Thesis (Ph. D.)--University of Chicago, Dept. of Astronomy and Astrophysics, August 1997. / Includes bibliographical references. Also available on the Internet.

We present the observations, reduction and preliminary analysis of a sample of 45 mid-to-high redshift galaxy clusters imaged with the Spitzer Space Telescope's MIPS camera at 24 ~m and selected from the Red Sequence Cluster Survey. The purpose of the data set is motivated by a broad review of studies into the evolutionary trends of galaxy clusters and their constituent galaxy populations, focusing specifically on recent results that indicate clusters are environmental drivers of dusty starburst and active galactic nuclei activity. To accommodate the large amount of data in hand, we have constructed an extensive data reduction pipeline for the MIPS data and describe its development and output in detail. Using the resulting catalogues for introductory analysis, we find strong evidence for an excess luminous infrared galaxy population in galaxy clusters at high redshift and discuss the implications of this discovery in terms of cluster evolution and motivate future work.

This thesis presents a study of high-redshift obscured (type-2) quasars, selected at mid-infrared and radio wavelengths. This population had remained elusive, even to hard X-ray surveys, and in Chapter 2 I compare the selection of type-2 quasars in X-ray and mid-infrared surveys, as well as explaining the criteria I will use to search for these objects at z ~ 2, around the peak in the unobscured (type-1) quasar activity. Chapter 3, presents a sample of radio-intermediate type-2 quasars selected from the criteria de- scribed in Chapter 2. Optical spectroscopy shows indeed that at least half of the objects have the characteristic narrow emission lines, and lie around the expected redshift of z = 2. The other half of the objects are consistent with also being type-2 quasars at similar redshifts, although no emission lines are visible. In Chapter 4,1 discuss the possibility of two types of obscured quasars, some obscured by a dusty torus and some by a dusty host galaxy, to explain the lack of emission lines in half of the sample. I model the number of type-1 quasars expected to follow similar selection criteria and at the same redshifts as our type-2 quasars, and find that the obscured quasars outnumber the unobscured by a ~2-3:1 ratio. I conclude that most supermassive black hole growth is obscured by dust. When comparing this to predictions from unified schemes, I find that this result is only consistent with the schemes provided host-obscuration is indeed happening. The lower ratio of type-2 to type-1 quasars inferred from X-ray surveys (~1:1) suggests that some of the type-2 quasars in this sample might be Compton thick. Radio data taken at three frequencies, are presented in Chapter 5, to study the spectral properties and intrinsic luminosities of our sample. I show that some type-2 quasars have flat radio spectra, which is inconsistent with obscuration by the torus, but consistent with host-obscuration. Some gigahertz-peaked spectra, characteristic of young radio jets, are present, but the majority of the sources have very steep spectra. These steep spectral indices can be explained by active developed jets in which continuous injection of electrons is accompanied by inverse-Compton losses against the cosmic microwave background. In Chapter 6, I select a similar sample of type-2 quasars in a different field, where X-ray data are available. The selection criteria are kept identical, except for the radio flux density cut, which is lowered. This is expected to introduce significant numbers of starburst contaminants. To filter these out, and due to a lack of spectroscopy, I use a bayesian method to fit the spectral energy distributions, obtain photometric redshifts, and select between a quasar and a starburst model. I measure the X-ray properties for the resultant sample of type-2 quasars. The entire sample is found to be Compton-thick, and repeating the modelling of Chapter 4, I find that the population of Compton-thick quasars is at least comparable to the population of unobscured quasars, and probably larger.

Mode of access: World Wide Web. / Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references (leaves 180-192). / Electronic reproduction. / Also available by subscription via World Wide Web / xviii, 192 leaves, bound col. ill. 29 cm

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第21610号 / 理博第4517号 / 新制||理||1648(附属図書館) / 京都大学大学院理学研究科生物科学専攻 / (主査)准教授 今元 泰, 教授 高田 彰二, 教授 杤尾 豪人 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

Measurements of hydrogen are important in our understanding of the Universe. Following reionization at z ∼ 6, most of the hydrogen outside galaxies is in an ionized state. Within galaxies, hydrogen passes through a neutral phase as it cools and collapses into molecular hydrogen and then to stars. This work centers around how galactic reservoirs of neutral hydrogen (HI) evolve over cosmic time. We know that cosmic star formation peaks at z ∼ 2 and sharply declines to the present day, yet we know very little about the gas reservoirs in individual galaxies that lead to star formation through these redshifts. The Very Large Array’s (VLA) recent upgrade has made it possible to probe a large instantaneous bandwidth with HI imaging surveys beyond the local Universe. The COSMOS HI Large Extragalactic Survey (CHILES) is a 1000-hour program using the Karl G. Jansky VLA that will image HI in a redshift range of 0 < z < 0.45. With our first epoch of data, we study the galaxy properties of a sample of ten nearby galaxies. We find that our data follow known scaling relations. Both theory and observations suggest that large-scale structure impacts galaxy evolution in addition to known trends in local density. We find that galaxy spins tend to be aligned with cosmic web filaments and a hint of the predicted transition mass associated with the spin angle alignment. With our second epoch of data from the CHILES survey, we probe the high-redshift regime. We present two new HI detections at z = 0.257 and z = 0.258, plus a stacked result at z ∼ 0.36. We combine these results with the previously published CHILES samples. This provides, for the first time, a continuous look at directly detected HI in emission over redshift range 0 < z < 0.45. We strengthen our epoch one comic web results, finding a perpendicular galaxy spin alignment with the cosmic web for a high-mass HI detection and a parallel galaxy spin alignment for a gas-rich low-mass HI detection embedded within a cosmic web filament. Having HI content, morphology, and kinematics, along with knowledge of the large-scale environments across substantial cosmic time spanning one-third the age of the Universe, will help shed light on the overall origin and fate of gas in galaxies.

