Full List
Radio radiation from interstellar molecules
B. Zuckerman and P. Palmer 1974, Annual review
of astronomy and astrophysics, 279-313
Over 20 radio molecules, composed of as many as
seven atoms have been observed. Questions concerning the detectability of
radio frequency transitions of a molecule in interstellar space are considered
along with estimates of molecular projected densities, envelopes around
far infrared sources and H II regions, and protostellar and stellar sources.
Optically dark nebulae are examined, taking into account densities, temperatures,
the anomalous absorption by H2CO, and dark clouds projected on distant continuum
sources. Molecular clouds associated with far infrared sources and H II
regions are discussed together with the galactic center, aspects of galactic
structure, isotopic abundances, and the isotropic background radiation.
interstellar matter, maser outputs, molecular energy
levels, radio emission, background radiation, brightness temperature, electron
transitions, far infrared radiation, galactic structure, h ii regions, hydroxyl
emission, line spectra, nebulae, optical thickness, stellar evolution
Chemical composition of extragalactic gaseous nebulae
M. Peimbert 1975, Annual review of astronomy and
astrophysics, 113-131
Chemical-abundance determinations for extragalactic
normal H II regions, nuclear H II regions of normal galaxies, and extragalactic
planetary nebulae are reviewed. Techniques for determining the He/H ratios
and heavy-element abundances of normal and nuclear H II regions are outlined,
and values of these factors are given for a number of well-observed galactic
as well as extragalactic regions. Determinations of abundance gradients
in gas clouds of other galaxies are reviewed, and possible ionization mechanisms
are considered for nuclear H II regions. The determinations are shown to
indicate that H II regions located in systems with high ratios of interstellar
to stellar matter are poorer in metal content than those located in systems
with low ratios, and that planetary nebulae may be primarily responsible
for helium enrichment of the interstellar medium. A certain pregalactic
helium abundance is postulated, and cosmological implications of this abundance
are considered in the framework of the standard big-bang model. It is concluded
that this postulated abundance implies an open universe with a deceleration
parameter of less than 0.09.
abundance, chemical composition, extraterrestrial
matter, intergalactic media, planetary nebulae, carbon, galactic evolution,
galactic nuclei, h ii regions, heavy elements, line spectra, orion constellation,
radiation spectra, stellar radiation, stellar spectra
Ultraviolet studies of the interstellar gas
L. Spitzer, Jr. and E. B. Jenkins 1975, Annual
review of astronomy and astrophysics, 133-164
Sounding-rocket and satellite UV observations of
interstellar gas clouds are reviewed with major attention given to Copernicus
observations of interstellar absorption lines. Analysis of typical absorption-line
data is outlined, and observations are reviewed for atomic hydrogen as well
as interstellar H2, HD, and CO molecules. Investigations of atomic abundances
in H I regions are summarized, measurements of atomic deuterium abundances
in the interstellar gas are examined, and the properties of ionized interstellar
gas are described. Theoretical analyses of the physical state of the interstellar
gas are summarized with respect to ionization by energetic radiation, cool
H I clouds, and the intercloud medium. The data obtained thus far are shown
to indicate mean temperatures of about 80 K, particle densities between
10 and 1000 per cu cm, and a depletion of heavy elements that becomes greatly
enhanced with increasing condensation temperature for those H I regions
with strong H2 lines.
interstellar gas, ionized gases, spaceborne astronomy,
stellar spectra, stellar spectrophotometry, ultraviolet radiation, absorption
spectroscopy, cosmic rays, deuterium, h i regions, hydrogen atoms, line
spectra, photomultiplier tubes, stellar evolution, ultraviolet spectrometers
High-velocity neutral hydrogen
G. L. Verschuur 1975, Annual review of astronomy
and astrophysics, 257-293
Current knowledge on high- and intermediate-velocity
neutral-hydrogen clouds in the vicinity of the Galaxy is reviewed. Surveys
of the emission from these clouds are briefly summarized together with the
properties, distributions, and present models of the clouds. Data on the
distribution of the clouds are presented in the form of several galactic
maps, and mass estimates for most of the clouds are examined. The data are
shown to suggest that the intermediate-velocity hydrogen is galactic and
located at least one kiloparsec from the sun, except for a cloud, the Magellanic
Stream, which is intergalactic. The high-velocity features are considered
to be part of a patchy intergalactic bridge between the Magellanic Clouds
and the Galaxy. The existence of high-velocity hydrogen near other spiral
galaxies is discussed, and several models are considered for the general
high-velocity hydrogen phenomenon, including the infall hypothesis and arguments
that the clouds are members of the local group or satellites of the Galaxy.
astronomical models, galactic structure, hydrogen
clouds, interstellar gas, spiral galaxies, galactic evolution, galactic
rotation, gas flow, magellanic clouds, milky way galaxy, random processes
The morphology of hydrogen and of other tracers in the Galaxy
W. B. Burton 1976, Annual review of astronomy and
astrophysics, 275-306
The paper reviews the relative overall morphological
characteristics of atomic hydrogen and other disk constituents that can
be observed by radio along transgalactic paths. Galactic radial distributions
are examined for neutral atomic hydrogen, molecular hydrogen, ionized hydrogen,
carbon monoxide, gamma rays, synchrotron radiation, supernova remnants,
and pulsars. Large-scale galactic motions inferred from 21-cm observations
are discussed, and detailed mapping of the galactic H I distribution is
evaluated. H I volume and column densities near the galactic plane are investigated,
warping of the H I layer in the outer parts of the Galaxy is described,
and evidence for a two-component model of the interstellar medium is presented.
It is shown that: (1) the galactic radial distributions examined are roughly
equivalent except for neutral hydrogen; (2) the extent of the galactic disk,
defined to half-maximum density, is approximately twice as large for H I
as for the other tracers; (3) the H I disk is considerably thicker in the
axial direction; and (4) the general picture emerging for the Galaxy is
consistent with available morphological information on external spiral galaxies.
astronomical models, galactic structure, hydrogen
atoms, hydrogen clouds, interstellar gas, astronomical maps, disks (shapes),
gas density, morphology, pulsars, supernova remnants, synchrotron radiation,
tracers
The radio continuum morphology of spiral galaxies
P. C. Van Der Kruit and R. J. Allen 1976, Annual
review of astronomy and astrophysics, 417-445
Radio observations are reviewed which have been
made with sufficient angular resolution to provide some structural details
of the radio continuum emission from the disks of normal spiral galaxies.
