ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • ASTROPHYSICS  (21)
  • 1980-1984  (21)
Collection
Keywords
Years
Year
  • 1
    facet.materialart.
    Unknown
    On the possibility of detecting very hot gas through absorption-line studies (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The possibility of detecting hot (T greater than or approximately equal to 10 to the 6th K) diffuse interstellar and intergalactic gas through absorption-line studies is assessed. Optical studies of semiforbidden lines are shown to be just beyond feasibility. X-ray absorption-line studies are concluded to be within the capability of future soft X-ray spectrographs, however. In particular, it is shown that the Bragg crystal spectrometer aboard Einstein could possibly have been used to detect O VII and O VIII lines against the Crab if they are present at plausible levels. Improvement of instrument parameters by only a small factor could make this the most important method available for studying hot interstellar, galactic halo and possibly even intergalactic gas.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 264
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 2
    facet.materialart.
    Unknown
    Orion's cloak as a model for supershells of gas around OB associations (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Orion OB1 was the association most heavily observed by the Copernicus satellite UV spectrometer, which detected very unusual, strong interstellar UV absorption lines. Negative velocity gas at -100 km/sec was also noted, together with the absence of a corresponding, very high positive velocity feature. These and other characteristics have led to the present inferrence of a radially expanding, thin, uniform and low column density shell of fast moving gas which surrounds the Ori OB1 and Lambda Ori regions. Inside this shell is a more slowly moving inhomogeneous region of higher density gas which produces the more sporadically distributed gas at velocities in the 30-100 km/sec range. Within this framework, it is suggested that the most recent supernova is seen in the highest velocity gas, while the composite effects of the history of supernova formation lie in the denser, slower material.
    Keywords: ASTROPHYSICS
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 3
    facet.materialart.
    Unknown
    Modelling the Local Interstellar Medium as a Supernova Remnant in a Multiphase Gas (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The construction of supernova remnant which is consistent with the observations and what it talls about the theory was investigated. It is argued that thermal evaporation and local inhomogeneity are crucial elements which are essential to any satisfactory description. It is concluded that: (1) a multiphase supernova remnant (SNR) seems to provide a plausible description of the local interstellar medium (ISM); (2) the local region could have been deficient in cool gas prior to the supernova both on theoretical and observational grounds; (3) the Sun may lie in a region towards the outside of the supernova remnant which hasn't yet come into pressure equilibrium with the hot gas; and (4) evaporative models give a much more satisfactory description of the O VI observations than Sedov Solutions.
    Keywords: ASTROPHYSICS
    Type: NASA. Goddard Space Flight Center Local Interstellar Medium, No. 81; p 287-296
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 4
    facet.materialart.
    Unknown
    The filaments of NGC 1275 - A collision between a galaxy and an accretion flow? (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Morphological evidence is presented (in the form of 3-A-bandpass Fabry-Perot images made with a CCD camera) that the two bright emission-line systems seen toward the galaxy NGC 1275 arise from a high-velocity impact of a foreground galaxy upon the accretion flow of gas cooling in the center of the Perseus cluster. The uniquely high optical-line luminosity of NGC 1275, in comparison with other central galaxies in clusters observed to have cooling flows, may be explained by energy deposited during the collision. Using additional information from 21-cm and extinction measurements, a rough model of the interaction is developed. Problems remain with this model - such as the likelihood of a gas-rich system penetrating to the cluster center. The kinematic structure of the optically emitting gas shows additional complex structure near the nucleus of NGC 1275.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 275; L27-L31
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
    Unknown
    The Gemini-Monoceros X-ray enhancement - A giant X-ray ring (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A 1.5 deg spatial resolution map of the 1/4 KeV diffuse X-ray background enhancement in the Gemini and Monoceros constellations is found to show a circular ring-shaped emission feature with a diameter of 20 deg. The feature and possible X-ray contributions from the Mon OB1 association and neighboring supernova remnants are discussed. From 300 pc, the region has a radius of 50 pc, with an emitting electron density of 0.01 per cu cm. A shell of expanding neutral hydrogen and nonthermal radio spur is observed outside the ring with the X-ray emitting pulsar PSR 0656 + 14 lying close to the center of the ring. Origins of the ring are discussed, ruling out formation by the association Mon OB1. The ring is considered to be a field supernova remnant formed by the progenitor of the central pulsar, and providing constraints on theories of remnant evolution. This conclusion is found to agree with estimated supernova rates, and the absence of additional examples of this stage of evolution is an observational selection effect.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 248
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 6
    facet.materialart.
