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 D 4000 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 \sim 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 .