The Prominent Dust Emission Feature near 8.9 μm in Four H II Regions
We present a mid-infrared study of four H II regions based on thecombination of Infrared Space Observatory (ISO) SWS observations withspatial information from SpectroCam-10 images and long-slit spectra. Wereport a prominent broad emission feature near 8.9 μm. The peakposition and width of this feature do not resemble known polycyclicaromatic hydrocarbon (PAH) or dust emission features. Its spatialdistribution is analyzed for two H II regions and is clearly distinctfrom that of the PAH emission features, being more similar to that ofthe ionized gas and especially to the spatial distribution of the dustcontinuum at 15 μm. Thus, the carrier of this band likely resideswithin the H II region. Possible carriers of this feature arehighlighted.
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Peering into the heart of a high-mass star forming region: Bispectrum speckle interferometry of the ultracompact H II region K3-50 A
We present K'-band bispectrum speckle interferometry of the ultracompactH II region K3-50A. Our image resolves the central 1''× 1'' regioninto at least 7 point-like objects. We find K'-band counterparts for allbut one of the N-band sources discovered by Okamoto et al.(\cite{Okamoto03}), and there are additional K'-band sources which wereunresolved in the N-band images. Our reconstructed image also revealsthe fine-structure of the cone-shaped nebulosity extending to the south.The brightest K'-band source is located exactly at the tip of thecone-shaped nebulosity. The nebula shows several arcs and theorientation of its main axis agrees very well with the direction of theCO outflow from K3-50A. This nebulosity therefore very likely representsthe clumpy inner surface of a partially evacuated cavity excavated bythe strong outflows.Based on observations obtained at the Special Astrophysical Observatorywith the 6 m telescope.
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K3-50A: An Ultracompact H II Region Ionized by a Massive Stellar Cluster
We have made imaging and spectroscopic observations of the ultracompactH II region K3-50A with a spatial resolution of 0.4" using a newmid-infrared instrument, the Cooled Mid-Infrared Camera andSpectrometer, on the 8.2 m Subaru Telescope. The spectra show thermaldust emission, 9.7 μm silicate absorption, and fine-structure lineemissions of [Ne II] at 12.8 μm, [Ar III] at 8.99 μm, and [S IV]at 10.51 μm. From the maps of the continuum, line emissions, and/orderived dust parameters, we identify eight mid-infrared sources inK3-50A. Especially the central [Ne II] emission has been resolved intotwo peaks clearly. The ionization condition is investigated with theline flux ratios I([Ar III])/I([Ne II]) and I([S IV])/I([Ne II]). It issuggested that the spectral types of the ionizing stars in K3-50Acorrespond to B0-O8 V, which is much later than O5.5 V, the typeestimated from radio continuum observations under a single-starassumption. The three line fluxes suggest a number of Ne+ions greater than what is ionized by a single star of any spectral type,but the numbers of Ar2+ and S3+ are similar tothat formed by a single O8-O9 V star and that by a single O7-O9 V star,respectively. From these features as well as the dust temperature andthe correspondence of each identified source with the near-infraredsource, we propose that K3-50A is excited by at least two (possiblythree) ionizing stars. This is the first convincing example that amassive stellar cluster is ionizing an ultracompact H II region.Based on data collected with the Subaru Telescope, which is operated bythe National Astronomical Observatory of Japan.
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VLA High-Sensitivity 4HE Imaging of Galactic H II Regions
We have carried out 8.3 GHz hydrogen and helium radio recombination lineand continuum observations of three Galactic H II regions with the NRAO140 Foot Telescope and the Very Large Array. These observations measurethe spatial variations in the singly ionized helium-to-hydrogenabundance ratio, 4He+/H+(y+), and probe for any localized enhancements iny+. The three observed regions (W43, NGC 6334A, and K3-50)are morphologically complex, and high-resolution, wide fieldobservations are crucial to measure the helium abundances on scales thatwould be associated with individual massive stars or clusters of stars.The nearly constant y+ value across the W43 source(+>W43=7.7%+/-1%) indicates that any ionizationcorrection over the spatial scales investigated is small. Suchionization corrections are important for calculating total abundances ofthe light element 3He, which is measured in the Galaxy via asingly ionized hyperfine transition. Localized enhancements in they+ value have been detected in both NGC 6334A(y+=20%+/-4%) and K3-50A (y+=24%+/-5%). The4He abundance results are discussed along with othermeasurements of the physical properties of these H II regions, such asthe kinematics and excitation.