    Unknown
    Supernova remnant revolution in an inhomogeneous medium. I - Numerical models (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The first numerical simulations of supernova remnant evolution in an inhomogeneous gas are presented. Evolution in the lowest density substrate (the intercloud) is assumed to be spherically symmetric with a large intercloud filling factor and many dense regions (clouds) within the remnant; however, mass momentum and energy transfer between cloud and intercloud are included and the position and morphology of individual clouds tracked. Evolution is considered in several different models of the interstellar medium, both those in which the intercloud gas is diffuse (0.001 to 0.01/cu cm) and those in which it is relatively dense (n approximately 0.3/cu cm) under a variety of assumptions about the efficiency of thermal evaporation from the clouds into the intercloud medium.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 247
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 7
    facet.materialart.
    Unknown
    Cloud fluid compression and softening in spiral arms and the formation of giant molecular cloud complexes (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: With regard to the galactodynamics of the cloudy interstellar medium, the paper considers the response of such a gas to a forcing potential in the tight-winding density wave theory. The cloud fluid is treated in the hydrodynamic limit with an equation of state which softens at high densities. It is shown that in the inner regions of the galaxy, cooling of the cloud fluid in the arms can result in gravitational instability and the formation of large bound complexes of clouds which are identified with the giant molecular clouds (GMCs). Masses, dimensions, distributions, and scale heights of the GMCs are predicted by the theory. It is suggested that the interstellar gas density in the disk is regulated by the gravitational instability mechanism in the arms which siphons material into star formation. Implications for the evolution of individual GMCs and for galactic morphology are discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 245
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 8
    facet.materialart.
    Unknown
    Galaxy formation in an intergalactic medium dominated by explosions (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The evolution of galaxies in an intergalactic medium dominated by explosions of star systems is considered analogously to star formation by nonlinearly interacting processes in the interstellar medium. Conditions for the existence of a hydrodynamic instability by which galaxy formation leads to more galaxy formation due to the propagation of the energy released at the death of massive stars are examined, and it is shown that such an explosive amplification is possible at redshifts less than about 5 and stellar system masses between 10 to the 8th and 10 to the 12th solar masses. Explosions before a redshift of about 5 are found to lead primarily to the formation of massive stars rather than galaxies, while those at a redshift close to 5 will result in objects of normal galactic scale. The model also predicts a dusty interstellar medium preventing the detection of objects of redshift greater than 3, numbers and luminosities of protogalaxies comparable to present observations, unvirialized groups of galaxies lying on two-dimensional surfaces, and a significant number of black holes in the mass range 1000-10,000 solar masses.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 243
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 9
    facet.materialart.
    Unknown
    X-ray emission from M87 - A pressure confined cooling atmosphere surrounding a low mass galaxy (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A conventional model for the mass of the galaxy M87 (500-billion solar masses) is used to show that a radiative cooling flow agrees well with spectroscopically derived mass flow rates (10 solar masses per year) and surface brightness profiles of X-ray emission around the galaxy. A temperature of 100-million K, and a density of a few x 10 to the -4th/cu cm are obtained without the use of a massive halo. The atmosphere contains 1-trillion solar masses of gas, with a temperature profile increasing outward and gas acting as a reservoir for the flow. The present models indicate that thermal conductivity in M87 is less than 0.002 of its classical value, and does not significantly affect properties of the surrounding gas.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 247
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 10
    facet.materialart.
    Unknown
    The contribution of young galaxies to the X-ray background (1980)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The contribution of young galaxies to the diffuse X-ray background is estimated and two mechanisms by which young galaxies may emit hard X-rays are considered. The first mechanism is direct thermal bremsstrahlung emission from a hot galactic wind powered by supernovae. Estimating mass-loss rates from galaxies by arguments based on metallicity and on the X-ray spectroscopic observations of rich clusters, it is shown that galactic winds may contribute substantially to the background. The second mechanism relies on the decreased metallicity of young galaxies to increase the number of supergiant stars and hence the numbers of hard X-ray binaries. This effect quantitatively explains the relatively large X-ray luminosity of the Magellanic clouds and also indicates that binaries in young galaxies may contribute a significant fraction of the diffuse X-ray background. Both mechanisms require that the epoch of galaxy formation be recent (redshift less than 2-3) in order to account for the observed spectral temperature (45 keV) of the hard X-ray background.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 237
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...