Spiral-like star-forming patterns in CALIFA early-type galaxies
  Based on a combined analysis of SDSS imaging and CALIFA integral field
spectroscopy data, we report on the detection of faint (24 < {\mu}$_r$
mag/arcsec$^2$ < 26) star-forming spiral-arm-like features in the periphery of
three nearby early-type galaxies (ETGs). These features are of considerable
interest because they document the still ongoing inside-out growth of some
local ETGs and may add valuable observational insight into the origin and
evolution of spiral structure in triaxial stellar systems. A characteristic
property of the nebular component in the studied ETGs, classified i+, is a
two-radial-zone structure, with the inner zone that displays faint
(EW(H\alpha)$\simeq$1{\AA}) low-ionization nuclear emission-line region (LINER)
properties, and the outer one (3{\AA}<EW(H\alpha)<~20{\AA}) HII-region
characteristics. This spatial segregation of nebular emission in two physically
distinct concentric zones calls for an examination of aperture effects in
studies of type i+ ETGs with single-fiber spectroscopic data.
