Dusty Regions Research Articles

Spectra of Fast J-Shocks in Dense, Star-Forming Regions

Stellar winds, bipolar outflows, and supernovae generate strong shocks in molecular clouds. If the molecular gas is magnetized and weakly ionized, shocks slower than about 40-50 kms−1 (C-shocks) emit primarily in the infrared. Faster shocks, or shocks in a weakly magnetized or more highly ionized medium (J–shocks), emit primarily in the ultraviolet and are thus harder to detect in dusty regions. J–shocks in molecular gas are usually dissociative, so that molecular emission lines from such shocks are produced by molecules formed behind the shock front. Observations of fast shocks in molecular clouds can provide valuable insights into energetic events occurring within them.

IRAS large-beam and ground-based small-beam measurements of the unidentified 11.3 and forbidden NE II 12.8 micron line fluxes in the starburst galaxy M82

view Abstract Citations (8) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS IRAS Large-Beam and Ground-Based Small-Beam Measurements of the Unidentified 11.3 and [Ne ii] 12.8 Micron Line Fluxes in the Starburst Galaxy M82 Levan, P. D. ; Price, S. D. Abstract The low resolution spectrometer data obtained by IRAS on M82, when compared with smaller ground-based beam 8-14 micron spectra, provide interesting beam-dependent ratios of the fluxes for the 'unidentified' 11.3 micron emission feature, the forbidden Ne II 12.8 micron fine structure line, and the 10 micron continuum. Specifically, the relative strengths of the 11.3 micron feature and the 10 continuum are constant for the small and large beam diameters, concordant with published interpretations of both as being associated with dusty regions of thermal radiation. By contrast, the relative strength of either the 11.3 micron feature or 10 micron continuum fluxes to the forbidden Ne II 12.8 micron line flux increases modestly from the smaller to the larger IRAS beam diameter. This is taken as evidence for significant amounts of warm dust above that associated with the H II regions in the nucleus of M82. Publication: The Astrophysical Journal Pub Date: January 1987 DOI: 10.1086/164904 Bibcode: 1987ApJ...312..592L Keywords: Astronomical Spectroscopy; Galactic Structure; Infrared Spectra; Line Spectra; Radiant Flux Density; Star Formation; Starburst Galaxies; Cosmic Dust; Galactic Nuclei; H Ii Regions; Infrared Astronomy Satellite; Neon; Astrophysics; GALAXIES: INDIVIDUAL MESSIER NUMBER: M82; GALAXIES: NUCLEI; INFRARED: SOURCES; INFRARED: SPECTRA; STARS: FORMATION full text sources ADS | data products SIMBAD (1) NED (1)

The binary system MWC 349

The ionized zone surrounding MWC 349 has been resolved using the VLA. On the basis of a radio continuum map, it is concluded that there is a physical interaction between the two stellar components of MWC 349, and that the system is therefore a binary. The B component can be classified as a B0 III star, yielding a distance of about 1.2 kpc for the binary. The low ratio of infrared to short-wavelength luminosity in the A component suggests a circumstellar dusty region of special geometry. It is proposed that an appreciable dust and gas disk surrounds the star, modifying the symmetry of its H II region, and yielding the low infrared luminosity and perhaps its extra circumstellar extinction.

Aspects of intestinal parasitism in villagers from rural peninsular India.

In 1977, a parasitological survey was undertaken of stool samples collected from 335 people from 5 villages in semi-arid regions of peninsular India. Stools, which were collected from various individuals in a stratified sample of 40 matched households from each village, were examined by standard diagnostic procedures. Eggs of Ascaris lumbricoides and protozoan cysts, which were identified on morphological grounds as belonging to Entamoeba spp., were most common. Other protozoan cysts were considered to be those of Balantidium coli, and eggs of hookworm and Hymenolepis nana were also observed in some of the stool specimens. The prevalence of parasitic infections varied between villages. The village with the highest prevalence of Ascaris (70%) appeared to have the greatest demands made on its meager drinking-water supply. This village is located in a dry, windy and dusty region and it is speculated that, in addition to well-established transmission mechanisms, the villagers may be exposed, perhaps through contamination of uncovered drinking-water wells and inhalation, to wind-borne Ascaris eggs. In 1967, a WHO Expert Committee Report on the Control of Ascariasis pointed out that information on the frequency of dust-borne infection with Ascaris in man was inadequate.

Near-infrared spectroscopy of possible precursors to planetary nebula - AFGL 618

A spectrum in the range 1.9--2.5 ..mu..m of the suspected protoplanetary nebula AFGL 618 is presented. It shows at least 11 members of the H/sub 2/, v = 1..-->..0 and v = 2..-->..1 rotation vibration branches. These lines appear to arise in a dusty region of shocked gas, and the line intensities are used to estimate shock velocity, preshock density, H/sub 2/ excitation temperature, and extinction to the emitting region. The observations are consistent with the suggested geometry of a double-lobed reflection nebula, banded about the center wih a ring of dusty material from which the H/sub 2/ lines are emitted.

