Showing papers by "Michael W. Werner published in 1995"

A Survey of Near Infrared Emission in Visual Reflection Nebulae

Abstract: We present a survey for extended 22 $\mu$m emission in 20 new visual reflection nebulae, illuminated by stars with temperatures of 3,600 --- 33,000 K We detect extended 22 $\mu$m emission in 13 new nebulae, illuminated by stars with temperatures of 6,800 -- 33,000 K For most of these 13 nebulae we have measured $J-K$, $H-K$, and $K-L'$, as well as obtaining surface brightness measurements at the wavelength of the 33 $\mu$m emission feature All of the reflection nebulae with extended near infrared emission in excess over scattered starlight have very similar near infrared colors and show the 33 $\mu$m feature in emission with similar feature-to-continuum ratios The 33 $\mu$m feature-to-continuum ratio ranges from $\sim$3 to $\sim$9, both within individual nebulae and from nebula to nebula, which suggests that the 33 $\mu$m feature and its underlying continuum arise from different materials, or from different ranges of sizes within a size distribution of particles No dependence on the temperature of the illuminating star is seen in the near infrared colors or 33 $\mu$m feature-to-continuum ratio, over a factor of two in stellar temperature This is similar to our previous IRAS results, in which we found no dependence of the ratio of 12 $\mu$m to 100 $\mu$m surface brightnesses in reflection nebulae illuminated by stars with temperatures of 5,000--33,000 K

Overview of the SIRTF mission

Abstract: A revised baseline mission concept for the Space Infrared Telescope Facility (SIRTF) has been developed by the SIRTF science and engineering teams over the past year This mission, which would be carried into solar orbit by a Delta 7920 launch vehicle, retains the key scientific capabilities of earlier mission concepts at a fraction of the mass and cost We review the scientific and technical innovations which have enabled this development

The Wide-Field Infrared Explorer (WIRE)

Abstract: The Wide-Field Infrared Explorer (WIRE) has just been selected by NASA for development under the Small Explorer (SMEX) program, on a schedule leading to launch in 1998. WIRE is a cryogenically-cooled infrared telescope designed to study the evolution of starburst galaxies. It takes advantage of recent advances in infrared detector technology to carry out deep surveys designed to detect distant galaxies at 12 and 25 µm. The WIRE instrument will be integrated with a SMEX spacecraft bus to be provided by the Goddard Space Flight Center and launched into a 500 km orbit by a Pegasus XL launch vehicle.

HST Observations of the Luminous IRAS Source FSC10214+4724: A Gravitationally Lensed Infrared Quasar

Abstract: We present an image of the redshift 2.3 IRAS source FSC10214+4724 at 0.8 microns obtained with the HST WFPC2 Planetary Camera. The source appears as an unresolved (< 0.06") arc 0.7" long, with significant substructure along its length. The arc is centered near an elliptical galaxy 1.18" to the north. An unresolved component 100 times fainter than the arc is clearly detected on the opposite side of this galaxy. The most straightforward interpretation is that FSC 10214+4724 is gravitationally lensed by the foreground elliptical galaxy, with the faint component a counterimage of the IRAS source. The brightness of the arc in the HST image is then magnified by ~100 and the intrinsic source diameter is ~0.01" (80 pc) at 0.25 microns rest wavelength. The bolometric luminosity is probably amplified by a smaller factor (~30), yielding an intrinsic luminosity ~2E13 solar luminosities. A detailed lensing model is presented which reproduces the observed morphology and relative flux of the arc and counterimage, and correctly predicts the position angle of the lensing galaxy. The model also predicts reasonable values for the velocity dispersion, mass, and mass-to-light ratio of the lensing galaxy. A redshift for the lensing galaxy of ~0.9 is consistent with the measured surface brightness profile from the image, as well as with the galaxy's SED.

Far-infrared studies of the Galactic Center Arc using the Kuiper Airborne Observatory

Abstract: Two molecular clouds are clearly interacting with the Galactic Center Radio Arc The HII regions located at both sites of interaction - the 'Arched Filaments' and G018-004 - are powerful sources of far-infrared radiation, each having a total luminosity of approx 10(exp 7) solar luminosity Using the University of Texas far-IR Photometer at 50 and 90 microns, we found that the emission is substantially more extended than the filamentary HII regions, and that, while the intensity peaks at the locations of the filaments, the dust temperature shows only weak variations, implying that the heating is relatively uniform The Arched Filaments were also observed with the University of Chicago far-IR Array Polarimeter, STOKES, at 100 microns The greater than 100 independently sampled positions cover most of the 5 ft x 7 ft area of the Arched Filaments The polarization is relatively strong (up to 94%) almost everywhere in this region Also, the slow and smooth variations of the polarization angles across the region are consistent with the large magnetic field strengths and the highly-ordered geometry deduced from radio measurements However, it appears that the magnetic field direction inferred from far-IR polarization (parallel to the Arched Filaments and following their curvature) is very different from that implied by the nonthermal radio filaments The magnetic field, gas motions, and gravitational potential gradient in the arched filament region are all consistent with gravitational shearing of the molecular cloud underlying the Arched Filaments

Infrared studies of galaxies from space

Abstract: The Kuiper Airborne Observatory has been a powerful instrument for the study of nearby galaxies, and SOFIA could probe still further into the local Universe. However, a comprehensive program of extragalactic exploration in the infrared - and in particular a study of galaxies at cosmological redshifts - requires the high sensitivity and complete wavelength coverage which is achievable only with a cryogenic telescope in space. This program was begun by IRAS and will be continued by the upcoming ISO (Infrared Space Observatory), WIRE (Wide field Infrared Explorer) and SIRTF (Space Infrared Telescope Facility) missions. This paper previews a set of extragalactic investigations which could be carried out by these missions.

SIRTF — The moderate mission

Abstract: The Space Infrared Telescope Facility (SIRTF) has been planned by NASA and the US scientific and aerospace communities as a cryogenically-cooled observatory for infrared astronomy from space. Within the past few years, severe pressures on NASA’s budget have led to the cancellation of many programs and to dramatic rescoping of others; SIRTF is in the latter category. This paper describes the resulting redefinition of SIRTF and the technical innovations which have made it possible to package SIRTF’s key scientific capabilities into the envelope of a moderate-class mission.