Engineering topics

Rice, W. L.

Publications and source records attributed to Rice, W. L..

7 records

NASA NTRS1988

IRAS observations of the globular cluster 47 Tucanae

Integrated and individual-star observations of 47 Tuc obtained at 12, 25, 60, and 100 microns by IRAS are reported. The data are presented in tables and brightness contour maps and analyzed. Features discussed include integrated light dominated by stellar photospheric emission, 12- and 25-micron excesses (associated with red giants in the outer region of the cluster), and a small excess at 100 microns (attributed to integrated-light heating of about 0.0003 solar mass of silicate dust within 6 arcmin of the cluster center). It is pointed out that this is much less dust than predicted by theoretical models of accumulation since the cluster passed through the Galactic plane about 30 Myr ago, and possible dust-removal mechanisms are considered.

Gillett, F. G.↗

NASA NTRS1987

The Arp Ring: Galactic or extragalactic?

The Arp Ring is a faint, loop-like structure around the northern end of M81 which becomes apparent only on deep optical photographs of the galaxy. The nature of the Ring and its proximity to M81 are uncertain. Is it simply foreground structure, part of this galaxy, or is it within the M81 system? Infrared Astronomy Satellite (IRAS) maps of the region show a far-infrared counterpart of the Ring. The infrared data are compared with previous optical and radio observations to try to ascertain its physical nature. The poor correlation found between the common infrared/optical structure and the distribution of extragalactic neutral hydrogen, and the fact that its infrared properties are indistinguishable from those of nearby galactic cirrus, imply that the Arp Ring is simply a ring structure in the galactic cirrus.

Abolins, J. A.↗

NASA NTRS1987

The luminosity function of the brightest galaxies in the IRAS survey

Results from a study of the far infrared properties of the brightest galaxies in the IRAS survey are described. There is a correlation between the infrared luminosity and the infrared to optical luminosity ratio and between the infrared luminosity and the far infrared color temperature in these galaxies. The infrared bright galaxies represent a significant component of extragalactic objects in the local universe, being comparable in space density to the Seyferts, optically identified starburst galaxies, and more numerous than quasars at the same bolometric luminosity. The far infrared luminosity in the local universe is approximately 25% of the starlight output in the same volume.

Soifer, B. T.↗

NASA NTRS1987

Physical processes and infrared emission from the Cassiopeia A supernova remnant

IRAS 12-100 micron data on the Cas A remnant are presented, and various physical mechanisms and astrophysical sites that may contribute to the observed infrared emission are analyzed. The contributions of various sources of infrared emission to the IRAS fluxes are found to be small. The residual infrared emission is attributed to thermal emission from dust which is swept up by the expanding supernova blast wave and collisionally heated by the postshock X-ray emitting gas. The calculations are consistent with a shock velocity of 1800 km/s and a preshock gas density of about 2/cu cm. The mass of the swept-up gas is about 0.6 solar mass. An excess of 12 micron thermal emission in the spectrum of Cas A suggests the presence of very small particles in the preshocked gas.

Dwek, E.↗

NASA NTRS1986

IRAS observations of the nuclear bulge of M31

IRAS observations of the nuclear bulge of M31 are reported. The 12-micron and 25-micron emission is attributed to circumstellar dust emission from late-type stars, while the 60 and 100-micron emission is attributed to interstellar dust emission. The total input rate of circumstellar gas and dust into the interstellar medium is estimated to be 0.015 solar masses/yr. The mass of dust in the interstellar medium estimated from the far-infared flux is about 1500 solar masses. The color temperature of the far-infrared-emitting dust is 45 K. The time required to accumulate the observed mass in interstellar dust is about 10 million yr. Either supernova-generated winds or star formation can deplete this gas without violating the observations.

Soifer, B. T.↗

NASA NTRS1986

IRAS observations of a small sample of blue irregular galaxies

IRAS satellite IR observations are presently used to investigate the properties of the dust in a small sample of irregular galaxies chosen to cover a wide range in levels of star formation activity. The irregulars are found to have comparatively normal IR properties; the only exception is NGC 1569, an irregular galaxy with intense global star formation which seems to have a larger dust fraction at temperatures whose energies peak at 25-60 microns, by comparison with other irregulars. DDO 47, the system with lowest star formation activity, has the lowest far-IR color temperature and highest ratio of IR to H-alpha flux; this is suggested to be due to the decreased importance of radiation from young stars in heating the dust.

Hunter, D. A.↗

NASA NTRS1986

IRAS 18333-2357 - An unusual source in M22

The present paper is concerned with a search for IRAS sources positionally associated with globular clusters. This search revealed a strong source with unusual infrared colors, IRAS 18333-2357, near the center of M22. M22 (NGC 6566) is a bright, nearby, metal-poor globular cluster. Attention is given to the observations, the mass and luminosity of IRAS 18333-2357, the mass-loss rate, and the nature of IRAS 18333-2357. It is concluded that IRAS 18333-2357 may possibly be a bipolar nebula similar to OH 0739-14 although element abundance arguments appear to favor a carbon-rich rather than oxygen-rich shell.

Gillett, F. C.↗