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At least 199 records · Page 11
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DOE OSTI2026

Deep X-Ray Observation of NGC 3221: Everything Everywhere All at Once

We present a comprehensive analysis of 475 ks (438 ks unpublished and 37 ks archival) XMM-Newton/EPIC-pn observations of a nearby, highly inclined, star-forming, luminous infrared galaxy NGC 3221 through spatial, temporal, and spectral information. We confirm the presence of a low-luminosity (presumably Compton-thick) active galactic nucleus (AGN). The 0.4–12 keV luminosity and the hardness ratio of the six ultraluminous X-ray sources previously identified in Chandra data exhibit diverse variability on day scales. The collective emission from unresolved sources exhibits a different day-scale variability. We have also discovered two new predominantly soft (<1 keV) sources. One of these has an enigmatic spectral shape featuring a soft component, which we interpret as a superbubble in NGC 3221, and a variable hard component from a compact object, unresolved from the superbubble. We do not confidently detect any X-ray emission from SN 1961L. The hot gas in the interstellar medium (ISM, out to ±6 kpc from the disk plane) and that in the extraplanar region (6–12 kpc) both require two thermal phases at ∼0.15 keV and ∼0.55 keV. The ∼0.55 keV component is fainter in the ISM than the ∼0.15 keV component, but the emission from the latter falls off more steeply with disk height than the emission from the former. This makes the extraplanar region hotter and less dense than the ISM. The proximity of NGC 3221 and the occurrence of the underluminous AGN offer a unique observing opportunity to study the hot diffuse medium along with nuclear and diskwide point sources.

Das, Sanskriti [Stanford Univ., CA (United States)↗
DOE OSTI2026

An Updated Picture of Presolar History from Short-lived Radioactive Isotopes and Inferences on the Birth of the Sun

We examine the origin of the short-lived radionuclides (SLRs; defined as having half-lives between 0.1 and 100 Ma) present in the early solar system (ESS) by investigating how predictions of their abundances in the interstellar medium (ISM) from steady-state equilibrium relate to their ESS values. For this, we take into account the non-negligible time t iso elapsed between the isolation of the presolar molecular cloud and the formation of the ESS, during which the SLRs decayed freely. We also consider the alternative scenario in which the presolar molecular cloud remained partially mixed with the ISM, with a mixing timescale t mix . We find that the ESS abundances of 107 Pd and 182 Hf produced by slow neutron captures (s-process) and of 53 Mn and 60 Fe produced by explosive nucleosynthesis can be consistently explained within these scenarios. Their required tiso is 9–12 Ma and their required tmix is 11–14 Ma (with one potential exception of t mix = 38 Ma), depending on galactic uncertainties, such as the galactic star formation history and efficiency and the star-to-gas mass ratio. Another s -process SLR, 205 Pb, has a more uncertain ESS value and falls within only some of these time values. The same applies to the SLRs produced by the p -process ( 92 Nb and 146 Sm), depending on the latter’s half-life. In agreement with previous studies, we find that the ESS abundances of the rapid neutron-capture isotopes ( 129 I, 244 Pu, and 247 Cm) and of the most short-lived radionuclides ( 26 Al, 36 Cl, and 41 Ca) cannot be explained by assuming steady-state equilibrium in the ISM.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1977

The interstellar medium in the direction of the Crab Nebula - Reconciling soft X-ray and radio observations

The total soft X-ray photoabsorption cross section of the interstellar medium (ISM) in the direction of the Crab Nebula is computed on the basis of a two-phase model of the ISM. This cross section is used to reanalyze Copernicus data on the X-ray spectrum of the Crab between 0.7 and 1.5 keV. The total hydrogen column density along the line of sight to that nebula is found to be approximately 2.6 by 10 to the 21st power H atoms/sq cm. This result is evaluated in light of the two-phase model of the ISM, and the predictions based on the X-ray data are compared with results of radio and UV observations. A discrepancy between the radio and X-ray measurements of the hydrogen column density is resolved by noting that 21-cm absorption measurements sample only the neutral hydrogen in clouds while X-ray measurements are sensitive to all forms of hydrogen in both cloud and intercloud regions. It is suggested that roughly 50% of the hydrogen in the direction of the Crab Nebula is in clouds and that 85% of this hydrogen is neutral and atomic.

Ride, S. K.↗
NASA NTRS1977

The conception, birth, and growth of a missile umbilical system

The design development was traced for the sprint 2 and improved sprint 2 missile system (ISMS) umbilical system. The unique system requirements, umbilical designs considered to meet the requirements, and the problems encountered and solutions derived during the design, and development testing of the selected systems are described. The sprint 2 development effort consisted of design, analysis, and testing activities. The ISMS effort involved the performance of an extensive trade study to determine the optimum design to meet the ISMS conditions.