Observed variations of disk brightness and spectral index with radius are
described for M51, NGC 891, the Galaxy, M101, and NGC 253. Observations
of spiral structure in maps of radio-continuum distributions are examined
along with evidence for density-wave compression in M51, the observed spiral
morphology in several other galaxies, and estimates of the amount of compression
in various galaxies. Some recent results obtained from radio-continuum observations
of H I regions in galaxies are summarized, the detection of radio emission
from supernova remnants is discussed, and mechanisms are considered which
have been proposed to explain the absence of radio emission from young supernova
remnants. Radio-emission distributions perpendicular to the planes of galaxies
are investigated, and evidence for extended radio halos and 'thick disks'
is evaluated.
galactic radiation, radio emission, spiral galaxies,
supernova remnants, angular resolution, astronomical maps, brightness temperature,
galactic structure, h i regions, radio astronomy, radio sources (astronomy)
Physical processes in comets
F. L. Whipple and W. F. Huebner 1976, Annual review
of astronomy and astrophysics, 143-172
The paper discusses physical processes in comets
which involve solar and nuclear radial forces that affect the motions of
gases and icy grains, gas-phase chemistry very close to the nuclei of large
comets near the sun, sublimation of icy grains, dissociation of parent molecules
into radicals and of radicals into atoms, and ionization by sunlight and
collisions. The composition and dimensions of nuclei are examined along
with variations in intrinsic brightness, the nature of volatiles, gas production
rates in the coma, characteristics of icy grains in the coma, and the structure
of streamers, ion tails, and dust tails. The structure of the coma is described
in detail on the basis of spectroscopic observations of several comets.
The origin of comets is briefly reviewed together with the relation of comets
to earth, the interplanetary complex, and the interstellar medium. Desirable
future observations are noted, especially by space missions to comets.
chemical composition, comet nuclei, comet tails,
comets, gas dynamics, abundance, astronomical spectroscopy, coma, cosmology,
granular materials, ice formation, molecular spectra, phase transformations,
radicals, sublimation
The interaction of supernovae with the interstellar medium
R. A. Chevalier 1977, Annual review of astronomy
and astrophysics, 175-196
The paper reviews the interaction of supernovae
with the interstellar medium. Topics pertinent to the evolution of a supernova
remnant which are considered include the transfer of energy to the interstellar
medium, the supernova ejecta, the effect of heat conduction, the radiative
shock phase, and the irregular structure of old remnants. Collective effects
of supernovae on the interstellar medium are described with attention to
the ionization, thermal, and kinetic energy. The subject of relativistic
particles is examined with reference to young supernova remnants, old supernova
remnants, and cosmic rays. Future prospects involve radio observations and
infrared studies of young supernova remnants and theoretical analyses of
the plasma physics of the remnants and the hot gas phase.
interstellar matter, supernova remnants, supernovae,
conductive heat transfer, cosmic rays, energy transfer, gamma rays, gas
ionization, kinetic energy, relativistic particles, shock wave interaction,
stellar mass ejection, taylor instability, x ray astronomy
Interstellar scattering and scintillation of radio waves
B. J. Rickett 1977, Annual review of astronomy
and astrophysics, 479-504
A review is presented on the interstellar scattering
and scintillation of radio waves; it relies heavily on the work of Lee and
Jokipi (1975), but almost all the tractable results are for weak scintillation
of the Rayleigh limit of strong scintillation. Attention is given to the
correlation functions, angular scattering, pulse broadening (with particular
consideration of the Crab Nebula, pulsar), and scintillations of intensity
vs time, space and frequency. It is found that the published observations
are compatible with both the Gaussian model and the more realistic power
law model with any alpha exceeding roughly 3.5. The only major conclusion
is that the interstellar irregularities are not homogeneously distributed
on scales of 100-1000 pc on either model.
interstellar extinction, pulsars, radio astronomy,
radio scattering, scintillation, astronomical models, extragalactic radio
sources, interstellar matter, plane waves, point sources, pulse duration,
radio interferometers, stellar spectra, time dependence
Formation and destruction of dust grains
E. E. Salpeter 1977, Annual review of astronomy
and astrophysics, 267-293
Recent studies of the destruction and formation
of interstellar dust grains are reviewed. Turnover rates are provided for
grain formation and destruction around cool stars, in planetary nebulae,
novae, and protostellar nebulae, by sputtering in supernova remnants and
cloud collisions, as well as in molecular clouds and H II regions. Attention
is given to solar-system and interstellar elemental abundances, absorption
lines in the interstellar medium, and the chemical physics of grain formation
and destruction. The theory of homogeneous nucleation is summarized, surface
nucleation and grain reprocessing are examined, and grain-grain collisions
are considered along with grain sputtering and UV effects on grains. Interstellar
extinction observations are evaluated, several grain models are assessed,
and the production of circumstellar dust near red giants, supergiants, IR
stars, novae, planetary nebulae, and very young stars is discussed. The
destruction of interstellar grains by supernova remnants and cloud-cloud
collisions is investigated together with grain formation in and near molecular
clouds and H II regions. It is concluded that the processes in and near
molecular clouds are numerically the most important.
abundance, cosmic dust, interstellar matter, molecular
collisions, nucleation, stellar envelopes, absorption spectra, cool stars,
grains, h ii regions, infrared stars, interstellar chemistry, molecular
spectroscopy, novae, optical properties, planetary nebulae, red giant stars,
stellar evolution, supergiant stars, supernova remnants, thermochemistry
Consequences of mass transfer in close binary systems
H. C. Thomas 1977, Annual review of astronomy and
astrophysics, 127-151
Theoretical and observational studies of mass transfer
in close binary systems are reviewed. The standard assumptions of the Roche
model and their limitations are outlined, and the three recognized cases
of mass transfer are distinguished and analyzed. Previous investigations
of mass or angular-momentum loss in case B are summarized, and earlier analyses
of mass transfer in Algol-type and W UMa-type systems are discussed. Mass
transfer in X-ray binaries is examined, mass transfer during and after the
X-ray binary stage is considered, and several possible scenarios are assessed
for the formation of a binary pulsar. Two unsolved theoretical problems
are noted: the amount of mass and angular-momentum loss from binary systems
and the outcome of mass transfer in contact configurations.
