Spatially-resolved stellar populations and kinematics with KCWI: probing
  the assembly history of the massive early-type galaxy NGC 1407
  Using the newly commissioned KCWI instrument on the Keck-II telescope, we
analyse the stellar kinematics and stellar populations of the well-studied
massive early-type galaxy (ETG) NGC 1407. We obtained high signal-to-noise
integral-field-spectra for a central and an outer (around one effective radius
towards the south-east direction) pointing with integration times of just 600s
and 2400s, respectively. We confirm the presence of a kinematically distinct
core also revealed by VLT/MUSE data of the central regions. While NGC 1407 was
previously found to have stellar populations characteristic of massive ETGs
(with radially constant old ages and high alpha-enhancements), it was claimed
to show peculiar super-solar metallicity peaks at large radius that deviated
from an otherwise strong negative metallicity gradient, which is hard to
reconcile within a `two-phase' formation scenario. Our outer pointing confirms
the near-uniform old ages and the presence of a steep metallicity gradient, but
with no evidence for anomalously high metallicity values at large
galactocentric radii. We find a rising outer velocity dispersion profile and
high values of the 4th-order kinematic moment -- an indicator of possible
anisotropy. This coincides with the reported transition from a bottom-heavy to
a Salpeter initial mass function, which may indicate that we are probing the
transition region from the `in-situ' to the accreted phase. With short
exposures, we have been able to derive robust stellar kinematics and stellar
populations in NGC 1407 to about 1 effective radius. This experiment shows that
future work with KCWI will enable 2D kinematics and stellar populations to be
probed within the low surface brightness regions of galaxy halos in an
effective way.
