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NASA NTRS1998

Far Infrared Line Profiles from Photodissociation Regions and Warm Molecular Clouds

This report summarizes the work done under NASA Grant NAG2-1056 awarded to the University of Colorado. The aim of the project was to analyze data obtained over the past several years with the University of Colorado far-infrared heterodyne spectrometer (Betz & Boreiko 1993) aboard the Kuiper Airborne Observatory. Of particular interest were observations of CO and ionized carbon (C II) in photodissociation regions (PDRs) at the interface between UV-ionized H II regions and the neutral molecular clouds supporting star formation. These data, obtained with a heterodyne spectrometer having a resolution of 3.2 MHz, which is equivalent to a velocity resolution of 0.2 km/s at 60 microns and 1.0 km/s at 300 microns, were analyzed to obtain physical parameters such as density and temperature in the observed PDR. The publication resulting from the work reported here is appended. No inventions were made nor was any federally owned property acquired as a result of the activities under this grant.

Boreiko, R. T.↗
NASA NTRS1998

Summary of Research on Research Award

During this grant period, we analyzed data obtained with the Kuiper Airborne Observatory. The goal of the research was to study the distribution of matter around very young stars. These studies resulted in greatly improved understanding of the environment in which stars form. In particular, we studied regions forming stars of intermediate mass. In the process of studying these regions, we found that the models of collapse of low mass stars did a good job of explaining our observations of those regions, but that the dust around more massive stars was distributed in different ways, usually less centrally condensed. We have submitted for publication a large paper, in which all our observations of intermediate mass star-forming regions are presented and analyzed. This paper will provide a valuable reference and will be the basis for future modeling of these sources, using codes that we have developed. In addition to direct studies of the dust, we have used the information from our studies of the dust to make more realistic models of the emission from molecules in star forming regions. In particular, we were able to dispense with ad hoc ideas about the temperature and put in temperature distributions determined from the modeling of the far-infrared observations.

Evans, Neal J., II↗
NASA NTRS1998

High Resolution Far-Infrared Studies of Compact Regions in Star-Forming Molecular Clouds

This grant supported the acquisition, analysis and publication of high spatial resolution observations of the far-infrared emission from compact regions of star-forming molecular clouds using the Kuiper Airborne Observatory. We studied regions which are forming stars of low and intermediate mass. In analyzing the data, we utilized radiative transfer codes, incorporating disk models and envelopes, including departures from spherical symmetry. These data, along with data at other wavelengths, were used to probe the distribution of dust temperature and density around young stars and to test theoretical predictions about star formation.

Mundy, Lee G.↗
NASA NTRS1994

Far-Infrared Line Observations of SGR A West

Using NASA's Kuiper Airborne Observatory (KAO), we have measured lines of [SIII] 19 and 33 micrometers, [FeIII] 23 micrometers, [OIII] 52 and 88 micrometers, [NIII] 57 micrometer, and [NII] 122 and 205 micrometers arising in the unusual HII region Sgr A West at the Galactic Center. The emission is consistent with photoionization of the low density (approximately 1000/cc) cavity gas, but the N+ emission could arise predominantly in the higher density "mini-spiral" ionized streamers unresolved in our beam.

Erickson, Edwin F.↗
NASA NTRS1998

Far Infrared Line Profiles from Photodissociation Regions and Warm Molecular Clouds

This report summarizes the work done under NASA Grant NAG2-1056 awarded to the University of Colorado. The aim of the project was to analyze data obtained over the past several years with the University of Colorado far-infrared heterodyne spectrometer aboard the Kuiper Airborne Observatory. Of particular interest were observations of CO and ionized carbon (C II) in photodissociation regions (PDRS) at the interface between UV-ionized H II regions and the neutral molecular clouds supporting star formation. These data, obtained with a heterodyne spectrometer having a resolution of 3.2 MHz, which is equivalent to a velocity resolution of 0.2 km s(exp -1) at 60 microns and 1.0 km s(exp -1) at 300 microns, were analyzed to obtain physical parameters such as density and temperature in the observed PDR.

