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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Model planetary nebulae the effect of shadowed filaments on low ionization potential ion radiation /

Katz, Andrew, January 1977 (has links)
Thesis--Wisconsin. / Vita. Bibliographical references: leaves 102-103.
12

The life spans of condensations in planetary nebulae

Holm, Albert Victor, January 1970 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
13

Model planetary nebulae : electron temperatures and ionization stratification /

Harrington, James Patrick January 1967 (has links)
No description available.
14

The Zanstra mechanism for nebular condensations

Daub, Clarence Theodore, January 1962 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1962. / Typescript. Includes abstract, computer source code, and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 26).
15

Morpho-kinematic modeling of planetary nebulae

Chan, Tsz-pan, Henry, 陳子斌 January 2009 (has links)
published_or_final_version / Physics / Master / Master of Philosophy
16

A new mid-infrared camera for ground-based astronomy and an infrared study of planetary nebulae.

Hora, Joseph Lee. January 1991 (has links)
This dissertation is composed of two parts. The first part is a description of the Mid-Infrared Array Camera (MIRAC), a new camera for ground-based astronomy. The second part of this dissertation is an infrared study of planetary nebulae utilizing observations with the new camera. MIRAC is a collaborative effort among the University of Arizona, Smithsonian Astrophysical Observatory, and Naval Research Laboratory. It currently utilizes a Hughes 20 x 64 Si:As IBC detector array, which is sensitive to infrared (IR) radiation from 2 to 26 μm. The camera is equipped with 10% bandwidth filters at 2.2, 3.8, 4.6, 8.8, 9.8, 11.7, and 12.5 μm, and a wide band 8.0 to 12.8 μm "N" filter. There is also a 20% filter at 20.5 μm, and a 8-14 μm CVF with a resolution of 1.8%. The MIRAC electronics provides timing signals and coadds successive frames at a maximum rate of 10 KHz for the full array, and higher rates for a partial array readout. The data are transferred via a serial interface to a PC for storage and further processing. The camera recently achieved a NEFD of.010 Jy/arcsec² at 8.8, 11.7, and 12.5 μm for a 900 second on-source integration on the Steward Observatory 1.5 m telescope. Planetary Nebulae (PN) are formed when a star is in the post-Asymptotic Giant Branch stage of evolution. The ejection of circumstellar material is an important enrichment mechanism for the interstellar medium. In many PN, there is an excess of emission in the IR, indicating the presence of dust. There are several different components seen in the IR emission, including a family of unidentified IR (UIR) emission features at 3.3, 6.2, 7.7, and 11.3 μm. Images in the near- and mid-IR are presented here for the following PN: IC 418, BD + 30°3639, J 900, NGC 2392, NGC 6543, AFGL 2688, and M 2-9. In IC 418 and BD + 30°3639, the SiC and UIR emission is seen to be spatially distinct from the IR continuum. In NGC 2392 and NGC 6543, evidence for excess emission is seen in the distribution of the near-IR flux. In the bipolar nebulae AFGL 2688 and M 2-9, structures in the IR emission are seen that could be related to the equatorial density enhancements that have caused the bipolar morphology.
17

Heavy element abundance in ionized nebulae

Tsamis, Ionnis January 2002 (has links)
No description available.
18

The Ionization of Planetary Nebulae : Proceedings of the 34th IAU Symposium

Williams, R. E. 08 1900 (has links)
The ionization of the most abundant elements in planetary nebulae has been determined for a number of models of nebulae at different epochs in their expansion. The values used for the temperatures and radii of the central stars and the sizes and densities of the shells have come from Seaton's evolutionary sequence. The ionizing radiation field has been taken from model atmosphere calculations of the central stars by Gebbie and Seaton, and Biihm and Deinzer. Emission -line fluxes have been calculated for the models and compared with observations of planetary nebulae by O'Dell, Osterbrock's group, and Aller and his collaborators. Results indicate that the central stars have strong He+ Lyman continuum excesses, similar to those predicted by Gebbie and Seaton. The mean abundance determinations for the nebulae made by Aller are confirmed, with the exception of nitrogen, which appears to be 3 or 4 times more abundant than his value. It is also seen that the electron temperatures of the nebulae are higher than previous theoretical determinations, providing better agreement with empirically derived values.
19

Light neutron-capture element abundances in planetary nebulae

Sterling, Nicholas Craig, January 1900 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.
20

Kinematic constraints on structuring of the optical emission-line nebula in NGC 1275

Chan, Chi-chung, Jeffrey, 陳祉聰. January 2012 (has links)
Bright optical nebulae are a relatively common feature of galaxy clusters with a central depression in their intracluster gas temperature suggestive of an X-ray cooling flow. In my thesis, I have measured, for the first time, the velocity field of nearly the entire optical nebula associated with NGC 1275, the central cD (giant elliptical) galaxy of the Perseus cluster. This nebula is the brightest example with the largest projected size in the sky. Our primary scientific objective is to address the physical processes that give rise to the complex morphology of this nebula, which comprises a multitude of mostly approximately radial but also a number of tangential emission-line _laments. This nebula spans up to ~140 kpc in the north-south direction, extending far beyond the half-light radius of NGC 1275. Popular models for the nature of the nebula invoke either an X-ray cooling flow, in which case the filaments should possess a velocity profile consistent with free fall, or gas drawn out from the central galaxy by buoyantly rising bubbles inflated by radio jets from the AGN, in which case the filaments should show a reversal in velocity along their lengths. We find that the velocity field of the nebula is incredibly complex, and in several important respects contradicts model predictions based on slit spectroscopy. We find that filaments previously thought to be very long integral structures actually comprise multiple shorter filaments that each have their own distinct kinematics. Furthermore, filaments that are apparently aligned and adjacent to each other often possess entirely different kinematics. We searched for filaments with velocity profiles consistent with free fall, but we could only find very few examples beyond the central bright nebular region where overlapping filaments complicate measurements of the individual filament kinematics. We also searched for filaments that show a reversal in velocity along their lengths, but again could find only several examples. Although the combination of a residual X-ray cooling flow and relatively cool gas drawn out by buoyant X-ray bubbles remains the most viable explanation for the nature of the nebula, both the morphology and kinematics of this nebula is complicated by the action of various X-ray bubbles that are currently expanding or rising through the nebula. As such, the velocity field of the filaments reflect the effects of the X-ray bubbles on the bulk flows within the intracluster medium, and trace streamlines that reveal motions in the surrounding X-ray gas. We point out evidences that support the idea that some filaments are being dragged by rising X-ray bubbles, others represent large-scale vortices behind bubbles, and yet others are draping the surface of and pushed outwards by expanding X-ray bubbles. / published_or_final_version / Physics / Master / Master of Philosophy

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