Engineering topics

Harvey, Paul M.

Publications and source records attributed to Harvey, Paul M..

26 records · Page 2

NASA NTRS1988

The origin of the infrared luminosity in Centaurus A

The origin of the infrared luminosity in Centaurus A is studied using new tracking and data acquisition techniques which yield diffraction-limited profiles at both 50 and 100 microns. Ninety percent of the 100 micron flux is found to originate in a source which extends 5 kpc along the optical dust lane that bisects the galaxy; the remaining 10 percent comes from an unresolved source coincident with the active radio nucleus. The extended 100 micron emission profile is fully consistent with a uniform disk of thermally radiating particles; when combined with results of previous studies at shorter wavelengths, these measurements indicate that nearly all of the infrared luminosity is produced by thermally emitting grains which are heated by massive young stars distributed throughout the optically thick dust lane.

Joy, Marshall↗

NASA NTRS1987

Infrared emission from young stars in the nucleus of M82

New observational and analytical techniques were used to obtain high-resolution NIR and FIR profiles of the luminous peculiar galaxy M82. The strongest NIR emission is found to be coincident with the dynamical center of the galaxy; a secondary NIR source, a factor of two fainter than the nucleus, is located 10 deg to the southewest. Simultaneous 40-micron and 100-micron profiles of M82 reveal an asymmetric distribution, with peak FIR emission diplaced about 5 arcsec to the west of center, and a plateau of emission extending about 5 arcsec to the east. The best positional determination indicates that the peak FIR emission from M82 is coincident with a cluster of young stars located to the southwest of the galactic nucleus at a projected distance of 10 arcsec (150 pc).

Joy, Marshall↗

NASA NTRS1987

Far-infrared detection of a circumstellar dust torus around Sharpless 106

High angular resolution scans at 42 and 95 microns have been obtained of the far-infrared source associated with S106. Using maximum entropy deconvolution techniques it is found that the far-IR-emitting dust appears to be distributed in a toroidal shape around the central star.This result is similar to the morphology implied to millimeter line and continuum mapping on a variety of size scales.

Harvey, Paul M.↗

NASA NTRS1987

Star formation in the large Magellanic cloud

What role the Large Magellanic Cloud (LMC), a dwarf irregular galaxy, plays in understanding infrared luminous galaxies is discussed. There are two main reasons the LMC may prove helpful. One, the LMC is only 55 kpc away, very nearby compared to much rarer high luminosity systems. Second, the environment in the LMC is distinctly different than in the Milky Way, at least those parts of the Milky Way interior to the sun, where most of the studies of massive star formation were concentrated. The LMC is an interacting system with a large amount of neutral hydrogen that is pushed around by the galaxy's encounter with the Milky Way. Perhaps a good understanding of star formation process in the LMC will provide guidance in the study of the infrared luminous galaxies. Two questions which will be addressed are: how is star formation in the LMC similar to the Milky Way Galaxy, and how is it different?

Jones, Terry Jay↗

NASA NTRS1987

A near-infrared study of the luminous merging galaxies NGC 2623 and ARP 148

As part of an investigation of the physical mechanisms which produce large infrared luminosities in interacting systems, multicolor near-infrared maps were obtained of the long tailed galaxy NGC 2623 and the ring galaxy Arp 148. The near-infrared broadband spectrum was decomposed to obtain the contribution of four processes: emission from evolved stars, nebular continuum emission, thermal reradiation, and extinction. This multicolor analysis, along with 2 micrometer maps and 10 micrometer measurements, is used to determine the structure of these interacting galaxies and to delineate regions of star formation.

Joy, Marshall↗

NASA NTRS1987

A near-infrared study of the luminous merging galaxies NGC 2623 and Arp 148

A broad-band spectral decomposition method has been developed to determine the contributions of evolved stars, H II regions, warm dust, and obscuration to the near-infrared continuum in interacting systems. The multicolor decomposition is applied to near-infrared measurements of the long-tailed galaxy NGC 2623 and the ring system Arp 148 to determine the galactic structure and to delineate regions of galactic activity. The infrared analysis confirms that these galaxies are coalescing; since a single nucleus is observed in the infrared, the merger must be complete. Arp 148 is found to be the product of a close collision of two galaxies, and the multicolor analysis implies that this system is in an early stage of coalescence. A substantial fraction of the nuclear regions of Arp 148 and NGC 2623 may be attributed to the presence of young stars.

Joy, Marshall↗

NASA NTRS1987

Optimal signal-to-noise in digital phase lock amplifiers

An expression for the optimal signal-to-noise ratio for linear phase lock amplifiers is derived. In its digital form the optimal method can be implemented by real-time signal processing techniques. The case of detector-noise-limited systems is analyzed in detail; it is found that the optimal technique can be used to eliminate effectively the detector's time constant from the set of parameters determining the overall efficiency. This has important implications for optical detection system design. Also reported is an experimental verification of the optimal method, thus establishing its practicality.

Doering, Charles R.↗

NASA NTRS1987

Molecular clouds in the outer galaxy. I - Far-infrared observations

From the Kuiper Airborne Observatory, far infrared emission were detected from 4 molecular clouds in the outer galaxy. Eleven areas in six clouds were observed at 50 and 100 microns. The far-infrared luminosities indicate the presence of stars with spectral types ranging from B3 to O7. Therefore, despite the fact that these clouds have lower CO line temperatures than comparable clouds in the inner galaxy, they are giving birth to massive stars.

Mead, Kathryn N.↗