Design and Application of High Resolution and Multiobject Spectrographs Dynamical Studies of Open Clusters /
My intention writing this thesis was not just to summarize and document what I have learned and accomplished since graduation. I was rather aiming to provide the reader with a comprehensive description on the theory and practice of modern astronomical spectrographs design, and to present some applic...
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| Dokumentumtípus: | Disszertáció |
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2008-09-11
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| Online Access: | http://doktori.ek.szte.hu/1135 |
| Tartalmi kivonat: | My intention writing this thesis was not just to summarize and document what I have learned and accomplished since graduation. I was rather aiming to provide the reader with a comprehensive description on the theory and practice of modern astronomical spectrographs design, and to present some application examples of such instrument. The word “comprehensive” in this context does not mean I tried to cover every single detail of the design process, but I was hoping to give all the theoretical background necessary to follow and justify the steps of the design and construction of a specific spectrograph I built in collaboration with the CfA OIR instrumental group. A significant fraction of this thesis (Part I) is therefore all about instrumentation. Chapter 1 might seem going too far back to the basics, but, again, I wanted to aid the reader with almost all theoretical background information. At the same time this introductory chapter is a little bit biased towards a specific type of spectrographs: a high resolution, high throughput, single object fiber-fed echelle – the subject of chapter 2. Through the example of TRES (the Tillinghast Reflector Echelle Spectrograph) I show how the theory applies to design and construction. TRES was just commissioned not so long ago, and so I barely had the chance to characterize the instrument, to carry out some scientific observations. Nevertheless I am able to close that chapter with the discussion of some initial results. However, since the making of TRES took more than four years, the tool for the science examples discussed is an other instrument: Hectochelle. The alignment and characterization of this multi-object, fiber fed echelle was one of my first tasks as a graduate student, therefore I felt to spare a chapter (3) on this work. Especially since high precision radial velocity measurements carried out with multi-object instruments is not straightforward. A lot depends on instrumental stability and calibration system design. Discussing these instrument-specific details leads to some general conclusions, which are not well documented in the literature. Therefore I attempt to summarize these in chapter 4, and this concludes the Instrumentation part. Part II is a short transition from instrument building to science applications, describing the specific data reduction (chapter 5) and analysis (6) tools used in Part III. The main emphasis is on describing how a grid of synthetic spectra is used to determine the most accurate radial velocities and derive astrophysical parameters for the stellar targets. In Part III science applications of Hectochelle are presented: utilizing the multi-object ca-pability for collecting hundreds of stellar spectra in open clusters in order to unveil kinematical structure. Because most stars are formed in clusters the processes responsible for cluster formation are important to include in any consideration of the mechanisms of star formation. Observations of very young clusters can provide clues to the initial conditions of cluster formation if the cluster has not dynamically relaxed. With this goal I have studied two of these very young systems, NGC 2264 (chapter 8) and the Orion Nebula Cluster (chapter 9). The outcome of these projects were the first direct evidence of kinematical substructure, likely left over from the primordial hierarchy. A third study is about a more evolved and relaxed cluster, M38 (NGC 1912). Despite of its age there is some dynamical “heat” in that system, likely caused by an other nearby cluster, NGC 1907. In chapter 10 I show some interesting findings regarding the kinematics of this cluster pair. To conclude, in chapter 11, I list some ongoing instrumental and science projects I am involved in, which are clear continuation of those topics discussed in detail throughout this thesis. |
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