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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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NASA NTRS1988

Far-infrared observations of a luminous dust-shrouded source in the nucleus of NGC 4945

High-resolution far-infrared observations of the galaxy NGC 4945 have been obtained from the Kuiper Airborne Observatory. Using new observational techniques and nonlinear deconvolution routines, it is found that virtually all of the far-infrared luminosity originates from a nuclear source no larger than 12 arcsec x 9 arcsec (225 pc x 170 pc) in extent. This size constraint, coupled with the far-infrared dust temperature, indicates that the source is deeply embedded in dust: the lower limit for the 100 micron optical depth is 0.35, which is by far the largest yet measured in an external galaxy. Published optical spectra of NGC 4945 reveal a heavily obscured nonthermal source which exhibits broad line profiles typical of a Seyfert 2 active nucleus; it is concluded that the far-infrared emission is probably due to thermal radiation from dust grains surrounding the nonthermal nuclear source. A compact cluster of massive young stars may also contribute to the infrared luminosity, but the evidence for such star-forming activity is weak.

Brock, David↗
NASA NTRS2006

Description of Light Ion Production Cross Sections and Fluxes on the Mars Surface using the QMSFRG Model

The atmosphere of Mars significantly attenuates the heavy ion component of the primary galactic cosmic rays (GCR), however increases the fluence of secondary light ions (neutrons, and hydrogen and helium isotopes) because of particle production processes. We describe results of the quantum multiple scattering fragmentation (QMSFRG) model for the production of light nuclei through the distinct mechanisms of nuclear abrasion and ablation, coalescence, and cluster knockout. The QMSFRG model is shown to be in excellent agreement with available experimental data for nuclear fragmentation cross sections. We use the QMSFRG model and the space radiation transport code, HZETRN to make predictions of the light particle environment on the Martian surface at solar minimum and maximum. The radiation assessment detector (RAD) experiment will be launched in 2009 as part of the Mars Science Laboratory (MSL). We make predictions of the expected results for time dependent count-rates to be observed by RAD experiment. Finally, we consider sensitivity assessments of the impact of the Martian atmospheric composition on particle fluxes at the surface.

Cucinotta, Francis A.↗
NASA NTRS1993

NGC 4314. II - Hubble Space Telescope I-band surface photometry of the nuclear region

We present an HST I-band Planetary Camera image of the nuclear region of NGC 4314, an anemic barred galaxy with recent star formation confined to a nuclear ring. These data resolve the nuclear ring into multiple sites of new star formation and resolve associated dust lanes into discrete clouds. Deconvolution results in at least 0.13 arcsec resolution, as demonstrated by the de Vaucouleurs r exp 1/4 law. Contrasted with similar studies of M87 and NGC 7457, we find no photometric evidence for an extreme concentration of stars in the center of NGC 4314. We identify an oval distortion of length 8 arcsec in the nuclear region, using ellipse-fitting routines and the unsharp masked frame. This nuclear bar has newer stars near its ends. We catalog 14 star clusters associated with H II regions in the nuclear ring. As an additional demonstration of the resolution achieved, the integral size distribution of these clusters is described by an exponential relationship which prevails down to 0.14 arcsec.

Benedict, G. F.↗
NASA NTRS1993

Star and cluster formation in NGC 1275

Luminous, blue, and unresolved objects have been found by imaging the nuclear region of the central galaxy in the Perseus Cluster, NGC 1275. Stellar formation in a cooling flow in which gas clouds confined by weak magnetic fields are allowed to remain at low densities is favored. Cloud-cloud collisions and coagulation in the high cloud density environment at the center of the galaxy then causes some clouds to become gravitationally unstable and to form globular clusters.

Richer, Harvey B.↗
NASA NTRS1984

Relativistic jet meets target - The gamma-rays from 3C 273

Gamma-rays dominate the emission from quasar 3C 273, although they cannot arise in its active center. Their origin is ascribed to a relativistic beam which entrains and clumps ambient cluster gas. Secondary electrons from nuclear collisions lead to bremsstrahlung gamma-rays and ultimately to a double radio source. This model requires a great deal of clumping of jet and target matter to get sufficient reactions to occur. The clumping required is consistent with the Liouville theorem, given the high collimation of the beam, which suggests that the process, however unexpected, is at least thermodynamically permitted. The present model is experimentally distinguishable from other models through its location of the X-ray source in the extended optical jet region, and through a number of detailed spectral features.

