Engineering topics

Arendt, Richard G.

Publications and source records attributed to Arendt, Richard G..

46 records · Page 3

NASA NTRS2000

Detection of the Near-IR Cosmic Infrared Background Using Alternative Models of Near-IR Galactic Emission in the DIRBE Data

The analysis portion of this task has been completed. New models were developed for the removal of the near-infrared emission of Galactic stars in the DIRBE data. Subtraction of these models from the observed emission attempted to achieve a better detection of the Cosmic Infrared Background at near-infrared wavelengths. The new models were found to provide a large improvement in the isotropy of the residual emission, however constraints on the intensity of the emission are not significantly improved. A paper detailing the procedures and results has been drafted, and will be completed next year. The draft of this paper is included as the final report on the contract.

Arendt, Richard G.↗

NASA NTRS1992

Infrared emission from X-ray and optically emitting regions in the Cygnus Loop supernova remnant

We present a new technique for analyzing the infrared (IR) emission of a supernova remnant (SNR) and apply it to the Cygnus Loop. The technique consists of a decomposition of the IR emission from the remnant (in all four IRAS bands) into two distinct emission components. The first component is spatially correlated with the X-ray emission from the remnant and arises from collisionally heated dust in the shocked gas. The second component is spatially correlated with the optical filaments and arises from dust which is radiatively or collisionally heated within the filaments, and from IR lines emitted by the shocked gas. The decomposition allows us to determine the characteristics of the dust, examine evidence for grain processing through the shock, constrain various remnant parameters, and demonstrate how the morphology of the environment determines the IR emission from the remnant.

Arendt, Richard G.↗

NASA NTRS1992

Dust-gas interactions and the infrared emission from hot astrophysical plasmas

Environments where the presence of dust is primarily inferred from its collisional interactions with the ambient gas are reviewed with emphasis on environments typically encountered behind fast (100 km/s or greater) shocks and in hot (few 10 exp 5 K) plasmas in galactic halos, some elliptical galaxies, or the intergalactic medium of galaxy clusters. The discussion covers interactions between dust grains and a hot gas, grain temperatures and infrared emission, supernova remnants and supershells, and dust and hot gas in, around, and between galaxies. Finally, future prospects in the field are briefly discussed.

Dwek, Eli↗

NASA NTRS1991

IRAS 15099 - 5856 and the composite supernova remnant G320.4 - 1.2

The supernova remnant (SNR) G320.4 - 1.2 is a composite SNR, containing both a shock-dominated shell, and a pulsar-dominated plerion. G320.4 - 1.2 is one of the few SNRs in which a pulsar has been detected. This paper reports on IRAS observations of this SNR. A pointlike source (IRAS 15099 - 5856) near the position of the pulsar appears quite prominently at 25 microns. The region appears more complex at 60 and 100 microns. Three models that may account for the IR emission of IRAS 15099 - 5856 are examined; none of these is entirely satisfactory. Some IR emission is detected from the brightest portion of the shell of this SNR, but this emission is nearly hidden by other confusing sources.

Arendt, Richard G.↗

NASA NTRS1991

An infrared analysis of Puppis A

A quantitative analysis of the infrared emission of the supernova remnant (SNR) Puppis A as seen by the Infrared Astronomical Satellite is presented. Physical parameters of the remnant (and the surrounding interstellar medium), including density, mass, temperature, and age are estimated. The infrared spectrum of Puppis A is fit by models of thermal emission from interstellar dust grains which have been swept up into the SNR where they are collisionally heated by the shocked gas. Evidence of an enhanced abundance of very small grains in the interstellar medium near Puppis A, and evidence of their destruction by the advancing blast wave, are found.

Arendt, Richard G.↗

NASA NTRS1990

Comparative morphological analysis of Puppis A at radio, infrared, optical, and X-ray wavelengths

This paper presents a new radio image of the supernova remnant Puppis A obtained with the Molonglo Observatory synthesis telescope (MOST) and the Parkes telescope, and infrared images of Puppis A and its surrounding medium obtained with the IRAS, and compares the remnant morphologies at radio, infrared, optical, and X-ray wavelengths. The radio image, which includes large-scale emission, shows a clumpy shell of emission with moderate central brightness. The infrared observations have the advantage of offering a detailed look at the medium into which the remnant is expanding. From the IR data, evidence is found of the remnant's expansion into a strong density gradient (distinct from the more gentle gradient of the Galactic plane). A strong isolated knot of enhanced X-ray and radio emission is a region of enhanced infrared emission as well. Detailed correlative analysis of the infrared, radio, and X-ray emission shows that the IR emission correlates very well with the X-ray emission, confirming the idea that the IR emission arises from dust that is collisionally heated by the shocked gas.

Arendt, Richard G.↗

NASA NTRS1989

Infrared emission from the supernova remnant Puppis A: Dust and gas parameters

The infrared (IR) spectra of collisionally heated dust at several regions across the supernova remnant (SNR) Puppis A were modelled. Through the comparison of the actual and model spectra, the possible range of gas density and temperature within these areas was narrowed down. From the models, information on the minimum and maximum dust grain sizes and the amount of sputtering which has occurred was found. Finally the mass of gas and dust, the IR luminosity, the effective thickness, and the length of time since the dust was swept up by the SNR were derived for these regions.

Arendt, Richard G.↗

NASA NTRS1989

An infrared survey of Galactic supernova remnants

A survey of Galactic supernova remnants (SNRs) in the infrared has been completed. Flux densities or upper limits on the flux densities have been measured for 157 objects in each of the four broad bands surveyed by the Infrared Astronomical Satellite (IRAS). Nearly one-third of the known SNRs exhibit some evidence of infrared emission. Confusion with other Galactic sources is a serious problem. Contour maps and halftone images are presented for 51 SNRs which are probable infrared sources. Initial analysis indicates that both the infrared spectra or colors and the ratio of infrared to radio brightnesses can discriminate between the youngest SNRs and older SNRs. In general, however, SNRs cannot be distinguished from other Galactic sources solely on the basis of their infrared colors. No apparent relation is found between the infrared surface brightnesses and the diameters of SNRs.

Arendt, Richard G.↗

NASA NTRS1988

The evolution of the radio emission from Kepler's Supernova remnant

High-resolution radio maps of Kepler's Supernova remnant (SNR) using all four arrays of the VLA have been obtained at wavelengths of 20 and 6 cm. They show the complete structure of the remnant; all features are resolved with sizes greater than about 2 arcsec, and the relative brightness of the smooth component near the center is about 1/4 the brightness of the rim. The results have been compared with earlier more limited data to measure changes in the remnant over a four-year time span. The SNR is expanding with a mean rate of R proportional to t exp 0.50 with considerable variations around the shell. Values range from R proportional to t exp 0.35 on the bright northern rim to R proportional to t exp 0.65 on the eastern part of the shell. The measurements are consistent with expansion into a variable circumstellar medium.

Dickel, John R.↗

NASA NTRS1987

Resolution of compact knots in Cassiopeia A

Observations of the young supernova remnant Cassiopeia A at a wavelength of 2 cm have resolved small knots. The flux density of these knots decays on a 1/e time scale of about 14 yr. This is faster than the decay of the smooth features. The pressure in these knots can be estimated at 4 x 10 to the 7th dynes/sq cm. This is somewhat greater than the pressure within the smooth component of the supernova remnant.

Arendt, Richard G.↗