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Session 103 - Galaxy Evolution.
Display session, Thursday, January 16
Metropolitan Ballroom,

[103.07] The Evolution of Faint Field Galaxies: Implications from the Hubble Deep Field

C. Gronwall (Wesleyan Univ.)

The Hubble Deep Field (HDF) is a four square arcminute area of the sky imaged for ten consecutive days with the Hubble Space Telescope. It is the deepest optical imaging survey of field galaxies in existence, reaching \sim 2-3 mag fainter than the deepest ground-based observations. In addition to its unprecedented depth, the spatial resolution of the HDF enables the measurement of structural and morphological parameters for an extremely faint sample of galaxies.

We (see Gronwall amp; Koo 1995) have developed a modeling technique which differs from previous work by adopting the very simple assumption that the local galaxy luminosity function and galaxy mix are not\/ well-defined. Instead, we use a non-negative least squares fitting technique to derive a set of best-fitting local luminosity functions for different galaxy spectral types. By only including traditional luminosity evolution (i.e., the photometric evolution of stars over time given reasonable assumptions of the star formation history of various galaxy types), plus the addition of galaxy reddening, we are able to fit the observed optical and near-IR galaxy counts, B-R colors, and redshifts of faint field galaxies extremely well to B \sim 25. We present the extension of the obove modeling technique to the multicolor photometric information and structural parameters (in particular, angular sizes) provided by the HDF. Our newst models also include additional evolutionary components -- merging and starbursting -- to try to constrain the relative importances of different forms of evolution in faint field galaxies.

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Program listing for Thursday