Morrison, P.↗
NASA NTRS2013

Massively Clustered CubeSats NCPS Demo Mission

Technologies under development for the proposed Nuclear Cryogenic Propulsion Stage (NCPS) will require an un-crewed demonstration mission before they can be flight qualified over distances and time frames representative of a crewed Mars mission. In this paper, we describe a Massively Clustered CubeSats platform, possibly comprising hundreds of CubeSats, as the main payload of the NCPS demo mission. This platform would enable a mechanism for cost savings for the demo mission through shared support between NASA and other government agencies as well as leveraged commercial aerospace and academic community involvement. We believe a Massively Clustered CubeSats platform should be an obvious first choice for the NCPS demo mission when one considers that cost and risk of the payload can be spread across many CubeSat customers and that the NCPS demo mission can capitalize on using CubeSats developed by others for its own instrumentation needs. Moreover, a demo mission of the NCPS offers an unprecedented opportunity to invigorate the public on a global scale through direct individual participation coordinated through a web-based collaboration engine. The platform we describe would be capable of delivering CubeSats at various locations along a trajectory toward the primary mission destination, in this case Mars, permitting a variety of potential CubeSat-specific missions. Cameras on various CubeSats can also be used to provide multiple views of the space environment and the NCPS vehicle for video monitoring as well as allow the public to "ride along" as virtual passengers on the mission. This collaborative approach could even initiate a brand new Science, Technology, Engineering and Math (STEM) program for launching student developed CubeSat payloads beyond Low Earth Orbit (LEO) on future deep space technology qualification missions. Keywords: Nuclear Propulsion, NCPS, SLS, Mars, CubeSat.

Robertson, Glen A.↗
NASA NTRS2019

Sub-Eddington Supermassive Black Hole Activity in Fornax Early-type Galaxies

We characterize the incidence and intensity of low-level supermassive black hole activity within the Fornax cluster, through X-ray observations of the nuclei of 29 quiescent early-type galaxies. Using the Chandra X-ray Telescope, we target 17 galaxies from the Hubble Space Telescope Fornax Cluster Survey, down to a uniform (3σ) limiting X-ray luminosity threshold of 5 x 10^(38) erg/s, which we combine with deeper, archival observations for an additional 12 galaxies. A nuclear X-ray point source is detected in 11 out of 29 targets. After accounting for the low-mass X-ray binary contamination to the nuclear X-ray signal, the X-ray active fraction is measured at 26.6% ± 9.6%. The results from this analysis are compared to similar investigations targeting quiescent early types in the Virgo cluster, as well as the field. After correcting for the different mass distributions, the measured Fornax active fraction is less than the field fraction, at more than 3σ, confirming that the funneling of gas to the nuclear regions of cluster members is inhibited compared to those galaxies in the field. At the same time, we find no statistically significant difference between Fornax and Virgo galaxies, with only marginal evidence for a lower active fraction in Fornax (1σ); if real, owing to Fornaxʼs higher galaxy number density, this could indicate that galaxy–galaxy interactions are more effective at gas removal than galaxy-gas effects.

Nathan Lee↗
NASA NTRS1972

Rapid evolution of galactic nuclei.

An evolutionary sequence is suggested for Virgo cluster galaxies, in a radial velocity-nuclear magnitude diagram. This evolution, on a time scale of about 100 m.y., is discussed in terms of the morphology and radial color variations of the galaxies, nuclear size and radio emission. An area scan and profiles of nuclei, obtained with image dissector equipment, are presented.

Tifft, W. G.↗
NASA NTRS1981

Study of the fluctuations in the cosmic X-ray background

The emerging picture indicates that neither the total cosmic X-ray background (CXB) flux nor the fluctuations are completely dominated by any single class of sources. Quasars clearly contribute a substantial fraction of the total flux while galaxy cluster X-ray sources and galactic nuclear activity also make nonnegligible contributions. It appears that from the large angular scale CXB galaxy correlations that no class of relatively low liminosity X-ray sources associated with galaxies can play a major role in supplying the total flux. The origin of the fluctuations looks more complex. It is hard to avoid the conclusion that the NGP-SGP difference and some other features of the CXB map are associated with the local anisotropy in the galactic distribution (the local supercluster). It also appears reasonable to some suppose that at least some large angular structures in the CXB are due to emission from hot galactic halo gs.

