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High redshift QSOs and cool dwarfs in the Deep Lens Survey

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/12852

High redshift QSOs and cool dwarfs in the Deep Lens Survey

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dc.contributor.author Thorman, Paul
dc.date.accessioned 2011-07-02T16:25:36Z
dc.date.available 2011-07-02T16:25:36Z
dc.date.issued 2011-07-02
dc.date.submitted May 2011
dc.identifier.uri http://hdl.handle.net/1928/12852
dc.description.abstract The Deep Lens Survey, a 20 deg2 optical survey, was used to search for two types of rare, very red objects: faint high-redshift (z > 5.4) quasars, which trace structure formation in the early Universe and can be used to study reionization; and ultracool dwarf stars and brown dwarfs, the most numerous constituents of our own Galaxy, which are seldom detected beyond the solar neighborhood due to their low luminosities. To distinguish between these two populations, we added near-infrared imaging to a portion of the Deep Lens Survey area, covering 1.12 deg2 with survey J-band (1.2 μm) imaging, and successfully targeting 181 out of a planned 280 very red targets over an additional 2.4 deg2. These observations were reduced and cataloged, producing colors or color limits for 1626 very red objects in the field. The colors were corrected using a combination of outside photometric standards and internal checks, and a model for the colors of the target populations was created from existing measurements in the literature. The relative classification probabilities were estimated for each object by using a color model, and those probabilities were used to generate Monte Carlo realizations of the populations, either for comparison to a simulated Galaxy (for ultracool dwarfs) or for the calculation of a luminosity function (for high-redshift QSOs). For QSOs, the results were consistent with the most recent work on faint QSOs: we measured a bright-end power-law slope of for the luminosity function. Citing the similarity to earlier results for brighter QSOs, we rule out QSOs as the dominant source of ionizing photons at the time of reionization (although they may have contributed at the 10-20% level). For ultracool dwarfs, the model that best reproduced our measured magnitudes was a sech2 vertical disk profile with for the earliest spectral type range (M9-L2), with hints of a lower scale height for later spectral types. We integrate a range of best-fit models to predict the number of ultracool dwarfs to be found in future surveys, and estimate the errors introduced into current surveys by over-simplified models of the Galaxy. Spectroscopic observations were obtained for a few of our very red objects; these are displayed and analyzed. Although none of the targeted objects was definitively identified as a QSO, they showed interesting and unusual spectral features nonetheless. The methods demonstrated here for probabilistic classification of galactic and extragalactic objects will be essential to exploit the full potential of future wide deep surveys, such as LSST. These surveys will reach such faint objects that spectroscopy will be difficult or impossible for many years to come, yet we have shown that the imaging alone, augmented when necessary with follow-up photometry in specific bands, can provide the classifications needed to explore these unknown populations. en_US
dc.description.sponsorship New Mexico Space Grant en_US
dc.language.iso en_US en_US
dc.subject Astronomy en_US
dc.subject Extragalactic en_US
dc.subject Galactic en_US
dc.subject Low-mass stars en_US
dc.subject Brown Dwarfs en_US
dc.subject Quasars en_US
dc.subject QSOs en_US
dc.subject.lcsh Quasars.
dc.subject.lcsh Dwarf stars.
dc.subject.lcsh Brown dwarf stars.
dc.subject.lcsh Cool stars.
dc.subject.lcsh Low mass stars.
dc.subject.lcsh Stars--Classification.
dc.title High redshift QSOs and cool dwarfs in the Deep Lens Survey en_US
dc.type Dissertation en_US
dc.description.degree Physics en_US
dc.description.level Doctoral en_US
dc.description.department University of New Mexico. Dept. of Physics & Astronomy en_US
dc.description.advisor Loomba, Dinesh
dc.description.committee-member Jones, Rhian
dc.description.committee-member McGraw, John
dc.description.committee-member Rand, Richard


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