angular momentum, binary stars, mass transfer,
stellar evolution, stellar models, x ray stars, algol, momentum transfer,
neutron stars, roche limit, stellar envelopes, stellar gravitation, stellar
mass accretion, supernova remnants, white dwarf stars, x ray binaries
Radio recombination lines
R. L. Brown, F. J. Lockman and G. R. Knapp 1978,
Annual review of astronomy and astrophysics, 445-485
At the time of the review of radio recombination
line research conducted by Dupree and Goldberg (1970), the subject was concentrated
almost exclusively on the observation and interpretation of lines from the
classic bright radio H II regions. With continuing improvements in the sensitivity
of telescopes and receivers, it has now become possible to use radio recombination
lines to explore a much broader range of phenomena. The formation and transfer
of radio recombination lines are discussed, taking into account the line
intensities and the line shape. Isothermal, homogeneous and heterogeneous,
plane-parallel nebulae are considered. The discussion is generalized to
a finite isothermal nebula with a continuous density gradient. The involved
relations are illustrated with the aid of an example involving an isothermal,
spherically symmetric nebula. Attention is given to heterogeneous nebulae
with a temperature gradient, heterogeneous nebulae observed with a finite
telescope beam, static nebulae, and expanding nebulae. An interpretation
of radio recombination lines is also provided.
astronomical spectroscopy, galactic structure,
h lines, radiative recombination, radio astronomy, radio spectroscopy, abundance,
c band, h ii regions, helium, heterogeneity, homogeneity, isothermal processes,
nebulae, spectral line width, temperature gradients
Gas phase reactions in astrophysics
W. D. Watson 1978, Annual review of astronomy and
astrophysics, 585-615
Aspects of charge transfer in atomic collisions
are considered, taking into account applications of charge transfer in astrophysics,
the determination of cross sections for charge transfer at energies below
a few eV, and current information of possible astrophysical relevance for
charge transfer. Interstellar molecule reactions in the gas phase are discussed,
giving attention to studies of interstellar molecule formation, the rate
coefficients for charge transfer collisions of possible astrophysical interest,
the ionization in diffuse and dense clouds, the determination of the proton
density and cosmic-ray flux in diffuse interstellar clouds from the abundance
of HD, reactions affecting the abundances of small molecules in diffuse
clouds of the interstellar medium, and aspects of isotope fractionation.
astrophysics, charge transfer, gas-gas interactions,
interstellar chemistry, interstellar gas, abundance, carbon compounds, cloud
physics, cosmic rays, fractionation, hydrogen compounds, molecular gases,
nitrogen compounds, oxygen compounds, proton density (concentration), reaction
kinetics
Compact H II regions and OB star formation
H. J. Habing and F. P. Israel 1979, Annual review
of astronomy and astrophysics, 345-385
Studies of compact H II regions and their association
with OB star formation are reviewed. Difficulties in observing compact objects
are summarized, radio observations of compact H II regions are examined,
and IR observations of sources associated with star formation are discussed.
Attention is also given to molecular masers associated with compact H II
regions and emission from molecular clouds containing such regions. The
relevance of compact objects to OB star formation is considered, particularly
in relation to the tendency of OB stars to form in groups and the formation
of individual objects.
b stars, h ii regions, o stars, radio astronomy,
star formation, astronomical maps, infrared astronomy, line spectra, masers,
molecular gases, optical thickness, physical properties, tables (data)
The violent interstellar medium
R. McCray and T. P. Snow, Jr. 1979, Annual review
of astronomy and astrophysics, 213-240
Observational evidence for high-velocity and high-temperature
interstellar gas is reviewed. The physical processes that characterize this
gas are described, including the ionization and emissivity of coronal gas,
the behavior and appearance of high-velocity shocks, and interfaces between
coronal gas and cooler interstellar gas. Hydrodynamical models for the action
of supernova explosions and stellar winds on the interstellar medium are
examined, and recent attempts to synthesize all the processes considered
into a global model for the interstellar medium are discussed.
galactic structure, interstellar gas, stellar winds,
supernovae, flow velocity, gas flow, gas ionization, gas temperature, high
temperature, hydrodynamics, kinetics, morphology, physical properties, shock
wave propagation, solar corona, thermal conductivity
Observed properties of interstellar dust
B. D. Savage and J. S. Mathis 1979, Annual review
of astronomy and astrophysics, 73-111
Recent information on the observed properties of
interstellar dust is reviewed, with an attempt made to clarify some of the
observational uncertainties associated with obtaining dust parameters. Attention
is given to interstellar extinction, the interstellar dust distribution,
the dust-to-gas ratio, and light scattering by dust grains. Interstellar
polarization is also examined, along with heavy-element depletion in the
interstellar medium, thermal emission from interstellar dust grains, diffuse
interstellar features, and the composition and origin of interstellar grains.
cosmic dust, interstellar extinction, interstellar
matter, heavy elements, interstellar radiation, light scattering, linear
polarization, thermal emission, ultraviolet radiation
Interstellar shock waves
C. F. McKee and D. J. Hollenbach 1980, Annual review
of astronomy and astrophysics, 219-262
The structure of interstellar shocks driven by
supernova remnants and by expanding H II regions around early-type stars
is discussed. Jump conditions are examined, along with shock fronts, post-shock
relaxation layers, collisional shocks, collisionless shocks, nonradiative
shocks, radiative atomic shocks, and shock models of observed nebulae. Effects
of shock waves on interstellar molecules are examined, with reference to
the chemistry behind shock fronts, infrared and vibrational-rotational cooling
by molecules, and observations of shocked molecules. Some current problems
and applications of the study of interstellar shocks are summarized, including
the initiation of star formation by radiative shock waves, interstellar
masers, the stability of shocks, particle acceleration in shocks, and shocks
in galactic nuclei.
