A Constant Bar Fraction out to Redshiftz∼ 1 in the Advanced Camera for Surveys Field of the Tadpole Galaxy

Bar-like structures were investigated in a sample of 186 disk galaxies largerthan 0.5 arcsec that are in the I-band image of the Tadpole galaxy taken withthe HST ACS. We found 22 clear cases of barred galaxies, 21 galaxies with smallbars that appear primarily as isophotal twists in a contour plot, and 11 casesof peculiar bars in clump-cluster galaxies, which are face-on versions of chaingalaxies. The latter bars are probably young, as the galaxies contain only weakinterclump emission. Four of the clearly barred galaxies at z~0.8-1.2 havegrand design spirals. The bar fraction was determined as a function of galaxyinclination and compared with the analogous distribution in the local Universe.The bar fraction was also determined as a function of galaxy angular size.These distributions suggest that inclination and resolution effects obscurenearly half of the bars in our sample. The bar fraction was also determined asa function of redshift. We found a nearly constant bar fraction of 0.23+-0.03from z~0 to z=1.1. When corrected for inclination and size effects, thisfraction is comparable to the bar fraction in the local Universe, ~0.4, astabulated for all bar and Hubble types in the Third Reference Catalogue ofGalaxies. The average major axis of a barred galaxy in our sample is ~10 kpcafter correcting for redshift with a LambdaCDM cosmology. Galaxy bars werepresent in normal abundance at least ~8 Gy ago (z~1); bar dissolution cannot becommon during a Hubble time unless the bar formation rate is comparable to thedissolution rate.Comment: to appear in ApJ, Sept 1, 2004, Vol 612, 18 pg, 12 figure