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Wynn-Williams, C. G.

Publications and source records attributed to Wynn-Williams, C. G..

At least 37 records · Page 2
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NASA NTRS1981

Infrared and radio observations of W51: Another Orion-KL at a distance of 7kpc

The bright infrared sources W51-IRS2 has at least three components with different physical and evolutionary properties. The spatial distribution and the near infrared spectra of the components in IRS2 are remarkably similar to, but more luminous than those found in Orion, where an H2 region of comparable linear size is also located close to a cluster of compact infrared sources. The characteristics of the nearby W51-NORTH H2O maser source, and the detection of 2 micro m H2 quadrupole emission in IRS2 indicate that the mass loss phenomena found in Orion-KL also exist in W51.

Genzel, R.↗
NASA NTRS1981

Infrared astronomy; Proceedings of the Symposium, Kona, HI, June 23-27, 1980

The role of infrared studies in numerous aspects of astronomy is examined. Topics include the composition of planetary atmospheres; spectrophotometric remote sensing of planets and satellites; thermal studies of planetary surfaces; infrared sources in dense molecular clouds; globules, dark clouds, and low mass pre-main sequence stars; protostellar objects; molecular hydrogen emission; and the Orion molecular cloud. Also considered are dust spectrophotometry; polarimetry of infrared sources; emission line observations of H II regions; observation and interpretation of emissions from the galactic plane; the galactic center; stellar content of extragalactic systems; star formation in galactic nuclei; and active extragalactic nuclei.

Wynn-Williams, C. G.↗
NASA NTRS1980

Extended 20 micron emission from the center of NGC 1068

Multiaperture photometry of the Seyfert galaxy NGC 1068 is reported which demonstrates that significant 20 micron emission originates at positions located more than 3 arcsec, or 260 pc, from the nucleus. These observations strongly support arguments that most of the infrared flux is thermal emission from dust. It is argued that the dust giving rise to this extended emission cannot be heated solely by a compact nuclear object. It is suggested that there is a powerful energy-generation mechanism, possibly an enormous burst of star formation, operating on a scale much larger than that identified with the visible nucleus.

Telesco, C. M.↗
NASA NTRS1980

IR observations of the double quasar 0957 + 561 A, B and the intervening galaxy

Infrared observations of the double quasar 0957 + 561 A, B and the intervening galaxy believed to be responsible for its double appearance by gravitational light deflection are reported. Observations were obtained of each quasar at 1.6 and 2.2 microns and of the 12.5 arcsec region centered between the two quasars at 1.2, 1.6 and 2.2 microns. Extended IR emission is observed in the vicinity of both quasars and is attributed to emission from the intervening galaxy. The two quasars are found to have a constant flux ratio in all observed wavelength ranges, consistent with the achromatic imaging predicted by the gravitational lens model, and to exhibit an unusual continuum distribution in the region 0.35-2.2 microns. The infrared observations are also consistent with a giant elliptical lens galaxy at a redshift of approximately 0.40.

Soifer, B. T.↗
NASA NTRS1979

The IR energy distribution of SS433

The infrared energy distribution of the emission-line object SS 433 in the range 1 to 10 microns is determined. Photometric measurements were made with a 2.2-m telescope using an InSb detector and a 6-arcsec diaphragm for 1.2- to 4.8-micron observations and a gallium-doped germanium bolometer with a 6-arcsec diaphragm for 8- to 13-micron observations. Results indicate the presence of substantial night-to-night flux density and color variations, and a decrease in flux density at wavelengths greater than 5 microns. The energy cut-off is used to estimate a physical size of 1 AU for the emitting region and an electron density of 10 to the 11th/cu cm on the basis of a model of reddened free-free emission from an ionized plasma, with self-absorption of radiation over 5 microns. The greater variability observed at longer wavelengths is also interpreted in terms of this model.