Clinical and Radiological Study in Sepiolite Workers

Abstract Radiological findings were evaluated on a mass survey (70 mm films) in four villages where mining and processing of sepiolite have occurred for more than 100 yr, together with a clinical and radiological study in 63 sepiolite trimming workers in Eskisehir, Turkey. Mineral fiber-related pleural diseases were not detected in those people who were exposed to sepiolite dust Although pulmonary fibrosis was encountered in 10 of 63 workers, no relationship between pulmonary fibrosis and sepiolite inhalation could be established. In contrast, all fibrotic patients were smokers and came from dusty rural regions where tremolite (asbestos) and zeolites are present. Three of them had also worked in dusty fields.

Clinical and radiological study in sepiolite workers.

Radiological findings were evaluated on a mass survey (70 mm films) in four villages where mining and processing of sepiolite have occurred for more than 100 yr, together with a clinical and radiological study in 63 sepiolite trimming workers in Eskisehir, Turkey. Mineral fiber-related pleural diseases were not detected in those people who were exposed to sepiolite dust. Although pulmonary fibrosis was encountered in 10 of 63 workers, no relationship between pulmonary fibrosis and sepiolite inhalation could be established. In contrast, all fibrotic patients were smokers and came from dusty rural regions where tremolite (asbestos) and zeolites are present. Three of them had also worked in dusty fields.

A model for the infrared brightening of a Nova shell

A model for grain formation in an expanding Nova shell is presented. It is shown that individual grains complete the growth within a very short time interval. In consequence the infrared brightening accompanied with visual darkening observed in several Novae is interpreted in terms of extension of dusty region in the ejected gas shell. Developments of infrared luminosity and visual magnitude are computed on the basis of a model, and compared with the observations of Nova Vul 1976, Nova Ser 1970, and Nova Aql 1975. The constancy and uniformity of grain temperatures for a long period after the infrared maximum observed in Nova Vul 1976 are also discussed.

Temporal changes in the flux of meteorites in the recent past

The depth variations of the fossil cosmic ray tracks and agglutinates have been examined in the (0.6–0.7)m deep Apollo 12 and 16 drive cores, in the 2.4 m Apollo 15 deep drill core and in a 0.6 m long section of the Apollo 17 deep drill core. These data indicate Moon-wide short duration episodes of impacts of meteorites of size 10 cm−1m on the lunar surface. Based on the longest continuous Apollo 15 deep drill core record, these impact episodes occurred about 150, 400 and 700 m.y. ago. The enhancements in the meteorite flux may be due to solar dynamical processes or they may be related to excursions of the solar system, once in each orbit, through a certain dusty region of the galaxy.

Binkhorst Intra-Ocular Implant as a Secondary Procedure

Summary This report will deal only with the Binkhorst intra-ocular implant as a secondary procedure mainly in traumatised eyes. If there is some controversy about the use of intra-ocular implants in elderly patients as a primary procedure then this controversy is multiplied many times in the type of patient I am about to describe. These operations extend over a nine-year period and total 48 implants. The great majority of patients operated upon have a unilateral traumatic cataract in a person who has not been able to tolerate a contact lens. The majority of the patients were farmers in the dusty regions of South Australia. This means, of course, that the indications are strictly limited. The average number of these operations per year is 5.3. Some of the eyes had been badly damaged with frequent iris loss and obviously this is one reason for the complications being so high. The dangers of publicity about intra-ocular implants are well recognised—if Mrs. A tells Mrs. B. that she does not need those terrible thick glasses because her eye surgeon put in an intra-ocular implant, there may be extreme pressure put on ophthalmologists to implant intra-ocular lens as a secondary procedure. If this paper makes you aware of the dangers of secondary implantation it will have served some purpose.

CRL 2688 - "THE EGG NEBULA" - PREPLANETARY NEBULA OR PROTOSTELLAR SYSTEM?

ABSTRACT A discussion of the available data for CRL 2688 suggests that it is most likely not a pre -main -sequence object, although it cannot be conclusively shown that it is an evolved star losing mass. Its spectrum in both the blue and near-infrared lacks the strong emission features seen in the spectra of young stars, and the energy distribution is more like those of evolved stars. The kinematic data from the optical spectrum and molecular radio observations imply that CRL 2688 may have a large peculiar velocity inappropriate for a young star. CRL 2688 is also not directly associated with emission nebulosity or a dusty region. Key words: infrared sources - planetary nebula - protostar

Galactic clouds of organic molecules

The discovery of immense organic clouds of gas embedded in the dusty regions of our Galaxy is of tremendous importance to the origin of life. It is within these clouds that the formation of stars and planetary systems is believed to take place. The collapse of these clouds to form stars takes place in a very small fraction of the astronomical lifetime of a star. It is precisely at this moment that the clouds of organic molecules appear.

