Field E+A galaxies at intermediate redshifts (0.3 < z < 1)

We select E+A candidates from a spectroscopic data set of similar to800 field galaxies and measure the E+A fraction at 0.3 < z < 1 to be 2.7% +/- 1.1%, a value lower than that in galaxy clusters at comparable redshifts (11% +/- 3%). HST WFPC2 imaging for five of our six E+A's shows that they have a heterogeneous parent population: these E+A's span a range in half-light radius (0.8 h(-1) kpc < r(1/2) < 8 h(-1) kpc) and estimated internal velocity dispersion (50 km s(-1) less than or similar to sigma(est) less than or similar to 220 km s(-1)), and they include luminous systems (-21.6 less than or equal to M-Bz - 5 log h less than or equal to - 19.2). Despite their diversity in some aspects, the E+A's share several common characteristics that indicate that the E+A phase is an important link in the evolution of star-forming galaxies into passive systems: the E+A's are uniformly redder than the blue, star-forming galaxies that make up the majority of the field, they are more likely to be bulge-dominated than the average field galaxy, and they tend to be morphologically irregular. We find that E+A's make up similar to9% of the absorption-line systems in this redshift range and estimate that greater than or similar to25% of passive galaxies in the local field had an E+A phase at z less than or similar to 1.