Barred galaxies at z > 0.7:: Nicmos Hubble Deep Field-North observations

Previous optical studies found an unexpected deficit of bars at z > 0.7. To investigate the effects of band shifting, we have studied the fraction of barred spiral galaxies in the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) Hubble Deep Field-North. At z > 0.7, we find at least four barred spiral galaxies, doubling the number previously detected. The number of barred galaxies is small because these ( and previous) data lack adequate spatial resolution. A typical 5 kpc bar at z > 0.7 is only marginally detectable for the Wide Field Planetary Camera 2 (WFPC2) at 0.8 mum; the NICMOS data even have lower resolution and can only find the largest bars. The average size of the four bars seen at z > 0.7 is 12 kpc. The fraction of such large bars (4/95) is higher than that seen in nearby spiral galaxies (1/44); all known selection effects suggest that the observed fraction is a lower limit. However, important caveats such as small numbers and difficulties in defining comparable samples at high and low redshifts should be noted. We conclude that there is no significant evidence of a decrease in the fraction of barred spiral galaxies beyond. z similar to 0.7