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The interaction of the planetary nebula NGC 6894 with the ISM magnetic field
We have obtained images of the planetary nebula NGC 6894 and the`stripes' near it and have analysed their morphologies. Our analysissuggests that the material of the stripes has been ionized by thecentral star of NGC 6894, and could have originated from the strippingof the halo of NGC 6894 by the interstellar medium (ISM). Based on thefact that the orientation of the stripes is parallel to the Galacticplane, we speculate that the morphology of the stripes is determined bythe Galactic magnetic field. The above interpretation requires themotion of NGC 6894 to be in a direction which is consistent withobservations. This work further stresses the significant role of the ISMmagnetic field in shaping haloes of planetary nebulae, and the potentialfor using planetary nebulae to probe the ISM.
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A Near-Infrared Study of the K3-50 Region of High-Mass Star Formation
Abstract image available at:http://adsabs.harvard.edu/abs/1996ApJ...460..744H
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The gasdynamic evolution of spherical planetary nebulae. Radiation-gasdynamics of PNe III.
Using a radiation-gasdynamics code the evolution of spherical planetarynebulae is followed, while taking into account the evolution of centralstar and the fast wind. These models show the importance of ionizationfronts for the structure of planetary nebulae, especially for the socalled multiple shell nebulae (MSPN). It is shown that the outer shellis formed by the ionization front while the inner shell is swept-up bythe fast wind. These models explain the emission profiles of the outershells as well as their various kinematic properties. Because they areshaped by the ionization front these outer shells only give indirectinformation on the AGB mass loss history. The models indicate thattypical MSPN structures point to mass loss variations during the AGBphase. The ionization also leads to a stalling of the expansion of thenebula, leading to nebulae with expansion ages lower than theirevolutionary age. Values for ionized mass and Zanstra temperatures arederived from the models.
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A bipolar outflow of ionized gas in K3-50A: H76 alpha radio recombination line and continuum observations of K3-50
The H II regions near K3-50 (G70.3 + 1.6) have been imaged at highangular resolution (approximately 1 sec .3) in the continuum and therecombination lines H76alpha and He76(sub alpha using theVery Large Array (VLA). The helium line is detected in only thebrightest component K3-50A while the hydrogen line is detected in threecomponents (K3-50A, B and C1). K3-50A shows a pronounced velocitygradient of approximately 150 km/sec/pc along its major axis (P.A. = 160deg); in addition a wide range of line widths are observed, from 20 to65 km/sec. Kinematics from the line data and the morphology of thecontinuum emission suggest that the ionized material associated withK3-50A is undergoing a high-velocity bipolar outflow.
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Strasbourg - ESO catalogue of galactic planetary nebulae. Part 1; Part 2
Not Available
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Mis-classified planetary nebulae
VLA Radio observations of a number of suspected planetary nebulae arepresented. Based on the morphology of the source, and on the IRAS farinfrared colors, some of these are shown to be compact HII regions. Mostof the other sources show no radio emission down to a level of 1 mJy andare either emission line stars, reflection nebulae, or galaxies. Theradio images of the resolved sources are presented, along with adiscussion of the detected sources. Also a brief description of some ofthe sources is given.
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Ultracompact H II regions - The impact of newly formed massive stars on their environment
An account is given of the current understanding of the physicalproperties, morphologies, dynamics, number, and Galactic and molecularenvironment distributions of ultracompact (UC) H II regions, which aremanifestations of newly formed massive stars still embedded in theirnatal molecular cloud. Recent models of the circumnebular dust indicatethat these cocoons are large, cool, and optically thick at wavelengthson the short side of a few microns. The existence of between 1700 and3000 UC H II regions in the Galaxy is too large a presence to beconsidered consistent with the short dynamical lifetimes of this verycompact stage of evolution.
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Multiple shell planetary nebulae.
Not Available
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Infrared and radio recombination line observations of K3-50
Br-alpha infrared and 110-alpha radio recombination line observations ofthe H II region K3-50 are reported. It is shown that pressure broadeningis important in the compact components. A visual extinction of notgreater than 190 mag is noted toward the core of component C1. Theresults reveal the presence of a disk of molecular material observededge-on.
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Misclassified planetary nebulae
In this paper 266 objects taken from catalogs and lists of planetarynebulas are discussed. Opinions are based on observations given in theliterature, on the vast photometric information collected by the IRASsatellite, plus on the observations from the ongoing project of aspectroscopic survey of all planetary nebulas. Of the objects, 199 aredefinitely rejected as planetary nebulas, 63 others are possibly notplanetary nebulas.
