Faint Galaxy Redshift Survey XIV : Galaxy Morphology in the HDF ( North ) and its Flanking Fields

Morphological classifications are reported for Hubble Space Telescope (HST) images of 241 galaxies in the Hubble Deep Field (HDF) and its Flanking Fields (FF) with measured redshifts in the interval 0.25 < z < 1.2, drawn from a magnitude-limited redshift survey to R = 24.0. The galaxies are divided into three groups with redshifts in the intervals [0.25,0.6], [0.6,0.8], [0.8,1.2]. R606 images from the first group and I814 images from the second and third groups are compared with B-band images of nearby galaxies. All classifications were therefore made at approximately the same rest wavelength. Selection biases are discussed. We corroborate and extend the results of earlier investigations by observing that: • Most intermediate and late-type galaxies with z ∼> 0.5 have morphologies that are dramatically different from those of local galaxies and cannot be shoehorned into the Hubble “tuning fork” classification scheme. • Grand-design spirals appear to be rare or absent for z ∼> 0.3. • Many Sa and Sb spirals with z ∼> 0.6 do not exhibit well-defined spiral arms. The arms of distant Sc galaxies appear more chaotic than those of their nearby counterparts. • The fraction of all galaxies that are of types Sc and Scd drops from 23% at z ∼ 0 to 5% for z > 0.6. • Barred spirals are extremely rare for z ∼> 0.5. • Roughly one in five galaxies with z ∼> 0.8 are compact objects that resemble local E, S0 or Sa galaxies. Based in part on observations obtained at the W.M. Keck Observatory, which is operated jointly by the California Institute of Technology and the University of California Dominion Astrophysical Observatory, National Research Council, 5071 West Saanich Road, Victoria, British Columbia, V9E 2E7, Canada:[email protected] Palomar Observatory, Mail Stop 105-24, California Institute of Technology, Pasadena, CA 91125 [email protected] Theoretical Astrophysics, California Institute of Technology, Mail Stop 130-33, Pasadena, CA 91125 [email protected] Current Address: Institute for Advanced Study, Olden Lane, Princeton, NJ 08540 [email protected] Hubble Fellow