Nordman, G. W.↗
NASA NTRS1983

The X-ray surface brightness of Kepler's supernova remnant

The first X-ray images of Kepler's supernova remnant (SN Ophiuchi 1604) are presented, and consequences for SNR models are discussed. Observations made with the Einstein Observatory Imaging Proportional Counter and High Resolution Imager show the remnant to be circular, with a strong shell brighter in the north than in the south. A flux of 1.2 x 10 to the -10th ergs/sq cm per sec was measured in the 0.15-4.5 keV region, which corresponds to an X-ray luminosity of 1.0 x 10 to the 36th ergs/sec at a distance of 5 kpc and an interstellar medium density of 2.8 x 10 to the 21st/sq cm. The X-ray observations do not allow the determination of whether the SNR is in the adiabatic or free expansion phase, but in either case it is shown that the mean ISM density must be greater than about 0.1/cu cm. In addition, the density of the X-ray emitting gas must be high, and its electron temperature must be fairly low. The high ISM densities derived for Kepler's SNR and other SNRs thus suggest an atypical ISM, possibly influenced by mass lost from the pre-supernova star.

White, R. L.↗
NASA NTRS1984

Spiral structure and star formation. II - Stellar lifetimes and cloud kinematics

The reliability studies using continuum gas dynamical calculations becomes questionable in connection with the apparent clumpiness of the Galaxy's interstellar medium (ISM). Roberts and Hausman (1984) have, therefore, presented a detailed model of a disk galaxy in which the ISM consists entirely of 'cloud particles', which orbit ballistically in the galaxy's gravitational field, collide inelastically with one another, and give birth to and subsequently interact with young star associations. The effects of changing the clouds's collisional mean free path have been examined, and the variations in the young star system's spiral morphology have been explored. The present investigation is concerned with a further study of this clumpy, cloudy ISM model, taking into account longer mean free path models likely to be appropriate for systems of molecular clouds. Attention is also given to the kinematics of clouds as they orbit under the influence of galactic gravity, collisions, and supernova remnants.

Hausman, M. A.↗
NASA NTRS1985

Local interstellar medium and gamma-ray astronomy

The recent improvement of the calibration of the galaxy counts used as an interstellar absorption tracer modifies significantly the picture of the local interstellar medium (ISM). Consequently, previous analyses of the gamma ray emission from the local ISM involving galaxy counts have to be revised. The implications regarding the cosmic ray (CR) density in the local ISM are considered and in particular within Loop I, a nearby supernova remnant (SNR).

Lebrun, F.↗
NASA NTRS1985

Acceleration of cosmic rays in supernova-remnants

It is commonly accepted that supernova-explosions are the dominant source of cosmic rays up to an energy of 10 to the 14th power eV/nucleon. Moreover, these high energy particles provide a major contribution to the energy density of the interstellar medium (ISM) and should therefore be included in calculations of interstellar dynamic phenomena. For the following the first order Fermi mechanism in shock waves are considered to be the main acceleration mechanism. The influence of this process is twofold; first, if the process is efficient (and in fact this is the cas) it will modify the dynamics and evolution of a supernova-remnant (SNR), and secondly, the existence of a significant high energy component changes the overall picture of the ISM. The complexity of the underlying physics prevented detailed investigations of the full non-linear selfconsistent problem. For example, in the context of the energy balance of the ISM it has not been investigated how much energy of a SN-explosion can be transfered to cosmic rays in a time-dependent selfconsistent model. Nevertheless, a lot of progress was made on many aspects of the acceleration mechanism.

Dorfi, E. A.↗
NASA NTRS1987

Diffuse and dark clouds in the interstellar medium

Observations of clouds in the ISM of the Galaxy and the Magellanic Clouds, obtained with the IUE satellite since its launch in 1978, are reviewed. Consideration is given to the techniques used to analyze IUE Maxwellian growth curves and oscillator strengths, the general structure of the Galactic ISM, the high-velocity clouds, heavy-element depletion, and observations toward strongly reddened stars in the outer portions of dark clouds. Theoretical models of interstellar dust formation and selective and nonselective removal of elements from dust grains are discussed; observations of reflection nebulae and their implications for light scattering by dust are examined; the dynamics and ionization structure of the Galactic halo ISM are described; and the Magellanic Cloud observations are briefly characterized. Diagrams, graphs, and tables of numerical data are provided.

De Boer, Klaas S.↗
NASA NTRS1988

Supernova remnants and the interstellar medium - Constraints from cosmic-ray acceleration

The reacceleration rate of cosmic rays by supernova (SN) remnants is calculated and expressed in terms of the parameters determining the cosmic ray model and the SN expansion. It is shown that the constraint on reacceleration derived from the B/C data leads to constraint on the expansion of SN remnants in the ISM and on the effective density of ISM. The effect of cloud evaporation is estimated and the expansion rate of supernova remnants, cosmic ray reacceleration, and the state of the ISM are solved for simultaneously. In the resulting self-consistent solution, SN remnants produce a reacceleration rate and an effective acceleration shock strength which is consistent with the values indicated by the cosmic ray data.

