Showing papers in "Astrophysical Journal Supplement Series in 1990"
TL;DR: In this paper, optical spectroscopic data are presented on the ionized nebulae associated with 14 galaxies that are strong far-IR emitters, which provide both qualitative and quantitative support for the superwind model in which the kinetic energy provided by SNe and winds from massive stars in a central starburst drives a large-scale outflow that can shock heat and accelerate ambient interstellar and circumgalactic gas.
Abstract: Optical spectroscopic data are presented on the ionized nebulae associated with 14 galaxies that are strong far-IR emitters. It is found that the data provide both qualitative and quantitative support for the 'superwind' model in which the kinetic energy provided by SNe and winds from massive stars in a central starburst drives a large-scale outflow that can shock heat and accelerate ambient interstellar and circumgalactic gas. Clear kinematic signatures of an outflow along the galaxy's minor axis are found for the three nearest far-IR galaxies (FIRGs). The FIRG nebulae are highly overpressured relative to the Galactic ISM, with the pressure dropping systematically with distance from the nucleus. Superwinds are energetically adequate to power both the observed optical and X-ray nebulae, and the relative emission-line intensities and their radial variations are consistent with ionization by wind-driven shocks, but not with photoionization by normal O stars or an AGN. The possible astrophysical implications of superwinds are discussed.
1,198 citations
TL;DR: In this paper, the results of the analysis of the X-ray data and the optical identification for the Einstein Observatory Extended Medium-Sensitivity Survey (EMSS) were presented.
Abstract: This paper presents the results of the analysis of the X-ray data and the optical identification for the Einstein Observatory Extended Medium-Sensitivity Survey (EMSS). The survey consists of 835 serendipitous sources detected at or above 4 times the rms level in 1435 imaging proportional counter fields with centers located away from the Galactic plane. Their limiting sensitivities are about (5-300) x 10 to the -14th ergs/sq cm sec in the 0.3-3.5-keV energy band. A total area of 778 square deg of the high-Galactic-latitude sky has been covered. The data have been analyzed using the REV1 processing system, which takes into account the nonuniformities of the detector. The resulting EMSS catalog of X-ray sources is a flux-limited and homogeneous sample of astronomical objects that can be used for statistical studies.
432 citations
TL;DR: In this article, the basic data needed to produce UV extinction curves for a sample of 78 stars, including spectral types, visual photometry, parameters used to produce fits to the UV extinction curve, distances to the program stars, and line-of-sight H I column densities, are presented.
Abstract: The basic data needed to produce UV extinction curves for a sample of 78 stars, including spectral types, visual photometry, parameters used to produce fits to the UV extinction curves, distances to the program stars, and line-of-sight H I column densities, are presented. The observational and numerical techniques used to obtain the results are discussed in detail. The UV extinction curves and their analytic fits are shown graphically.
418 citations
339 citations
TL;DR: A high-resolution spectroscopic survey of 671 G and K field giants is described in this article, where the Johnson colors have been calibrated against recent, accurate effective temperature, T(eff), measurements for stars in the range 3900-6000 K.
Abstract: A high-resolution spectroscopic survey of 671 G and K field giants is described. Broad-band Johnson colors have been calibrated against recent, accurate effective temperature, T(eff), measurements for stars in the range 3900-6000 K. A table of polynomial coefficients for 10 color-T(eff) relations is presented. Stellar atmosphere parameters, including T(eff), log g, Fe/H, and microturbulent velocity, are computed for each star, using the high-resolution spectra and various published photometric catalogs. For each star, elemental abundances for a variety of species have been computed using a LTE spectrum synthesis program and the adopted atmosphere parameters. 62 refs.
308 citations
TL;DR: The VLA has been used in its A-, B-, C-, and D configurations to make 1.49 GHz maps of sources in both the original and revised IRAS Bright Galaxy Samples of strong extragalactic sources selected at a wavelength of 60 microns as discussed by the authors.
