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We present new HST/WFC3-IR narrow-band [Fe II] images of protostellar jets in the Carina Nebula. Combined with five previously published sources, we have a sample of 18 jets and two Herbig-Haro (HH) objects. All of the jets we targeted with Wide-Field Camera 3 (WFC3) show bright infrared [Fe II] emission, and a few Ha candidate jets are confirmed as collimated outflows based on the morphology of their [Fe II] emission. Continuum-subtracted images clearly separate jet emission from the adjacent ionization front, providing a better tracer of the collimated jet than Ha and allowing us to connect these jets with their embedded driving sources. The [Fe II] 1.64 mu m/Ha flux ratio measured in the jets is greater than or similar to 5 times larger than in the adjacent ionization fronts. The low-ionization jet core requires high densities to shield Fe+ against further ionization by the FUV radiation from O-type stars in the H II region. High jet densities imply high mass-loss rates, consistent with the intermediate-mass driving sources we identify for 13 jets. The remaining jets emerge from opaque globules that obscure emission from the protostar. In many respects, the HH jets in Carina look like a scaled-up version of the jets driven by low-mass protostars. Altogether, these observations suggest that [Fe II] emission is a reliable tracer of dense, irradiated jets driven by intermediate-mass protostars. We argue that highly collimated outflows are common to more massive protostars, and that they suggest the outflow physics inferred for low-mass stars formation scales up to at least similar to 8 M-circle dot.

In this thesis, the background and technical theory of the receivers are discussed. Methods used to search for periods, correlations, and delays in the time series of class II methanol masers at 6668 MHz and 12178 MHz are presented together with the observed variability of these sources. Background theory is given on, the processes by which massive stars are formed. The theory of astronomical masers and methanol maser excitation is given in detail. The receiver testing and observation technique chapters describe: the results and methods used to calibrate the two receivers, namely 2.5-cm and 4.5-cm, with central frequencies of 6668 MHz and 12178 MHz respectively, as well as data cap- ture methods for spectroscopic observations. The laboratory square law detector or radiometer was also calibrated to ensure that the noise diode temperature was accurately determined. There is 8.3 per cent deviation from an ideal square law detector. The time series and spectra for one methanol source, G351.42+0.64 which serves as a control source at 6668 MHz and 12178 MHz, one irregularly varying methanol source G351.78-0.54 at 6668 MHz, seven known quasi-periodic and periodic sources (G9.62+0.20E, G12.89+0.49, G188.95+0.89 and G328.24-0.55, at both 6668 MHz and 12178 MHz, and G331.13-0.24, G338.93-0.06, and G339.62-0.12, at 6668 MHz), and seven new methanol maser source regions (G0.092+0.663, G6.189-0.358, G8.832- 0.028, G8.872-0.493, G348.617-1.162, G351.688+0.171 and G358.460-0.391, at both 6668 MHz and 12178 MHz) are shown and discussed. The seven new sources were from the 6668-MHz Methanol Multi-Beam (MMB) survey Catalogues I and II. Periods were searched for using the Lomb-Scargle and epoch-folding methods. The quasi-periodic and periodic sources show diverse waveforms and diverse periods be- tween 29 and 511 days. From the seven new methanol maser sources, G8.872-0.493 (76 day period) and G358.460-0.391 (187 day period) both at 6668 MHz, were found to be variable and they are possible new candidates for the periodic or quasi-periodic group of sources. The Colliding Wind Binary (CWB) model is proposed by van der Walt (2011) as the source of the observed periodic variability in these regions. The properties of the binary systems using the 29 and 511 day period are discussed as well as the common features in the time series, such as long-term variations and flares. The source of the periodicities has not been finally determined but the foundation has been laid.