Wandel, A.↗
NASA NTRS1989

Infrared and radio emission from S0 galaxies

Far-IR data are presented on 74 early-type S0 galaxies that were selected on the basis of the availability of radio-continuum measurements. Most of the galaxies are detected at IR wavelengths with IRAS, indicating the presence of a cold interstellar medium (ISM) in these galaxies. The mass of gas in these systems is estimated to lie in the range of 10 to the 7th to 10 to the 10th solar. The most massive ISM in some S0s approaches that found in some spirals. The brighter IR-emitting galaxies all lie close to a relationship established for gas-rich spiral galaxies. None of these galaxies have large ratio fluxes, suggesting that strong nuclear radio sources or extended radio lobes and jets are absent or suppressed. Strong radio emission is found among those galaxies that are either faint or not detected at IR wavelengths. The absence of an ISM suggests that these galaxies are of an earlier type that those that have large IR fluxes.

Bally, John↗
NASA NTRS1989

Metamorphism of cosmic dust: Processing from circumstellar outflows to the cometary regolith

Metamorphism of refractory particles continues in the interstellar medium (ISM) where the driving forces are sputtering by cosmic ray particles, annealing by high energy photons, and grain destruction in supernova generated shocks. Studies of the depletion of the elements from the gas phase of the interstellar medium tell us that if grain destruction occurs with high efficiency in the ISM, then there must be some mechanism by which grains can be formed in the ISM. Most grains in a cloud which collapses to form a star will be destroyed; many of the surviving grains will be severely processed. Grains in the outermost regions of the nebula may survive relatively unchanged by thermal processing or hydration. It is these grains which one hopes to find in comets. However, only those grains encased in ice at low temperature can be considered pristine since a considerable degree of hydrous alteration might occur in a cometary regolith if the comet enters the inner solar system. The physical, chemical and isotopic properties of a refractory grain at each stage of its life cycle will be discussed.

Nuth, Joseph A., III↗
NASA NTRS1989

Methodology for analysis and simulation of large multidisciplinary problems

The Integrated Structural Modeling (ISM) program is being developed for the Air Force Weapons Laboratory and will be available for Air Force work. Its goal is to provide a design, analysis, and simulation tool intended primarily for directed energy weapons (DEW), kinetic energy weapons (KEW), and surveillance applications. The code is designed to run on DEC (VMS and UNIX), IRIS, Alliant, and Cray hosts. Several technical disciplines are included in ISM, namely structures, controls, optics, thermal, and dynamics. Four topics from the broad ISM goal are discussed. The first is project configuration management and includes two major areas: the software and database arrangement and the system model control. The second is interdisciplinary data transfer and refers to exchange of data between various disciplines such as structures and thermal. Third is a discussion of the integration of component models into one system model, i.e., multiple discipline model synthesis. Last is a presentation of work on a distributed processing computing environment.

Russell, William C.↗
NASA NTRS1990

Probing the possibility of a C-12/C-13 galactic abundance gradient

High S/N (equal to or greater than 500) observations of interstellar CH+ with the 3.0 m telescope were performed at Lick Observatory and with the 4.0 m telescope at CTIO, of the reddened, early-type stars HD 183143, HD 24432, and HD 157038 in an effort to probe the existence of a C-12/C-13 abundance gradient in our Galaxy. Previous very high quality optical observations of interstellar CH+ toward five stars within 1 kpc of the Sun have yielded a precise weighted mean C-12/C-13 isotope ratio of 43 plus or minus 4 (1 sigma) (Hawkins, Jura, and Meyer 1985; Hawkins and Jura 1987). The isotope ratios derived toward four lines of sight in the local ISM are uniform within 12 percent. The similarity among these carbon isotope ratios determined in diffuse clouds possessing different physical conditions precludes the possibility that the CH+ molecule is suffering from isotope selective effects in these regions. The precise C-12/C-13 derivable from high quality observations of (12)CH+ and (13)CH+ provide the unique opportunity to probe the homogeneity of the ISM in a large scale and the history of nucleosynthesis in our Galaxy. Since CH+ seems to be the most sensitive probe of C-12/C-13 in the diffuse ISM, observations toward more distant stars located up to 2.5 kpc from the Sun are the best way to study the possibility of a Galactic (C-12/C-13) abundance gradient. The researcher obtained 4232 angstrom data toward all three of the stars mentioned above, 3957 angstrom data toward HD 183143 and HD 157038, and 3745 angstrom data toward HD 157038. Because of the poorer quality of the HD 24432 spectrum, and its weaker CH+ absorption lines, the satellite (13)CH+ line was not detected, and thus only a lower limit on the C-12/C-13 ratio toward this star was obtained. The results obtained from careful reduction and analysis of the data toward these stars in the Northern and Southern Hemispheres are presented.