Abstract: The VLA has been used in its A-, B-, C-, and D-configurations to make 1.49 GHz maps of sources in both the original and revised IRAS Bright Galaxy Samples of strong extragalactic sources selected at a wavelength of 60 microns. Integrated 1.49 GHz flux densities were obtained from the lowest resolution maps, and maps were made with higher resolution so that nearly all of the radio sources have been at least partially resolved. Only NGC 1377 was not detected at 1.49 GHz. An atlas of contour maps, a table of total flux densities plus other radio source parameters, and references to published radio maps are given. Since the infrared and radio continuum brightness distributions of IR-selected galaxies are usually similar, these high-resolution radio maps can be used as substitutes for the unavailable IR maps to indicate the sizes and precise locations of the IR-emitting regions.
253 citations
TL;DR: In this paper, the first consistent abundance analysis of both H II regions and SNRs in the Magellanic Clouds is presented, and the importance of this overall abundance pattern for the determination of the star formation history in the Clouds is addressed.
Abstract: The first consistent abundance analysis of both H II regions and SNRs in the Magellanic Clouds is presented. Detailed modeling of the SNRs results in abundance measures in good agreement with those from H II regions, confirming the overall accuracy of the generalized modeling code MAPPINGS for both photoionized and shock-excited nebulae. A differential analysis performed between SNRs and the Galactic Herbig-Haro (H-H) objects for elements heavier than Ar reveals that there is no difference for grain depletion in either Cloud SNR or Galactic H-H objects. It shows that there is no measurable zero point error between the Fe abundances determined from supergiants and those determined from SNRs. This permits the two traditionally separated abundance scales of the H II regions and supergiants to be combined for the first time into one comprehensive system for the first time. The importance of this overall abundance pattern for the determination of the star formation history in the Clouds is addressed. 118 refs.
251 citations
TL;DR: In this paper, a large grid of equilibrium models suitable for adiabatic and nonadiabatic seismological investigations of pulsating white dwarfs of the DAV and DBV types is presented and discussed in detail.
Abstract: A large grid of equilibrium models suitable for adiabatic and nonadiabatic seismological investigations of pulsating white dwarfs of the DAV and DBV types is presented and discussed in detail. The basic structure of the models is that of a layered configuration consisting of an almost pure carbon core surrounded by an almost pure helium layer, itself surrounded by an almost pure hydrogen layer. Models are computed for three masses, and the helium layer mass is varied. The effects of varying the assumed convective efficiency are investigated. A special sequence is computed to explore the effects of changing the composition gradient scale height in transition regions. Models using two different sets of radiative opacities for the same compositions are obtained to test the sensitivity of the pulsation properties to this component of the constitutive physics. These experiments constitute by far the most extensive study that has been performed to provide suitable models for pulsating white dwarfs. 110 refs.
246 citations
TL;DR: In this article, a model of stars of various masses and rotational parameters was developed and compared with observations of stars in open clusters of various ages in order to analyze the evolution of rotating stars from the early premain sequence to an age of 1.7 x 10 to the 9th yrs.
Abstract: Models of stars of various masses and rotational parameters were developed and compared with observations of stars in open clusters of various ages in order to analyze the evolution of rotating stars from the early premain sequence to an age of 1.7 x 10 to the 9th yrs. It is shown that, for stars older than 10 to the 8th yrs and less massive than 1.1 solar mass, the surface rotation rates depend most strongly on the properties of the angular momentum loss. The trends of the currently available observations suggest that the rotation periods are a good indicator of the field-star ages.
227 citations
TL;DR: In this paper, velocity histograms, galaxy positions, and velocity dispersions are presented for 69 nearby Abell clusters, and the authors conclude that the formation of cD galaxies is dominated by the local, rather than global, cluster environment.
