Constraints on Cosmological Models from the HST Medium Deep Survey

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Session 54 -- HST Medium Deep Survey
Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm

[54.06] Constraints on Cosmological Models from the HST Medium Deep Survey

Myungshin Im, Richard E. Griffiths, Stefano Casertano, Kavan U. Ratnatunga, \& Lyman W. Neuschaefer (Johns Hopkins University)

We compare the results from the HST Medium Deep Survey (MDS) with the predictions of various models of galaxy evolution. We show the predicted distributions of the morphological properties of faint galaxies, i.e. sizes, axis ratio distributions, colors, redshift distribution, and number-magnitude counts vs. morphology. We compare these predictions with results from the MDS, a Key Project using the Hubble Space Telescope which has obtained more than 15,000 high resolution faint galaxy images from randomly selected fields via HST parallel observations.

We have performed this comparison using data from both WF/PC and WFPC2, i.e. pre- and post-refurbishment. We confirm our earlier finding of an excess of small galaxies and the paucity of large galaxies compared to the standard no-evolution model and the mild luminosity evolution models, and we find a considerable number of small elliptical galaxies with exponential profiles, which may be dwarf galaxies. The numbers of (larger) elliptical galaxies with $r^{0.25}$ surface brightness profiles is close to that predicted by the mild- or no-evolution models.

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