Boreiko, R. T.↗
NASA NTRS1997

Sofia Science Working Group

The purpose of this grant was to enable the Principal Investigator (P.I.) to travel to and participate in the meetings and activities of the NASA SOFIA Science Working Group (SSWG), and to spend time working on some of the associated technical issues relating to the SOFIA (Stratospheric Observatory for Infrared Astronomy) project. The SOFIA Science Working Group was established to help develop the plans and specifications for the next-generation airborne observatory ("SOFIA"), which is now under development. The P.I. was asked to serve on the SSWG due to his experience in airborne astronomy: he has developed several astronomical instruments for the Kuiper Airborne Observatory NASA's previous airborne astronomy platform (which was decommissioned in 1995 in preparation for SOFIA). SOFIA, which will be a 747 SP aircraft carrying a 2.7 meter diameter telescope, is a joint project sponsored by NASA and DLR (the German space agency), and is now under development by a consortium including Universities Space Research Association (USRA), Raytheon, Sterling Software, and United Airlines. Further details on the SOFIA project can be found on the internet at http: //sofia. arc. nasa. gov. Rather than develop the SOFIA observatory in-house, NASA decided to privatize the project by issuing a Request for Proposals (RFP). The respondents to this RFP were consortia of private organizations which together had the required facilities and expertise to be able to carry out the project; the winner was the group led by USRA. One of the main roles of the SSWG was to help develop the technical specifications for the SOFIA observatory. In particular, the SSWG provided advice to NASA on the specifications that were written into the RFP, particularly those which had an important impact on the scientific productivity of the observatory. These specifications were discussed at the meetings of the SSWG, which were held primarily at NASA/Ames (in California) and at NASA Headquarters (in Washington DC). Apart from these meetings, members of the SSWG were expected to perform more detailed analyses of the impact of certain parameters and specifications on the performance of astronomical instruments. The SSWG ended its activities with the selection of the USRA team in January 1997.

Zmuidzinas, J.↗
NASA NTRS1999

The Circumstellar Environment of Low Mass Star Forming Regions

The final technical report of the NASA grant project is presented. The goals of the grant were to: (1) analyze the data from the Far-Infrared (FIR) Camera on board the Kuiper Airborne Observatory (KAO); (2) acquire additional data at other wavelengths for models and (4) to develop source models for the Young stellar objects (YSOs)under study. The complete Spectral Energy Distribution (SED) from 10 microns out to 1.3 mm for all sources being studied have been obtained. The FIR imaging data was processed to reveal the maximum angular resolution possible, which allows us to model the disk. To model the disk we have the high resolution millimeter interferometry data. In summary the results to date are: (1) the vast majority of embedded YSOs in Taurus are compact at 100 microns. The models mos consistent with our data and other observations are either dominated by disk emissions, or envelopes that have relatively steep density gradients; (2) the submillimeter/millimeter photometer suggests that models are very successful. Disk emission plays an important role and must be considered when predicting the overall emission. (3) in the two cases, where we seem to have extended emission, we have to investigate other possible source models than a Shu collapse.