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Multiple-shell planetary nebulae. I - Morphologies and frequency of occurrence
The physical nature of multiple shell planetary nebulae (MSPNs) arestudied using PN imagery survey data obtained at the Kitt Peak NationalObservatory during November 1982 and October 1985. The morphologies ofthe MSPNs are classified based on the relation between the shells andthe morphologies of the outer shell. It is observed that there are typeI MSPNs that have an outer shell with limb brightness, and type II whoseouter shell lacks brightness. The size of the outer shell, outer/innerradii ratio, radio luminosity of the whole nebula, and the outer/innersurface brightness ratio are analyzed in terms of morphology. It isobserved that for type I MSPNs, the outer shell is 0.5-1.0 pc, the radiiratio is greater than 2, and the surface brightness ratio is 0.005 orless; and for the type II nebulae, the shell size is 0.5 pc, the radiiratio is less than 2, and the inner surface brightness is 0.25. Thefrequency of multiple-shell occurrence is derived and compared withtheoretical predictions.
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Filled-aperture maps of selected H II regions at 3.5 millimeters
Observations of the 3.5-mm continuum emission of 11 H II regions,obtained with the 12-m NRAO mm-wave telescope at Kitt Peak, arereported. The data are presented in maps and characterized in comparisonwith cm-wavelength maps. The 3.5-mm emission is attributed mainly tobremsstrahlung, with no statistically significant dust emission.
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Dust-distances to planetary nebulae
Accurate new extinction constants have been measured for the planetarynebulae considered by Lutz in her earlier studies of distances. Insteadof fitting a curve to all the stellar data as in the past, the nebularextinction was bracketed with a range in color excess, and the distancesof the stars falling within the band were averaged. This procedure isless distorted by patchiness along the line of sight, and readily allowscomputation of an error. The derived distances marginally support thedistance scale used by Cahn and Kaler as well as the distance methodemployed by Daub.
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A catalogue of distances of planetary nebulae
This catalog contains distances of 468 galactic planetary nebulae pluslower limits to 61 objects and upper limits for 134 nebulae. Thedistances were calculated assuming a relationship between the nebularionized mass and radius.
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Index and cross-identification of planetary nebulae
The index of 86 discovery lists of planetary nebulae contains all theknown planetary nebulae in the Galaxy, including the probable, possibleand misclassified objects. A cross-identification gives all the names ofthe 1518 PN ordered by increasing galactic longitude.
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Internal motions in ten planetary nebulae
The results of a spectroscopic study carried out on the forbidden O IIIlines at wavelengths 4959 and 5007 A of ten nebulae from the Catalogueof Galactic Planetary Nebulae of Perek and Kohoutek (1967) arepresented. Individual objects are described, and the relevance of thedata for models formulated by other authors is addressed. It isconcluded that the forbidden O III expansion velocities derived for theten nebulae indicate that nine of these nebulae closely fit theevolutionary trend of the expansion velocity given by Sabbadin et al.(1982), and that NGC 6857 is an H II region and not a genuine planetarynebula.
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An extensive galactic search for conformer II glycine
The most extensive galactic search reported to date for conformer IIglycine, a higher energy form of the simplest amino acid has beenconducted. The search utilized four glycine transitions at centimeterwavelengths and 21 at millimeter wavelengths to observe 18 galacticmolecular sources and one comet. No conformer II glycine lines weredetected, and measurements of representative sources were used tocompute upper limits on total column densities. Several unidentifiedlines were detected and are reported here with some suggested possibleidentifications.
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Measurements of expansion velocities in planetary nebulae
A scanning Fabry-Perot interferometer is used on the 1.5-m fluxcollector, Tenerife, to obtain forbidden O III 5007 A emission lineprofiles at the centers of 33 planetary nebulae. The observations aremade at a resolution of approximately 3 km/s through entrance aperturesof 5, 10 or 18 arcsec diameter. Small young nebulae are chosen to formthe majority of the sample, and the shell expansion velocities arededuced from the observations using a simple spheroidal model for thenebular shell. These new data, together with published expansionvelocity data for other nebulae, are used to investigate therelationship between the expansion velocities and the nebular radii. Itis shown that two possible relationships exist; a comparison withtheoretical radiation pressure-driven nebular shell models implies twodistinct evolutionary sequences characterizing nebulae of 'high' and'low' mass.