gas expansion, interstellar gas, shock wave propagation,
h ii regions, interstellar chemistry, nebulae, radiative transfer, shock
fronts, supernova remnants
Nuclear abundances and evolution of the interstellar medium
P. G. Wannier 1980, Annual review of astronomy
and astrophysics, 399-437
Observations of molecular and elemental abundances
in the interstellar medium (ISM) are reviewed, with special attention given
to isotope ratios. The derivation of molecular isotope abundances for the
ISM is discussed, along with H and C fractionation. Millimeter- and centimeter-wave
spectra of giant clouds are examined with respect to isotope abundances
of C, O, N, Si, S, and D. Evidence for the current enrichment of the ISM
by mass loss from evolved stars is considered, together with chemical abundance
gradients in H II regions and planetary nebulae. Cosmic-ray observations
pertaining to abundances in the ISM are summarized, with emphasis on available
results for Ne, Mg, Si, Fe, and Ni. The observations reviewed are shown
to support arguments in favor of: (1) the cosmological production of D and
He-3; (2) the production of the CNO elements by hydrostatic hydrogen burning;
(3) the nucleosynthesis of Ne, Mg, Si, S, Fe, and Ni as a result of He burning;
(4) solar abundances of interstellar S, Fe, and Ni; and (5) a direct association
between observed inhomogeneities in the ISM and mass loss from evolved stellar
objects.
abundance, interstellar chemistry, interstellar
matter, cosmic rays, galactic nuclei, h ii regions, nitrogen isotopes, nuclear
fusion, oxygen isotopes, planetary nebulae, silicon isotopes, spatial distribution,
stellar mass ejection, sulfur isotopes
Envelopes around late-type giant stars
B. Zuckerman 1980, Annual review of astronomy and
astrophysics, 263-288
Studies of the circumstellar envelopes of late-type
giants are reviewed. The chemical composition of circumstellar material
is examined, with emphasis on the gas-phase composition, isotopic abundance,
and dust grains. Physical properties of circumstellar shells are discussed
in terms of radial structure and azimuthal shapes. Observations of maser
emission and mass loss by late-type giants are briefly summarized. Late
stages of evolution are considered for stars with circumstellar envelopes,
including apparently single stars, multiple systems, and symbiotic stars.
giant stars, late stars, stellar envelopes, chemical
composition, cosmic dust, interstellar masers, stellar evolution, stellar
mass ejection
Masers
M. J. Reid and J. M. Moran 1981, Annual review
of astronomy and astrophysics, 231-276
Observations and theories that describe the characteristics
of interstellar masers are described, with particular attention given to
what has been and can be learned about star formation through the study
of masers. Then, observations and theories pertaining to stellar masers
are examined, with emphasis on the information maser emission can provide
about these evolved stars and their mass loss. Attention is then given to
radiative transfer theory as developed for astronomical masers; saturation,
the apparent brightness distribution of the emission, the source of the
input radiation that is amplified, and pump mechanisms are considered. The
use of masers as probes of the electron distribution in the interstellar
medium by means of scattering is reviewed. Finally, consideration is given
to the recent measurements of proper motions of H2O masers and to the use
of masers as direct indicators of galactic and extragalactic distances through
trigonometric and statistical parallax measurements.
interstellar masers, interstellar radiation, radiative
transfer, stellar evolution, water masers, electron distribution, microwave
probes, microwave scattering, radiation distribution, saturation, stellar
models
X-ray-imaging observations of clusters of galaxies
W. Forman and C. Jones 1982, Annual review of astronomy
and astrophysics, 547-585
Einstein X-ray imaging observations, made to illustrate
the variety of phenomena that can be considered through X-ray image analysis,
are presented. Attention is given to general cluster properties and intracluster
gas. Individual clusters are discussed (considering classification and dynamical
evolution), and X-ray images are used to determine cluster mass distribution
and to examine distant clusters. X-ray observations have contributed information
in regard to processes affecting galaxies, the intracluster medium, and
the cluster itself. Analyses have traced massive halos around dominant galaxies
in unevolved clusters, and have helped define the cluster gravitational
potential. In addition, multi-component double clusters have been discovered,
and material which has been ram-pressure stripped from a hot corona around
the M86 galaxy in Virgo was observed. Finally, quantitative estimates of
the fractions of young and evolved clusters and determinations of total
cluster mass are possible using X-ray observations.
galactic clusters, galactic evolution, x ray astronomy,
x ray imagery, interstellar gas, mass distribution, reviewing, virgo galactic
cluster
Molecular clouds in galaxies
M. Morris and L. J. Rickard 1982, Annual review
of astronomy and astrophysics, 517-545
A classification scheme for describing the molecular
morphology of galaxies based on a differentiation between central regions
and disks is presented. OH and CO absorption surveys are discussed, and
the distribution of molecular material within galaxies is considered in
terms of carbon monoxide emission maps. The presence of molecular clouds
in the central regions of galaxies is discussed for OH absorption line anomalies,
correlations of molecular sources with nuclear activity, and Seyfert galaxies.
In addition, the existence of molecular clouds in galactic disks (spiral
arms, bars, and giant complexes) is considered, and models for star formation
are proposed. Finally, extragalactic chemistry and the detection of extragalactic
masers are discussed.
galaxies, interstellar matter, molecular clouds,
abundance, carbon monoxide, hydroxyl emission, milky way galaxy, seyfert
galaxies
Interstellar molecular hydrogen
J. M. Shull and S. Beckwith 1982, Annual review
of astronomy and astrophysics, 163-190
Recent progress in the detection of H2 in the interstellar
medium is reviewed. The hydrogen molecule is discussed in terms of properties,
and collisional excitation and dissociation rates. Molecular hydrogen formation
and cooling and heating by H2 are also discussed. Ultraviolet studies provided
information for the study of the formation-destruction equilibrium of H2,
the kinetic temperature of the cloud, the hydrogen particle density, and
the ultraviolet radiation field. Infrared observations in Orion and the
planetary nebula NGC 7027 reveal two detections of vibrationally excited
H2. In addition, thermal and nonthermal excitation mechanisms are discussed.
