Showing papers by "Michael W. Werner published in 1998"

Mid-Infrared Imaging of a Circumstellar Disk around HR 4796: Mapping the Debris of Planetary Formation

Abstract: We report the discovery of a circumstellar disk around the young AO star, HR 4796, in thermal infrared imaging carried out at the W.M. Keck Observatory.

Mid-Infrared Imaging of Orion BN/KL. II. Luminosity Sources, Extinction Distribution, and the Nature of IRc2

Abstract: We have obtained array camera images of the Orion BN/KL infrared complex at nine wavelengths between 4.8 and 20 mue.

High Spatial Resolution Imaging of Arp 220 from 3 - 25 microns

Abstract: Images of Arp 220 from 3.45 to 24.5 $\mu$m with 0.5'' resolution are presented which clearly separate the nucleus into at least two components. The western component is about three times more luminous than the eastern component, but the silicate absorption in the fainter, eastern component is roughly 50% greater than the absorption in the western component. Each component is marginally resolved. The two components seen at 24.5 $\mu$m are identified with the two radio components. The western source most likely coincides with the high extinction disk previously suggested to exist in Arp 220, while the eastern nucleus is identified with a faint highly reddened source seen in HST 2.2 $\mu$m NICMOS images. The two nuclei together account for essentially all of the measured 24.5 $\mu$m flux density. Two models are presented, both of which fit the observations. In one, the majority of the total luminosity is produced in an extended star formation region and in the other most of the luminosity is produced in the compact but extincted regions associated with the two nuclei seen at 24.5 $\mu$m. In both pictures, substantial luminosity at 100 $\mu$m emerges from a component having a diameter of 2--3'' ($\sim$1kpc).

Do the Infrared Emission Features Need Ultraviolet Excitation

Abstract: We present the results of imaging spectroscopy of the reflection nebula vdB 133, obtained with the infrared camera and circular variable filter wheel on the Infrared Space Observatory. Our observations reveal the infrared emission features (IEFs), at 6.2, 7.7, 8.7, 11.3, and 12.7 μm, and associated 5-15 μm continuum emission. The stellar system illuminating vdB 133 has the lowest ratio of ultraviolet (shortward of 0.4 μm) to total flux of any stars demonstrated to date to excite the IEFs and associated continuum emission from adjacent interstellar dust, as opposed to circumstellar dust. The low fraction of UV flux from this system poses a problem for existing models for the emission mechanism and emitting material, which all require substantial UV radiation for the excitation of the IEFs and associated continuum.

The Distribution of Mid- and Far-Infrared Emission in 10 Interacting Galaxy Systems

Abstract: A sample of 10 interacting and merging galaxy systems has been mapped at mid-infrared (10 μm) and far-infrared (100–160 μm) wavelengths with spatial resolutions of 4''and 45'', respectively. The interacting and merging systems are known to be strong IRAS sources; however, the IRAS data contain limited information concerning the distribution of infrared emission between the two galaxies in each pair and no information on the distribution within each galaxy. The observations presented here show that in five of the seven paired systems, one galaxy is the dominant or the only infrared source. There is a good correlation between the Hα and infrared emission levels for these galaxies, indicating that the infrared emission is closely tied to dust heated by young stars. There is also a good spatial correlation between the Hα, infrared, and radio continuum morphologies of these systems, which further strengthens the belief that the infrared, as well as the radio emission, is associated with regions of active star formation. The 10 μm emission is concentrated around the nuclei of most of these galaxies, indicating that the highest levels of current star formation activity are also confined to the near-nuclear regions. Some systems, however, show evidence for significant star formation activity throughout the outer disk regions of the galaxies. All the sample galaxies that are bright in the infrared also have optical indications of high levels of star formation or nuclear activity, suggesting that these conditions are necessary in order for a galaxy to exhibit excess infrared emission.

High Resolution Mid-Infrared Imaging of the Nucleus of NGC 1068

Abstract: We interpret the faint optical counterpart to the mid-infrared southern extension as being due to partial obscuration by the intervening disk of the host galaxy.

Quantum well infrared photodetector research and development at Jet Propulsion Laboratory

Abstract: One of the simplest device realizations of the classic particle-in-the-box problem of basic quantum mechanics is the Quantum Well Infrared Photodetector (QWIP). In this paper we discuss the optimization of the detector design, material growth and processing that has culminated in realization of 15 micron cutoff 128 X 128 QWIP focal plane array camera, hand-held and palmsize 256 X 256 long-wavelength QWIP cameras and 648 X 480 long-wavelength camera, holding forth great promise for myriad applications in 6 - 25 micron wavelength range in science, medicine, defense and industry. In addition, we present the recent developments in broadband QWIPs, mid-wavelength/long-wavelength dualband QWIPs, long- wavelength/very long-wavelength dualband QWIPs, and high quantum efficiency QWIPs for low background applications in 4 - 26 micrometer wavelength region for NASA and DOD applications.

HST Imaging Polarimetry of the Gravitational Lens FSC10214+4724

Abstract: We present imaging polarimetry of the extremely luminous, redshift 2.3 IRAS source FSC10214+4724. The observations were obtained with HST's Faint Object Camera in the F437M filter, which is free of strong emission lines. The 0.7 arcsec long arc is unresolved to 0.04 arcsec FWHM in the transverse direction, and has an integrated polarization of 28 +/- 3 percent, in good agreement with ground-based observations. The polarization position angle varies along the arc by up to 35 deg. The overall position angle is 62 +/- 3 deg east of north. No counterimage is detected to B = 27.5 mag ($3\sigma$), giving an observed arc to counterimage flux ratio greater than 250, considerably greater than the flux ratio of 100 measured previously in the I-band. This implies that the configuration of the object in the source plane at the B-band is different from that at I-band, and/or that the lensing galaxy is dusty.

