of the 2s{sub 1/2}−2p{sub 3/2} transition, and therefore also gives rise to stimulated fine structure emission at λ=3.04 cm (rest-frame). We show that simplified models of the DCBH scenario amplify the CMB by up to a factor of ∼10{sup 5}, above which the maser saturates. Hyperfine splitting of the 3 cm transition gives rise to a characteristic broad (FWHM ∼ tens of MHz in the observers frame) asymmetric line profile. This signal subtends an angular scale of ∼1–10 mas, which translates to a flux of ∼0.3–3 μJy, which is detectable with ultra-deep surveys being planned with SKA1-MID. While challenging, as the signal is visible for a fraction of the collapse time of the cloud, the matching required physical conditions imply that a detection of the redshifted 3-cm emission line could provide direct evidence for the DCBH scenario.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2009

Progress Toward a Compact, Highly Stable Ion Clock

There was an update on the subject of two previous NASA Tech Briefs articles: Compact, Highly Stable Ion Clock (NPO-43075), Vol. 32, No. 5 (May 2008), page 63; and Neon as a Buffer Gas for a Mercury-Ion Clock (NPO-42919), Vol. 32, No. 7 (July 2008), page 62. To recapitulate: A developmental miniature mercury-ion clock has stability comparable to that of a hydrogen-maser clock. The ion-handling components are housed in a sealed vacuum tube, wherein a getter pump maintains the partial vacuum, and the evacuated tube is backfilled with mercury vapor in a neon buffer gas. There was progress in the development of the clock, with emphasis on the design, fabrication, pump-down, and bake-out of the vacuum tube (based on established practice in the travelingwave- tube-amplifier industry) and the ability of the tube to retain a vacuum after a year of operation. Other developments include some aspects of the operation of mercury-vapor source (a small appendage oven containing HgO) so as to maintain the optimum low concentration of mercury vapor, and further efforts to miniaturize the vacuum and optical subsystems to fit within a volume of 2 L.

Prestage, John↗
DOE OSTI2014

Class I methanol (CH{sub 3}OH) maser conditions near supernova remnants

We present results from calculations of the physical conditions necessary for the occurrence of 36.169 (4{sub –1}-3{sub 0} E), 44.070 (7{sub 0}-6{sub 1} A {sup +}), 84.521 (5{sub –1}-4{sub 0} E), and 95.169 (8{sub 0}-7{sub 1} A {sup +}) GHz methanol (CH{sub 3}OH) maser emission lines near supernova remnants (SNRs), using the MOLPOP-CEP program. The calculations show that given a sufficient methanol abundance, methanol maser emission arises over a wide range of densities and temperatures, with optimal conditions at n ∼ 10{sup 4}-10{sup 6} cm{sup –3} and T > 60 K. The 36 GHz and 44 GHz transitions display more significant maser optical depths compared to the 84 GHz and 95 GHz transitions over the majority of physical conditions. It is also shown that line ratios are an important and applicable probe of the gas conditions. The line ratio changes are largely a result of the E-type transitions becoming quenched faster at increasing densities. The modeling results are discussed using recent observations of CH{sub 3}OH and hydroxyl (OH) masers near the SNRs G1.4–0.1, W28, and Sgr A East.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1991

Excitation of millimeter and submillimeter water masers

The excitation of maser emission in millimeter and submillimeter transitions of interstellar and circumstellar water is considered. An escape probability method is used to determine the equilibrium populations in 349 rotational states of both ortho- and para-water under varying conditions of gas temperature, density, water abundance, and radiation field. It is shown that, under those conditions believed to prevail around late-type stars and within star-forming regions, strong millimeter and submillimeter water maser emission can be generated by collisional excitations by H2. Several maser transitions can have strengths close to that of the 22 GHz line. The water maser line which can be observed from mountaintop facilities and those which will require air- or space-borne platforms are indicated. The exact portion of parameter space in which each maser transition exhibits peak emission is shown.

Neufeld, David A.↗
NASA NTRS1993

A shock origin for interstellar H2O masers

We present a comprehensive model for the powerful H2O masers observed in starforming regions. In this model the masers occur behind dissociative shocks propagating in dense regions. This paper focuses on high-velocity dissociative shocks in which the heat of H2 reformation on dust grains maintains a large column of 300 - 400 K gas, where the chemistry drives a considerable fraction of the oxygen not in CO to form H2O. The H2O column densities, the hydrogen densities, and the warm temperatures produced by these shocks are sufficiently high to enable powerful maser action, where the maser is excited by thermal collisions with H atoms and H2 molecules. A critical ingredient in determining the shock structure is the magnetic pressure, and the fields required by our models are in agreement with recent observations. The observed brightness temperatures are the result of coherent velocity regions which have dimensions in the shock plane that are five to 50 times the postshock thickness.