Finally, it is noted that increased ultraviolet sensitivity is necessary
for thorough H2 studies.
h lines, hydrogen clouds, interstellar chemistry,
molecular clouds, molecular excitation, molecular rotation, molecular spectra,
energy of formation, gas dissociation, infrared astronomy, molecular collisions,
molecular energy levels, ultraviolet astronomy, vibrational spectra
The search for infrared protostars
C. G. Wynn-Williams 1982, Annual review of astronomy
and astrophysics, 587-618
A review of the search for infrared sources in
star-forming regions, and studies of these sources and nearby interstellar
matter, are presented. Particular attention is given to those objects at
infrared wavelengths, and studies are directed toward the early evolution
of massive-type stars. Star formation regions, globules and submillimeter
sources, and infrared sources are discussed, and clustering and location
of the infrared sources are considered. It is determined that the probable
angular diameters of infrared sources in molecular clouds are less than
or on the order of 10-10 to the 3rd AU, and that the most prominent absorption
features are at 9.7 and 3.07 microns. In addition, infrared sources in molecular
clouds are found to be among the most highly polarized of all astronomical
objects. Finally, it is determined that OB stars generally form in groups
at molecular cloud peaks and that they can reach large luminosities and
begin ionizing radiation production, and, in the embedded stage and later,
luminous stars undergo anisotropic mass loss.
infrared astronomy, interstellar matter, molecular
clouds, protostars, stellar evolution, emission spectra, gas flow, interstellar
masers, line spectra, star clusters, stellar luminosity, stellar mass ejection,
tables (data)
Interstellar ammonia
P. T. P. Ho and C. H. Townes 1983, 239-270
Investigations and results on interstellar NH3
are discussed. The physics of the molecule, its interstellar excitation,
and its formation and dissociation mechanisms are reviewed. The observing
techniques and instruments, including single-antenna facilities, infrared
and submillimeter techniques, and interferometric studies using the Very
Large Array are briefly considered. Spectral data analysis is discussed,
including the derivation of optical depths, excitation measurements, ortho-para
measurements, and cross sections. Progress achieved in understanding the
properties and evolution of the interstellar medium through NH3 studies
is reviewed, including observations of nearby dark clouds and of clumping
effects in molecular clouds, as well as interferometric observations of
hot molecular cores in Orion, W51, and Sagittarius A. Research results on
extragalactic NH3, far-infrared, submillimeter, and midinfrared NH3 observations
are described.
ammonia, astronomical maps, interstellar gas, molecular
excitation, reaction kinetics, far infrared radiation, hyperfine structure,
microwave emission, microwave interferometers, radio astronomy, submillimeter
waves, very large array (vla)
Dust in galaxies
W. A. Stein and B. T. Soifer 1983, 177-207
The manifestations of dust in the Galaxy, in normal
galaxies, active nuclei galaxies (ANGs), and in QSOs are discussed. Findings
on the composition, abundance, size distribution, and global properties
of the Galaxy's dust obtained with absorption and emission studies are reviewed.
The properties of dust in other galaxies, the variation of those properties
among galaxies, and the effect of the dust on the appearance of galaxies
are considered, discussing the LMC, M51, and M82 as examples. Evidence for
the existence of dust in the nuclei of ANGs and in QSOs is examined with
regard to reddening, dust emission and absorption, and polarization. The
question of the existence of intergalactic dust is briefly addressed.
cosmic dust, galaxies, intergalactic media, milky
way galaxy, quasars, absorption spectra, abundance, active galaxies, chemical
composition, emission spectra, interstellar extinction, particle size distribution
Recent developments concerning the Crab Nebula
K. Davidson and R. A. Fesen 1985, 119-146
This review is concerned with supernova (SN) ejecta
now seen as thermal gas in the Crab Nebula. Some background information
about the Crab is provided. The distance of the Crab Nebula is between 1500
and 2200 pc, and most of the nebular mass is in gaseous filaments with emission-line
spectra. The spectroscopic determinations of the nebular mass and chemical
composition are reviewed, taking into account emission-line observations,
composition analyses, dust, differences among filaments, and the need for
more observational abundance studies and better ionization models. The pre-SN
star and the SN event are discussed, and some morphological questions are
explored. Attention is given to the star's mass (actually its core mass),
the supernova event, certain aspects which are not yet very well understood,
the filamentary structure, and questions regarding a halo.
crab nebula, ejecta, supernova remnants, abundance,
astronomical spectroscopy, filaments, morphology, nebulae, stellar mass
High-resolution optical and ultraviolet absorption-line studies of interstellar gas
L. L. Cowie and A. Songaila 1986, 499-535
Recent progress in the characterization of the
interstellar medium (ISM) by means of optical and UV spectral data is summarized.
The gas is studied by focusing on background stars whose spectra can be
accurately modeled to provide the light source for the absorption-line scans.
The capabilities of earth- and space-based instruments which have been and
are used for the surveys are delineated. The distributions of diffuse gas
densities and characteristics of the cold, warm and hot gas in the Galaxy
are described in terms of the elemental abundances, kinetics and distributions
of the gas. Particular note is taken of gas in the solar neighborhood and
around SNR, and of absorption-line data of cosmological significance.
absorption spectra, interstellar gas, ubv spectra,
abundance, cosmology, line spectra, molecular clouds, supernova remnants
The dynamical evolution of H II regions - Recent theoretical developments
H. W. Yorke 1986, 49-87
Recent H II line observations of stellar systems
are discussed with regard to the capabilities of current models of stellar
formation, structure and dynamics. Observations of emission nebulae arising
from the interaction between the interstellar medium and evolving stars
are summarized and time scales of stellar evolution are examined. A system
of basic equations that consider MHD flows, radiation transfer, ionization,
recombination, thermal energy balance, boundary conditions and initial values
is defined for the density and temperature range of H II regions. Current
numerical models for the evolution of H II regions are summarized. Planned
observations of ultracompact H II regions, blisters and champagne flow are
described.
h ii regions, interstellar matter, molecular clouds,
boundary conditions, boundary value problems, ionization, magnetohydrodynamics,
nebulae, radiative transfer, recombination reactions, stellar evolution
The IRAS view of the Galaxy and the solar system
C. A. Beichman 1987, 521-563
Data from IRAS observations of the solar system
and the Galaxy are compiled and analyzed in a general review. Sections are
devoted to the zodiacal dust cloud, comets and asteroids, the search for
Planet X, the formation of low-mass and high-mass stars, and the IR characteristics
of different types of stars and of novae and supernovae. Consideration is
given to protoplanetary disks and the Vega phenomenon, limits on brown dwarfs,
and the diffuse Galactic emission.
