A study of diverse stellar outflows
Başlık:
A study of diverse stellar outflows
Yazar:
Graham, Matthew, author.
ISBN:
9780438085428
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (206 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Özet:
In this thesis, a number of diverse examples of stellar outflows from stars at various stages in their evolution are observationally investigated and discussed. High-resolution MERLIN 5 GHz continuum observations of the binary proplyd system, LV 1 (168-326SE and 168-326NW), in the Orion nebula are presented. Accurate astrometric alignment allows a detailed comparison between these data and published HST H? and [O III] images. Thermal radio sources coincide with the two proplyds and originate in the ionized photoevaporating flows seen in optical emission lines. Flow velocities of ~ 50km s-1 from the ionized proplyd surfaces and ≥ 100 km s-1 from a possible micro-jet have been detected using the Manchester Echelle Spectrometer (MES). A third radio source is found to coincide with a region of extended, high-excitation, optical line emission that lies between the binary proplyds 168-326SE and 168-326NW. This is modelled as a bowshock due to the collision of the photoevaporating flows from the two proplyds. Both a thermal and a non-thermal origin for the radio emission in this collision zone are considered. In an MES position-velocity array of [O III] line profiles, the proplyd, LV 5 (158-323), is found to be associated with a spatially-unresolved feature with a radial velocity of ~ -100kms-1 with respect to the systemic radial velocity. This is identified as the kinematical counterpart of a jet, which is shown using HST imagery to take the form of a displaced, ionized knot. An elongated jet has previously been seen to project from the proplyd, GMR 15 (161-307). A feature, coincident with GMR 15, with a radial velocity of ~ 80 km s-1 with respect to the systemic is also identified in the same MES position-velocity array. An alternative origin for proplyd jets is also explored. The most prominent Herbig-Haro (HH) object, HH 201, in the Orion nebula is investigated using optical spectroscopy along with optical and infrared images. An infrared Subaru H2 u = 1 - 0 S(l) image of the region surrounding HH 201's optical line emission has yielded the discovery of a faint H2 finger associated with HH 201. The finger is found to precede the optical line emission, which is inconsistent with this H2 emission being produced within a bowshock. The origin of this finger is discussed in the context of the current understanding of HH objects and the Orion molecular fingers. Multi-epoch HST [S II] images are used to measure the proper motions of the various knots present in the filamentary structure of HH 201. Tangential velocities of between 40km s-1 and 178km s-1 are found and the general structure of the tangential flow is shown by means of a multi-epoch difference image. [S II] spectra taken with the RGO spectrograph are used to spectroscopically resolve the velocity profile of HH 201 into distinct components with radial velocities of between -267km s-1 and -9 km s-1. Using the [S11] line ratios, the local electron density of gas at the various velocities is found to be between 830 cm-3 and 12200 cm-3. Combining radial and tangential velocities, the angle between the direction of motion of the optically-emitting region and the line of sight is found to be approximately 30°; the emission knots and radial velocity components are assumed to correspond to condensations in a bowshock. The giant, faint filamentary shell, DEM 171, in the Magellanic bridge is found to be expanding at approximately 37km s-1. A supernova and stellar wind origin are both explored as possible causes for the expanding shell. A stellar wind origin would imply a mass loss rate of order 10-5 M?-1, indicating that it could be caused by a Wolf-Rayet star. A number of blue stars are found to lie within the shell and one is identified as a Wolf-Rayet candidate. High-resolution, spatially-resolved, longslit profiles of the [O III] emission line of the highest galactic latitude planetary nebula (PN), LoTr 5, have been obtained with the MES on the San Pedro Martir (SPM) 2.1-m telescope. These are compared with a deep narrow-band [O III] mosaic image obtained with the same system. This faint nebula, at a distance of ≥ 500 pc from the galactic plane is found to be expanding asymmetrically into the tenuous galactic halo. Some form of bipolar structure is suggested by modelling the position-velocity arrays of line profiles and the new [O III] image. Evidence for interaction of the envelope of LoTr 5 with its local interstellar medium is also considered. Deep imagery and longslit spectroscopy of the complex PN, NGC 6302, also taken with the MES on the SPM telescope show NGC 6302 to extend further than previously detected. Complex kinematics are observed in its faint outer-reaches and radial velocities with respect to the systemic of ~210km s-1 are detected. The origin of the observed kinematics have yet to be considered in detail, but a structure involving periodic cavities seems to be suggested. The observational work described above is accompanied by some technical work, which has been carried out on the Manchester Low-Dispersion Robotic Spectrometer (MLDRS) for the Liverpool John Moores University (LJMU) robotic telescope.
Notlar:
School code: 1543
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(686960.1) | 686960-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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