Wynn-Williams, C. G.↗
NASA NTRS1979

Two-micron spectrophotometry of the galaxy NGC 253

A very strong Brackett-gamma hydrogen emission line and the 2.3-micron CO stellar absorption feature have been measured in NGC 253. The presence and strength of the CO feature indicate that late-type giant stars produce most of the 2.2-micron continuum emission, while the rate of ionization implied by strength of the Brackett-gamma line indicates that much, perhaps all, of the luminosity detected at far-infrared wavelengths originates from a large number of OB stars. As compared with the corresponding region of the Galaxy, the number of massive young stars in the central 200 pc of NGC 253 is 30 times greater, but the total mass of stars is roughly the same.

Wynn-Williams, C. G.↗
NASA NTRS1979

New multiple systems in molecular clouds

Twenty-micron searches of the dense cores of the molecular clouds S140, S255, and Cepheus A have revealed the existence of multiple sources of infrared radiation which seem to be precursors to Trapezium-like clusters of OB stars. Two of the new sources are extended with unusually low color temperatures, less than 100 K. Observations with the Very Large Array with 1 mJy sensitivity have shown that three and possibly four of the infrared sources are associated with small H II regions. Multiple systems appear to be the rule rather than the exception in molecular clouds.

Beichman, C. A.↗
NASA NTRS1979

An infrared study of the NGC 7538 region

Infrared observations of the NGC 7538 region at wavelengths from 1 micron to 1 mm are presented and analyzed with the aim of understanding both the large-scale structure of this region of current star formation and the properties of the individual compact objects within it. At far-infrared wavelengths (25-130 microns), emission is seen from the visible H II region, from the vicinity of the previously known maser sources and dust-embedded compact HII regions, and from a new region called NGC 7538(E). Coincident with NGC 7538(E) are a point-like 1-25 micron infrared source, NGC 7538-IRS9, which probably provides the power for the far-infrared emission, and an extended source of 2.2 micron emission which appears to be an infrared reflection nebula. The compact H II regions, the maser sources and IRS9 are located within a dense molecular cloud at the edge of the optical H II region. This cloud, which has a mass of approximately 9000 solar masses, is detected in emission at 1 mm. The NGC 7538 region appears to contain examples of different stages in the formation of massive stars; it is suggested that the center of star formation is moving systematically to the southeast in this region.

Werner, M. W.↗
NASA NTRS1979

Detection of Jupiter's ring at 2.2 microns

Reflected sunlight from the Jovian ring discovered by the Voyager spacecraft was detected at 2.2 microns. A chopping secondary photometric system and an indium antimonide photovoltaic apparatus were used in the detection. The search for the ring was conducted at 2.2 microns because at this wavelength scattered radiation from the planetary disk is reduced by the strong molecular absorption features in Jupiter's atmosphere.

Becklin, E. E.↗
NASA NTRS1979

Two-micron spectrophotometry of the galaxy NGC 253

A very strong Brackett-gamma hydrogen emission line, and the 2.3 micron CO stellar absorption feature were measured in NGC 253. The presence and strength of the CO feature indicates that late type giant stars produce most of the 2.2 micron continuum emission, while the rate of ionization implied by strength of the Brackett-gamma line indicates that much, perhaps all, of the luminosity detected at far infrared wavelengths originates from a large number of OB stars. As compared to the corresponding region of the Galaxy, the number of massive young stars in the central 200 pc of NGC 253 is thirty times greater, but the total mass of stars is roughly the same.

Wynn-Williams, C. G.↗
NASA NTRS1978

Two-micron line emission from the H II region G 333.6-0.2

Spectrophotometry of the H II region G 333.6-0.2 with a resolution of approximately 100 shows strong emission lines of hydrogen and helium superimposed on a continuum. Spatial variations in the equivalent widths of the lines suggest the presence of very hot (at least 600 K) dust grains within the region. The shape of this very powerful H II region indicates that its dense ionized core is being continuously replenished from a reservoir of neutral gas.

