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Session 105 - Galaxies: Counts & Kinematics.
Display session, Saturday, January 10
Detailed images from the Hubble Space Telescope (HST) have sparked a surge of interest in morphological peculiarities in both distant and local galaxies. Several groups have developed criteria by which to classify peculiarities in galaxy morphology (e.g., Abraham et al. 1996, Naim et al. 1997).
In order to study peculiar galaxies at high redshifts, it is crucial to have a solid understanding of both the morphological peculiarities in local galaxies and the appearance of local galaxies if they were observed at higher redshifts.
We are developing several algorithms to quantify the types and degree of peculiarity seen in galaxy morphology. These algorithms, or peculiarity indices, are sensitive to several different types of features. The indices are applied initially to two samples: a local galaxy sample, comprised of a subset of the Frei, et al. 1996 ``Catalog of Nearby Galaxies,'' along with several merger candidates from Hibbard amp; van Gorkom 1996 and from a run on the Lick Observatory Nickel 40-inch telescope by one of the authors (KLW); and (2) a sample of simulated z \sim 0.8 galaxies. The images of the local galaxies are resampled, and noise is added, to reflect the sampling and noise levels found in the Hubble Deep Field (HDF). The galaxy sizes and surface brightnesses are cosmologically shifted to simulate observations of these galaxies through the HST F814W (\sim I) filter at z \sim 0.8.
This study expands upon previous work by providing a realistic view of which local morphological features we can expect to measure robustly when observed at high redshifts with the current observational technology.
We also demonstrate the effectiveness of our peculiarity indices in differentiating between ``normal'' (i.e., Hubble Sequence type) galaxies and ``peculiar'' galaxies at these two epochs.
Program listing for Saturday