Two Moderate-Redshift Analogs to Compact Massive Early-Type Galaxies at
  High Redshifts
  From a search of a portion of the sky covered by the SDSS and UKIDSS
databases, we have located 2 galaxies at z~0.5 that have properties similar to
those of the luminous passive compact galaxies found at z~2.5. From Keck
moderate-resolution spectroscopy and laser-guided adaptive-optics imaging of
these galaxies, we can begin to put together a more detailed picture of what
their high-redshift counterparts might be like. Spectral-synthesis models that
fit the u to K photometry also seem to give good fits to the spectral features.
  From these models, we estimate masses in the range of 3-4 10^11 M_sun for
both galaxies. Under the assumption that these are spheroidal galaxies, our
velocity dispersions give estimated masses about a factor of 3 smaller.
However, our high-resolution imaging data indicate that these galaxies are not
normal spheroids, and the interpretation of the kinematic data depends
critically on the actual morphologies and the nature of the stellar orbits.
While recent suggestions that the population of high-redshift compact galaxies
is present locally as the inner regions of local massive elliptical galaxies
are quite plausible, the peak mass surface densities of the two galaxies we
discuss here appear to be up to a factor of 10 higher than those of the highest
density local ellipticals, assuming that our photometric masses are roughly
correct. It thus seems possible that some dynamical "puffing-up'' of the
high-redshift galaxies might still be required in this scenario.