infrared astronomy, milky way galaxy, solar system,
spaceborne astronomy, asteroids, brown dwarf stars, comets, diffuse radiation,
infrared astronomy satellite, protoplanets, zodiacal dust
The local interstellar medium
D. P. Cox and R. J. Reynolds 1987, 303-344
Observations and theoretical models of the local
interstellar medium (LISM), defined as the region within a column density
contour of 10 to the 19th H atoms/sq cm, are reviewed. The existence and
nature of the Local Bubble and its boundary are examined; and consideration
is given to the LISM as an active supernova remnant, confined bubbles, theoretical
models of the LISM, cavity geometry, clouds within the Local Bubble, solar-backscatter
and other observations of local clouds, ionization mechanisms in clouds,
and the implications of clouds for the evolution of the LISM.
astronomical models, interstellar gas, interstellar
matter, astronomical spectroscopy, conductive heat transfer, milky way galaxy,
radiative heat transfer, spatial distribution, supernova remnants
The IRAS view of the extragalactic sky
B. T. Soifer, G. Neugebauer and J. R. Houck 1987,
187-230
The IR-observable characteristics of the extragalactic
sky are reviewed, summarizing the results of recent studies based on the
IRAS survey, which covers over 96 percent of the sky to about 500 mJy at
12, 25, and 60 microns and to about 1.5 Jy at 100 microns. The numerical
and morphological data are described; possible mechanisms for the IR emission
are discussed; and the object classes are considered separately. Consideration
is given to spiral and disk galaxies, barred and ring galaxies, irregular
and dwarf galaxies, blue compact galaxies, elliptical and S0 galaxies, AGN
observations (BL Lacs and OVV quasars, Seyfert galaxies, and quasars), highly
luminous IR galaxies, and the cosmological implications of the IRAS findings.
Diagrams, graphs, and tables are provided.
astronomical spectroscopy, galactic structure,
infrared spectra, intergalactic media, satellite observation, sky, active
galactic nuclei, compact galaxies, disk galaxies, dwarf galaxies, infrared
astronomy satellite, radiant flux density, ring galaxies, spiral galaxies
Polarization properties of extragalactic radio sources
D. J. Saikia and C. J. Salter 1988, 93-144
Polarization (P) observations of extragalactic
radio sources are reviewed, with an emphasis on theoretical implications.
Topics examined include specification of P using the Stokes parameters,
the P of synchrotron emission, the Faraday effect and depolarization, surveys
and catalogs of integrated linear P, the effects of the Galaxy on source
P, circular P, magnetic-field structures, and rotation measures and depolarization.
Particular attention is given to the radio and optical P of AGN, the alignment
of core P with radio structure, VLBI polarimetry, the variability of linear
P, and the cosmological interpretation of P observations (clusters of galaxies,
the intergalactic magnetic field, and P of the microwave background). Contour
maps of typical objects are provided.
extragalactic radio sources, interstellar magnetic
fields, polarization characteristics, quasars, bibliographies, circular
polarization, computational astrophysics, depolarization, faraday effect,
linear polarization, magnetic properties, optical polarization, radio galaxies,
relic radiation, synchrotron radiation, variability
Large-scale expanding superstructures in galaxies
G. Tenorio-Tagle and P. Bodenheimer 1988, 145-197
Recent observational and theoretical investigations
of large (100 pc or greater) expanding shell-type structures in galaxies
are reviewed. The evidence from the Galaxy, the Magellanic Clouds, and other
nearby galaxies is compiled in tables and analyzed, and consideration is
given to theoretical models based on (1) the effect of stars in clusters
and associations (SN explosions and stellar winds, galactic differential
rotation, and expanding H II regions), (2) the effect of radiation pressure,
and (3) cloud/galactic-disk collisions. The sensitivity of the model predictions
to assumptions about the initial condition of the interstellar matter and
the star-formation process is discussed, with a focus on the close interrelationship
of star formation, stellar evolution, and the interstellar medium.
galactic structure, interstellar matter, magellanic
clouds, milky way galaxy, h alpha line, h i regions, h ii regions, irregular
galaxies, kinetic energy, radiation pressure, spiral galaxies, star clusters
Supernovae and supernova remnants
K. W. Weiler and R. A. Sramek 1988, 295-341
Observational data on SN and SNRs obtained during
the period 1983-1987 are compiled in tables, graphs, contour maps, and sample
images and reviewed, with an emphasis on new discoveries and controversial
issues. Topics addressed include type I and type II optical SN, radio SN,
theoretical models of SN origin, and SN rate estimates. Consideration is
given to extragalactic and Galactic SNRs of the Balmer-dominated, oxygen-rich,
plerionic-composite, and evolved classes; centrally influenced SNRs; SNR
evolution; relations among SNR parameters; and the SN-SNR connection. A
number of recently discovered plerionic-composite SNRs are listed and briefly
characterized in an appendix.
radio emission, stellar luminosity, supernova remnants,
supernova 1987a, crab nebula, magellanic clouds, radio astronomy, stellar
envelopes, stellar mass ejection
The Orion Molecular Cloud and star-forming region
R. Genzel and J. Stutzki 1989, 41-85
The interstellar matter and star formation in the
Orion region is discussed. The large-scale molecular cloud and its structure,
origin, and kinematics are described. The stellar component in and around
the cloud is examined, and the interaction of the massive stars in Orion
A with their surroundings is described. The BN-KL infrared cluster and its
environment are discussed.
molecular clouds, orion nebula, star formation,
h ii regions, interstellar magnetic fields, interstellar matter, o stars,
spatial distribution, star distribution
Kinematics, chemistry, and structure of the Galaxy
G. Gilmore, K. Kuijken and R. F. G. Wyse 1989,
555-627
The physical characteristics of the Galaxy are
described and discussed in terms of the origin of the Galaxy. The information
about early Galactic evolution provided by density laws and data on chemical
abundances, kinematics, and ages of stars near the sun is reviewed. Recent
results regarding the shape of the stellar distribution in the Galactic
spheroid are summarized and the importance of observed relations betweeen
kinematics and chemistry is discussed. Available data and analyses are reviewed
to show that the sum of all available information strongly suggests that
the extreme Population II subdwarf system formed during a short-lived period
of dissipative collapse of the proto-Galaxy. The nature and evolutionary
status of the thick disk is examined, and the status of 'missing' matter
in the thin disk is reviewed.
galactic structure, interstellar chemistry, kinematics,
chemical evolution, color-magnitude diagram, disk galaxies, late stars,
metallicity, milky way galaxy
Interaction between the solar wind and the interstellar medium
T. E. Holzer 1989, 199-234
The heliospheric and interstellar parameters of
importance in the interaction between the solar wind and the ISM are discussed.