Space Infrared Telescope Facility (SIRTF) enters development

Abstract: The Space IR Telescope Facility (SIRTF), the last of NASA's 'Great Observatories' is entering its development phase. Ongoing advances in IR detector technology, coupled with innovative choices in orbit and system architecture, have maintained the vitality of SIRTF's scientific capability at a small fraction of the original development cost. The great sensitivity of SIRTF and its high observing efficiency promise to yield a rich legacy of science results. SIRTF is on a fast-track development schedule, with launch in December 2001. While the current baseline calls for a minimum 2.5-year cryogenic lifetime, recent programmatic and engineering development suggest that a 5-year lifetime is within reach. More than 75 percent of the SIRTF observing time will be available to the general community. We summarize the scientific capabilities and the technical specifications for the mission, including descriptions of the three-instrument payload. We will focus on the SIRTF science observations concepts, and describe SIRTF's seven observing modes - the modes by which the community will interface with the Observatory. The pre- and post-launch user services available at the SIRTF Science Center will also be presented. We include a listing of events likely to be of interest to potential SIRTF users between now and launch.

Mid-infrared Imaging of a Circumstellar Disk Around HR 4796: Mapping the Debris of Planetary Formation

Abstract: We report the discovery of a circumstellar disk around the young A0 star, HR 4796, in thermal infrared imaging carried out at the W.M. Keck Observatory. By fitting a model of the emission from a flat dusty disk to an image at lambda=20.8 microns, we derive a disk inclination, i = 72 +6/-9 deg from face on, with the long axis of emission at PA 28 +/-6 deg. The intensity of emission does not decrease with radius as expected for circumstellar disks but increases outward from the star, peaking near both ends of the elongated structure. We simulate this appearance by varying the inner radius in our model and find an inner hole in the disk with radius R_in = 55+/-15 AU. This value corresponds to the radial distance of our own Kuiper belt and may suggest a source of dust in the collision of cometesimals. By contrast with the appearance at 20.8 microns, excess emission at lambda = 12.5 microns is faint and concentrated at the stellar position. Similar emission is also detected at 20.8 microns in residual subtraction of the best-fit model from the image. The intensity and ratio of flux densities at the two wavelengths could be accounted for by a tenuous dust component that is confined within a few AU of the star with mean temperature of a few hundred degrees K, similar to that of zodiacal dust in our own solar system. The morphology of dust emission from HR 4796 (age 10 Myr) suggests that its disk is in a transitional planet-forming stage, between that of massive gaseous proto-stellar disks and more tenuous debris disks such as the one detected around Vega.

Quantum well infrared photodetectors (QWIPs) for astronomy

Abstract: In recent years, many research groups in the world have demonstrated large format Quantum Well Infrared Photodetector (QWIP) focal plane arrays for various thermal imaging applications. QWIPs as opposed to conventional low bandgap infrared detectors, are limited by thermionic dark current and not tunneling currents down to 30K or less. As a result the performance of QWIPs can be substantially improved (orders of magnitude) by cooling from 70K to 30K. Cooling does not induce any nonuniformity or 1/f noise in QWIP focal plane arrays. In this paper, we discuss the development of highly uniform long- wavelength QWIPs for astronomical applications.

High Resolution Mid-Infrared Imaging of the Nucleus of NGC 1068

Abstract: We have obtained mid-infrared images of the nucleus of NGC 1068 from the Hale 5 m telescope at Mt. Palomar with diffraction-limited resolution and high sensitivity at 8.8, 10.3, and 12.5 microns. Deconvolved images show that the infrared emission extends north to south in the inner 2", consisting of a central peak, a component extending 1" north of the central source, a component extending 1" south of the central source, and several smaller structures located 1" to the northeast. The central peak is extended 0.4" N-S and unresolved ( = 2 pc^2, and may thus contain a compact source such as a parsec-scale torus. We observe a correspondence between the northern extension and the northeastern sources appearing on the mid-infrared images and the [OIII] clouds A-C & E. We interpret the faint optical counterpart to the mid-infrared southern extension as being due to partial obscuration by the intervening disk of the host galaxy. The N-S extension of the mid-infrared emission coincides with one wall of the conical narrow line region and aligns with the N-S orientation of the radio jet close to the nucleus. We interpret the infrared emission as arising from optically thick dust lining the walls of the low density cavity formed by the radio jet and heated by radiation from the central source.

The Wide-Field Infrared Explorer (Wire) Mission

Abstract: The Wide-Field Infrared Explorer (WIRE) (Schember et al 1996 and references within) is a small spaceborne telescope specifically designed to study the evolution of starburst galaxies This powerful astronomical instrument will be capable of detecting typical starburst galaxies at z ~ 05, ultraluminous infrared galaxies beyond а z~2, and luminous protogalaxies beyond z ~ 5 The WIRE survey, to be conducted during a four month period in 1998, will cover over 100 deg2 of high Galactic latitude sky at 25 μm and 12 μm