Abstract: Velocity histograms, galaxy positions, and velocity dispersions are presented for 69 nearby Abell clusters. The shape of the cumulative distribution for R = 1 or more clusters does not match the predictions of standard CDM models for any biasing parameter b. The only models consistent with the median and maximum dispersions of the sample are those of b about 1.6-2.0 and in which clusters are identified in three dimensions. Velocity dispersions of high-redshift systems appear fundamentally different from those of nearby clusters. The median dispersion of the subset of 25 cD clusters is similar to that of non-cD systems. A substantial fraction of the cD galaxies have velocities significantly different from the mean of their parent clusters. Three of these have 4 s or more measured redshifts. These last two results suggest that the formation of cD galaxies is dominated by the local, rather than global, cluster environment.
202 citations
TL;DR: In this paper, a grid has been constructed of theoretical evolution sequences of models for low-metallicity stars from the premain-sequence to the giant branch phases to study the history of surface Li abundance during standard stellar evolution.
Abstract: A grid has been constructed of theoretical evolution sequences of models for low-metallicity stars from the premain-sequence to the giant branch phases. The grid is used to study the history of surface Li abundance during standard stellar evolution. The Li-7 observations of halo stars by Spite and Spite (1982) and subsequent observations are synthesized to separate the halo stars by age. The theory of surface Li abundance is illustrated by following the evolution of a reference halo star model from the contracting fully convective premain sequence to the giant branch phase. The theoretical models are compared with observed Li abundances. The results show that the halo star lithium abundances can be explained in the context of standard stellar evolution theory using completely standard assumptions and physics.
TL;DR: In this article, the Gibbs energy of formation for species of chemical elements and compounds in their gas and condensed phases determines their relative abundances in a mixture in chemical equilibrium, which is more general and more powerful than previous abundance determinations in multiphase astrophysical mixtures.
Abstract: Minimization of the Gibbs energy of formation for species of chemical elements and compounds in their gas and condensed phases determines their relative abundances in a mixture in chemical equilibrium. The procedure is more general and more powerful than previous abundance determinations in multiphase astrophysical mixtures. Some results for astrophysical equations of state are presented, and the effects of condensation on opacity are briefly indicated.
TL;DR: In this article, Correlations between chromospheric activity at Ca II H and K and effective surface temperature and rotation are identified, and several new stars with chromospherical Ca IIH and K emission are discovered.
Abstract: New observations of the Ca II H and K and H-epsilon region and/or the Balmer H-alpha line are presented for 100 mostly very active stars but also for weak or inactive stars with suspected activity. Correlations between chromospheric activity at Ca II H and K and H-alpha and effective surface temperature and rotation are identified, and several new stars with chromospheric Ca II H and K emission are discovered. No single activity-rotation relation can be derived for all luminosity classes, and there is clear evidence that evolved stars are generally more active than main-sequence stars of the same rotation period. Binary within the evolved stars appears to play no role, while main-sequence binary stars show generally higher levels of activity than their single counterparts. Chromospheric emission in the Ca II H and K lines depends on surface temperature in that flux declines with cooler temperature.
TL;DR: In this article, un catalyseur de 1992 radiosource de plan galactique, observees en VLA, comprenant les positions, les densites de flux and les diametres, est presente
Abstract: Un catalyseur de 1992 radiosource de plan galactique, observees en VLA, comprenant les positions, les densites de flux et les diametres, est presente
TL;DR: In this article, neutral hydrogen observations of a large sample of dwarf and other low surface brightness galaxies are reported, and a detailed discussion and error analysis of the observations are presented, and spectra are displayed for 329 galaxies detected for the first time, or detected with substantially better signal-to-noise ratios than achieved previously.
Abstract: The paper reports neutral hydrogen observations of a large sample of dwarf and other low surface brightness galaxies. A detailed discussion and error analysis of the observations are presented, and spectra are displayed for 329 galaxies detected for the first time, or detected with substantially better signal-to-noise ratios than achieved previously. The positions on the sky of 667 galaxies meeting the present selection criteria north of delta = 38 deg are shown. The distribution of the redshifts of galaxies detected at Green Bank is illustrated. The Green Bank detections tapered off strongly below the median H I flux of 3.7 Jy km/s detected at Arecibo: only 12 percent of the Green Bank sample was detected with smaller fluxes.