Butner, Harold M.↗
NASA NTRS1998

Submillimeter Imaging of Dust Around Main Sequence Stars

This grant was to image circumstellar dust disks surrounding main-sequence stars. The delivery of the SCUBA detector we had planned to use for this work was delayed repeatedly, leading us to undertake a majority of the observations with the UKT14 submillimeter detector at the JCMT (James Clerk Maxwell Telescope) and optical imagers and a coronagraph at the University of Hawaii 2.2-m telescope. Major findings under this grant include: (1) We discovered 5 asymmetries in the beta Pictoris regenerated dust disk. The discovery of these asymmetries was a surprise, since smearing due to Keplerian shear should eliminate most such features on timescales of a few thousand years. One exception is the "wing tilt" asymmetry, which we interpret as due to the scattering phase function of dust disk particles. From the wing tilt and a model of the phase function, we find a disk plane inclination to the line of sight of < 5 degrees. Other asymmetries (e.g. the butterfly asymmetry) suggest a disk that has been recently disturbed. We searched for possible nearby perturbers but found no clear candidates. Low mass stars (M dwarfs) and brown dwarfs would have fallen beneath the sensitivity threshhold of our survey, however. (2) We calculated a set of disk models to assess the detectability of dust disks around stars as a function of (a) distance, (b) disk, inclination (c) dust optical depth/mass, and (d) imaging resolution. These models guided our observational strategy on Mauna Kea. (3) We performed a coronagraphic survey of approx. 100 main-sequence stars in search of additional examples of circumstellar disks. The best new candidate disk, around the 5 M(sun) star BD+31deg.643, is distinguished by its large extent (few x 10( exp 3) AU). This disk, if real, cannot be rotationally supported. We suggest that the dust particles are ejected from a smaller, unseen disk (Kuiper Belt?) by strong radiation pressure forces due to the high luminosity central star. (4) SCUBA images of circumstellar dust disks were obtained at 850 gm in 1997/8. These images show extended, asymmetric emission, but have a signal-to-noise ratio too low to permit disk mapping to large projected distances. Our images of beta Pic, in particular, are in agreement with those obtained by Holland et al., and appear to confirm the blob-structure reported first by these authors. We have not yet been able to confirm that the structure is intrinsic to the disk, since beta Pic is at -50 degree declination, and suitable observing opportunities from northern latitudes are comparatively rare (even at the +20 degree latitude of JCMT). It is possible, for instance, that the main 850 micro-m blob is merely a galaxy or other high-z source projected onto the beta Pic mid-plane.

Jewitt, David↗
NASA NTRS1999

A High Spatial Resolution Study of Far IR Emission of Galaxies

This grant funded observations and data reduction on the Kuiper Airborne Observatory. The research project was successfully completed. New insights into the distribution of far infrared emission across star-forming galaxies was obtained, and student training was achieved. The efforts contributed towards new observing strategies that will impact future NASA missions. The results of the effort have been presented in several papers in the refereed literature, including: "Morphology of Far Infrared Emission in Galaxies". "Far Infrared Thermal Emission from the Inner Cooling Flow Region of NGC1275". "Distribution of Light in the'Dusty-Hand'Galaxy NGC2146". Presentations of the results of this program have also been given at the following meetings and symposia: "High Spatial Resolution Study of the Active Cooling Flow Galaxy NGC 1275" "The Extent of Far IR Emission in Luminous Galaxies".

Lester, Dan↗
NASA NTRS1999

Thermal Emission Spectroscopy of 1 Ceres: Evidence for Olivine

Thermal emission spectra of the largest asteroid 1 Ceres obtained from the Kuiper Airborne Observatory display features that may provide information on its surface mineralogy. A plot of the Ceres spectrum (calibrated using alpha Boo as a standard) divided by a standard thermal model (STM) is shown. Also shown is the emissivity spectrum deduced from reflectivity measurements for olivine grains <5 microns in diameter. The general shape of the Ceres and the olivine curves agree in essential details, such as the maxima from 8 to 12 microns, the minimum between 12 and 14 microns, the broad peak near 17.5 micron, and the slope beyond 22 micron. (Use of the 10 to 15-micron grain reflectivities provides a better match to the 12- to 14-micron dip. We used a value of unity for beta, the beaming factor associated with small-scale surface roughness in our STM. Adjustment of beta to a lower value raises the long-wavelength side of the Ceres spectrum, providing an even better match to the olivine curve.) The emissivity behavior roughly matches the emission coefficients which were calculated for olivine particles with a particle radius of 3 microns. Their calculations show not only the negative slope from 23 to 25 pm, but a continued decrease past 30 micron. The Ceres emissivity is thus similar to that of small olivine grains from 8 to 30 micron, but olivine's emissivity is lower from 5 to 8 pm.

