Caltech faint galaxy redshift survey. XIV. galaxy morphology in the rubbledeep field (north) and its flanking fields to z=1.21

Morphological classifications are reported for Hubble Space Telescope image s of 241 galaxies in the Hubble Deep Field and its flanking fields with mea sured redshifts in the interval 0.25 < z < 1.2, drawn from a magnitude-limi ted 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, and 0.8-1.2. R-606 imag es from the first group and I-814 images from the second and third groups a re 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 investigat ions by observing that 1. Most intermediate- and late-type galaxies with z greater than or similar to 0.5 have morphologies that are dramatically different from those of loc al galaxies and cannot be shoehorned into the Hubble "tuning fork" classifi cation scheme; 2. Grand-design spirals appear to be rare or absent for z greater than or s imilar to 0.3; 3. Many Sa and Sb spirals with z greater than or similar to 0.6 do not exhi bit well-defined spiral arms, and the arms of distant Sc galaxies appear mo re chaotic than those of their nearby counterparts; 4. The fraction of all galaxies that are of types Sc and Scd drops from 23% at z similar to 0 to 5% for z > 0.6. 5. Barred spirals are extremely rare for z greater than or similar to 0.5; 6. Roughly one in five galaxies with z greater than or similar to 0.8 is a compact objects that resembles local E, SO, or Sa galaxies. 7. Peculiar galaxies are more common beyond z = 0.3, especially among late- type spirals, than they are at z similar to 0; 8. Merging galaxies, particularly those with three or more components, also become more common with increasing redshift. On the basis of these and similar observations, it is inferred that the dev elopment of pronounced spiral structure was delayed until similar to5 Gyr a nd that most bulges are probably not formed by disintegrating bars. Major m orphological changes were still taking place only similar to5 Gyr ago, even though changes in the integrated light of most galaxies were then much slo wer than they were similar to 10 Gyr ago.