Formation of Blue-cored Dwarf Early-type Galaxies in a Cluster
  Environment: a Kinematical Perspective
  The presence of blue cores in some dwarf early-type galaxies (dEs) in galaxy
clusters suggests the scenario of late-type galaxy infall and subsequent
transformation into red, quiescent dEs. We present Gemini Multi-Object
Spectrographs long-slit spectroscopy of two dEs with blue cores (dE(bc)s), EVCC
591 and EVCC 516, located at the core and outskirt of the Virgo cluster,
respectively. We obtained their internal kinematics along the major axis out
to, at least, ~ 1 effective radius. EVCC 591 shows evidence of a kinematically
decoupled core (KDC) with a size of 2" (160 pc), exhibiting an inverted pattern
for velocity with respect to the main body of its host galaxy. The rotation
curve of the stellar component in the inner region of EVCC 591 is steeper than
that in the rest of the galaxy. On the other hand, overall velocity profiles of
stellar and ionized gas components of EVCC 516 show no signature of significant
rotation. The occurrence of a KDC and zero rotation in the internal kinematics
along with the central star formation support the scenario of gas-rich
dwarf-dwarf mergers in the formation of these two dE(bc)s. Furthermore,
evolution of dE(bc)s in a cluster environment into ordinary dEs with KDCs is
possible based on their structural properties. We suggest that at least some of
the dE(bc)s in the Virgo cluster were formed through dwarf-dwarf mergers in
lower density environments before they subsequently fell into the cluster; they
were then quenched by subsequent effects within the cluster environment.