TL;DR: In this paper, a model for accelerating the unique particle abundances of energetic particles is proposed, which can be unified into a description of the particles from impulsive flares and compared with particles in space.
Abstract: Observations of solar energetic particles from impulsive flares are reviewed. Consideration is given to observations of electron events, He-3 rich events, and heavy-nuclei-rich events. It is found that these observations can be unified into a description of the particles from impulsive flares. The observations are compared with observations of gamma-ray line in impulsive flares and particles in flares and compared with particles in space. A model for accelerating the unique particle abundances of energetic particles is proposed.
TL;DR: In this paper, the authors examined the frequency and the formation mechanism of 74 B2-B5 IV or V stars, and the results of their radial velocities were combined with those of a previous study of 42 similar stars.
Abstract: Twenty coude spectra were obtained for each of the 74 B2-B5 IV or V stars, and the results of their radial velocities were combined with those of a previous study of 42 similar stars, to examine the frequency and the formation mechanism of these binaries. New improved orbital elements are listed for nine known double-lined and 26 single-lined spectroscopic binaries. It is found that, systems with periods of 0.01 yr to 100,000 yrs, have secondary frequencies that fit the Salpeter (1955) luminosity function (but not the van Rhijn function), indicating that these systems were formed primarily by capture. For systems with periods shorter than 0.01 yr, the separations of components are only a few stellar radii, suggesting that these systems have undergone mass transfer; their secondary masses have no direct information concerning the formation mechanism. 53 refs.
TL;DR: In this article, a complete sample of 1093 galaxies with m(pg) less than or equal to 15.5 mag in a 6-deg-wide strip crossing the north Galactic pole is presented.
Abstract: Redshifts and morphological types are presented for a complete sample of 1093 galaxies with m(pg) less than or equal to 15.5 mag in a 6-deg-wide strip crossing the north Galactic pole. Also presented are redshifts for an additional 92 fainter galaxies in the same strip. Outside of the core of the Coma Cluster, both early- and late-type galaxies trace essentially the same structures in redshift space. Thinner slices illustrate the small velocity dispersion perpendicular to the surfaces in the survey.
TL;DR: In this paper, the observations spectroscopiques of 7 quasars of le systeme limite Lyman (SLL) showed a redshift of 2.9 and 3.2.
Abstract: Les observations spectroscopiques de 7 quasars, dont le systeme limite Lyman (SLL) a un redshift compris entre 2.9 et 3.2, sont presentees. Les raie d'absorption sont identifiees. Les densites de colonne des elements lourds et HI, associes aux SLLs, sont determinees
TL;DR: In this article, the observations polarimetriques optiques d'un ensemble, complet jusqu'a la magnitude B = 16.2, de 114 quasars du Palomar-Green Bright Quasar Survey are presentees.
Abstract: Les observations polarimetriques optiques d'un ensemble, complet jusqu'a la magnitude B = 16.2, de 114 quasars du Palomar-Green Bright Quasar Survey sont presentees. La distribution et la variabilite de la polarisation sont analysees.
TL;DR: In this paper, the observations of supernova remnants with the imaging detectors of the Einstein Observatory are summarized and the X-ray surface brightness contours of 47 remnants are shown together with gray-scale pictures.
Abstract: This paper summarizes the observations of Galactic supernova remnants with the imaging detectors of the Einstein Observatory. X-ray surface brightness contours of 47 remnants are shown together with gray-scale pictures. Count rates for these remnants have been derived and are listed for the HRI, IPC, and MPC detectors.
TL;DR: In this paper, an extensive spectroscopic study of 10 rich southern X-ray clusters of galaxies is presented, where between 40 and 200 redshifts have been obtained in the field of each of the clusters, which cover a wide range of morphological types and richnesses.
