skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Where to draw the line: Chasing energy extrapolations, cluster convergence, and molecular trajectories

Publication Date:
Research Org.:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org.:
OSTI Identifier:
Report Number(s):
IS-T 3208
DOE Contract Number:
Resource Type:
Country of Publication:
United States

Citation Formats

Boschen, Jeffery. Where to draw the line: Chasing energy extrapolations, cluster convergence, and molecular trajectories. United States: N. p., 2017. Web. doi:10.2172/1417979.
Boschen, Jeffery. Where to draw the line: Chasing energy extrapolations, cluster convergence, and molecular trajectories. United States. doi:10.2172/1417979.
Boschen, Jeffery. Sat . "Where to draw the line: Chasing energy extrapolations, cluster convergence, and molecular trajectories". United States. doi:10.2172/1417979.
title = {Where to draw the line: Chasing energy extrapolations, cluster convergence, and molecular trajectories},
author = {Boschen, Jeffery},
abstractNote = {},
doi = {10.2172/1417979},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Sat May 06 00:00:00 EDT 2017},
month = {Sat May 06 00:00:00 EDT 2017}

Other availability
Please see Document Availability for additional information on obtaining the full-text document. Library patrons may search WorldCat to identify libraries that hold this thesis or dissertation.

Save / Share:
  • CO(J = 1 ..-->.. O) observations with 45'' resolution at over 200 positions along the major axes of 42 Virgo cluster spiral galaxies were obtained using the FCRAO 14-meter telescope. Analyses indicate that for the Sa-Sb and highest-luminosity Sc Virgo galaxies, the molecular gas contents and distributions have not been strongly affected by the cluster environment. While it also may be that the conversion of H I into H/sub 2/ is enhanced in low-mass galaxies by an interaction with the intracluster medium these results strongly suggest that the attainment of an H/sub 2/-dominated ISM is a function of galaxy mass.more » These outer-cluster low-mass Virgo Sc galaxies have large massive star formation rates and high central H I surface densities, indicating that atomic gas plays a direct role in star formation in these systems. Galaxies that are H I-deficient by a factor of 10 are gas-deficient (H I + H/sub 2/) by only a factor of 2-3, due to the survival of large quantities of molecular gas. The massive-star formation rates, as indicated by H..cap alpha.., and far-infrared emission, are also lower by factors of approx. 2-3 in galaxies which are HI-deficient by a factor of 10.« less
  • This dissertation addresses several problems in the study of the dusty, gaseous envelopes commonly found around highly evolved stars. Most of the objects observed are M or N giants and are typically long-period variables. Some objects with hotter central stars were observed which may be young or forming planetary nebulae. Through a long-term monitoring project, properties of circumstellar ground rotational state OH masers were studied. It was found that for most sources, the variations of the OH masers at 1612, 1665, and 1667 MHz smoothly tracked the stellar variations, indicating that the masers are saturated and radiatively pumped. Extensive monitoringmore » data were obtained on the unusual object U Orionis, which has shown non-periodic maser variations and may be in transition from one evolutionary stage to another. By carefully measuring the relative phase of variation of maser emission arising from the front and back of the circumstellar object IRC + 10011, the linear diameter of its envelope was determined. This was the first statistically significant measurement using this technique. To further investigate the excitations and pumping of circumstellar OH, a thorough search for OH masers in the two rotational states just above the ground state was undertaken. Sensitive upper limits on many sources were obtained and a new 6035 MHz OH maser in the object Vy 2-2 was detected. This source is thought to be young, compact planetary nebula. The masers may reside in the remnant of a red giant envelope.« less
  • Results are presented from a millimeter and submillimeter spectral line survey of the core of the Orion molecular cloud (OMC-1). The millimeter-wave survey, conducted at the Owens Valley Radio Observatory (OVRO), covers a 55 GHz interval in 1.3 mm (23 GHz) atmospheric window and contains emission from 29 molecules. Together with the frequency selective submillimeter observations of H/sub 2/D/sup +/ (372.4 GHz), Cl(492.2 GHz), NH/sub 3/ (572.5 GHz), and HCl (625.9 GHz) performed from the NASA Kuiper Airborne Observatory, over 800 emission lines have been detected from 33 chemically distinct species during the course of this work. The uniformly calibratedmore » results from the unique and extensive OVRO spectral line survey place significant constraints on models of interstellar chemistry, and have allowed the chemical composition of the various regions in OMC-1 to be definitively characterized. A global analysis of the observed abundances showed that the markedly different chemical composition of the kinematically distinct Orion subsources may be simply interpreted in the framework of an evolving, initially quiescent, gas phase chemistry influenced by the process of massive star formation.« less
  • The heating of gas in optically thick molecular clouds with embedded luminosity sources is studied. The dust is heated by the flow of infrared luminosity out of the cloud and assumes temperatures which range from 10 to 300/sup 0/K. The gas is weakly coupled to the radiation field and is generally cooler than the dust. The main heating mechanisms for the gas are by direct collisions with the dust grains and by collisions with H/sub 2/O molecules, which are radiatively excited by dust infrared emission. The latter process is quantitatively treated in a simple model of the thermal balance inmore » such clouds. The effects of each cloud parameter on the thermal structure and the emergent molecular line intensities are studied for a linearly expanding cloud. H/sub 2/O lines appear both in emission at long wavelengths (lambda approx.> 100 and in absorption at shorter wavelengths. Line shapes often show the asymmetric P-Cygni features, and line strengths range up to approx. 10/sup -3/erg cm/sup -2/s/sup -1/sr/sup -1/; H/sub 2/O lines are sensitive to cloud optical depth and dust temperature. CO and Cl lines appear in emission, and the strongest lines (approx. 10/sup -4/erg cm/sup -2/s/sup -1/sr/sup -1/) are at longer wavelengths than the H/sub 2/O lines.« less