Turner, E. L.↗
NASA NTRS1995

Competition of supermassive black holes and galactic spheroids in the destruction of globular clusters

The globular clusters that we observe in galaxies may be only a fraction of the initial population. Among the evolutionary influences on the population is the destruction of globular clusters by tidal forces as the cluster moves through the field of influence of a disk, a bulge, and/or a putative nuclear component (black hole). We have conducted a series of N-body simulations of globular clusters on bound and marginally bound orbits through poetentials that include black hole and speroidal components. The degree of concentration of the spheroidal component can have a considerable impact on the extent to which a globular cluster is disrupted. If half the mass of a 10(exp 10) solar mass spheroid is concentrated within 800 pc, then only black holes with masses greater than 10(exp 9) solar mass can have a significant tidal influence over that already exerted by the bulge. However, if the matter in the spheroidal component is not so strongly concentrated toward the center of the galaxy, a more modest central black hole (down to 10(exp 8) solar mass) could have a dominant influence on the globular cluster distribution, particularly if many of the clusters were initially on highly radial orbits. Our simulations show that the stars that are stripped from a globular cluster follow orbits with roughly the same eccentricity as the initial cluster orbit, spreading out along the orbit like a 'string of pearls.' Since only clusters on close to radial orbits will suffer substantial disruption, the population of stripped stars will be on orbits of high eccentricity.

Charlton, Jane C.↗
NASA NTRS1993

Protogalactic mergers and cosmochronology

We construct schematic models for chemical evolution and cosmochronology within the expanding and collapsing protogalactic halo followed by formation of the local disk. Star formation is associated with both the rate of protogalactic mergers and the intrinsic gas density of protogalactic clouds and the disk. This leads naturally to a scenario in which star formation in the disk can be delayed by several billion years relative to the formation of the oldest globular clusters. We analyze various cosmochronometers in the context of this model and show that the apparent differences between the maximum globular-cluster ages, the white-dwarf cooling age, and nuclear chronometric ages can be understood. The merger models which satisfy the age constraints imply a relatively late forming peak in luminosity and therefore may be consistent with the observed peak in galaxy number counts at intermediate redshifts. Versions of the model with and without nonbaryonic dark matters can yield significant dark baryonic halos.

Mathews, G. J.↗
NASA NTRS1997

Synchrony of clonal cell proliferation and contiguity of clonally related cells: production of mosaicism in the ventricular zone of developing mouse neocortex

We have analyzed clonal cell proliferation in the ventricular zone (VZ) of the early developing mouse neocortex with a replication-incompetent retrovirus encoding human placental alkaline phosphatase (AP). The retrovirus was injected into the lateral ventricles on embryonic day 11 (E11), i.e., at the onset of neuronogenesis. Three days postinjection, on E14, a total of 259 AP-labeled clones of various sizes were found in 7 fetal brains. There are approximately 7 cell cycles between E11 and E14 (), and there is a 1-2 cell cycle delay between retroviral injection and the production of a retrovirally labeled "founder" cell; thus, we estimate that the "age" of the clones was about 5-6 cell cycles. Almost one-half of the clones (48.3%) identified were pure proliferating clones containing cells only in the VZ. Another 18.5% contained both proliferating and postproliferative cells, and 33.2% contained only postproliferative cells. It was striking that over 90% of the clonally related proliferating cells occurred in clusters of two or more apparently contiguous cells, and about 73% of the proliferating cells occurred in clusters of three or more cells. Regardless of the number of cells in the clone, these clusters were tightly packed and confined to a single level of the VZ. This clustering of proliferating cells indicates that clonally related cells maintain neighbor-neighbor relationships as they undergo interkinetic nuclear migration and progress through several cell cycles, and, as a result, the ventricular zone is a mosaic of small clusters of clonally related and synchronously cycling cells. In addition, cells in the intermediate zone and the cortical plate were also frequently clustered, indicating that they became postproliferative at a similar time and that the output of the VZ is influenced by its mosaic structure.

NASA Discipline Neuroscience↗
NASA NTRS1992

Off-center nuclei in galaxies

The nucleus of a galaxy orbits around the mass centroid. Orbital motions appear overstable in numerical experiments started with a galaxy's nucleus at rest atop its mass centroid. The amplitude doubles in 6-10 orbital periods. Orbits precess, nutate, and change their amplitudes, but they keep fairly constant periods. Orbital periods are in resonance with local particle motions, and amplitudes reach a core radius. This resonance suggests that center motions are a local, rather than a global, phenomenon. The overstability implies that a galaxy cannot be formed in nature with its nucleus at rest atop its mass centroid, and that nuclei orbit the mass centroid in real galaxies. These center motions should show up observationally as a shift of the nucleus away from the center defined by nearby isophotes. Off-center nuclei have been reported in many galaxies (e.g., M33, M101, NGC 3379, NGC 3384). Other kinds of observations confirmed the picture of nonsteady galactic centers as well. Gas trapped in moving nuclear regions of a galaxy should show strange flow patterns with possible shocks. The nuclear regions of galaxies including Milky Way and of globular clusters are not likely to be in a static steady state.

