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CHAPTER 2 Surface photometry of
nearby field galaxies

Originally published as R.A. Jansen, M. Franx, D. Fabricant & N. Caldwell, 2000a
The Astrophysical Journal Supplement Series, vol. 126, p. 271

We have obtained integrated spectra and multifilter photometry for a representative sample of 200 nearby galaxies. These galaxies span the entire Hubble sequence in morphological type, as well as a wide range of luminosities (MB = -14 to -22) and colors (B-R = 0.4 to 1.8). Here we describe the sample selection criteria and the U, B, R surface photometry for these galaxies. The spectrophotometric results will be presented in a companion paper. Our goals for the project include measuring the current star formation rates and metallicity of these galaxies, and elucidating their star formation histories, as a function of luminosity and morphology. We thereby extend the work of Kennicutt (1992a) to lower luminosity systems. We anticipate that our study will be useful as a benchmark for studies of galaxies at high redshift. We discuss the observing, data reduction, and calibration techniques and show that our photometry agrees well with previous work in those cases in which earlier data are available. We present an atlas of images, radial surface brightness profiles, and color profiles as well as tables of derived parameters. The atlas and tables of measurements will be made available electronically. We study the correlations of galaxy properties determined from the galaxy images. Our findings include the following: (1) colors determined within the effective radius correlate better with morphological type than with and (2) 50% of the low-luminosity galaxies are bluest in their centers.


W

ITH the advent of the Hubble Space Telescope, 8 m-class ground-based telescopes, and effective new instruments, it is now possible to study the colors, morphologies, and spectra of large samples of distant, faint galaxies. Frequently, our interpretation of such data is limited by the scarcity of good comparison samples in the local universe. Because distant galaxies subtend angles comparable to spectrograph slit widths, we usually obtain integrated spectra, while the same slits sample only the nuclear regions of nearby galaxies. This observational issue complicates the comparison of distant and nearby galaxy spectra.

     In a pioneering effort, Kennicutt (1992a, 1992b) obtained integrated spectrophotometry for 90 galaxies spanning the entire Hubble sequence. This study has had broad application for the study of galaxy spectral properties at both high and low redshift. Kennicutt's study is, however, limited to the brightest galaxies of each morphological type, and no uniform, multiple-filter, surface photometry is available for these galaxies. Also, only half of Kennicutt's sample of 90 galaxies was observed at 5-7Å spectral resolution by trailing the image of a galaxy across a long slit. The remaining half was observed at 15-20Å resolution through a 45.5" circular aperture.

     With our Nearby Field Galaxy Survey, our goal is to significantly extend Kennicutt's work. We have obtained integrated and nuclear spectroscopy and U, B, R surface photometry for a sample of 196 galaxies in the nearby field. This sample includes galaxies of all morphological types and spans 8 mag in luminosity. We include galaxies from a broad range of local galaxy densities, attempting to avoid a bias toward a particular environment. Our use of the term ``field'' corresponds to that of Koo & Kron (1992) and Ellis (1997).


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