Wynn-Williams, C. G.↗
NASA NTRS1978

Infrared observations of the galactic center. III - 2.2 micron spectroscopy

Observations of the B-gamma line at 2.17 microns are presented for the central few parsecs of the galactic-center region. The surface-brightness distribution of the line with 3.3- and 6.6-arcsec resolution has been sampled in 25 locations. The results show that the ionized gas is concentrated within the central parsec of the galactic-center region; the fine-scale structure seen at 10 microns does not appear to be present in the ionized gas. For the central parsec (20 arcsec) the equivalent width of the B-gamma line is, within large uncertainties, independent of the 2-micron continuum flux; for radial distances of the order of 30 arcsec the line equivalent width drops significantly. A comparison of the B-gamma line strength with radio observations shows that the 2.2-micron extinction is consistent with the 2.7 mag determined from the reddening of late-type stars. Observations of the CO band at 2.3 microns in the central 30 arcsec are also presented; they strengthen the interpretation that the 2-micron flux arises from late-type giant stars.

Neugebauer, G.↗
NASA NTRS1977

Airborne far-infrared observations of the galactic center region

Maps of a region 10 arcmin in diameter around the galactic center made simultaneously in three wavelength bands at 30, 50, and 100 microns with about 1 arcmin resolution are presented, and the distribution of far-IR luminosity and color temperature across this region is derived. The position of highest far-IR surface brightness coincides with the peak of the late-type stellar distribution and with the H II region Sgr A West. The high spatial and temperature resolution of the data is used to identify features of the far-IR maps with known sources of near-IR, radio continuum, and molecular emission. The emission mechanism and energy sources for the far-IR radiation are analyzed qualitatively, and it is concluded that all of the observed far-IR radiation from the galactic-center region can be attributed to thermal emission from dust heated both by the late-type stars and by the ultraviolet sources which ionize the H II regions. A self-consistent model for the far-IR emission from the galactic-center region is presented. It is found that the visual extinction across the central 10 pc of the Galaxy is only about 3 mag and that the dust density is fairly uniform in this region. An upper limit of 10 million suns is set on the luminosity of any still unidentified source of 0.1- to 1-micron radiation at the galactic center.

Gatley, I.↗
NASA NTRS1977

Infrared studies of H II regions and dust clouds near K3-50

Ground-based infrared observations of the K3-50 region are reported at wavelengths between 2 and 34 microns as well as at 1 mm. The main results are that (1) the visible nebular K3-50 is displaced from its infrared and radio counterparts; (2) component Cl (the OH source ON-3) appears very faint at wavelengths not exceeding 20 microns and is therefore probably obscured by several hundred magnitudes of visual extinction; (3) both K3-50 and component C are associated with separate condensations of molecular hydrogen, each of about 3000 solar masses; and (4) there are no strong sources in this region at 20 microns other than those associated with H II condensations.

Wynn-Williams, C. G.↗
NASA NTRS1977

On the infrared emission from SGR B2

Results are reported for 2.2-micron observations of a 3.5 by 4 arcmin region centered on Sgr B2. More than 30 discrete sources stronger than 10 magnitudes (60 mJy) were found, but no extended emission stronger than about 80 mJy was seen with the 15-arcsec beam. All the emission objects are shown to have colors typical of stars reddened by 10 to 35 magnitudes, and it is postulated that they are all unrelated field stars at unknown distances along the line of sight to the H II region. It is concluded that there is no evidence for a statistical excess of 2.2-micron sources in the direction of Sgr B2. A previously reported observation of extended emission in the same region is attributed to source confusion and the limited number of scans made.

Becklin, E. E.↗
NASA NTRS1977

On the relationship between the infrared source CRL 2591 /UOA-27/ and its radio and H2O counterparts

Recent radio, infrared, and H2O maser observations show that there is a 7-arcsec angular separation between the protostarlike infrared source CRL 2591 and the compact H II region which has until now been identified with it, while the H2O maser coincides with the infrared source. This result, together with an extension of photometric measurements to 20 microns and a much improved upper limit to its angular size, reinforces the apparent similarity of CRL 2591 to the BN object in Orion and to W3/IRS 5.

Wynn-Williams, C. G.↗
NASA NTRS1976

Late-type giants and supergiants in the galactic center

An absorption feature at 2.3 microns attributed to CO molecules in stellar atmospheres has been found in some, but not all, of the infrared sources within 20 arcsec of the galactic center. The absorption is characteristic of that found in M-type giant and supergiant stars. The infrared source coincident with the sub-arcsecond nonthermal radio source does not show CO absorption.

Neugebauer, G.↗