AAS 205th Meeting, 9-13 January 2005
Session 94 From Protogalaxies to Large Surveys: Tracing the Galaxy Evolution
Poster, Wednesday, January 12, 2005, 9:20am-6:30pm, Exhibit Hall

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[94.09] The deepest Near-Ultraviolet images taken with HST

D. de Mello (GSFC/CUA), Y. Wadadekar, S. Casertano (STScI), J. P. Gardner (GSFC)

We will present the preliminary analysis of the deepest HST U-band images obtained using WFPC2 as part of the parallel observations of the Hubble Ultra Deep Field Survey. Two fields were observed; one overlaps substantially with the GOODS survey area and the other overlaps with the GEMS survey area. Each field includes several hundred exposures with a total exposure time of 323.1 ks and 278.9 ks respectively. The 10\sigma limiting magnitude measured over 0.2 arcsec2 is 27.5 magnitudes, about 0.5 magnitudes deeper than the F300W image in the HDF-N and 0.7 magnitudes deeper than that in the HDF-S.

We constructed registered, cosmic ray rejected, drizzled images using a customized processing pipeline. A special effort was made to remove CTE trails from cosmic rays. We then matched the U-band sources with those in the ACS images (B,V,i,z) taken during the GOODS observations of the CDF-S and obtained photometric redshifts for 201 matched objects. Our preliminary results show that the redshift distribution is bimodal and peaks at z=0.7 and z=1.6. We found that one third of the galaxies have SEDs typical of starbursts and most of the other two thirds of late-type galaxies. However, a small number of objects (12) have SEDs typical of early-type galaxies; visual inspection shows that two of them are classical ellipticals with distinct blue cores. Galaxy morphology was evaluated by measuring the light concentration (C), asymmetry (A), and clumpiness (S) of the GOODS/ACS images in the rest-frame B band using the method by Conselice (2003). We found that a large number of the near-UV bright objects have low concentration and high asymmetries typical of mergers and ultraluminous infrared galaxies.

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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.