Witteborn, F. C.↗
NASA NTRS1999

A Polarimeter for SOFIA: Summary of Research

The purpose of this research was to study designs for a far-infrared polarimeter for SOFIA that would greatly surpass the performance of the earlier polarimeter, Stokes, used on the Kuiper Airborne Observatory. Specifically we wished to gain the sensitivity to observe much fainter objects, to provide a choice of passbands, to reduce systematic errors, and to improve the efficiency. All of these objectives were successfully addressed. The gain in sensitivity will be achieved in part by the superior capabilities of SOFIA but to an even greater extent by the incorporation of new-technology detector arrays. We are developing superconducting transition-edge detectors using the "pop-up" design conceived by Dr. Harvey Moseley. The choice of passbands is achieved by providing three alternative optical paths, each with its own spectral filter, half-wave plate, and pupil tens. A new investigation has shown that multiwavelength observations provide an essential feature of far-infrared polarimetry. The principal source of systematic errors in observations of extended objects has been unknown polarization in the reference beams. We have developed a strategy for estimating these errors.

Hildebrand, Roger H.↗
NASA NTRS1997

SOFIA Science Working Group

The SOFIA Science Working Group was established to help develop the plans and specifications for the next-generation airborne observatory ("SOFIA"), which is now under development. The P.I. has developed several astronomical instruments for the Kuiper Airborne Observatory, NASA's previous airborne astronomy platform (which was decommisioned in 1995 in preparation for SOFIA). SOFIA, which will be a 747 SP aircraft carrying a 2.7 meter diameter telescope, is a joint project sponsored by NASA and DLR (the German space agency), and is now under development by a consortium including Universities Space Research Association (USRA), Raytheon, Sterling Software, and United Airlines. Rather than develop the SOFIA observatory in-house, NASA decided to privatize the project by issuing a Request for Proposals (RFP). The respondents to this RFP were consortia of private organizations which together had the required facilities and expertise to be able to carry out the project; the winner was the group led by USRA. One of the main roles of the SSWG was to help develop the technical specifications for the SOFIA observatory. In particular, the SSWG provided advice to NASA on the specifications that were written into the RFP, particularly those which had an important impact on the scientific productivity of the observatory. These specifications were discussed at the meetings of the SSWG, which were held primarily at NASA/Ames (in California) and at NASA Headquarters (in Washington DC). Apart from these meetings, members of the SSWG were expected to perform more detailed analyses of the impact of certain parameters and specifications on the performance of astronomical instruments. The SSWG ended its activities with the selection of the USRA team in January 1997.

Zmuldzinas, J.↗
NASA NTRS1998

A Study of Photon-Dominated Regions in Reflection Nebulae

The goals of this research were to determine the physical conditions of the Photon-Dominated Regions (PDRS) surrounding the cooler stars (B0-A0) of several reflection nebulae and to test theoretical "low-density" PDR models. In contrast to the substantial investigation on "high-density" PDRS, " low-density" PDRs have been adequately modelled, but have not been adequately tested. At the start of this project, we had reduced Kuiper Airborne Observatory spectra of several far-infrared (FIR) fine structure lines on eight reflection nebulae that cover a range in cooler stellar spectral types (A0-B0). We analyzed these data in the context of "los-density" PDR models asking the question: Do the physical conditions in these reflection nebulae change with stellar spectral type as predicted?

