Old age and super-solar metallicity in a massive z~1.4 early-type galaxy
  from VLT/X-Shooter spectroscopy
  We present the first estimate of age, stellar metallicity and chemical
abundance ratios, for an individual early-type galaxy at high-redshift (z =
1.426) in the COSMOS field. Our analysis is based on observations obtained with
the X-Shooter instrument at the VLT, which cover the visual and near infrared
spectrum at high (R >5000) spectral resolution. We measure the values of
several spectral absorptions tracing chemical species, in particular Magnesium
and Iron, besides determining the age-sensitive D4000 break. We compare the
measured indices to stellar population models, finding good agreement. We find
that our target is an old (t > 3 Gyr), high-metallicity ([Z/H] > 0.5) galaxy
which formed its stars at z_{form} > 5 within a short time scale ~0.1 Gyr, as
testified by the strong [\alpha/Fe] ratio ( > 0.4), and has passively evolved
in the first > 3-4 Gyr of its life. We have verified that this result is robust
against the choice and number of fitted spectral features, and stellar
population model. The result of an old age and high-metallicity has important
implications for galaxy formation and evolution confirming an early and rapid
formation of the most massive galaxies in the Universe.