Chan Man Ho = 中微子星的形成與特徵 / 陳文豪. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 84-87). / Text in English; abstracts in English and Chinese. / Chan Man Ho = Zhong wei zi xing de xing cheng yu te zheng / Chen Wenhao. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- History of dark matter research --- p.1 / Chapter 1.2 --- Method of searching for dark matter --- p.3 / Chapter 1.2.1 --- Observation of dark matter --- p.3 / Chapter 1.2.2 --- N-body simulation --- p.4 / Chapter 1.3 --- Candidates of dark matter --- p.7 / Chapter 1.3.1 --- Properties of neutrinos --- p.8 / Chapter 1.3.2 --- Neutrino oscillation --- p.9 / Chapter 1.3.3 --- Decay of neutrinos --- p.10 / Chapter 1.4 --- Origin of neutrino dark matter --- p.11 / Chapter 2 --- Properties of Neutrino Stars --- p.16 / Chapter 2.1 --- Hydrostatic Equilibrium --- p.16 / Chapter 2.2 --- Ultra-relativistic degenerate neutrino star --- p.17 / Chapter 2.2.1 --- Trajectory inside an ultra-relativistic neutrino star --- p.19 / Chapter 2.2.2 --- Rotation curve of an ultra-relativistic neutrino star --- p.20 / Chapter 2.3 --- Non-relativistic neutrino star --- p.21 / Chapter 2.3.1 --- Trajectories inside a non-relativistic neutrino star --- p.22 / Chapter 2.3.2 --- Rotation curve of non-relativistic neutrino stars --- p.24 / Chapter 2.4 --- Neutrino Mixing correction --- p.24 / Chapter 3 --- Neutrino star in galaxy --- p.26 / Chapter 3.1 --- Neutrino star in galactic center --- p.26 / Chapter 3.1.1 --- The rate of change of mass of neutrino star --- p.27 / Chapter 3.1.2 --- Motion inside the neutrino star in milky way --- p.27 / Chapter 3.2 --- Neutrino star in Milky Way --- p.30 / Chapter 3.2.1 --- Components of Milky Way --- p.32 / Chapter 3.2.2 --- Dark matter component in Milky Way --- p.33 / Chapter 4 --- Hot gas and Neutrino star in cluster --- p.40 / Chapter 4.1 --- Neutrino dark matter model --- p.41 / Chapter 4.1.1 --- Cowsik and McClelland model --- p.41 / Chapter 4.1.2 --- Treumann et al. model --- p.42 / Chapter 4.2 --- NFW universal dark matter profile --- p.43 / Chapter 4.3 --- Probing dark matter distribution --- p.44 / Chapter 4.4 --- Neutrino stars in clusters --- p.48 / Chapter 4.5 --- Heat source of hot gas --- p.52 / Chapter 4.5.1 --- Infall and compressional heating --- p.53 / Chapter 4.5.2 --- Heating by ejection from galaxies --- p.53 / Chapter 4.5.3 --- Heating by galaxy motion --- p.54 / Chapter 4.5.4 --- Heating by relativistic electrons --- p.55 / Chapter 4.5.5 --- Heating by photons from neutrino decay --- p.55 / Chapter 5 --- Formation of neutrino star --- p.58 / Chapter 5.1 --- Hydrodynamic code --- p.58 / Chapter 5.2 --- Hydrodynamic evolution of neutrino star --- p.61 / Chapter 5.2.1 --- Result of the simulation --- p.61 / Chapter 5.2.2 --- Scaling law of neutrino star formation --- p.66 / Chapter 5.2.3 --- Oscillation in neutrino star --- p.67 / Chapter 5.3 --- Expected Observational Results --- p.69 / Chapter 6 --- Discussion and conclusion --- p.72 / Chapter 6.1 --- Conclusion --- p.72 / Chapter 6.2 --- discussion --- p.74 / Chapter A --- Derivation of TOV equation --- p.76 / Chapter B --- Equation of state of degenerate ideal gas --- p.80 / Chapter C --- Derivation of oscillation period --- p.82 / Bibliography --- p.84

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

IRC+10420 is a massive (> 20M☉), very luminous (> 〖10〗^6L☉) star that is in the rare phase of evolution from the red supergiant to the luminous blue variable or Wolf-Rayet phase. Previous observations reveal that the circumstellar envelope is rich in molecular gas, and can be detected out to a radius of about 8” = 6.0 X 〖10〗^17 cm. Observations in CO also reveal that the global massloss rate of IRC+10420 has changed dramatically over the last 6000 years, comprising two major episodes of mass loss lasting for about 1000 and 4000 years respectively separated by period of very low mass-loss rate lasting for about 1000 years. Surprising, previous observation in SiO(J = 2 - 1) revealed a ring-like enhancement at a radius of about 1” (7.5X 〖10〗^16 cm) from the star, contrary to the expectation that SiO molecules should be frozen onto dust grains very close to the star (within ～ 〖10〗^16cm). This ring-like enhancement has been attributed to a large-scale shock produced by interactions between faster and slower moving portions of the expanding envelope. In this thesis, we mapped the circumstellar envelope in SiO(J = 1 - 0) to better constrain the physical conditions (gas density, temperature and SiO abundance) in the SiO-emitting gas. We find a similar ring-like enhancement in SiO(J = 1 - 0) but located further out at a radius of about 2” (1.5 X 〖10〗^17 cm), and confirm that the SiO emission extends as far out as the CO envelope. The computed SiO(J = 2-1)/SiO(J = 1-0) line ratio significantly exceeds unity at radius out to about the location of the ring-like enhancement (2”), and drops to a value of about unity beyond this radius. From a one-dimensional non-local thermodynamic equilibrium model, we explore the physical conditions that can reproduce the observed brightness temperatures in both SiO(J = 10) and SiO(J = 2-1) as well as their line ratio as a function of radius. The SiO-emitting gas is required to have a density that is much higher (from a factor of a few to about two orders of magnitude) than has been inferred for the CO-emitting gas at the same radii. The required surface filling factor of the SiO-emitting gas depends on their unknown gas-phase SiO abundance; for an abundance of ～〖10〗^(-5), as inferred just above the photospheres of lowmass evolved stars, the surface filling factor of these condensations range from ～0.001 to ～0.1. Thus, the SiO emission from the envelope of IRC+10420 most likely originates from dense condensations that are immersed in more diffuse gas that produces the bulk of the observed CO emission. We reason that the SiO-emitting condensations correspond to the dust clumps detected in reflected light with the Hubble Space Telescope. These dust clumps are distributed from near the star out to a radius of 2”, spanning the same extent as the peaks of SiO- (and CO-) emitting envelope. We show that these dust clumps are expanding in every direction away from the stars at a velocity that is significantly higher than the CO-emitting gas, and anticipate that shocks thus generated heats up the dust clumps to release SiO into the gas phase. / published_or_final_version / Physics / Master / Master of Philosophy

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published_or_final_version / Physics / Master / Master of Philosophy