No description available.

Density Functional Theory (DFT) and time-dependent Density Functional Theory (TD-DFT) are powerful tools for modeling orbital energy in conjugated molecules and have been useful tools for research in organic photovoltaics. In this work, DFT is first used to explain the red shift in the absorption spectrum and increased absorption observed in MEH-PPV. Initially, the modeling of the red-shift in the absorption peak of MEH-PPV is studied using Gaussian 03 software with the global hybrid functional B3LYP for exchange-correlation and the 6-31G basis set. DFT and TD-DFT are used to separately study the effects of polymer chain length, carbon-carbon double-bond stretching, and the polymer in solution vs. in gas space on red shift in absorption spectrum. Next, Gaussian 09 software and the same B3LYP functional and 6-31G basis set are used to study interchain and intrachain interactions of MEH-PPV in solution. The red shift in the absorption peaks for three MEH-PPV configurations (single-chain pentamer, two stacked pentamers, and decamer) are compared with experimental results for five different solvents (chloroform, toluene, xylene, dichloromethane, and chlorobenzene). This investigation indicates that inter-chain interactions dominate in “good” aromatic solvents as compared to “poor” non-aromatic solvents. The results suggest that inter-chain charge transfer interactions play a critical role in real solutions and inter-chain aggregation takes precedence over intra-chain aggregation in aromatic solvents. In the final section of the study, accurate values for the range-separation parameter (w) for three lengths of MEH-PPV polymer (trimer, tetramer, and pentamer) in five different solvents (chloroform, chlorobenzene, xylene, Tetrahydrofuran, and dichloromethane) are reported using the range-separated functionals wB97XD and CAM-B3LYP. Using these data, range separation parameters are predicted and used for longer polymer chains in chloroform solution. The differences in the range separation parameters for the different solvents is statistically significant and gives further insight into the polymer/solvent interaction.

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Galaxies grow and evolve via the repeated process of hierarchical merging, with smaller galaxies being cannibalized by larger and correspondingly brighter ones. Thus in galaxy clusters it is the brightest cluster galaxy (BCG) that lies at the top of the galaxian food chain and deep within the cluster potential the BCG grows to become one of the most massive galaxies in the universe. Baryonic feedback processes associated with the formation of the BCG (eg., AGN, star formation, stellar winds and chemical enrichment) affect the balance between heating and cooling of the intra-cluster medium (ICM) which in turn, through replenishment of the cold gas reservoir of the BCG, feeds back on these processes. This interconnection between the BCG and the state of the cluster gas has direct implications for theories of both galaxy and cluster evolution. Thanks to recent advances in observational techniques it has become possible to study the link between BCG and host cluster properties across a wide range of multi-wavelength information. Using deep imaging data taken with the Canada-France-Hawaii Telescope as part of the Canadian Cluster Comparison Project. (CCCP). we examine the surface brightness distributions in g' and r' of 28 BCGs in a redshift range 0.15 z 0.55 residing in massive clusters with Tx > 5 and compare them to the global X-ray properties of their hosts. We fit R1/4 models to the surface brightness profiles and find that the Kormendy relation of BCGs, when corrected for passive evolution. is consistent with that of the local elliptical population. We identify a subset of BCGs with extraordinarily blue centers (0.1 < dlog(g' - r')/dlog(r) < 1.3 within 15 h70-1 kpc) extending several times the fwhm of the psf. These objects all lie on the most luminous side of the scatter in the Lx-Tx relation for a given T1, an effect which previous authors have shown can be explained by cooling of the ICM (McCarthy et al. 2004). We find independent evidence from previous studies that these systems are all hosts of recent star formation. The blue cores in these BCGs cause them to be displaced from the red sequences of their host clusters; in the most extreme cases this displacement is 11-nag. These findings are contradictory to the current paradigm of elliptical galaxy formation within clusters where star formation is thought to have a negligible effect in the most massive cluster ellipticals at late cosmic times. Furthermore BCG total magnitude is found to correlate with host cluster deviation from the mean Lx-Tx relation. We argue that cooling and pre-heating of the Intra-Cluster-Medium has an important affect on the global and structural properties of the stellar component of BCGs. Not all BCGs are red and dead, there is a need to incorporate an external source of cold gas replenishment into quenching models of galaxy formation in clusters in order to reconcile these observations.