Origin of Elements

WE believe the recent report in Nature1 under this title to be misleading in the light of recent observations. The recent measurement2 of a=12C/13C=75 (+25, −15) for the ζ Oph cloud is interesting but not surprising because it can be regarded as a confirmation of earlier work3, as pointed out in ref. 1, and the conclusion that the relative abundance of 13C in the ζ Oph cloud seems to be terrestrial is quite straightforward. It would be an unwarranted assumption to extrapolate the results from ζ Oph (and other tenuous clouds) to the dense, dusty regions of both the galactic centre and the Orion Nebula.

The Rotation and Mass of the Inner Parts of NGC 4826.

view Abstract Citations (38) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Rotation and Mass of the Inner Parts of NGC 4826. Rubin, V. C. ; Burbidge, E. Margaret ; Burbidge, G. R. ; Prendergast, K. H. Abstract In this paper we describe our attempt to measure the rotation of the Sb galaxy NGC 4826 The structure of this system is rather unusual; the outer part is composed of smooth stellar spiral arms and the inner dust lane seen over half of the galaxy is very prominent. Since ionized gas is found only in the dusty regions we have been able to measure the rotation and hence the mass distribution and mass only of these inner parts out to a radius of about 2 kpc. This mass turns out to be 1010 M0. The density-curve is very steep over this region If the density remained constant between 2 and 8 kpc, at the value it has at 2 kpc from the center, then the total mass would be about 10" M0. Publication: The Astrophysical Journal Pub Date: April 1965 DOI: 10.1086/148183 Bibcode: 1965ApJ...141..885R full text sources ADS | data products NED (4) SIMBAD (1)

Luminosity Distribution of the Spiral Galaxy NGC 5055.

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Luminosity Distribution of the Spiral Galaxy NGC 5055. Fish, Robert A. Abstract The luminosity distribution of XGC 5055 was studied with photographic photometry on the UB V system. On comparison of the luminosity distribution with the mass distribution found previously (Burbidge, E. M., Burbidge, G. K., and Prendergast, K. H. Astrophys. J. 131, 282, 1960), the mass-to-light ratios in each color are observed to rise at first, then decrease steadily on proceeding outwards from the nucleus. The over-all photographic M7L ratio for the galaxy out to 150" is 5.46. Three different indices of asymmetry are constructed from the photometric information. They reveal that the light distribution within 50" of the nucleus is inherently asymmetric, but that beyond 50" the three-dimensional light distribution is nearly axially symmetrical. Due to scattering and absorption of light the observed isophotes deviate widely from ellipses. If the albedo of the obscuring material is low, the intrinsic M7L ratios must vary only slowly from 50" outwards; if it is high the measured change of M7L by a factor of 5 between 50" and 150" represents very nearly the intrinsic change. The null effect of scattering on the average luminosity of NGC 5055 results from the inclination angle of the galaxy. If high scattering efficiency is a universal property of the obscuring matter in spiral galaxies, then very little light is degraded into the infrared, and photons entering the scattering layer are simply redirected toward normal emergence. Because of this redirection a face-on spiral must appear brighter and bluer than it would if no obscuring matter were present. The magnitude of this effect is evaluated by means of Holmberg's photometry (Lund Medd. Ser. II, No. 136, 1958); it is about 0.42 in total photographic brightness and 0.04 in color. The redirection of photons should be most prominent in the dusty regions of the face-on galaxy, creating an anomalous relative brightness and blueness of the spiral arms. Publication: The Astronomical Journal Pub Date: March 1961 DOI: 10.1086/108547 Bibcode: 1961AJ.....66R.283F full text sources ADS |

The Association of Gas and Dust from 21-CM Hydrogen Radio Observations.

view Abstract Citations (109) References (10) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Association of Gas and Dust from 21-CM Hydrogen Radio Observations. Lilley, A. E. Abstract Dust clouds in Taurus, Orion, and Perseus have been observed by means of the 21-cm hyperfine emission line of interstellar hydrogen. Dust clouds at intermediate galactic latitudes are strong 21-cm emitters when compared to adjacent, less dusty regions. Coincident values of gas and dust optical depths show a good correlation for these clouds. Assuming similar distributions in distance for the gas and dust, a determination follows for the average interstellar spatial density ratio of gas to dust. The individual observed values of the gas-to-dust density ratio range from 250 and have a mean value of 100. A minimum mass of 21,000 Mo is obtained for the H I the dust complex. The results indicate the dust content to be approximately 200 Mo, 1 per cent of the gas content. The gas and dust data, when compared with stellar-distribution data, suggest similar distributions of gas, dust, and stars in the anticenter. Publication: The Astrophysical Journal Pub Date: May 1955 DOI: 10.1086/146022 Bibcode: 1955ApJ...121..559L full text sources ADS |