AAS 203rd Meeting, January 2004
Session 131 Galaxy Evolution with HST Surveys
Oral, Thursday, January 8, 2004, 2:00-3:30pm, Centennial III

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[131.02] The morphological evolution of distant galaxies from the ACS/WFC UDF parallel observations

F. Menanteau, N. Benitez, H.C. Ford (JHU), G.D. Illingworth (UCO/Lick Obs.), J.P. Blakeslee, G.R. Meurer (JHU)

We present a detailed morphological analysis of distant field galaxies using the extremely deep ACS images from the public UDF-NICMOS parallel observations obtained in the F435W (B), F606W (V), F775W (i) and F850LP (z) filters. We segregate galaxies according to the Hubble scheme using a combination of visual classifications and objective machine based analysis. We use the bulge-to-disk (B/D) ratio as well as the Asymmetry (A) and Central Concentration (C) parameters to characterize galaxies up to iAB ~26 mag. We compute galaxy number counts as a function of morphological type and compare our results with those in the HDF-North and the model predictions from different PLE models. We take advantage of the multi-color dataset and estimate redshifts for our sample using the Bayesian photometric redshift (BPZ) which enables us to construct redshift distributions for the whole sample as well as a function of morphology. Finally, using stellar population synthesis models and a maximum likelihood approach, we compute the star-formation rate (SFR) for galaxies up to z~1 for different morphological types. We discuss our results in the context of galaxy formation models from number counts, redshift distributions and SFR. ACS was developed under NASA contract NAS 5-32864, and this research is supported by NASA grant NAG5-7697.

The author(s) of this abstract have provided an email address for comments about the abstract: felipe@pha.jhu.edu

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.