The observationally inferred values of these parameters, including the uncertainties,
are addressed, and the basic physical processes that are likely to be important
in the interaction are examined theoretically. The theory is combined with
observational information in an effort to develop the currently most likely
picture of the heliosphere as it is shaped by the local ISM.
interstellar gas, plasma interactions, solar wind,
cosmic dust, cosmic rays, heliosphere, magnetohydrodynamic flow, plasma
dynamics
A new component of the interstellar matter - Small grains and large aromatic molecules
J. L. Puget 1989, 161-198
Predictions from dust models constructed to account
for the interstellar extinction curve are in conflict with emission data.
This paper shows that the introduction of small grains and large aromatic
molecules as a new component of the interstellar matter can resolve this
conflict. Observational evidence for the existence of very small grains
is also reviewed, along with the physics of IR emission by thermal fluctuations
and its relation to very small particles.
aromatic compounds, cosmic dust, interstellar chemistry,
interstellar matter, astronomical models, astronomical photometry, emission
spectra, infrared radiation, interstellar extinction, spectral energy distribution
The soft X-ray background and its origins
D. McCammon and W. T. Sanders 1990, 657-688
A review on the soft X-ray background is presented,
with emphasis on diffuse galactic emission. Particular attention is given
to emission mechanisms for the galactic diffuse background, the observational
data, models of the 0.5-1 keV and of the 70-284 eV emission, and limits
on the extragalactic flux.
background radiation, cosmic x rays, interstellar
gas, astronomical models, diffuse radiation, electromagnetic spectra, emission
spectra, extraterrestrial radiation, intergalactic media
Interstellar dust and extinction
J. S. Mathis 1990, 37-70
It is noted that the term 'interstellar dust' refers
to materials with rather different properties, and that the mean extinction
law of Seaton (1979) or Savage and Mathis (1979) should be replaced by the
expression given by Cardelli et al. (1989), using the appropriate value
of total-to-selective extinction. The older laws were appropriate for the
diffuse ISM but dust in clouds differs dramatically in its extinction law.
Dust is heavily processed while in the ISM by being included within clouds
and cycled back into the diffuse ISM many times during its lifetime. Hence,
grains probably reflect only a trace of their origin, although meteoritic
inclusions with isotopic anomalies demonstrate that some tiny particles
survive intact from a supernova origin to the present.
cosmic dust, interstellar extinction, interstellar
matter, emission spectra, far ultraviolet radiation, milky way galaxy, near
infrared radiation, polarized radiation, silicates
Extragalactic H II regions
G. A. Shields 1990, 525-560
Observational and theoretical studies of extragalactic
H II regions are reviewed. The physical properties of H II regions, their
distribution in galaxies, and extinction are discussed. The use of photoionization
models for such regions is considered. Attention is then given to the morphology
and kinematics of GEHRs (giant extragalactic H II regions) and their use
as distance indicators. Also considered are the ionizing stars and chemical
abundance measurements.
h ii regions, hot stars, intergalactic media, ionized
gases, molecular clouds, orion nebula, astronomical models, interstellar
matter, irregular galaxies, magellanic clouds, spiral galaxies, star formation
Theories of the hot interstellar gas
L. Spitzer, Jr. 1990, 71-101
The paper comments on a few simplified models for
the hot interstellar gas (HIG), indicating the assumptions made and the
general character of the results along with some of the main problems remaining.
Three scenes in the evolution of the HIG are examined: First, the explosion
of a supernova ejects a rapidly expanding envelope, whose interaction with
the surrounding medium produces the hot gas. Then, as this heated gas expands,
it encounters regions whose internal density is well above the average.
These regions (clouds) are compressed by the hot gas, are heated by conduction,
and sometimes evaporate or are disrupted. In the final scene, the remnant
of heated gas surrounding one or more supernovae can rise to appreciable
distances from the galactic plane and may produce a hot galactic corona
before it falls back down or escapes the Galaxy entirely. The vertical structure
of the ISM is also treated, again on the basis of simple models.
high temperature gases, interstellar gas, supernova
remnants, astronomical models, interstellar magnetic fields, ionized gases,
stellar envelopes, thermal conductivity
Masses and evolutionary status of white dwarfs and their progenitors
V. Weidemann 1990, 103-137
It has recently become firmly established that
the white-dwarf (WD) number-mass distribution is sharply peaked around an
average mass of about 0.60 solar mass. It has also become clear that WDs
are the final stage of stellar evolution for low- and intermediate-mass
stars all the way up to the lower limiting mass for carbon ignition. These
results suggest that heavy mass loss occurs during pre-WD evolution. Since
normal stellar wind can only explain this mass loss, if at all, for low-mass
stars, additional mass loss on the AGB has to be invoked and has indeed
been inferred from observations of circumstellar shells. It is therefore
a natural assumption to identify the planetary nebula stage as post-AGB
and the central stars of the planetary nebulae as immediate progenitors
of white dwarfs. It is pointed out that this evolutionary connection is
now firmly established and is strongly supported by a similarly sharply
peaked mass distribution for the central stars of planetary nebulae.
stellar evolution, stellar mass, white dwarf stars,
asymptotic giant branch stars, dark matter, planetary nebulae, red shift,
stellar luminosity, stellar mass ejection
Distribution of CO in the Milky Way
F. Combes 1991, Annual review of astronomy and
astrophysics, 195-237
Investigations of the Galactic CO distribution
are reviewed. The main results of these studies is the finding that the
CO and H I distributions are very different. H2 molecules dominate the central
ISM, while atomic gas is much more important in the outer parts of the Galaxy.