Miller, R. H.↗
NASA NTRS1996

The Long and the Short of Gamma-Ray Bursts

We report evidence from the Third BATSE Gamma-Ray Burst Catalog that long (T(sub 90) greater than 10 s) and short (T(sub 90) less than 10 s) gamma-ray bursts (GRBS) represent distinct source populations. Their spatial distributions are significantly different, with long bursts having = 0.282+/- 0.014 but short bursts having = 0.385 +/- 0.019, differing by 0.103 +/- 0.024, significant at the 4.3 or level. This implies different spatial origin and physical processes for long and short bursts. Long bursts may be explained by accretion-induced collapse. Short bursts require another mechanism, for which we suggest neutron star collisions. These are capable of producing neutrino bursts as short as a few milliseconds, consistent with the shortest observed timescales in GRBS. We briefly investigate the parameters of clusters in which neutron star collisions may occur, and discuss the nuclear evolution of expelled and accelerated matter.

Katz, J. I.↗
NASA NTRS2005

Determining the Locations of Brown Dwarfs in Young Star Clusters

Brown dwarfs are stellar objects with masses less than 0.08 times that of the Sun that are unable to sustain nuclear fusion. Because of the lack of fusion, they are relatively cold, allowing the formation of methane and water molecules in their atmospheres. Brown dwarfs can be detected by examining stars' absorption spectra in the near-infrared to see whether methane and water are present. The objective of this research is to determine the locations of brown dwarfs in Rho Ophiuchus, a star cluster that is only 1 million years old. The cluster was observed in four filters in the near-infrared range using the Wide-Field Infra-Red Camera (WIRC) on the 100" DuPont Telescope and Persson's Auxiliary Nasymith Infrared Camera (PANIC) on the 6.5-m Magellan Telescope. By comparing the magnitude of a star in each of the four filters, an absorption spectrum can be formed. This project uses standard astronomical techniques to reduce raw frames into final images and perform photometry on them to obtain publishable data. Once this is done, it will be possible to determine the locations and magnitudes of brown dwarfs within the cluster.

Porter, Lauren A.↗
NASA NTRS1984

The X-ray features of a single-lobed radio galaxy in Abell 754

New radio, optical and X-ray observations of a galaxy with one-sided radio structure located 2.2 Mpc from the center of Abell 754 are reported. From the optical spectra, the cluster membership of the galaxy is confirmed and it is noted that no emission lines are found. An X-ray source with Lx of approximately 2 x 10 to the 43rd erg/s (0.5-3.0 keV) is located in the nucleus (diameter, less than 4 kpc). There is also a weak X-ray extension to the southeast. The central radio source has a luminosity of about 10 to the 41st ergs/s with a diameter of less than 1.5 kpc. A straight radio feature of low surface brightness (a 'jet' or 'tail') extends 170 kpc to the southeast, ending in a diffuse lobe which is oriented in PA of about 45 deg. Consideration is given to pressure balance between the various radio components and the cluster gas, and also to four processes for the origin of the nuclear X-ray emission. Alternative interpretations of the data are given for a classical tailed radio galaxy and for a truly one-sided radio source.

Harris, D. E.↗
NASA NTRS1990

H I absorption toward cooling flows in clusters of galaxies

An H I survey of 14 cooling flow clusters and two noncooling flow clusters was conducted, and H I absorption features were detected against the nuclear radio continuum sources of two cooling flow dominant (CFD) galaxies, 2A 0335 + 096 and MKW3s. The absorption features are broad and redshifted with respect to the stellar absorption-line velocity of the CFDs by 90-225 km/s. This indicates that the H I is falling onto, and is probably gravitationally bound to, the CFDs. The kinematics of the H I clouds suggest a possible kinematic link between the warm and cold phases of the intracluster medium. The clouds are orders of magnitude smaller in radius and mass and larger in density than Galactic H I clouds. The detected CFDs have mass-accretion rates that are about 2.5 times larger than the CFDs that were not detected.

Mcnamara, Brian R.↗