Abstract: An extensive spectroscopic study of 10 rich southern X-ray clusters of galaxies is presented. Between 40 and 200 redshifts have been obtained in the field of each of the clusters, which cover a wide range of morphological types and richnesses. Applying rigorous statistical analyses to the total data base of 1000 precise radial velocities provides the necessary information to undertake a thorough dynamical investigation of these individual clusters and of cluster systems in general. 92 refs.
TL;DR: In this article, a new and more accurate table of solar oscillation frequencies has been compiled, which are presented as functions of radial order n and spherical harmonic degree l, are averages over azimuthal order and therefore approximate the normal mode frequencies of a nonrotating, spherically symmetric sun, near solar minimum.
Abstract: Solar oscillations have been observed at three different spatial scales at Big Bear Solar Observatory during 1986-1987 and, using three data sets, a new and more accurate table of solar oscillation frequencies has been compiled. The oscillations, which are presented as functions of radial order n and spherical harmonic degree l, are averages over azimuthal order and therefore approximate the normal mode frequencies of a nonrotating, spherically symmetric sun, near solar minimum. The table contains frequencies for most of the solar p and f modes with l between 0 and 1860, n between 0 and 26, and oscillation mode frequencies between 1.0 and 5.3.
TL;DR: A list of the 21 mass-losing red supergiants (20 M type, one G type; L greater than 100,000 solar luminosities) within 2.5 kpc of the sun is compiled in this article.
Abstract: A list of the 21 mass-losing red supergiants (20 M type, one G type; L greater than 100,000 solar luminosities) within 2.5 kpc of the sun is compiled. These supergiants are highly evolved descendants of main-sequence stars with initial masses larger than 20 solar masses. The surface density is between about 1 and 2/sq kpc. As found previously, these stars are much less concentrated toward the Galactic center than W-R stars, which are also highly evolved massive stars. Although with considerable uncertainty, it is estimated that the mass return by the M supergiants is somewhere between 0.00001 and 0.00003 solar mass/sq kpc yr. In the hemisphere facing the Galactic center there is much less mass loss from M supergiants than from W-R stars, but, in the anticenter direction, the M supergiants return more mass than do the W-R stars. The duration of the M supergiant phase appears to be between 200,000 and 400,000 yr. During this phase, a star of initially at least 20 solar masses returns perhaps 3-10 solar masses into the interstellar medium.
TL;DR: In this paper, almost 3000 stellar sources which have been searched for maser emission from the H2O, SiO, and/or OH molecules are catalogued, including alternate names, the 1950 epoch position, velocity, spectral type, variability type, and period, as well as the references for both the detections and non-detections for each of the three molecules.
Abstract: Almost 3000 stellar sources which have been searched for maser emission from the H2O, SiO, and/or OH molecules are catalogued. Of the sources listed, 368 were detected in H2O, 209 in SiO, and 713 in OH. The catalog includes basic information about the stars including alternate names, the 1950 epoch position, velocity, spectral type, variability type, and period, as well as the references for both the detections and nondetections for each of the three molecules.
TL;DR: In this article, CCD images of a volume and luminosity limited sample of 51 Markarian and NGC Seyfert galaxies were used to show that the galaxies nearly always possess mechanisms for transporting material into their nuclei.
Abstract: CCD images of a volume- and luminosity-limited sample of 51 Markarian and NGC Seyfert galaxies show that Seyfert galaxies nearly always possess mechanisms for transporting material into their nuclei. A subset of Seyfert galaxies with amorphous morphologies, some of which may be remnants of past interactions, constitutes approximately one-fifth of the sample. The colors and exponential disk parameters of Seyfert galaxies are generally similar to those of spiral galaxies without active nuclei. Images of the galaxies are presented along with aperture magnitudes. 90 refs.
TL;DR: In this article, the number of C IV absorption systems per unit redshift range is found to decrease with increasing redshift in the range z(abs) = 1.3-3.7 in a manner which is inconsistent with a constant comoving density of absorbers.
