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The 4.57 meter millimetre wave telescope at the University of British Columbia has been used to partially map a region around Lk Hα101 one half degree in diameter centered on α(1950) = 04H26M34s.0 (right ascension), Ϭ (1950) = 35°13'00" (declination) in the J=1—0 transition of ¹²C¹⁶O. Our ¹²CO results show a wide region of ¹²CO emission, but the exact boundaries are as yet undetermined. The north and west boundaries have been determined. We suspect the emission extends as far as a visual extinction of 1 magnitude which covers a region almost one degree across and several degrees long. The average radiation temperature, T*A , is 10 K. Within our survey field we found a large fragmented area with five hot spots (20 K). Since ¹³CO observations were not made ¹³CO data was generated from the ¹²CO observations. Both the ¹²CO and ¹³CO temperature contours have five hot spots within a single envelope of colder CO emission located southeast of Lk Hα101. Three CO clouds (#1, #2, and #3) are resolved at Lk Hα101 (7.2,-10.8), Lk Hα(101 (0.0,-10.8), and LkHα101 (7.2,-5.4). Their masses were calculated from the generated 13CO column densities and are 49M, 41M, and 25M respectively. Two other clouds (#4 and #5) on the limit of resolution are located at Lk Hα101 (3.6,-5.4) and Lk Hα101 (0.0,-1.8) and have masses of 11M0 and 25M0. Each of these fragments is embedded in the same 13 K ¹²CO contour centered on Lk Hα101 (3.6,-7.2). The mass is calculated from the fabricated ¹³CO data and should not be relied upon very strongly. It is in error by at most a factor of two. Peak HI emission contours (Dewdney and Roger 1981) are anticorrelated to our peak CO contours. The HI lies to the northwest. This indicates that the peak CO and HI features are located in different regions. The peak HI column densities derived from both the fabricated ¹²CO data and HI observations agree. They are ~1.3 x 10²¹ atoms cm⁻². From star counts we made of the region we see that the stronger CO emission correlates with regions of stronger visual extinction. The peak HI occurs where the extinction is low. The exciting star has presumably been able to dissociate H2 into HI to the northwest where the visual extinction is lower. Dewdney and Roger (1981) have modelled this asymmetry reasonably well by assuming there is a steep discontinuity of density near Lk Hα101 to the east. The positions of infrared stars from the Steward Observatory Near Infrared Photographic Sky Survey provide meager evidence for the 'Blister' model (Israel 1977, Gilmore 1978) and suggest that star formation was initiated on the edge of the cloud and proceeded inwards. Our CO hot spots could well be the next generation of infrared stars. Confirmation will require a more complete map with better resolution of the region around Lk Hα101 (3.6,-7.2). / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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IRAS observations of extragalactic objects are analyzed, supplemented by optical spectroscopy and 10 μm photometry. The relationship between various forms of activity in the nuclei of spiral galaxies and their mid- to far-infrared spectral energy distributions is explored. It is shown that more than 70% of galaxies with F₆₀/F₂₅ ≤ 3 are Seyferts, while the remainder have bright optical emission lines in their nuclear spectra. It is argued that most Seyferts are powered by their active nuclei at 25 μm, while there is some indication that Seyferts with large F₆₀/F₂₅ flux ratios are undergoing starbursts in the vicinity of their nuclei. The properties of a sample of bright, extragalactic IRAS sources are studied. A catalog containing total infrared and blue fluxes, distance estimates, recession velocities, and morphological classifications for these objects is presented. The brightest sources at mid- to far-infrared wavelengths are (in order of frequency) nearby, normal spiral galaxies; galaxies with disturbed or irregular morphology (often known as interacting galaxies); type 2 Seyferts; and dust-embedded type 1 Seyferts. All of these sources are dominated by thermal emission from dust. The dust in the peculiar, irregular, and Seyfert galaxies is exposed to a higher mean intensity of radiation. Moreover, these IR-active galaxies tend to have strong, compact nuclear sources at 11 μm, whether or not they contain a known Seyfert nucleus. The distinctive spectral behavior of IR-luminous galaxies is shown to result from the presence of compact, dust-dominated IR nuclear sources, which are the predominant cause of IR luminosities above 10¹¹ L(⊙). Compact IR sources are always associated with a dust-embedded region of ionized gas in the galaxy's nucleus, which may exhibit Seyfert, LINER, or H II region characteristics. The luminosity of the compact nuclear source is well correlated with its 60/100 μm color. This relationship is a vital clue to the nature of these sources and has potential application as a standard candle.

The uses of the bispectrum for recovering the images of one-dimensional infrared astronomical speckle data are examined in detail. An analytic model for the bispectral transfer function, the variance, and the covariance of the bispectrum are developed. The models are evaluated by Monte Carlo integration and the results are compared to sample estimates of the same quantities obtained from simulated data. For comparison, the same sample quantities are computed from observed data. The bispectrum is shown to be useful for determining estimates of the object phase. A recursive method which is used to obtain the object phase estimates is introduced. Since the bispectrum provides multiple estimates of each object phase, a number of methods for combining the multiple estimates are developed and compared. Many techniques have been proposed to determine the phase of images which have been atmospherically distorted. Among these techniques are the Knox-Thompson, and the Simple Shift-and-Add algorithms. These methods are compared to the bispectrum via an objective measure which is developed. Optimization techniques are used to great success. A model for the bispectrum of a binary star is developed and fit to the image bispectrum by the Levenberg-Marquardt algorithm for non-linear least squares. The ability of the algorithm to determine binary star parameters from the bispectrum is tested with both simulated and observed data. Since the bispectrum may not always be available, a method is developed which determines binary star parameters from the image Fourier transform. The full set of object phases and moduli are determined by use of the conjugate gradient and conjugate direction algorithms in the last section. Two starting points for each algorithm are employed. The first starting point uses the estimates of the object phases obtained from the recursive bispectrum technique. The second assumes no information is known about the object. The speed of convergence of each algorithm is analyzed and recommendations are made for future use.

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.

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One of the most fundamental probes of the physics that underpins galaxy evolution is the star formation rate (SFR) as a function of cosmic time. In addition, the statistical prop- erties of galaxy populations are another important key to understand how the universe has been evolving. It is known that the far-infrared emission from galaxies is strongly correlated with obscured star formation and forms a significant part of cosmic infrared background. We thus investigate the variation of the SFR of galaxies over time by com- paring predictions of the L-Galaxies semi-analytic model with observations of the far infrared (FIR) luminosity and number counts. In the first part of this thesis, we follow the star formation histories (SFHs) of galaxies and use these to construct stellar spectra in post-processing. We then contrast model SFHs from the Millennium Simulation with observed ones from the VESPA algorithm as applied to the SDSS-7 catalogue when this has been characterized by mass and colour of galaxies. In order to investigate the SAM model prediction, I extend L-galaxies to predict far infrared fluxes and construct mock catalogues which are fed into SMAP in order to provide simulated maps. LFs have also been estimated for model galaxies at different redshifts. The results are compared with observations from Herschel. To conclude, our model under- estimates the number density of galaxies at bright sources (e.g fluxes above 0.02 Jy) also does not produce high luminosity objects especially at higher redshifts (e.g z > 1) . We show that by fitting the simulated IR luminosity function to observed LIR, our model is able to produce more bright sources at high redshifts and match reasonably well to the observed number counts.

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