Spectroscopy Of Emission Lines Research Articles

Density wave kinematics and giant molecular association formation in M51

view Abstract Citations (68) References (48) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Density Wave Kinematics and Giant Molecular Association Formation in M51 Rand, Richard J. Abstract The small-scale kinematics of the molecular, atomic, and ionized gas components along the major and minor axes of M51, derived from optical emission-line spectroscopy and CO and HI interferometric observations, are compared with the predictions of current models of the gaseous response to a density wave. Determinations of the gas surface density and observations of the kinematics are used to test quantitatively the two suggested mechanisms of arm and interarm giant molecular association (GMA) formation. The possible connection between GMA formation and the triggering of star formation is briefly discussed. Attention is also given to the difficulties associated with the existence of bound arm GMAs, and it is shown how these could be alleviated if the GMAs were not bound. Publication: The Astrophysical Journal Pub Date: June 1993 DOI: 10.1086/172725 Bibcode: 1993ApJ...410...68R Keywords: Density Distribution; Galactic Structure; Interstellar Gas; Molecular Clouds; Spiral Galaxies; Astronomical Spectroscopy; Galactic Nuclei; Galactic Rotation; Star Formation; Very Large Array (Vla); Astrophysics; GALAXIES: INDIVIDUAL MESSIER NUMBER: M51; GALAXIES: KINEMATICS AND DYNAMICS; ISM: MOLECULES; RADIO LINES: ISM full text sources ADS | data products SIMBAD (2) NED (1)

Infrared line diagnostics of active galactic nuclei

Emission-line spectroscopy in the infrared has advantages over optical methods, particularly for investigating active galaxies with nuclei obscured by dust. We predict intensities and ratios of the near-, mid-, and far-infrared ionic fine-structure lines from active galactic nuclei (AGNs) of the LINER and Seyfert types, and starbursts, using Ferland's photoionization code CLOUDY. Several infrared line ratio diagrams effectively distinguish emission from these sources and from shocks and photodissociation regions (PDRs) in the neutral interstellar medium of the host galaxy. We have studied extensively the effects of varying the important model parameters, including ionization parameter, density, and optical depth. We also show how detailed infrared spectroscopy can reveal the presence of density inhomogeneities and abundances anomalies and determine the slope of the ionizing continuum and the amount of reddening and the reddening law. Further measurements of infrared line ratios can determine whether the observed coronal emission lines in Seyfert nuclei arise from a diffuse low-density gas spread over hundreds of parsecs or from high-density gas intermediate in location and properties between the broad- and narrow-line regions. As a test, we compared the predictions of our model and others to the observed line ratios of the starburst galaxy M82 and of the Galactic center. No single-zone model adequately predicted all of the observed lines, but a simple combination of a starburst plus photodissociation region of higher density gave a good fit for M82. Finally, we use our model predictions to estimate the detectability of infrared fine- structure lines in various active galaxies, using current and planned ground, airborne, and space-based instruments. Many informative lines are detectable currently; nearly all of the important lines should soon be detected by the Infrared Space Observatory.

Spatial heterodyne spectroscopy for the exploration of diffuse interstellar emission lines at far-ultraviolet wavelengths

Spatial heterodyne spectroscopy (SHS) is a new instrumental technique for interference spectroscopy which promises to extend into the FUV (1200-2000 A) spectral region the large throughput advantage at high spectral resolution usually associated with Fabry-Perot and Michelson interferometers. In addition, SHS systems are compact in size, can be field-widened to increase their throughput even further, have no moving parts, and can be built in all-reflection configurations. SHS appears to be well suited for high resolution, space-based spectroscopy of faint interstellar emission lines in the ultraviolet. This has significant implications for the study of the dynamics and distribution of hot gas within the Galactic disk and halo. For example, a field-widened SHS incorporating 5 x 5 cm gratings could obtain a radial velocity resolved (20 km/s), 3 deg angular resolution map of the high-latitude interstellar C IV 1550 emission in less than 1 year.

H-Alpha and OI 7774 Spectroscopy of Algol-Type Binaries

Spectroscopic observations are presented showing evidence of mass transfer activity in Algol-type eclipsing binaries. Traditional Hα emission line spectroscopy is discussed along with absorption line spectroscopy of the O I 7774 A multiplet. Eclipse effects in both lines are discussed, along with a new non-LTE model for Hydrogen line spectrum synthesis.

