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CHAPTER 1 Introduction and
Summary



The interpretation of observations of distant galaxy samples is limited by our partial knowledge of the spectrophotometric properties of the local field galaxy population. In particular, the range in properties as a function of galaxy luminosity has not been studied systematically. To remedy this situation, optical spectrophotometric and photometric observations were obtained for 196 nearby galaxies that form a representative sample of the local field population. These galaxies span the entire Hubble sequence in morphological type, as well as a wide range of luminosities and colors.
In this thesis, the galaxy selection, the observations and data reduction are described, and two atlases of the primary data products are presented: one of the images and radial profiles of surface brightness and color, the other of the nuclear and integrated spectra. Furthermore, the first results of a study of the spectrophotometric properties of the sample are discussed, focusing on the use of [O II] as a tracer of star formation and on quantitative measurements of galaxy morphology. The spectrophotometric database is anticipated to be useful as a benchmark for studies of galaxies at both low and high redshifts.


T

HE commissioning of a new generation of large aperture telescopes and recent advances in instrumentation have resulted in a flood of spectroscopic, photometric, and morphological data on faint and distant galaxies. Where previously only the brightest objects could be observed in detail, now distant galaxies are routinely sampled well down the galaxy luminosity function. The purpose of this observational drive to reach farther and fainter has been either the derivation of the parameters of the cosmological world model, or the detection of the formation and subsequent evolution of galaxies.
        In the past decade deeper and higher resolution observations of the intermediate and high redshift universe have produced many surprising discoveries (see Ellis 1997 for a comprehensive review). These include (1) the large excess of faint blue galaxies compared to expectations (Broadhurst et al. 1988; Colless et al.1990), (2) moderate to strong luminosity evolution (Odewahn et al. 1996; Ellis et al. 1996; Lilly et al. 1995) which is morphologically segregated (Hammer et al. 1997; Driver et al. 1998), and (3) evolution of galaxy morphologies as evident from, e.g., the decline of barred spiral galaxies with redshift (Abraham et al. 1996), the increased rate of galaxy mergers (Glazebrook et al. 1995; Abraham et al. 1996; van Dokkum et al. 1999), and the appearance of ``chain galaxies'', very compact star forming galaxies and other apparently proto-galactic systems (Cowie, Hu & Songaila 1995; Steidel et al. 1996). At redshifts z \gtrsim 3 recent observations indicate a prevalence of small, proto-galactic, actively star forming systems (e.g., Stern & Spinrad 1999; Franx et al. 1997; Dey et al. 1998; Weymann et al. 1998; Spinrad et al. 1998; Chen, Lanzetta & Pascarelle 1999; van Breugel et al. 1999; Hu, McMahon, & Cowie 1999). The combined star formation rate in the universe appears to peak near a redshift of one, although the data do not exclude a constant high rate of star formation until z~1 and a steep decline ever since (Madau et al. 1996; Madau, Pozzetti & Dickinson 1998).


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