On small scales, H2 is very clumpy and so might be a better tracer of spiral
structure than the atomic component. The physical state of Galactic H2 is
considered, emphasizing the extent of its concentration in clouds. Statistics
concerning the mass spectrum of the clouds, their size-linewidth relations,
and the issue of whether they are gravitationally bound or pressure-supported
are addressed. Clouds in the Galactic center are described. Finally, the
outer parts of the Galaxy and the z-distribution of the CO emission, including
plane thickness and warping of the plane, are considered.
carbon monoxide, hydrogen, interstellar gas, milky
way galaxy, spatial distribution, galactic structure, gamma ray astronomy,
h ii regions, mass spectra, molecular clouds, molecular gases
Galactic and extragalactic supernova rates
S. Van Den Bergh and G. A. Tammann 1991, 363-407
Recent research on Galactic and extragalactic supernova
(SN) rates is reviewed. SN frequencies, luminosities, and discovery probabilities
are addressed. The inclination and radial distance effect on the likelihood
of discovery is examined, and SN rates are considered as a function of parent
galaxy luminosity. Relative SN frequencies in different types of galaxies
and the transformation of such frequencies into absolute ones are discussed.
The determination of Galactic SN rates from radio SNRs and the mass spectrum
of star formation is examined. SN rates in Local Group galaxies is addressed.
galactic evolution, local group (astronomy), milky
way galaxy, supernovae, error analysis, spiral galaxies, star formation
rate, stellar luminosity, supernova remnants
Type Ia supernovae as standard candles
D. Branch and G. A. Tammann 1992, Annual review
of astronomy and astrophysics, 359-389
The status of the observational homogeneity of
Ia supernovae is summarized. The calibration of the SN Ia absolute magnitude
is then discussed, with attention given to historical galactic supernovae,
SNe Ia in the Virgo cluster, thermal emission, and nickel-cobalt radioactivity.
Finally, prospects for applications of SNe Ia as distance indicators for
cosmology are examined.
cosmology, interstellar extinction, stellar luminosity,
supernova remnants, white dwarf stars, chandrasekhar equation, light curve,
visible spectrum
Radio emission from normal galaxies
J. J. Condon 1992, Annual review of astronomy and
astrophysics, 575-611
Radio emission from normal galaxies is reviewed
with emphasis on those aspects of radio emission and recent star formation
that are common to most normal galaxies and their application to a simple
model consistent with the data. The discussion covers the range of source
properties found in the population of normal galaxies, characteristics of
free-free emission and synchrotron radiation that are needed to interpret
observations of normal galaxies, frequently used equations and their consequences
for real observations, FIR/radio correlation, and population-synthesis models
relating FIR/radio emission to recent star formation.
cosmic rays, radio emission, radio sources (astronomy),
star formation, starburst galaxies, synchrotron radiation, black holes (astronomy),
h ii regions, infrared radiation, relativistic particles
Dust-gas interactions and the infrared emission from hot astrophysical plasmas
E. Dwek and R. G. Arendt 1992, Annual review of
astronomy and astrophysics, 11-50
Environments where the presence of dust is primarily
inferred from its collisional interactions with the ambient gas are reviewed
with emphasis on environments typically encountered behind fast (100 km/s
or greater) shocks and in hot (few 10 exp 5 K) plasmas in galactic halos,
some elliptical galaxies, or the intergalactic medium of galaxy clusters.
The discussion covers interactions between dust grains and a hot gas, grain
temperatures and infrared emission, supernova remnants and supershells,
and dust and hot gas in, around, and between galaxies. Finally, future prospects
in the field are briefly discussed.
cosmic dust, high temperature plasmas, infrared
sources (astronomy), interstellar gas, particle interactions, thermal emission,
cosmic plasma, galactic clusters, interstellar extinction, interstellar
matter, milky way galaxy, polarized light, reflection nebulae, supernova
remnants
Theory of interstellar shocks
B. T. Draine and C. F. McKee 1993, Annual review
of astronomy and astrophysics, 373-432
The physical principles underlying the theoretical
understanding of the structure of interstellar shock waves are outlined.
Attention is given to single fluid shocks, with emphasis on fluid equations,
jump conditions, and collisionless and radiative shocks. Multifluid shocks
in weakly ionized gas are examined, with reference to fluid equations, atomic
and molecular processes, the role of dust grains, length scales, critical
ionization velocity, magnetic precursors to J-type shocks, and numerical
modeling. Multifluid shocks in ionized gas, instabilities in shock waves,
dust in shocks, and shock chemistry are also discussed.
fluid dynamics, interstellar space, ionized gases,
shock wave propagation, stellar winds, cosmic plasma, interstellar gas
Supernova 1987A revisited
R. McCray 1993, Annual review of astronomy and
astrophysics, 175-216
Updates on research on SN 1987A are provided, with
emphasis on the aftermath of the explosion: the interpretation of the light
curve and spectrum, the physics of the envelope, and the interaction of
the supernova with its circumstellar envelope. UVOIR light curves, gamma
rays and hard X-rays, and dust formation are examined, and explosion dynamics
is explored. Attention is given to optical and IR spectrum development,
with emphasis on the photospheric spectrum, nebular spectrum, ionization,
emission-line profiles, line strengths, and iron, cobalt, and nickel. The
circumstellar environment is discussed, with special reference to progenitor
mass loss, circumstellar ring and nebulosity, radio emission, and soft X-rays.
light curve, stellar envelopes, stellar spectra,
supernova 1987a, electromagnetic spectra, gamma ray spectra, x ray sources
Millimeter and submillimeter interferometry of astronomical sources
A. I. Sargent and W. J. Welch 1993, Annual review
of astronomy and astrophysics, 297-343
An overview of millimeter and submillimeter interferometry
of astronomical sources is presented, with emphasis on studies of the interstellar
medium in the Milky Way and other galaxies. Molecular gas in nearby galaxies,
IR luminous galaxies, radio galaxies, and protogalaxies are examined. Consideration
is given to evolved stars and to the ISM and star formation, with emphasis
on molecular cloud condensations, bipolar outflows, circumstellar disks,
and environmental effects. Interferometry of the solar system is discussed
as well. The instruments that are currently operating at the shorter wavelengths
are reviewed, with emphasis on their special attributes and their relevance
to atmospheric effects. Instrumental function and sensitivity are also discussed.
astronomical interferometry, cosmic dust, interstellar
matter, microwave spectra, molecular spectra, emission spectra, millimeter
waves, submillimeter waves