The Spatial Distribution and Kinematics of Stellar Populations in E+A Galaxies

We use long-slit spectroscopic observations of the sample of E+A galaxiesdescribed by Zabludoff et al. to constrain the nature of the progenitors andremnants of the E+A phase of galaxy evolution. We measure spatially-resolvedkinematic properties of the young (<~1 Gyr) and old (> few Gyr) stellarpopulations. The young stellar populations are more centrally concentrated thanthe older populations, but they are not confined to the galaxy core (radius <~1 kpc). The kinematics of the old stellar population place 16 of 20 of our E+Ason a trend parallel to the Faber-Jackson relation that is offset by $\sim$ 0.6mag in R. Eighteen of 20 E+As have v/sigma < 1. As the young stars in thesesystems evolve, the luminosity offset will disappear and the remnants will bepressure-supported systems that lie on the Faber-Jackson relation. AlthoughZabludoff et al. spectroscopically selected the most extreme E+A galaxies inthe local volume, the sample is kinematically diverse: velocity dispersionsrange from <~ 30 km/s to ~ 200 km/s over a luminosity range of M_R = -19 to -22+ 5 log h. Combining these results with an estimate of the number of galaxiesthat experience an E+A phase, we conclude that the E+A phase of galaxyevolution is important in the development of a large fraction ofspheroid-dominated galaxies over a wide range of luminosities and masses. Ourkinematic observations, together with evidence that E+As have recently evolvedfrom a vigorous star forming phase to a quiescent phase (e.g. Couch andSharples, Caldwell et al.) and that many have tidal features consistent withdisk-like progenitors (Zabludoff et al.), indicate that these galaxies areundergoing a transformation from star-forming, disk-dominated galaxies intoquiescent, spheroid-dominated galaxies.Comment: ApJ accepted, 40 pages including 16 embedded figures; figure 5 now properly included and a small change made to figure 15 captio