Symmetrical jet action in the R Aquarii binary system

Collimated mass flow in opposite directions is detected in the R Aqr binary-system jet by means of high-resolution long-slit spectroscopy of several optical emission lines. Also presented are images of the jet structure in the forbidden line of O III, which clearly show bipolar symmetry extending to distances of about 2750 AU on either side of the central Mira variable. The Mira light was greatly reduced by utilization of a vignetting disk on the window of the imaging CCD. This result confirms the recent report of morphological evidence for an R Aqr jet from the detection of bipolar radio continuum emission at 6 cm, and provides the necessary kinematical evidence to show that jet action is actually taking place.

Optical Imagery of Nova Remnants

AbstractResolved nebular remnants of classical novae are discussed in terms of size, surface brightness, and shape. A list of 26 known resolved remnants is given. The conditions necessary for visibility of a resolved remnant are discussed. The structure of remnants can be studied at optical wavelengths by direct imaging and by long-slit or otherwise spatially resolved spectroscopy of emission lines. Based on recent spatiokinematic studies, most nebular remnants are prolate in outline, with sub-structure that has been characterized as consisting of “polar blobs” and “equatorial rings”. The mechanism that shapes the remnants is not yet known with certainty. There is room for much additional work in discovering new remnants and in characterizing those that are known.

New observations of a large concentration of ClO in the springtime lower stratosphere over Antarctica and its implications for ozone‐depleting chemistry

We have made new measurements of stratospheric chlorine monoxide (ClO) at McMurdo Station, Antarctica, during the austral spring of 1987. Rotational emission line spectroscopy, employing a ground‐based detector, was used to determine mixing ratio profiles over the range ∼17–45 km. A spectral band pass double that was used for similar measurements in 1986 allowed an improvement to be made in the definition of the anomalous low‐altitude stratospheric ClO layer associated with springtime ozone depletion. A peak mixing ratio of 1.6±0.4 parts per billion by volume (ppbv) (95% confidence level) was found at 19.5±1 km at midday during the period September 20–24, 1987. The observed peak mixing ratio and diurnal behavior are discussed in relation to chemical depletion theories. Calculations indicate that the large observed ClO concentration provides an efficient closure for a catalytic Cl cycle through the ClO dimer mechanism, yielding good agreement with various observed features of O3 depletion.

High-Resolution Emission-Line Spectroscopy of Be Stars: Comparison of Hα and Weak Emission Lines

AbstractFor a number of bright southern Be stars, high-resolution, high S/N spectroscopy has been performed for Hα, Si II λ6371 and four Fe II emission lines. With the exception of four stars, both Hα and weak emission line profiles exhibit resolved double-peak structure. Peak separation increases with stellar projected rotational velocity. In many cases, Hα profiles (but not Fe II lines) show resolved fine-structure (inflections in the flanks) indicating a two-component structure of the disk. Envelope models with arbitrary density and rotational velocity laws have been fitted to the Fe II line profiles with satisfactory results. It is found that the innermost Hα disk component also emits the Fe II lines and has an average outer radius of 5 r*; density falls off as r-l.5 or more rapidly. The outer disk component emits the faint and narrow secondary component of Hα lines with average outer radius 20 r*. The envelopes of the four stars with a strong, dominating single peak both in Hα and Fe II either are dominated by strong radial motions or, more likely, have elliptical disk-like structure.

The structure and dynamics of ringed galaxies. III - Surface photometry and kinematics of the ringed nonbarred spiral NGC 7531

view Abstract Citations (34) References (77) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Structure and Dynamics of Ringed Galaxies. III. Surface Photometry and Kinematics of the Ringed Nonbarred Spiral NGC 7531 Buta, R. Abstract The photometric and kinematic properties of the southern galaxy NGC 7531, a large example of a nonbarred spiral possessing a very bright inner ring, are explored via UVBRI surface photometry and emission-line spectroscopy. The galaxy is a global, two-armed spiral galaxy possessing a bright inner ring with a radius of 2.3 kpc. The ring has an average surface brightness in blue light of four to six times higher than in NGC 1433, and is 2.5 times smaller in size. The ring is a zone of active star formation and H II region concentration. The light distribution within NGC 7531 cannot be modelled in terms of a simple combination of an r exp 1/4 spheroid, exponential disk, and ring. A Fourier analysis suggests that the 'intermediate zone' between the inner ring and the outer arms is intrinsically oval with a phase of about 100 deg with respect to the line of nodes in the galaxy plane. Publication: The Astrophysical Journal Supplement Series Pub Date: May 1987 DOI: 10.1086/191190 Bibcode: 1987ApJS...64....1B Keywords: Astronomical Photometry; Celestial Mechanics; Galactic Structure; Spiral Galaxies; Astronomical Models; Astronomical Spectroscopy; H Ii Regions; Kinematic Equations; Luminosity; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 7531; GALAXIES: INTERNAL MOTIONS; GALAXIES: STELLAR CONTENT; GALAXIES: STRUCTURE; NEBULAE: H II REGIONS full text sources ADS | data products SIMBAD (2) NED (2) Related Materials (3) Part 1: 1986ApJS...61..609B Part 2: 1986ApJS...61..631B Part 5: 1987ApJS...64..383B