Hollenbach, David↗
NASA NTRS1985

Far-infrared and submillimeter photometry of evolved stars

Broad-band photometric observations at far infrared and submillimeter wavelengths (lambda is greater than 30 microns and less than 1) provide a unique probe of circumstellar shells in evolved objects and of the mass loss processes which produce them. The problems which these observations explore include: dust properties and dust-to-gas ratios in the outflowing material, the mass and structure of the circumstellar shell, and the pumping mechanism for maser emission. This contribution reviews the early work in this still largely unexploited field and reports results in each of the areas listed above. The dramatic advances forthcoming in this area from the IRAS satellite are previewed along with further progress which will come from the next generation of infrared and submillimeter telescopes.

Werner, M. W.↗
DOE OSTI2017

The Molecular Gas Environment in the 20 km s{sup −1} Cloud in the Central Molecular Zone

We recently reported a population of protostellar candidates in the 20 km s{sup −1} cloud in the Central Molecular Zone of the Milky Way, traced by H{sub 2}O masers in gravitationally bound dense cores. In this paper, we report molecular line studies with high angular resolution (∼3″) of the environment of star formation in this cloud. Maps of various molecular line transitions as well as the continuum at 1.3 mm are obtained using the Submillimeter Array. Five NH{sub 3} inversion lines and the 1.3 cm continuum are observed with the Karl G. Jansky Very Large Array. The interferometric observations are complemented with single-dish data. We find that the CH{sub 3}OH, SO, and HNCO lines, which are usually shock tracers, are better correlated spatially with the compact dust emission from dense cores among the detected lines. These lines also show enhancement in intensities with respect to SiO intensities toward the compact dust emission, suggesting the presence of slow shocks or hot cores in these regions. We find gas temperatures of ≳100 K at 0.1 pc scales based on RADEX modeling of the H{sub 2}CO and NH{sub 3} lines. Although no strong correlations between temperatures and linewidths/H{sub 2}O maser luminosities are found, in high-angular-resolution maps we note several candidate shock-heated regions offset from any dense cores, as well as signatures of localized heating by protostars in several dense cores. Our findings suggest that at 0.1 pc scales in this cloud star formation and strong turbulence may together affect the chemistry and temperature of the molecular gas.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1978

A new, compact far-infrared source in the W31 region

In a survey of the W31 region, a compact far-infrared source was detected at the position of the radio continuum source G 10.6-0.4. Associated with this infrared source and in close coincidence with its position is an H II region with a compact core and extended halo as well as OH and H2O masers. An extended molecular cloud, centered on these sources, has also been detected. The compact source and associated masers may be located at the H II region-molecular-cloud interface in a thin shocked layer of neutral gas driven into the molecular cloud by the expansion of the H II region. The compact H II region is depleted of dust and must be surrounded by a very dense shell of dust and gas (hydrogen number density in excess of 200,000 per cu cm). The source probably represents an early stage of stellar evolution.

Fazio, G. G.↗
DOE OSTI2017

Detection of 36 GHz Class I Methanol Maser Emission toward NGC 4945

We have searched for emission from the 36.2 GHz (4{sub −1}→3{sub 0}E) methanol transition toward NGC 4945, using the Australia Telescope Compact Array. 36.2 GHz methanol emission was detected offset southeast from the Galactic nucleus. The methanol emission is narrow, with a line width <10 km s{sup −1} and a luminosity five orders of magnitude higher than Galactic class I masers from the same transition. These characteristics combined the with physical separation from the strong central thermal emission suggests that the methanol emission is a maser. This emission is a factor of ∼90 more luminous than the widespread emission detected from the Milky Way central molecular zone. This is the fourth detection of extragalactic class I emission and the third detection of extragalactic 36.2 GHz maser emission. These extragalactic class I methanol masers do not appear to be simply highly luminous variants of Galactic class I emission and instead appear to trace large-scale regions of low-velocity shocks in molecular gas, which may precede, or be associated with, the early stages of large-scale star formation.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1981

High velocity molecular emission in Orion - A case for stellar winds

On the basis of data from the literature and observations of both a variety of molecules in the high-velocity source of the Orion molecular cloud and high-velocity emissions in other molecular clouds, it is proposed that the high-velocity source consists of clumps of dense molecular gas which are accelerated by the high-velocity stellar wind of a pre-main sequence star. Some of the H2O maser emissions, and the H2 and Herbig-Haro-type emissions, are attributed to shocks associated with the breakup of the protostellar cocoon.

Kuiper, T. B. H.↗