Deep multicolor surveys of the galaxy population

Details Deep multicolor surveys of the galaxy population Deep multicolor surveys of the galaxy population

Oct 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999phdt........11s&link_type=abstract

Thesis (PhD). THE JOHNS HOPKINS UNIVERSITY, Source DAI-B 60/04, p. 1652, Oct 1999, 158 pages.

Mathematics

Logic

Cosmology, Infrared Surveys, Ultraviolet Surveys, Galactic Evolution

Scientific paper

I present various surveys that benefit from the tremendous improvements in observational astronomy in recent years and I develop new techniques to analyze data obtained in these new generation of surveys. In participation of upcoming, very deep near-infrared galaxy surveys, I constructed a survey aimed at determining the near-infrared luminosity function of galaxies. The evolutionary effects are much weaker at the red end of the atmospheric window ranging from the near- ultraviolet to about 2.2 μ m than in the optical and UV bands, as the infrared light coming from a galaxy is dominated by the old stellar population, while optical luminosity is strongly affected by the star formation history of galaxies. Measuring the luminosity function of galaxies is essential to interpret future surveys. Utilizing my deep, large area, multi-color optical galaxy survey, I studied the structure evolution of the Universe on cosmologically relevant scales. The multicolor nature of the survey (B, V, R and I bands) made it possible to estimate the radial distance to a very large number of galaxies very efficiently. Using these photometric redshifts, one can reduce the effects of galaxy evolution by analyzing galaxies at roughly the same redshift (lookback time). Due to the large area (about 1.5 square degrees) and very faint limiting magnitude (I = 23.8), structure evolution can be studied with a very high precision. I also propose a new object detection technique to replace traditional methods that use a single band or an arbitrarily co-added image. Our new technique uses all available bands of a survey and provides a nearly optimal way to take advantage of all the information available. We demonstrate the strength of this technique using the Hubble Deep Field, where we show that we can extend the detection limit significantly. We also show that this method can identify a significant number of objects that traditional techniques usually can not detect. Finally I propose a new technique based on the Karhunen Loève transformation to construct an orthonormal base system that takes advantage of the multicolor nature of the data and takes into account the symmetries of galaxy images. I discuss the practical consequences of this method in image compression as well as the possibility of using these orthonormal bases to study the evolution of galaxy structure in an objective manner.

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