We present the analysis of the deepest near-UV image obtained with Hubble Space Telescope using the WFPC2 ( F300W ) as part of the parallel observations of the Hubble Ultra Deep Field campaign .
The U-band 10 \sigma limiting magnitude measured over 0.2 arcsec ^ { 2 } is m _ { AB } =27.5 which is 0.5 magnitudes deeper than that in the Hubble Deep Field North .
We matched the U-band catalog with those in the ACS images ( B , V , i , z ) taken during the Great Observatories Origins Deep Survey observations of the Chandra Deep Field South and obtained photometric redshifts for 306 matched objects .
We find that the UV-selected galaxies span all the major morphological types at 0.2 < z _ { phot } < 1.2 .
However , disks are more common at lower redshifts , 0.2 < z _ { phot } < 0.8 .
Higher redshift objects ( 0.7 < z _ { phot } < 1.2 ) are on average bluer than lower - z and have spectral type typical of starbursts .
Their morphologies are compact , peculiar or low surface brightness galaxies .
Despite the UV-selection , 13 objects have spectral types of early-type galaxies ; two of them are spheroids with blue cores .
The evolutionary synthesis code , Starburst99 , was used to age-date the UV-selected galaxies which were found to have rest-frame colors typical of stellar populations with intermediate ages > 100 Myr .
The average half-light radius ( rest-frame 1200–1800 Å ) of the UV-selected galaxies at 0.66 < z _ { phot } < 1.5 is 0.26 \pm 0.01 arcsec ( 2.07 \pm 0.08 kpc ) .
The UV-selected galaxies are on average fainter ( M _ { B } =–18.43 \pm 0.13 ) than Lyman Break Galaxies ( M _ { B } =–23 \pm 1 ) .
Our sample includes early-type galaxies that are presumably massive and forming stars only in their cores , as well as starburst-type systems that are more similar to the LBGs , although much less luminous .
This implies that even the starbursts in our sample are either much less massive than LBGs or are forming stars at a much lower rate or both .
The low surface brightness galaxies have no overlap with the LBGs and form an interesting new class of their own .