Introduction to Hinotori

The HINOTORI mission is dedicated to solar flare observations mainly in the X-ray energy band. The instruments on board conduct (1) hard X-ray imaging of solar flares by means of rotating modulation collimators, (2) wide energy band spectroscopy in the range from 2 keV to several MeV as well as (3) high resolution crystal spectroscopy of iron emission lines. Several hundred flares have been recorded and analyses are under way. A description of HINOTORI and the characteristics of the instruments are presented.

Velocity dispersions of knots in VELA X and Puppis A

view Abstract Citations (9) References (18) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Velocity dispersions of knots in VELA X and Puppis A. Shull, P., Jr. Abstract Very high resolution spectroscopy of optical emission lines indicates that the velocity dispersions of knots in Vela X and Puppis A result primarily from turbulence within the emitting regions. Line-of-sight velocity dispersions (half-widths at half-maximum) for the observed knots in both remnants are about 20-30 km/s. In Vela X, these include thermal velocity dispersions of roughly 16 km/s for hydrogen and 4 km/s for nitrogen. The knots themselves move randomly relative to each other, with speeds up to 30 km/s in Vela X and between 30-80 km/s in Puppis A. Occasionally, diffuse components of the filaments are observed in Puppis A. These diffuse components have velocity dispersions between 55 and 80 km/s, but the relative contributions of turbulent and thermal motions to the dispersions are unknown. The results are compared with theory and previous observations. Direct photographs may be able to show if the forbidden O III knots are less spatially dispersed than the forbidden N II, forbidden S II, forbidden O II, and H I knots. Publication: The Astrophysical Journal Pub Date: June 1983 DOI: 10.1086/161032 Bibcode: 1983ApJ...269..218S Keywords: Astronomical Spectroscopy; Supernova Remnants; Velocity Distribution; High Resolution; Image Processing; Microdensitometers; Nitrogen Ions; Oxygen Spectra; Radial Velocity; Shock Waves; Sulfur; Temperature Measurement; Turbulence; Astrophysics full text sources ADS | data products SIMBAD (4)

The evolution of a low temperature linear discharge plasma

The time evolution of a low temperature large linear discharge in a confining magnetic field has been followed from the initial plasma formation to the afterglow. Extensive diagnostics such as Thomson scattering, inteferometry, emission line spectroscopy and Langmuir probes were used to study the plasma in the density and temperature range 1013<Ne<1015 cm-3, 0.5<Te<3 eV. Diagnostics of the gas breakdown phase indicate that the plasma forms in channels and shows evidence of current filaments. After the plasma current is clamped, the plasma mixes and becomes spatially homogeneous in the axial direction with boundary layers of only a few centimeters. The afterglow plasma density decays exponentially with a decay time proportional to the square root of ion mass, as predicted by models of end loss from a theta pinch. However, the observed decay times are about a factor of three larger than those anticipated for such models, due to end stoppering by the electrodes.

An investigation of the energy exchange mechanisms involving the 2 3S metastable level in an RF helium plasma

The energy exchange mechanisms present in a pure helium and a helium-neon plasma were investigated using spectroscopic diagnostic techniques. The plasma was spatially resolved and only the volume element at the plasma centerline was considered in the energy- exchange analysis. The experiment was conducted with a constant total pressure of 0·7 torr, a fixed oscillator frequency of 4 MHz, and a constant input power of 1·8 kW. Emission line spectroscopy was used to determine the population densities of 16 levels in the n 3 S, n 3 P, and n 3 D series. Spatially resolved, self-absorption measurements of the 2 3 P-2 3 S transition were used to determine the 2 3 S metastable level number density. The electron number density of 3·3 × 10 13 cm -3 was determined from the spatially resolved H β blue wing profile, and a lower bound excitation temperature of 8800 °K was determined from a Boltzmann plot of the spatially resolved lower bound levels of the excited helium. The addition of 10% and 20% by volume of neon gas caused a measurable decrease in the population densities of the lower bound levels of helium, while the electron number density and lower bound excitation temperature remained unchanged. Three energy exchange models (local thermal equilibrium, corona, and collisional- radiative) were examined, and the collisional-radiative model was found to best describe the excitation processes for the 2 3 S level. This model was also appropriate for describing the helium-neon plasma at this level.