Rodr??guez et al. (2003b) used Very Large Array (VLA) in addition of Pie Town antenna (PT antenna) to observe the low mass protostellar system, L1551 IRS 5 at 3.5 cm. Their radio map showed two main results: a number of knots along the two extend radio jets driven from L1551 IRS 5 and the southern jet shows a peculiar bend at about 0.006 to the southwest of the driving source. To inves- tigate how the knots formed and what causes the bend in southern jet, I found three data sets reliable to make the maps from the VLA online data archive comprising 1994, 2002 and 2003. The 3.5 cm radio continuum maps of three epochs showed similar jets structure. I denoted the knots as RK A, B, C, D, E, F and G. For interpreting the nature of the knots seen in both jets and variations in the intensity/structure of the southern jet, I make the difference maps for multi-epoch comparison. There are no significant residuals (> 4_) for above-mentioned knots. We measure the velocities of the RKs relative to RK A: RK C (19 ± 13 kms?1), RK D (7.5 ± 4.7 kms?1 between epoch 1994 and 2002, 85 ± 20 kms?1 between epoch 2002 and 2003), RK E (72 ± 24 kms?1) and RK G (24 ± 32 kms?1). And the intrinsic velocity of RK B relative to southern protostar is 3.8 ± 2.8 kms?1. All of them are insignificant (< 4 _). However, I detected a positive residual with highly significant (> 6_) in all difference maps. I denoted it as RK H. And I obtained a significant proper motion of RK H (128 ± 18 kms?1). RK B, C, D, E, F and G are not likely formed by enhancement in mass loss or internal shock because their 4_ upper limit velocities are much slower than jet velocities of their corresponding jet. They can be interpreted by either the model of interaction of the binary jets or interaction with ambience cloudlets. Since the flux density of RK H is roughly constant within 1_ so that it is not likely formed by enhancement in mass loss but it can be explained by internal shock. / published_or_final_version / Physics / Master / Master of Philosophy

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (p. [143]-151).

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IceCube is the largest operating neutrino observatory. An array of photomultiplier tubes deployed throughout a cubic kilometre of the Antarctic ice at the South Pole detect the Cherenkov radiation from neutrino-nucleon interactions. IceCube is capable of detecting neutrinos over a large energy range. The physics manifesto includes dark matter searches, cosmic ray observation, all sky point source searches, and particle physics parameter constraints. Astrophysical neutrinos are expected to originate from hadronic interactions in some of the most energetic regions in the Universe. The detection of high energy astrophysical neutrinos will provide direct information about the astrophysical sources that produced them. This thesis concentrates on the cascade channel for neutrino detection. Two separate studies are performed; a high energy cascade analysis and a parameterisation of the production of muons within hadronic cascades. The experimental data for the cascade analysis was taken by IceCube from April 2008 to May 2009 when the first 40 IceCube strings were deployed and operational. The analysis was designed to isolate the astrophysical neutrino signal from the atmospheric and muon background. Fourteen cascade-like events were observed, on a background of 2.2 ⁺⁰·⁶ ₋₀·₈ atmospheric neutrino events and 7.7 ± 1.0 atmospheric muon events. This gives a 90% confidence level upper limit of ΦlimE²≤ 7.46 × 10⁻⁸ GeVsr⁻¹s⁻¹cm⁻² , assuming an E⁻² spectrum and a neutrino flavour ratio of 1 : 1 : 1, for the energy range 25.12 TeV to 5011.87 TeV. Decay of hadronic particles in cascades produces muons. If the muons are energetic enough they can significantly alter the topology of the cascade and hence the reconstruction of the event in an analysis. The production of high energy muons within hadronic cascades was simulated and parameterised using Pythia and GEANT simulation programs.

Magnetic fields play a fundamental role in the evolution of astrophysical systems. These fields can be studied through wide-field spectropolarimetry, which allows for faint polarised signals to be detected at relatively low radio frequencies. An interferometric polarisation mode has recently become available at the Giant Metrewave Radio Telescope (GMRT). A detailed analysis of the GMRT’s instrumental response is presented. The findings are used to create a polarisation pipeline, which in combination with rotation measure (RM) Synthesis is used for the detection of extended linearly polarised emission at 610 MHz. A number of compact sources are detected and their Faraday depth and polarisation fraction are reported for the first time. New holography observations of the GMRT’s primary beam are presented. Instantaneous off-axis polarisation is substantial and scales with the Stokes I beam. The developed beam models are used to reduce direction-dependent instrumental polarisation, and the Stokes I beam is shown to deviate from circular symmetry. A new technique for electric vector polarisation angle calibration is developed that removes the need for known sources on the sky, eliminates ionospheric effects, and avoids a flaw in current methods which could erroneously yield multiple Faraday components for sources that are well-parameterised by a single RM. A sample of nine galaxies from two Southern Compact Groups are then presented, with constraints being placed on the polarised fraction, RM, spectral index, star formation rate, companion sources, and hydrodynamical state. One galaxy has a displaced peak of radio emission that is extended beyond the disk in comparison to the near-IR disk – suggesting the radio disturbance may be a consequence of ram pressure stripping. Linear polarisation is detected from the core of NGC 7552 at 610 MHz, while another three galaxies ESO 0353–G036, NGC 7590, and NGC 7599 are found to be unpolarised. An analysis of additional extended sources allows for an FR-I and an FR-II radio source to be morphologically classified. Finally, spatial spectral variations are identified in the youngest known Galactic supernova remnant G1.9+0.3, with flatter spectra in the NW and SE. Models of cosmic ray acceleration at oblique shocks suggest the variation is most consistent with an ambient B field perpendicular to the axis of bilateral symmetry. For the first time, the presence of polarised emission is detected. There is increased ordering of the B field in the NW and strong Faraday depolarisation must also be present. An intrinsically radially-oriented field could be provided by a systematic gradient in RM of 140 rad m-2 from N to S and can also explain the depolarisation. Such a gradient may be caused by an anisotropic regular magnetic field within the remnant or in an intervening Faraday screen. The lack of strong constraints on the RM, and the remnant’s current evolutionary stage, leave open the possibility that Rayleigh–Taylor instability formation has not yet fully taken place.

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Thesis (M.Sc.)--Saint Mary's University, 2008. / Includes abstract and appendix. Supervisor: David Clarke. Includes bibliographical references (leaves 88-90).