Hawkins, Isabel↗
NASA NTRS1990

Radiative magnetized thermal conduction fronts

The evolution of plane-parallel magnetized thermal conduction fronts in the interstellar medium (ISM) was studied. Separating the coronal ISM phase and interstellar clouds, these fronts have been thought to be the site of the intermediate-temperature regions whose presence was inferred from O VI absorption-line studies. The front evolution was followed numerically, starting from the initial discontinuous temperature distribution between the hot and cold medium, and ending in the final cooling stage of the hot medium. It was found that, for the typical ISM pressure of 4000 K/cu cm and the hot medium temperature of 10 to the 6th K, the transition from evaporation to condensation in a nonmagnetized front occurs when the front thickness is 15 pc. This thickness is a factor of 5 smaller than previously estimated. The O VI column densities in both evaporative and condensation stages agree with observations if the initial hot medium temperature Th exceeds 750,000 K. Condensing conduction fronts give better agreement with observed O VI line profiles because of lower gas temperatures.

Borkowski, Kazimierz J.↗
NASA NTRS1990

Current star formation in S0 galaxies: NGC 4710

Elliptical (E) and lenticular (S0) galaxies lack the substantial interstellar medium (ISM) found in the star-forming spiral galaxies. However, significant numbers of E and S0 galaxies are known to contain detectable amounts of interstellar matter (e.g., Jura 1988). Thus, it is worth investigating whether these galaxies are currently able to form stars from their ISM, or whether they should be consigned to the dustbin of inert objects (Thronson and Bally 1987). The results strongly imply that current star formation is responsible for NGC 4710's far infrared and radio continuum properties. If this is indeed the case, then one expects this star formation to be fueled by molecular gas, which is presumably dominated by H2 and can be traced by the CO-12 J=1 to 0 line. Both Kenney and Young (1988) and Sage and Wrobel (1989) have detected such an emission line from NGC 4710, and infer the presence of more than 10(exp 8) solar mass of H2. The origin of the molecular gas in NGC 4710 remains a mystery. The galaxy is very deficient in HI (Kenney and Young, in preparation), suggesting that it originally was a spiral galaxy from which the outer, mainly atomic, gas was stripped by the ram pressure of the Virgo Cluster's intracluster medium, leaving only a central interstellar medium (ISM) rich in molecular gas. Alternatively, the CO may have originated via stellar mass loss with subsequent cooling, cooling flows, or capture from a gas-rich companion. Information on the morphology and kinematics of the CO can be compared with that of the galaxy's other gases and stars to distinguish among these various possible origins for the molecular gas. Major axis CO mapping with single dishes indicate an unresolved source. Thus, a millimeter array is currently being used to image NGC 4710 in CO to provide the needed morphological and kinematical data.

Wrobel, J. M.↗
NASA NTRS1991

The interstellar C-H stretching band near 3.4 microns - Constraints on the composition of organic material in the diffuse interstellar medium

The composition and history of dust in the diffuse ISM was studied using 3600-2700/cm absorption spectra of objects which have widely varying amounts of visual extinctions along different lines of sight. The 3300/cm and 2950/cm features are attributed to O-H and C-H stretching vibrations, respectively. The O-H feature in OH 32.8-0.3 is suggestive of circumstellar water ice and is probably not due to material in the diffuse ISM. The features in the 3100-2700/cm region are attributed either to C-H vibrations or to M stars. The spectra of the latter show a series of narrow features in this region that are identified with photospheric OH. Objects in which these bands are seen include OH 01-477, T629-5, and the Galactic center source IRS 7. The C-H stretch feature of diffuse ISM dust has subpeaks which fall within 5/cm of C-H stretching vibrations in the -CH2- and -CH3 groups of saturated aliphatic hydrocarbons.

Sandford, S. A.↗
NASA NTRS1990

The interstellar medium in galaxies - An overview

Recent observational developments on the subject of the interstellar medium in galaxies are summarized, with emphasis placed on global properties. The properties and distribution of the ISM in the solar neighborhood and in the Galactic plane are examined and a number of results from the most important observational probes (HI, CO, and infrared) are described. A recent development is the observation of the ISM in galaxies of all morphological types, early to late. These developments are summarized and the properties of different types of galaxies are compared to one another. The origin of radio galaxies, the effect of environment, and the prospects for direct observations of ISM evolution in galaxies are discussed.

Knapp, G. R.↗