Meixner, Margaret↗
NASA NTRS1994

Comet Shoemaker-Levy 9 Impact Press Conference

A Press conference held on July 20, 1994 is presented. Leading off the press conference was an announcement about a major discovery that was made possible from the study of the impact. The participants in the panel were: (1) Roger Yelle from the University of Arizona, (2) Renee Prange of the Institute Astrophysique Spatiale, (3) Lucy McFadden of the University of California, and the University of Maryland, (4) David Levy, the co-discoverer of the Shoemaker-Levy comet. The moderator for this conference was Steven Maran of the Goddard Space Flight Center. Roger Yelle, who had been working on analyzing spectrographic evidence, made the announcement that sulfur in the form of S2 had been discovered. There was also discussion about the interactions of the atmosphere with the fragments. This interaction had caused a shift in the aurora of Jupiter. The observations of the impact sites made by amatuers were discussed. A summary of the observations from different observatories was also given. Included in these observations were reports from the airborne Kuiper Observatory Telescope and the McDonald observatory.

Source record↗
NASA NTRS1998

Sources of Terrestrial Volatiles

Atmospheres are found enveloping those planets and satellites best able to hold them. The obvious conclusion is that volatile escape must have played nearly as great a role as volatile supply. A consequence of this view is that volatile supplies were probably much greater than the atmospheres that remain. The likeliest candidates are sources associated with the main events of planetary accretion itself such as volatile-rich planetesimals, or direct gravitational capture of nebular gases. Late asteroidal or cometary volatile-rich veneers are attractive, but they present quantitative difficulties. Comets in particular are inadequate, because the associated mass of stray comets that would have been scattered to the Oort Cloud or beyond is excessive. This difficulty applies to Uranus-Neptune planetesimals as well as to a putative massive early Kuiper Belt. Another potential problem with comets is that the D/H ratio in the three comets for which this has been measured is about twice that of Earth's oceans. Objects falling from a much augmented ancient asteroid belt remain a viable option, but timing is an issue: Can the depopulation of the asteroid belt be delayed long enough that it makes sense to talk of asteroids as a late veneer? Early accretion of asteroids as objects scattered into the maw of infant Earth makes more sense. Another appealing candidate population of volatile-rich objects for the inner solar system would be scattered planetesimals associated with the accretion of Jupiter, for two reasons: (1) Before there was Jupiter, there was no object in the solar system capable of expelling comets efficiently, and (2) the cross section of the inner solar system to stray objects was Greater when there were m many planetesimals.

Zahnle, K. J.↗
NASA NTRS1998

A Study of Photon-Dominated Regions in Reflection Nebulae

The goals of this research were to determine the physical conditions of the Photon-Dominated Regions (PDRS) surrounding the cooler stars (BO-AO) of several reflection nebulae and to test theoretical "low-density" PDR models. In contrast to the substantial investigation on "high-density" PDRS, "low-density" PDRs have been adequately modelled, but have not been adequately tested. At the start of this project, we had reduced Kuiper Airborne Observatory spectra of several far-infrared (FIR) fine structure lines on eight reflection nebulae that cover a range in cooler stellar spectral types (AO-BO). We analyzed these data in the context of "low-density" PDR models asking the question: Do the physical conditions in these reflection nebulae change with stellar spectral type as predicted? A brief description of the findings as well as a short list of names and dates of anticipated publications are presented.

Meixner, Margaret↗
NASA NTRS1997

Final Technical Report

Support for reduction and analysis of observations made with the Yorkes Observatory 60-channel far infrared camera on the Kuiper Airborne Observatory was funded through Federal Grant. Data was reduced and made available to the research group at Yorkes and guest observers, The reduced date is indexed on the World Wide Web. Portion of the data have been reported in the attached references.

Harper, D. A.↗
NASA NTRS1999

Operation of the University of Hawaii 2.2M Telescope on Mauna Kea

This paper presents a final report from March 1, 1997-February 28, 1999 on the Operation of the University of Hawaii 2.2M Telescope on Mauna Kea. The topics include: 1) Telescope and Instrumentation (Newsletter and Documentation, Scheduling Periods); and 2) Scientific Highlights (The Outer Solar System-Trans-Neptunian Objects and the Kuiper Belt, Comet Hale-Bopp, Near-Earth Asteroids, Asteroid Families, and Galileo Mission Support).

McLaren, Robert A.↗