Abstract: New spectroscopic observations of 11 very high redshift QSOs have been combined with previously published data on 55 QSOs to enhance the redshift coverage of a large survey for C IV absorption. The sample is used to discuss the evolution of the properties and distribution of the gas clouds giving rise to heavy element absorption in the QSO spectra. The number of C IV absorption systems per unit redshift range is found to decrease with increasing redshift in the range z(abs) = 1.3-3.7 in a manner which is inconsistent with a constant comoving density of absorbers. Thus, the properties of the absorbers are almost certainly evolving with time. The peak in the C IV two-point correlation function on velocity scales of 200-600 km/s appears to have the same power in high-redshift and low-redshift subsamples. The evolution of the number of observed C IV systems is interpreted as a systematic change in the mean C IV column density of the clouds. 44 refs.
TL;DR: In this article, the vitesse d'une enveloppe entourant une perturbation de densite spherique avec une sur-densite fractionnaire moyenne Δρ/ρ, dans un univers de Friedmann, peut etre developpee en puissance de Δρ /ρ.
Abstract: La vitesse d'une enveloppe entourant une perturbation de densite spherique avec une sur-densite fractionnaire moyenne Δρ/ρ, dans un univers de Friedmann, peut etre developpee en puissance de Δρ/ρ. En considerant que v est la vitesse d'une enveloppe non-perturbee de meme rayon, le changement de vitesse fractionnaire de l'enveloppe perturbee est donnee par Δv/v -1/3×f 1 (Ω)×(Δρ/ρ) + 4/63×f 2 (Ω)×(Δρ/ρ) 2 + O(Δρ/ρ) 3 . Les coefficients f 1 (Ω) et f 2 (Ω) sont determines pour Ω 1.
TL;DR: An overview of the current status of high spectral resolution soft X-ray observations of solar flares is given in this article, focusing primarily on recent results and interpretations of results obtained from orbiting Bragg crystal spectrometers flow during the last solar maximum.
Abstract: An overview of the current status of high spectral resolution soft X-ray observations of solar flares is given. The review concentrates primarily on recent results and interpretations of results obtained from orbiting Bragg crystal spectrometers flow during the last solar maximum on the US DoD P78-1 spacecraft, the NASA SMM, and the ISAS Hinotori spacecraft. Results and several key issues regarding interpretation of the spectra are presented. Specifically, the dynamics of coronal flare plasmas as revealed by X-ray line profiles and wavelength shifts are discussed. Recent results concerning the theory of chromospheric evaporation are given. The temperature of coronal flare plasma is discussed within the context of a differential mission measure. Results concerning electron density measurements, nonequilibrium processes, and relative element abundances are also reviewed.
TL;DR: In this paper, the authors identify 361 premain-sequence (PMS) emission-line stars that might have dusty circumstellar environments, 361 PMS stars that are associated with 304 separate IRAS sources were identified.
Abstract: To aid in finding premain-sequence (PMS) emission-line stars that might have dusty circumstellar environments, 361 PMS stars that are associated with 304 separate IRAS sources were identified. These stars include 200 classical T Tauri stars, 25 weak-lined (naked) T Tauri stars, 56 Herbig Ae/Be stars, six FU Orionis stars, and two SU Aurigae stars. All six of the FU Orionis stars surveyed by IRAS were detected. Of the PMS-IRAS Point Source Catalog (PSC) associations, 90 are new and are not noted in the PSC. The other 271 entries include 104 that are correctly identified in the PSC but have not yet appeared in the literature, 56 more that can be found in both the PSC and in the published and unpublished iterature, and 111 that are in the literature but not in the PSC. Spectral slope diagrams constructed from the 12-, 25-, and 60-micron flux densities reveal unique distributions for the different PMS subclasses; these diagrams may help identify the best candidate PMS stars for observations of circumstellar dust. 30 refs.