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Positions of OH maser sources determined with the 100-m telescope
Results of determinations of the positions of 65 OH masers, primarilyOH/IR sources, made with the Effelsberg 100-m telescope are reported.Positional determinations were made with an accuracy of approximately 10arcsec on regular offset grids on the basis of simultaneous observationsat 1612 and 1667 MHz. Positions, source types and principle line radialvelocities are presented for the sources, and it is noted that althoughthree of the sources show only one 1612-MHz component, they are alsoprobably OH/IR sources. In addition, six of the objects are found to becertain type I OH sources, associated with recently formed massivestars, while type I identifications of five others are probable. Inaddition, the 1665-MHz emission from the source ON-3 is observed tooriginate 2.3 arcmin from the position of interferometrically determined1720-MHz emission. Positions are also presented for the calibrationsources W 3(OH), Ori KL and VX Sgr, for which 1612- and 1665/1667-MHzemission are found to coincide.
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The oxygen enrichment of the Galaxy
Oxygen-to-hydrogen ratios are calculated for the 97 planetary nebulaefor which there are sufficient data and for which the correction forunobserved ionization states is not too large. The ratios are stronglycorrelated with population type. Almost all planetaries with absoluteLSR radial velocity greater than about 85 km/s and distance from thegalactic plane greater than 1 kpc have low O/H; high values of O/H areconfined to the galactic disk. The radial gradient within the disk isnot easily discerned from the planetaries. An apparent gradient is seenbecause the planetaries with distances from the galactic center greaterthan about 11 kpc are dominantly halo objects with high velocity orlarge distance from the plane. The planetaries are divided into relativeage groups which depend upon the nebular velocities, distances from thegalactic plane, excitation levels, and He/H ratios. The mean O/H foreach group increases with decreasing age. The available evidence showsthat this effect is not due to nuclear processing in individual starsand is consequently an effect of galactic evolution. Galactic O/H hasincreased by a factor of between 5 and 10 from the time of the formationof the early halo to the present, consistent with earlier studies. Therelative oxygen enrichment rate of the Galaxy is characterized by alarge early increase from the old to the intermediate halo, followed bya smaller but steady relative enrichment rate among the identified agegroups.
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Evolution of planetary nebulae and their nuclei - Temperatures of nebular nuclei
Not Available
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Compact H II regions in the far-infrared
Far-infrared (40-150 microns) observations of W51 (G49.5-0.4), K3-50, DR21, NGC 7538, and W3(OH) are presented and discussed. At thesewavelengths each source is dominated by a small bright component closelyassociated with a compact H II region. Their spectra can be explained asemission by dust at temperatures of 30-50 K. Some of the objects appearto be optically thick out to wavelengths of about 60 microns. Of the 10source components in the five regions, at least four may be powered bypre-main-sequence stars. The far-infrared data are consistent withdepletion of volatile components of the dust within compact H IIregions, but do not clearly require destruction or expulsion ofrefractory grains. The bulk of the dust which emits primarily in thefar-infrared must lie in a dense shell immediately outside the ionizedzone. The sources are possible precursers to open clusters with stellarmasses in the range from 1,000 to 10,000 solar masses.
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The enrichment of nitrogen and helium in planetary nebulae
The reported investigation is concerned with the determination of thevalidity of the N/O = N(+)/O(+) relation, the degree of the enrichmentof nitrogen, and the correlation between N/O and He/H. The generalvariation of N/O with position in the galaxy is also studied. For mediumexcitation planetaries it is found to be generally true that N(+)/O(+) =N/O, at least roughly to within the accuracy of the observations. Basedon the medium-excitation planetaries, N/O is clearly correlated withHe/H. The correlation becomes stronger when the sample of nebulae isrestricted to the disk.
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Statistical properties of planetary nebulae: graphic presentation.
Abstract image available at:http://adsabs.harvard.edu/abs/1978A&AS...33..223S
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New and misclassified planetary nebulae
The paper tabulates the designations, names, coordinates, discoverydates and discoverers of 226 new objects which have been classified asplanetary nebulae since the publication of the Catalogue of GalacticPlanetary Nebulae in 1966. A group of eight objects called possibleproto-planetary nebulae is also added. These objects may be in an earlystage of evolution of a planetary nebulae or even in the stage of apossible planetary nebulae progenitor. A total of 34 objects previouslymisclassified as planetary nebulae is appended.
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Bibliographical index of planetary nebulae for the period 1965-1976.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...30..217A&db_key=AST
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