Observations and Models of Infrared Debris Disk Signatures and their Evolution

Persistent Link:
http://hdl.handle.net/10150/202982
Title:
Observations and Models of Infrared Debris Disk Signatures and their Evolution
Author:
Gaspar, Andras
Issue Date:
2011
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
In my thesis I investigate the occurrence of mid-infrared excess around stars and their evolution. Since the launch of the first infrared satellite, IRAS, we have known that a large fraction of stars exhibit significant levels of infrared emission above their predicted photospheric level. Resolved optical and infrared images have revealed the majority of these excesses to arise from circumstellar disk structures, made up of distributions of planetesimals, rocks, and dust. These structures are descriptively called debris disks. The first part of my thesis analyzes the Spitzer Space Telescope Observations of δ Velorum. The 24 μm Spitzer images revealed a bow shock structure in front of the star. My analysis showed that this is a result of the star’s high speed interaction with the surrounding interstellar medium. We place this observation and model in context of debris disk detections and the origin of λ Boötis stars. The second part of my thesis summarizes our observational results on the open cluster Praesepe. Using 24 μm data, I investigated the fraction of stars with mid-infrared excess, likely to have debris disks. I also assembled all results from previous debris disk studies and followed the evolution of the fraction of stars with debris disks. The majority of debris disks systems are evolved, few hundred million or a Gyr old. Since the dissipation timescale for the emitting dust particles is less than the age of these systems, they have to be constantly replenished through collisional grinding of the larger bodies. The last two chapters of my thesis is a theoretical analysis of the collisional cascade in debris disks, the process that produces the constant level of dust particles detected. I introduce a numerical model that takes into account all types of destructive collisions in the systems and solves the full scattering equation. I show results of comparisons between my and other published models and extensive verification tests of my model. I also analyze the evolution of the particle size distribution as a function of the variables in my model and show that the model itself is quite robust against most variations.
Type:
text; Electronic Dissertation
Keywords:
Modeling; Planetary Systems; Spitzer Space Telescope; Stars; Astronomy; Debris Disks; Infrared
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Astronomy
Degree Grantor:
University of Arizona
Advisor:
Rieke, George H.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleObservations and Models of Infrared Debris Disk Signatures and their Evolutionen_US
dc.creatorGaspar, Andrasen_US
dc.contributor.authorGaspar, Andrasen_US
dc.date.issued2011-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractIn my thesis I investigate the occurrence of mid-infrared excess around stars and their evolution. Since the launch of the first infrared satellite, IRAS, we have known that a large fraction of stars exhibit significant levels of infrared emission above their predicted photospheric level. Resolved optical and infrared images have revealed the majority of these excesses to arise from circumstellar disk structures, made up of distributions of planetesimals, rocks, and dust. These structures are descriptively called debris disks. The first part of my thesis analyzes the Spitzer Space Telescope Observations of δ Velorum. The 24 μm Spitzer images revealed a bow shock structure in front of the star. My analysis showed that this is a result of the star’s high speed interaction with the surrounding interstellar medium. We place this observation and model in context of debris disk detections and the origin of λ Boötis stars. The second part of my thesis summarizes our observational results on the open cluster Praesepe. Using 24 μm data, I investigated the fraction of stars with mid-infrared excess, likely to have debris disks. I also assembled all results from previous debris disk studies and followed the evolution of the fraction of stars with debris disks. The majority of debris disks systems are evolved, few hundred million or a Gyr old. Since the dissipation timescale for the emitting dust particles is less than the age of these systems, they have to be constantly replenished through collisional grinding of the larger bodies. The last two chapters of my thesis is a theoretical analysis of the collisional cascade in debris disks, the process that produces the constant level of dust particles detected. I introduce a numerical model that takes into account all types of destructive collisions in the systems and solves the full scattering equation. I show results of comparisons between my and other published models and extensive verification tests of my model. I also analyze the evolution of the particle size distribution as a function of the variables in my model and show that the model itself is quite robust against most variations.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectModelingen_US
dc.subjectPlanetary Systemsen_US
dc.subjectSpitzer Space Telescopeen_US
dc.subjectStarsen_US
dc.subjectAstronomyen_US
dc.subjectDebris Disksen_US
dc.subjectInfrareden_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineAstronomyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorRieke, George H.en_US
dc.contributor.committeememberPsaltis, Dimitriosen_US
dc.contributor.committeememberÖzel, Feryalen_US
dc.contributor.committeememberApai, Dánielen_US
dc.contributor.committeememberSu, Kate Y. L.en_US
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