The Morphological Diversities among Star-forming Galaxies at High Redshifts in the Great Observatories Origins Deep Survey**Based on observations obtained with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS 5-26555.
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We used the deep, multiwavelength images obtained by the Great Observatories Origins Deep Survey (GOODS) to identify 4700 Lyman break galaxies (LBGs) at z > 2.5, and 292 starburst galaxies at z 1.2. We present the results from morphological analysis based on light profile shape and ellipticity for 1333 of the most luminous LBGs. About 40% of LBGs at z 3 have exponential profiles, 30% of the galaxies have steep (r 1/4-like) profiles, and 30% of LBGs have multiple cores of disturbed morphologies suggestive of close pairs or mergers. The fraction of spheriod-like LBGs decrease by about 15% from z 5 to 3. A comparison of LBGs with the starburst galaxies at z 1.2 shows that disklike and merger morphologies are dominant, but the fraction of spheroid-like profiles is about 20% higher among LBGs. The ellipticity distribution for LBGs exhibits a pronounced skew toward high ellipticities ( > 0.5), which cannot be explained by morphologies similar to the local disks and spheroids viewed at random orientations. The peak of the distribution evolves toward lower , from 0.7 at z = 4 to 0.5 at z = 3. The ellipticity distribution for the z 1.2 galaxies is relatively flat, similar to that seen for present-day galaxies. The dominance of elongated morphologies suggests that in a significant fraction of LBGs we may be witnessing star formation in clumps along gas-rich filaments, or the earliest gas-rich bars that encompass essentially the entire visible galaxy. 2006. The American Astronomical Society. All rights reserved.
