Engineering topics

Boggess, N.

Publications and source records attributed to Boggess, N..

8 records

NASA NTRS1994

COBE diffuse infrared background experiment observations of Galactic reddening and stellar populations

This Letter describes the results of an initial study of Galactic extinction and the colors of Galactic stellar populations in the near-IR using the Diffuse Infrared Background Experiment (DIRBE) aboard the Cosmic Background Explorer (COBE) spacecraft. The near-IR reddening observed by DIRBE is consistent with the extinction law tabulated by Rieke & Lebofsky (1985). The distribution of dust and stars in most of the first and fourth quadrants of the Galactic plane (0 deg less than l less than 90 deg, and 270 deg less than l less than 360 deg, respectively) can be modeled as a stellar background source seen through up to approximately 4 mag of extinction at 1.25 micrometers. The unreddened near-IR colors of the Galactic disk are similar to those of late-K and M giants. The Galactic bulge exhibits slightly bluer colors in the 2.2-3.5 micrometers range, as noted by Terndrup et al. (1991). Star-forming regions exhibit colors that indicate the presence of a approximately 900 K continuum produced by hot dust or polycyclic aromatic hydrocarbons (PAHs) contributing at wavelengths as short as 3.5 micrometers.

Arendt, R. G.↗

NASA NTRS1984

The Infrared Astronomical Satellite (IRAS) mission

The Infrared Astronomical Satellite (IRAS) consists of a spacecraft and a liquid helium cryostat that contains a cooled IR telescope. The telescope's focal plane assembly is cooled to less than 3 K, and contains 62 IR detectors in the survey array which are arranged so that every source crossing the field of view can be seen by at least two detectors in each of four wavelength bands. The satellite was launched into a 900 km-altitude near-polar orbit, and its cryogenic helium supply was exhausted on November 22, 1983. By mission's end, 72 percent of the sky had been observed with three or more hours-confirming scans, and 95 percent with two or more hours-confirming scans. About 2000 stars detected at 12 and 25 microns early in the mission, and identified in the SAO (1966) catalog, have a positional uncertainty ellipse whose axes are 45 x 9 arcsec for an hours-confirmed source.

Neugebauer, G.↗

NASA NTRS1984

The IRAS minisurvey

Before the main Infrared Astronomical Satellite (IRAS) all-sky survey was started, a preliminary survey of 900 sq deg was carried out. Some results from this 'minisurvey' are given here. The completeness of the minisurvey at galactic latitudes from 20 to 40 deg drops sharply at flux densities below 0.4, 0.4, 0.5, and 2.5 Jy at 12, 25, 60, and 100 microns, respectively. The corresponding surface densities of point sources brighter than these flux levels are 1.1, 0.4, 0.65, and 1.25/sq deg, respectively. Outside the galactic plane, the majority of the sources at 12 and 25 microns are stars, while galaxies make up a significant proportion of 60 micron sources. The 100 micron band is dominated by emission from interstellar dust over much of the minisurvey area.

Rowan-Robinson, M.↗

NASA NTRS1984

IRAS observations of the diffuse infrared background

IRAS data reveal bright emission from interplanetary dust which dominates the celestial background at 12, 25, and 60 microns except near the galactic plane. At 100 microns, interplanetary dust emission is prominent only near the ecliptic plane; diffuse galactic emission is found over the rest of the sky. At the galactic poles, the observed brightness implies that A(v) is likely to be of order 0.1 mag. The angular variation of the zodiacal emission in the ecliptic plane and in the plane at elongation 90 deg, and an annual modulation of the ecliptic pole brightness, are generally consistent with previously determined interplanetary dust distributions.

Hauser, M. G.↗

NASA NTRS1984

Infrared cirrus - New components of the extended infrared emission

Extended sources of far-infrared emission superposed on the zodiacal and galactic backgrounds are found at high galactic latitudes and near the ecliptic plane. Clouds of interstellar dust at color temperatures as high as 35 K account for much of this complex structure, but the relationship to H I column density is not simple. Other features of the extended emission show the existence of warm structures within the solar system. Three bands of dust clouds at temperatures of 150-200 K appear within 10 deg on both sides of the ecliptic plane. Their ecliptic latitudes and derived distances suggest that they are associated with the main asteroid belt. A third component of the 100-micron cirrus, poorly correlated with H I, may represent cold material in the outer solar system or a new component of the interstellar medium.

Low, F. J.↗

NASA NTRS1984

IRAS images of the galactic center

Some preliminary IRAS results in the form of images at 12, 25, 60, and 100 microns of an 8 deg x 15 deg area around the galactic center are presented. These absolute intensity maps have unprecedented sensitivity combined with high angular resolution, wide field coverage, and large wavelength range. They give a broad view of the central galaxy revealing previously unseen details, especially in regions far from the central few arcmin. Well-defined infrared features in the nucleus correspond to the nuclear radio sources Sgr A, B2, C, and D. Extremely faint structures are detected, such as the cold molecular cloud associated with Sgr B2 which has never before been detected at wavelenths shorter than 40 microns.

Gautier, T. N.↗

NASA NTRS1984

Infrared emission from M31

Maps of M31 have been obtained at wavelengths of 12, 25, 60, and 100 microns. Emission is detected from the center and from a ring of 50 arcmin radius. The ring is that also seen in H I, in H II, and in radio continuum radiation. The spectrum of the central emission suggests a hotter dust temperature than in the ring. M31 is a weak infrared source, the radiation measured longward of 12 microns being only 3 percent of its total luminosity. The two closest companion galaxies, M32 and NGC 205, have also been detected.

Habing, H. J.↗

NASA NTRS1984

Infrared galaxies in the IRAS minisurvey

A total of 86 galaxies have been detected at 60 microns in the high galactic latitude portion of the IRAS minisurvey. The surface density of detected galaxies with flux densities greater than 0.5 Jy is 0.25 sq deg. Virtually all the galaxies detected are spiral galaxies and have an infrared to blue luminosity ratio ranging from 50 to 0.5. For the infrared-selected sample, no obvious correlation exists between infrared excess and color temperature. The infrared flux from 10 to 100 microns contributes approximately 5 percent of the blue luminosity for galaxies in the magnitude range 14 less than m(pg) less than 18 mag. The fraction of interacting galaxies is between one-eighth and one-fourth of the sample.

Soifer, B. T.↗